Introduction

The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It has up to six layers of nerve cells. It is covered by the meninges and often referred to as gray matter^[1]. The cortex is gray because nerves in this area lack the insulation (myelin) that makes most other parts of the brain appear to be white^[2]

External features

• Pole-frontal, occipital, temporal
• Surface- superolateral, medial, inferior
• Border- supero-medial, inferolateral, medial-sulci and gyri present
• Surface area of cortex-2200cm²

Lobes of cerebral hemisphere and cortical functional area-(brodmann area-47)

Frontal-motor (4, 6, 8, supplementary motor area)

Parietal-sensory [(3, 1, 2), (5, 7, 40)] and secondary somaesthetic areas

Temporal-auditory (41, 42, 22)

Occipital-vision (17, 18, 19)

Speech area

Motor speech – ant area (44, 45)

                         Sup. Area

Sensory speech- reading Centre (39)

                  Area 40

                  Wernicke’s area (22)

Smell and gustatory area-area 28 and area43

TYPES OF CORTEX :

Based on the differences in laminar organization the cerebral cortex can be classified into two types,

1.  Neocortex :  large area of cortex which has six cell layers
2. Allocortex : much smaller area of cortex  that has three or four layers

• The neocortex is also known as the isocortex or neopallium and is the part of the mature cerebral cortex with six distinct layers. Examples of neocortical areas include the granular primary motor cortex, and the striate primary visual cortex.
• The allocortex is the part of the cerebral cortex with three or four layers, and has three subtypes

1. Paleocortexwith three cortical laminae,
2. Archicortexwhich has four or five
3. Periallocortex transitional area adjacent to the allocortex,  .

 Examples of allocortex are the olfactory cortex and the hippocampus.

BLOOD SUPPLY AND DRAINAGE :

The main arteries supplying the cortex are.

• Anterior cerebral artery -anterior portions of the brain, including most of the frontal lobe.
• Middle cerebral artery – parietal lobes, temporal lobes, and parts of the occipital lobes. splits into two branches to supply the left and right hemisphere, where they branch further.
• Posterior cerebral artery– supplies the occipital lobes.
• The circle of Willisis the main blood system that deals with blood supply in the cerebrum and cerebral cortex.

The cerebral cortex is involved in several functions of the body including:

• Determining intelligence
• Determining personality
• Motor function
• Planning and organization
• Touch sensation
• Processing sensory information
• Language processing

The cerebral cortex contains:

1. Sensory areas: receive input from the thalamus and process information related to the senses. They include the visual cortex of the occipital lobe, the auditory cortex of the temporal lobe, the gustatory cortex, and the somatosensory cortex of the parietal lobe. Within the sensory areas are association areas that give meaning to sensations and associate sensations with specific stimuli.
2. Motor areas: including the primary motor cortex and the premotor cortex, regulate voluntary movement ^[2].

Histological structure-layers of laminae

1. Molecular or plexiform layer
2. External granular layer
3. Outer pyramidal layer
4. Inner granular layer
5. Inner pyramidal layer
6. Polymorphous or multiform layer

Area

1. Frontal
2. Parietal
3. Temporal
4. Occipital
5. Frontal lobe

-Precentral cortex/ Excitomotor area of cortex

      -Major area

      -Function- centre of planned action

      -Centre of higher function- Emotions, learning, memory and behavior

      -Cause autonomic change during emotional conditions

      -Seat of intelligence-register short term memory

      -Called organ of mind

      -Control of intellectual activities

-prefrontal cortex/orbito frontal cortex

Applied aspects-

Cause- ablation of prefrontal cortex

Feature- flight of idea, emotional instability, euphoria, loss of moral and social sense

Functional abnormal- hyperphagia, sphincters control loss, disorientation and tremors, impairment of memory, lack of attention and concentration, lack of initiative and decrease intellectual activity.

2. Parietal lobe

-Primary sensory area (3,1,2)

-secondary sensory area

-sensory association area (5,7)

Function of parietal lobe

-1^st somatic sensory area

      -Localize, analyze and discriminate cutaneous and proprioceptive sense

      -Area 3 – touch, pressure, position, vibration

      -Area 1- cutaneous and joint sense

      -Area 2 – deep sense from muscle and joints

-2^nd somatic sensory area

      From S1 and thalamus directly

      Perception of sensation

-Sensory association area (5,7)

      -Discriminate stimuli related to intensity

      -warm, warmer, cold, colder

3. Temporal lobe

-Association auditory cortex

-Speech comprehension

-Important in naming

-Memory-b/l medial temporal lobe near hippocampus

-Superior part of contralateral visual field

Function of temporal lobe

-Wernicke speech comprehension-dominant side

-Verbal learning

-Hallucination include gustatory, visual, auditory, with emotion

-Lyrics in dominant lobe

-Harmony and melody is impaired by lesion of non-dominant

4. Occipital lobe

-smallest of four paired lobes in the human cerebral cortex

 landmark: calcrine fissure

      Lingual gyrus

      Fusiform gyrus

Function :visualcortex

Primary visual cortex

-process information from sensory receptors on retinas

-left half of each eye sends information to left hemisphere

-right half of each eye sends information to right hemisphere

Disorder

-blind sight

-alexia

Applied anatomy and physiology of CORTEX

• Cortical diseases fall into two major categories, degenerative and developmental.
• In degenerative conditions such as Alzheimer’s disease, progressive cell loss leads to functional deficits and cognitive decline.
• In developmental disorders however, failures in cellular migration, cortical maturation or synaptic pruning, can lead to dysplasias or learning disorders.
• Neurodegenerative diseases such as Alzheimer’s diseaseand Lafora disease, show as a marker, an atrophy of the grey matter of the cerebral cortex.
• Alzheimer’s disease disrupts this communication among neurons, resulting in loss of function and cell death. Alzheimer’s disease typically destroys neurons and their connections in parts of the brain involved in memory, including the entorhinal cortex and hippocampus. It later affects areas in the cerebral cortex responsible for language, reasoning, and social behavior. Eventually, many other areas of the brain are damaged. Over time, a person with Alzheimer’s gradually loses his or her ability to live and function independently.
• Dementia with Lewy Bodies

Other diseases of the central nervous system include neurological disorders such as epilepsy, movement disorders, and difficulties in speech (aphasia).

Brain damage from disease or trauma, can involve damage to a specific lobe such as in frontal lobe disorder, and associated functions will be affected. The blood-brain barrier that serves to protect the brain from infection can become compromised allowing entry to pathogens.

The developing fetus is susceptible to a range of environmental factors that can cause birth defects and problems in later development. Maternal alcohol consumption for example can cause fetal alcohol spectrum disorder. Other factors that can cause neurodevelopment disorders are toxicants such as drugs, and exposure to radiation as from X-rays. Infections can also affect the development of the cortex. A viral infection is one of the causes of lissencephaly, which results in a smooth cortex without gyrification.

A type of electrocorticography called cortical stimulation mapping is an invasive procedure that involves placing electrodes directly onto the exposed brain in order to localize the functions of specific areas of the cortex. It is used in clinical and therapeutic applications including pre-surgical mapping.

Cranial nerves 

Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing.

The cranial nerves emerge from the central nervous system above the level of the first vertebrae of the vertebral column.^] Each cranial nerve is paired and is present on both sides. There are conventionally twelve pairs of cranial nerves, which are described with Roman numerals I–XII. Some considered there to be thirteen pairs of cranial nerves, including cranial nerve zero. The numbering of the cranial nerves is based on the order in which they emerge from the brain and brainstem, from front to back.

Most typically, humans are considered to have twelve pairs of cranial nerves (I–XII),

 The nerves are: the olfactory nerve (I), the optic nerve (II), oculomotor nerve (III), trochlear nerve (IV), trigeminal nerve (V), abducens nerve (VI), facial nerve (VII), vestibulocochlear nerve (VIII), glossopharyngeal nerve (IX), vagus nerve (X), accessory nerve (XI), and the hypoglossal nerve (XII).

FUNCTION :

The cranial nerves provide motor and sensory supply mainly to the structures within the head and neck. The sensory supply includes both “general” sensation such as temperature and touch, and “special” senses such as taste, vision, smell, balance and hearing. The vagus nerve (X) provides sensory and autonomic (parasympathetic) supply to structures in the neck and also to most of the organs in the chest and abdomen

Applied anatomy and physiology of cranial nerves

l  Compression

Nerves may be compressed because of increased intracranial pressure, a mass effect of an intracerebral haemorrhage, or tumour that presses against the nerves and interferes with the transmission of impulses along the nerve.

Loss of function of a cranial nerve may sometimes be the first symptom of an intracranial or skull base cancer.

An increase in intracranial pressure may lead to impairment of the optic nerves (II) due to compression of the surrounding veins and capillaries, causing swelling of the eyeball (papilloedema)¹. A cancer, such as an optic nerve glioma, may also impact the optic nerve (II). A pituitary tumour may compress the optic tracts or the optic chiasm of the optic nerve (II), leading to visual field loss.

A pituitary tumour may also extend into the cavernous sinus, compressing the oculuomotor nerve (III), trochlear nerve (IV) and abducens nerve (VI), leading to double-vision and strabismus. These nerves may also be affected by herniation of the temporal lobes of the brain through the falx cerebri.

The cause of trigeminal neuralgia, in which one side of the face is exquisitely painful, is thought to be compression of the nerve by an artery as the nerve emerges from the brain stem. An acoustic neuroma, particularly at the junction between the pons and medulla, may compress the facial nerve (VII) and vestibulocochlear nerve (VIII), leading to hearing and sensory loss on the affected side.²

l  Stroke :

Occlusion of blood vessels that supply the nerves or their nuclei, an ischemic stroke, may cause specific signs and symptoms relating to the damaged area. If there is a stroke of the midbrain, pons or medulla, various cranial nerves may be damaged, resulting in dysfunction and symptoms of a number of different syndromes.³ 

Thrombosis, such as a cavernous sinus thrombosis, refers to a clot (thrombus) affecting the venous drainage from the cavernous sinus, affects the optic (II), oculomotor (III), trochlear (IV), opthalamic branch of the trigeminal nerve (V1) and the abducens nerve (VI).²

l  Inflammation

Inflammation of a cranial nerve can occur as a result of infection, such as viral causes like reactivated herpes simplex virus, or can occur spontaneously. Inflammation of the facial nerve (VII) may result in Bell’s palsy.

Multiple sclerosis, an inflammatory process resulting in a loss of the myelin sheathes which surround the cranial nerves, may cause a variety of shifting symptoms affecting multiple cranial nerves. Inflammation may also affect other cranial nerves^3. Other rarer inflammatory causes affecting the function of multiple cranial nerves include sarcoidosis, miliary tuberculosis, and inflammation of arteries, such as granulomatosis with polyangiitis.²

l  Other

Trauma to the skull, disease of bone, such as Paget’s disease, and injury to nerves during surgery are other causes of nerve damage.

Peripheral nerves

Peripheral nerves reside outside your brain and spinal cord. They relay information between your brain and the rest of your body.

The peripheral nervous system is divided into two main parts:

1. Autonomic nervous system (ANS): Controls involuntary bodily functions and regulates glands.
2. Somatic nervous system (SNS): Controls muscle movement and relays information from ears, eyes and skin to the central nervous system.

1.Autonomic nervous system

The autonomic nervous system (ANS) controls involuntary responses to regulate physiological functions.The brain and spinal cord of the central nervous system are connected with organs that have smooth muscle, such as the heart, bladder, and other cardiac, exocrine, and endocrine related organs, by ganglionic neurons. 

The most notable physiological effects from autonomic activity are pupil constriction and dilation, and salivation of saliva. 

The autonomic nervous system is always activated, but is either in the sympathetic or parasympathetic state. Depending on the situation, one state can overshadow the other, resulting in a release of different kinds of neurotransmitters.

a.       Sympathetic nervous system

The sympathetic system is activated during a “fight or flight” situation in which mental stress or physical danger is encountered. Neurotransmitters such as norepinephrine, and epinephrine are released, which increases heart rate and blood flow in certain areas like muscle, while simultaneously decreasing activities of non-critical functions for survival, like digestion. The systems are independent to each other, which allows activation of certain parts of the body, while others remain rested.

b.      Parasympathetic nervous system

Primarily using the neurotransmitter acetylcholine (ACh) as a mediator, the parasympathetic system allows the body to function in a “rest and digest” state.Consequently, when the parasympathetic system dominates the body, there are increases in salivation and activities in digestion, while heart rate and other sympathetic response decrease.

Unlike the sympathetic system, humans have some voluntary controls in the parasympathetic system. The most prominent examples of this control are urination and defecation.]

c.       Enteric nervous system

There is a lesser known division of the autonomic nervous system known as the enteric nervous system. Located only around the digestive tract, this system allows for local control without input from the sympathetic or the parasympathetic branches, though it can still receive and respond to signals from the rest of the body. The enteric system is responsible for various functions related to gastrointestinal system^4.

2. somatic nervous system

The somatic nervous system includes the sensory nervous system and the somatosensory system and consists of sensory nerves and somatic nerves, and many nerves which hold both functions.

1. Cervical spinal nerves (C1–C4)

The first 4 cervical spinal nerves, C1 through C4, split and recombine to produce a variety of nerves that serve the neck and back of head.

Spinal nerve C1 is called the suboccipital nerve, which provides motor innervation to muscles at the base of the skull. C2 and C3 form many of the nerves of the neck, providing both sensory and motor control. These include the greater occipital nerve, which provides sensation to the back of the head, the lesser occipital nerve, which provides sensation to the area behind the ears, the greater auricular nerve and the lesser auricular nerve.

The phrenic nerve is a nerve essential for our survival which arises from nerve roots C3, C4 and C5. It supplies the thoracic diaphragm, enabling breathing. If the spinal cord is transected above C3, then spontaneous breathing is not possible.[citation needed]

b. Brachial plexus (C5–T1)

The last four cervical spinal nerves, C5 through C8, and the first thoracic spinal nerve, T1, combine to form the brachial plexus, or plexus brachialis, a tangled array of nerves, splitting, combining and recombining, to form the nerves that subserve the upper-limb and upper back. Although the brachial plexus may appear tangled, it is highly organized and predictable, with little variation between people. See brachial plexus injuries.

1. Lumbosacral plexus (L1–Co1)

The anterior divisions of the lumbar nerves, sacral nerves, and coccygeal nerve form the lumbosacral plexus, the first lumbar nerve being frequently joined by a branch from the twelfth thoracic. For descriptive purposes this plexus is usually divided into three parts:

• lumbar plexus
• sacral plexus
• pudendal plexus

Applied anatomy and physiology of peripheral nerves

• Peripheral neuropathy,:

It is a result of damage to the nerves located outside of the brain and spinal cord (peripheral nerves), often causes weakness, numbness and pain, usually in the hands and feet. It can also affect other areas and body functions including digestion, urination and circulation.

Peripheral neuropathy can result from traumatic injuries, infections, metabolic problems, inherited causes and exposure to toxins. One of the most common causes is diabetes.

Peripheral neuropathy can affect one nerve (mononeuropathy), two or more nerves in different areas (multiple mononeuropathy), or many nerves (polyneuropathy). Carpal tunnel syndrome is an example of mononeuropathy. Most people with peripheral neuropathy have polyneuropathy.

• Carpel tunnel syndrome

Carpal tunnel syndrome is a common condition that causes pain, numbness, and tingling in the hand and arm. The condition occurs when one of the major nerves to the hand — the median nerve — is squeezed or compressed as it travels through the wrist. 

Carpal tunnel syndrome occurs when the tunnel becomes narrowed or when tissues surrounding the flexor tendons swell, putting pressure on the median nerve.

• Brachial plexus injury

The brachial plexus is the network of nerves that sends signals from your spinal cord to your shoulder, arm and hand. A brachial plexus injury occurs when these nerves are stretched, compressed, or in the most serious cases, ripped apart or torn away from the spinal cord.

Minor brachial plexus injuries, known as stingers or burners, are common in contact sports, such as football. Babies sometimes sustain brachial plexus injuries during birth. Other conditions, such as inflammation or tumors, may affect the brachial plexus.

The most severe brachial plexus injuries usually result from automobile or motorcycle accidents. Severe brachial plexus injuries can leave your arm paralyzed, but surgery may help restore function.

Symptoms :

• A feeling like an electric shock or a burning sensation shooting down your arm.
• Numbness and weakness in your arm.
• Weakness or inability to use certain muscles in your hand, arm or shoulder.
• Complete lack of movement and feeling in your arm, including your shoulder and hand.
• Severe pain
• Lumbar plexus block

Lumbar plexus is an advanced regional anesthesia technique, practiced by relatively few, experienced regional anesthesiologists.

Indicated in number of lower extremity procedures. It has been shown to be particularly useful for femoral shaft and neck fractures, knee procedures, and procedures involving the anterior thigh. 

• Lumbar plexus injury :Lumbosacral plexopathy (LSP): an injury to the nerves in the lumbar or sacral plexus.

Neurologic signs of lumbosacral plexus injuries consist of motor deficit with flaccid paralysis associated with sensory deficits to all types of stimulation in the territory of the damaged nerve roots: a lower motor neuron paralysis.

Patients with LS plexopathy usually present with low back and/or leg pain. They can also experience motor weakness, other sensory symptoms of numbness, paresthesia, and/or sphincter dysfunction

References :

1. Britton, the editors Nicki R. Colledge, Brian R. Walker, Stuart H. Ralston ; illustrated by Robert (2010). Davidson’s principles and practice of medicine (21st ed.). Edinburgh: Churchill Livingstone/Elsevier. p. 1166. ISBN978-0-7020-3085-7.
2. Anthony S. Fauci; T. R. Harrison; et al., eds. (2008). Harrison’s principles of internal medicine(17th ed.). New York [etc.]: McGraw-Hill Medical. pp. 2583–2587. ISBN 978-0-07-147693-5.
3. Britton, the editors Nicki R. Colledge, Brian R. Walker, Stuart H. Ralston ; illustrated by Robert (2010). Davidson’s principles and practice of medicine(21st ed.). Edinburgh: Churchill Livingstone/Elsevier. pp. 1164–1170, 1192–1193. ISBN 978-0-7020-3085-7.
4. https://en.wikipedia.org/wiki/Peripheral_nervous_system#Autonomic_nervous_system (assessed on 09/01/22).

JOINTS

A joint is defined as a connection between two bones in the skeletal system.

Joints can be classified by the type of the tissue present (fibrous, cartilaginous or synovial), or by the degree of movement permitted (synarthrosis, amphiarthrosis or diarthrosis).

CLASSIFICATION:

1. Classification by type of tissue:
2. Fibrous – bones connected by fibrous tissue.
3. Cartilaginous – bones connected by cartilage.
4. Synovial – articulating surfaces enclosed within fluid-filled joint capsule

2. Classification by degree of movement:
3. Synarthrosis – immovable.
4. Amphiarthrosis – slightly mov
5. Diarthrosis – freely moveable
6. Fibrous Joints

A fibrous joint is where the bones are bound by a tough, fibrous tissue. These are typically joints that require strength and stability over range of movement.

Fibrous joints can be further sub-classified into sutures, gomphoses and syndesmoses.

a.1 Sutures

Sutures are immovable joints (synarthrosis), and are only found between the flat,           plate-like bones of the skull.

There is limited movement until about 20 years of age, after which they become fixed      and immobile. They are most important in birth, as at that stage the joints are not    fused, allowing deformation of the skull as it passes through the birth canal.

a.2 Gomphoses

Gomphoses are also immovable joints. They are found where the teeth articulate with their sockets in the maxilla (upper teeth) or the mandible (lower teeth).

The tooth is bound into its socket by the strong periodontal ligament.

a.3 Syndesmoses

Syndesmoses are slightly movable joints (amphiarthroses).

They are comprised of bones held together by an interosseous membrane. The          middle radioulnar joint and middle tibiofibular joint are examples of a syndesmosis           joint.

1. Cartilaginous

In a cartilaginous joint, the bones are united by fibrocartilage or hyaline cartilage.

There are two main types: synchondroses (primary cartilaginous) and symphyses (secondary cartilaginous).

b.1 Synchondroses

In a synchondrosis, the bones are connected by hyaline cartilage. These joints are     Immovable (synarthrosis).

-Example of a synchondrosis is the joint between the diaphysis and epiphysis of a             growing long bone.

b.2 Symphyses

Symphysial joints are where the bones are united by a layer of fibrocartilage. They are slightly movable (amphiarthrosis).

-Examples include the pubic symphysis, and the joints between vertebral bodies.

1. Synovial

A synovial joint is defined by the presence of a fluid-filled joint cavity contained within a fibrous capsule.

They are freely movable (diarthrosis) and are the most common type of joint found in the body.

Synovial joints can be sub-classified into several different types, depending on the shape of their articular surfaces and the movements permitted:

c.1 Hinge – permits movement in one plane – usually flexion and extension.

E.g. elbow joint, ankle joint, knee joint.

c.2 Saddle – named due to its resemblance to a saddle on a horse’s back. It is        characterised by opposing articular surfaces with a reciprocal concave-convex shape.

E.g. carpometacarpal joints.

c.3 Plane – the articular surfaces are relatively flat, allowing the bones to glide over     one another.

E.g. acromioclavicular joint, subtalar joint.

c.4 Pivot – allows for rotation only. It is formed by a central bony pivot, which is            surrounded by a bony-ligamentous ring

E.g. proximal and distal radioulnar joints, atlantoaxial joint.

c.5 Condyloid – contains a convex surface which articulates with a concave elliptical       cavity. They are also known as ellipsoid joints.

E.g. wrist joint, metacarpophalangeal joint, metatarsophalangeal joint.

c.6 Ball and Socket – where the ball-shaped surface of one rounded bone fits into the         cup-like depression of another bone. It permits free movement in numerous axes.

E.g. hip joint, shoulder joint.

Structures of a Synovial Joint

• A synovial jointis characterised by the presence of a fluid-filled joint cavity contained within a fibrous capsule.
• It is the most commontype of joint found in the human body, and contains several structures which are not seen in fibrous or cartilaginous joints.
• The three main features of a synovial jointare:
• Articular capsule
• Articular cartilage
• Synovial fluid.

• Articular Capsule

The articular capsule surrounds the joint and is continuous with the periosteum of articulating bones.

It consists of two layers:

1. Fibrous layer (outer) – consists of white fibrous tissue, known the capsular ligament. It holds together the articulating bones and supports the underlying synovium.
2. Synovial layer (inner)– a highly vascularised layer of serous connective tissue. It absorbs and secretes synovial fluid, and is responsible for the mediation of nutrient exchange between blood and joint. Also known as the synovium.

• Articular Cartilage

The articulating surfaces of a synovial joint (i.e. the surfaces that directly contact each other as the bones move) are covered by a thin layer of hyaline cartilage.

The articular cartilage has two main roles: (i) minimising friction upon joint movement, and (ii) absorbing shock.

• Synovial Fluid

The synovial fluid is located within the joint cavity of a synovial joint. It has three primary functions:

-Lubrication

-Nutrient distribution

-Shock absorption.

Articular cartilage is relatively avascular, and is reliant upon the passive diffusion of nutrients from the synovial fluid.

Accessory Structures of a Synovial Joint

• Accessory Ligaments :

The accessory ligaments are separate ligaments or parts of the joint capsule.

They consist of bundles of dense regular connective tissue, which is highly adapted for resisting strain. This resists any extreme movements that may damage the joint.

• Bursae :

A bursa is a small sac lined by synovial membrane, and filled with synovial fluid.

Bursae are located at key points of friction in a joint. They afford joints greater freedom of movement, whilst protecting the articular surfaces from friction-induced degeneration

They can become inflamed following infection or irritation by over-use of the joint (bursitis).

Innervation

Synovial joints have a rich supply from articular nerves.

The innervation of a joint can be determined using Hilton’s Law – ‘the nerves supplying a joint also supply the muscles moving the joint and the skin covering their distal attachments.’

Articular nerves transmit afferent impulses, including proprioceptive (joint position) and nociceptive (pain) sensation

Vasculature

Arterial supply to synovial joints is via articular arteries, which arise from the vessels around the joint. The articular arteries are located within the joint capsule, mostly in the synovial membrane.

A common feature of the articular arterial supply is frequent anastomoses (communications) in order to ensure a blood supply to and across the joint regardless of its position. In practice this usually means arteries are above and below a joint, curving round each side of it and joining via small connecting vessels.

The articular veins accompany the articular arteries and are also found in the synovial membrane.oint Stability

The stability of joints is a topic of great clinical importance; it explains why some joints are more prone to dislocation and injury than others. It also underlies the clinical basis of treating joint injuries.

Shape, Size and Arrangement of Articular Surfaces :

The joints of the body come in all shapes and sizes. The most important factor to consider here is the relative proportion of the two articulating surfaces.

For example, in the shoulder joint, the humeral head of the upper arm is disproportionately larger than the glenoid fossa of the scapula that it sits in – making the joint more unstable, as there is less contact between the bones.

In contrast, the acetabulum of the pelvis fully encompasses the femoral head, and this makes the hip-joint far more stable. However, whilst the hip is more stable, the shoulder has a greater range of  movement. Each joint has this trade-off that is particular to its function.

• Ligaments

The ligaments of a joint prevent excessive movement that could damage the joint. As a general rule, the more ligaments a joint has, and the tighter they are, the more stable the joint is.

However, tight ligaments restrict movement, and this is why extra stability of a joint comes at the cost of loss of mobility. If disproportionate, inappropriate or repeated stress is applied to ligaments, they can stretch, tear or even damage the bone they attach to – this is why sportspeople are more susceptible to ligament injuries.

Tone of Surrounding Muscles

The tone of the surrounding muscles contributes greatly to the stability of a joint. A good example of this is the support provided by the rotator cuff muscles, which keep the head of the humerus in the shallow glenoid cavity of the scapula. If there is a loss of tone, such as in old age or stroke, the shoulder can dislocate.

Dislocations of the shoulder joint can tear the rotator cuff muscles, making the patient more susceptible to further injuries.

Similarly, the tone of muscles around the knee are crucial to its stability. Through inappropriate or unbalanced training, the knee can be made prone to injury through muscle imbalance. This can lead to chronic pain.

Applied anatomy and physiology of joints

• Damaging the cartilage of joints (articular cartilage) or the bones and muscles that stabilize the joints can lead to joint dislocationsand osteoarthritis. Swimming is a great way to exercise the joints with minimal damage.
• A joint disorder is termed arthropathy, and when involving inflammationof one or more joints the disorder is called arthritis. Most joint disorders involve arthritis, but joint damage by external physical trauma is typically not termed arthritis.
• Arthropathies are called polyarticular(multiarticular) when involving many joints and monoarticular when involving only a single joint.
• Arthritis is the leading cause of disability in people over the age of 55. There are many different forms of arthritis, each of which has a different cause. The most common form of arthritis, osteoarthritis(also known as degenerative joint disease), occurs following trauma to the joint, following an infection of the joint or simply as a result of aging and the deterioration of articular cartilage. Furthermore, there is emerging evidence that abnormal anatomy may contribute to early development of osteoarthritis. Other forms of arthritis are rheumatoid arthritis and psoriatic arthritis, which are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. Additionally, there is a less common form of gout that is caused by the formation of rhomboidal-shaped crystals of calcium pyrophosphate. This form of gout is known as pseudogout.
• Temporomandibular joint syndrome(TMJ) involves the jaw joints and can cause facial pain, clicking sounds in the jaw, or limitation of jaw movement, to name a few symptoms. It is caused by psychological tension and misalignment of the jaw (malocclusion), and may be affecting as many as 75 million Americans.

CARDIOVASCULAR SYSTEM ANATOMY & PHYSIOLOGY

The heart is the pump responsible for maintaining adequate circulation of oxygenated blood around the vascular network of the body. It is a four-chamber pump, with the right side receiving deoxygenated blood from the body at low pressure and pumping it to the lungs (the pulmonary circulation) and the left side receiving oxygenated blood from the lungs and pumping it at high pressure around the body (the systemic circulation).

The myocardium (cardiac muscle) is a specialised form of muscle, consisting of individual cells joined by electrical connections. The contraction of each cell is produced by a rise in intracellular calcium concentration leading to spontaneous depolarisation, and as each cell is electrically connected to its neighbour, contraction of one cell leads to a wave of depolarisation and contraction across the myocardium.

This depolarisation and contraction of the heart is controlled by a specialised group of cells localised in the sino-atrial node in the right atrium- the pacemaker cells.

1. These cells generate a rhythmical depolarisation, which then spreads out over the atria to the atrio-ventricular node.
2. The atria then contract, pushing blood into the ventricles.
3. The electrical conduction passes via the Atrio-ventricular node to the bundle of His, which divides into right and left branches and then spreads out from the base of the ventricles across the myocardium.
4. This leads to a ‘bottom-up’ contraction of the ventricles, forcing blood up and out into the pulmonary artery (right) and aorta (left).
5. The atria then re-fill as the myocardium relaxes.

The ‘squeeze’ is called systole and normally lasts for about 250ms. The relaxation period, when the atria and ventricles re-fill, is called diastole; the time given for diastole depends on the heart rate.

The Coronary Circulation

The heart needs its own reliable blood supply in order to keep beating- the coronary circulation. There are two main coronary arteries, the left and right coronary arteries, and these branch further to form several major branches (see image). The coronary arteries lie in grooves (sulci) running over the surface of the myocardium, covered over by the epicardium, and have many branches which terminate in arterioles supplying the vast capillary network of the myocardium. Even though these vessels have multiple anastomoses, significant obstruction to one or other of the main branches will lead to ischaemia in the area supplied by that branch.

APPLIED ANATOMY AND PHYSILOGY OF CVS

Cardiovascular System

The cardiovascular system is a circulatory system comprising the heart, blood vessels and the cells and plasma that make up the blood. The blood vessels of the body represent a closed delivery system, which transports blood around the body, circulating substances such as oxygen, nutrients and hormones to the organs and tissues. The circulatory system also acts to remove metabolic wastes such as carbon dioxide and other unwanted products. The heart is a specialised muscle, the principal function of which is to act as a pump to maintain the circulation of blood within the blood vessels.

The three main types of blood vessel are arteries, veins and capillaries.

1. Arteries

The afferent blood vessels carrying blood away from the heart. The walls (outer structure) of arteries contain smooth muscle fibres that contract and relax in response to the sympathetic nervous system.

2. Veins

The efferent blood vessels returning blood to the heart. The walls (outer structure) of veins consist of three layers of tissues that are thinner and less elastic than the corresponding layers of arteries. Veins include valves that aid the return of blood to the heart by preventing blood from flowing in the reverse direction.

The basic structure of the vessel wall is similar in all blood vessels with the tunica intima or endothelium lining the vessel’s lumen. Externally is a connective tissue, the tunica adventitia which is slightly thicker in arteries. The middle layer is a layer of smooth muscle, the tunica media, which is much thicker in arteries and which is largely responsible for the peripheral control of blood pressure. The endothelial lining of veins is enveloped to form valves which, with external muscle influence, assist in propelling blood back to the heart (valves are rarely taken into consideration during venepuncture, but they can be used to benefit or to hinder successful cannulation of a vein).

3.Capillaries

These are narrow, thin‐walled blood vessels (approximately 5–20 µm in diameter) that connect arteries to veins. Capillary networks exist in most of the tissues and organs of the body, and the narrow cell walls allow exchange of material between the contents of the capillary and the surrounding tissue. The networks are the site of gas, nutrient and waste exchange between the blood and the respiring tissues.

• Cardiac Cycle

The cardiac cycle is defined as the sequence of pressure and volume changes that take place during cardiac activity. The time of a cycle in a healthy adult is approximately 0.9 seconds, although it varies considerably, giving an average pulse rate of around 70 beats per minute (bpm). There are two elements of the cardiac cycle:

• Systole: rapid contraction of heart, 0.3 sec
• Diastole: resting phase, 0.5 sec.

• Heart Rate (HR)

The number of ventricular contractions occurring in one minute.

The heart rate will vary depending on age, anxiety and the presence of systemic pathology. Average heart rates are illustrated below.

Table- Average heart rates.

• Tachycardia

Tachycardia refers to a rapid heart rate (>100 bpm in adults). Tachycardia may be a perfectly normal physiological response to stress or exercise. However, depending on the mechanism of the tachycardia and the health status of the patient, tachycardia may be harmful and require medical treatment.

Tachycardia can be harmful in two ways. First, when the heart beats too rapidly, it may pump blood less efficiently. Second, the faster the heart beats, the more oxygen and nutrients it requires. As a result, the patient may feel out of breath or, in severe cases, suffer chest pain. This can be especially problematic for patients with ischaemic heart disease.

• Bradycardia

Bradycardia is defined as a resting heart rate <60 bpm in adults. It is rarely symptomatic until the rate drops below 50 bpm. It is quite common for trained athletes to have slow resting heart rates, and this should not be considered abnormal if the individual has no associated symptoms.

Bradycardia can result from a number of causes which can be classified as cardiac or non‐cardiac. Non‐cardiac causes are usually secondary, and can involve drug use or misuse; metabolic or endocrine issues (especially related to the thyroid), neurologic factors, and situational factors such as prolonged bed rest. Cardiac causes include acute or chronic ischaemic heart disease, vascular heart disease or valvular heart disease.

The blood is driven through the vascular system by the pressure produced on ejection of the blood from the ventricles followed by the elastic response of the major arteries .

• Mitral valve regurgitation

A backflow of blood caused by failure of the heart’s mitral valve to close tightly.

Mitral valve regurgitation is a condition in which the heart’s mitral valve doesn’t close tightly, which allows blood to flow backward in the heart.

Symptoms include shortness of breath, fatigue, lightheadedness and a rapid, fluttering heartbeat.

• Mitral stenosis 

It is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heartMitral stenosis is a valvular heart disease characterized by the narrowing of the orifice of the mitral valve of the heart.

• Aortic stenosis

Narrowing of the valve in the large blood vessel branching off the heart (aorta).

This narrowing keeps the valve from opening fully, reducing blood flow to the body and making the heart work harder.

The heart may weaken, causing chest pain, fatigue and shortness of breath.

• Aortic regurgitation (AR)

It is also known as aortic insufficiency (AI), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. As a consequence, the cardiac muscle is forced to work harder than normal.

• Endocarditis

An infection of the heart’s inner lining, usually involving the heart valves.

Endocarditis usually occurs when germs from elsewhere in the body travel through the blood and attach to damaged areas of the heart. People with damaged or artificial heart valves or other heart conditions are most at risk.

Symptoms vary based on the severity of the infection, but may include fevers, chills and fatigue.

• Left-sided heart failure

It is a heart condition where the muscle on the left side of the heart is diminished and the pump doesn’t work to the body. Left-sided heart failure is defined not as a disease, but a process. Left-sided heart failure occurs when the left ventricle, the heart’s main pumping power source, is gradually weakened. When this occurs, the heart is unable to pump oxygen-rich blood from the lungs to the heart’s left atrium, into the left ventricle and on through the body and the heart has to work harder.

• Chronic heart failure

A chronic condition in which the heart doesn’t pump blood as well as it should.

Heart failure can occur if the heart cannot pump (systolic) or fill (diastolic) adequately.

Symptoms include shortness of breath, fatigue, swollen legs and rapid heartbeat.

• Acute circulatory failure

It is a clinical syndrome characterized by inadequate effective blood flow and reduced tissue perfusion with decreased delivery of oxygen to the capillaries. The reduction in oxygen delivery leads to impaired oxidative metabolism, lactic acidosis, and cell death.

• Sinus tachycardia

It is an elevated sinus rhythm characterized by an increase in the rate of electrical impulses arising from the sinoatrial node. In adults, sinus tachycardia is defined as a heart rate greater than 100 beats/min (bpm).

• Sinus bradycardia

It is a type of slow heartbeat. A special group of cells begin the signal to start your heartbeat. These cells are in the sinoatrial (SA) node. Normally, the SA node fires the signal at about 60 to 100 times per minute at rest. In sinus bradycardia, the node fires less than 60 times per minute.

• Acute Massive pulmonary embolism

Massive pulmonary embolism is defined as obstruction of the pulmonary arterial tree that exceeds 50% of the cross-sectional area, causing acute and severe cardiopulmonary failure from right ventricular overload.

• Myocardial infraction

A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle.The most common symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck or jaw.Often it occurs in the center or left side of the chest and lasts for more than a few minutes. The discomfort may occasionally feel like heartburn. Other symptoms may include shortness of breath, nausea, feeling faint, a cold sweat or feeling tired.

• Atrial fibrillation (A-fib)

It is an irregular and often very rapid heart rhythm (arrhythmia) that can lead to blood clots in the heart. A-fib increases the risk of stroke, heart failure and other heart-related complications.

During atrial fibrillation, the heart’s upper chambers (the atria) beat chaotically and irregularly  out of sync with the lower chambers (the ventricles) of the heart. For many people, A-fib may have no symptoms. However, A-fib may cause a fast, pounding heartbeat (palpitations), shortness of breath or weakness.

APPLIED ANATOMY AND PHYSIOLOGY OF RESPIRATORY SYSTEM

Applied Anatomy

Introduction

Lungs, the complicated and delicate organs carrying out very precise bodily functions, are safely encasedinandprotectedbytheribcage.Nevertheless, theyarevulnerablewheretheyhavetocomeintocontact with the outside world. The long passage leading to it from the nostrils, the airway, is charged with some important functions which are essentially protective.

The respiratory system is made up of the organs included in the exchange of oxygen and carbon dioxide.

Respiratory tract is divided into two parts:

1. Upper respiratory tract
2. Lower respiratory tract

The upper respiratory tract is made up of the:

• Nose
• Nasal cavity
• Sinuses
• Larynx
• Trachea

The lower respiratory tract is made up of the:

• Lungs
• Bronchi and bronchioles
• Air sacs (alveoli)

The nose

• Thenasalcavityisdividedintotwohalvesbythe nasal septum.
• The entrance of each nostril is coveredby skin with hair and is called the
• Nasal valvesare the narrowest portion of the nostril and demarcate the vestibulefromthenasalcavityproper.
• The lateral wall of the nose has three projecting shelves of bone known as turbinatesor Theseservetoincreasethesurfaceareaofthenasalcavity. Theturbinatesarelabeledsuperior,middle,inferiorand thespaceundereachiscalledasthemeatus.
• Therearetwotypesofepitheliumwithinthenose: olfactoryandrespiratory.
• Traumatothecribriformplate may shear the olfactory neurons resulting in loss of

BLOOD SUPPLY

Blood supply to the nose is by both internal and externalcarotidarteries.

Little’s area (Kiesselbach’s plexus) isanareawhereseveralvesselsanastomoseontheanterior septum. It is a frequent site ofepistaxis..

VENOUS DRAINAGE

Venousdrainageofthenoseistotheophthalmicand facialveinsandthepterygoidandpharyngealplexuses.

Venous drainage is, therefore, both intracranial and extracranial.

NEVOUS SUPPLY

• The nose receives sensory, special sensoryand autonomic nerve
• Sensory nerve supply is by the first and the second branches of the trigeminal nerves.
• Special sensory supply is by the olfactory nerves.
• The autonomic nerve supply provides secretomotor and vasomotor control.
• The sympathetic fibres arise from the firstfivethoracicsegmentsofthespinalcordandsynapse inthesuperiorcervicalganglionandthepostganglionic fibres run with the blood vessels to the nose. An increase in sympathetic tone causes vasoconstriction and decreased Theparasympatheticsupplytothenoseisfrom the lacrimal nucleus with the fibres leaving the brain stem inthenervusintermedius.

FUNCTIONS OF NOSE

• Provides an airway for respiration, acts as only externally visible part of the respiratory system
• Moistening (humidifying) and warming the entering air.
• Filtering inspired air and cleaning it of foreign matter.
• Serving as a resonating chamber for speech.
• Housing the olfactory receptors.

PARANASAL SINUS

Several bones that form the walls of the nasal cavity contain air-filled spaces called the paranasal sinuses, which are named after their associated bones; maxillary, frontal, sphenoidal and ethmoidal sinuses.

The paranasal sinuses communicate with the nasal cavity via several openings, and thereby also receive the inhaled air and contribute to its humidifying and warming.

 In addition, the mucous membrane and respiratory epithelium that lines both the nasal cavity and the paranasal sinuses traps any harmful particles, dust or bacteria.

PHARYNX

After passing through the nasal cavity and paranasal sinuses, the inhaled air exits through the choanae into the pharynx. The pharynx is a funnel-shaped muscular tube that contains three parts.

1. Nasopharynx
2. Oropharynx
3.  

• The nasopharynx is the first and superior most part of the pharynx, found posterior to the nasal cavity. This part of the pharynx serves only as an airway, and is thus lined with respiratory epithelium. Inferiorly, the uvula and soft palate swing upwards during swallowing to close off the nasopharynx and prevent food from entering the nasal cavity.
• The oropharynx is found posterior to the oral cavity and communicates with it through the oropharyngeal isthmus. The oropharynx is a pathway for both the air incoming from the nasopharynx and the food incoming from the oral cavity. Thus, the oropharynx is lined with the more protective non-keratinizing stratified squamous epithelium.
• The laryngopharynx (hypopharynx) is the most inferior part of the pharynx. It is the point at which the digestive and respiratory systems diverge. Anteriorly, the laryngopharynx continues into the larynx, whereas posteriorly it continues as the esophagus. 

LARYNX

Following the laryngopharynx, the next and last portion of the upper respiratory tract is the superior part of the larynx.

The larynx is a complex hollow structure found anterior to the esophagus. It is supported by a cartilaginous skeleton connected by membranes, ligaments and associated muscles.

Above the vocal cords, the larynx is lined with stratified squamous epithelium like the laryngopharynx. Below the vocal cords, this epithelium transitions into pseudostratified ciliated columnar epithelium with goblet cells (respiratory epithelium). 

Besides its main function to conduct the air, the larynx also houses the vocal cords that participate in voice production. The laryngeal inlet is closed by the epiglottis during swallowing to prevent food or liquid from entering the lower respiratory tract.

Lower respiratory tract

The lower respiratory tract refers to the parts of the respiratory system that lie below the cricoid cartilage and vocal cords, including the inferior part of the larynx, tracheobronchial tree and lungs.

TRACHEORONCHIAL TREE

The tracheobronchial tree is a portion of the respiratory tract that conducts the air from the upper airways to the lung parenchyma. It consists of the trachea and the intrapulmonary airways (bronchi and bronchioles).The trachea is located in the superior mediastinum and represents the trunk of the tracheobronchial tree. The trachea bifurcates at the level of the sternal angle (T5) into the left and right main bronchi, one for each lung.

• The left main bronchus passes inferolaterally to enter the hilum of the left lung. On its course, it passes inferior to the arch of the aorta and anterior to the esophagus and thoracic aorta.
• The right main bronchus passes inferolaterally to enter the hilum of the right lung. The right main bronchus has a more vertical course than its left counterpart and is also wider and shorter. This makes the right bronchus more susceptible to foreign body impaction.

The left main bronchus divides into two secondary lobar bronchi, while the right main bronchus divides into three secondary lobar bronchi that supply the lobes of the left and right lung, respectively.

Each of the lobar bronchi further divides into tertiary segmental bronchi that aerate the bronchopulmonary segments. The segmental bronchi then give rise to several generations of intrasegmental (conducting) bronchioles, which end as terminal bronchioles. Each terminal bronchiole gives rise to several generations of respiratory bronchioles. Respiratory bronchioles extend into several alveolar ducts, which lead into alveolar sacs, each of which contains many grape-like out pocketings called alveoli. Since they contain alveoli, these structures mark the site where gas exchange begins to occur.

LUNGS

The lungs are a pair of spongy organs located within the thoracic cavity.

The right lung is larger than the left lung and consists of three lobes (superior, middle and inferior), which are divided by two fissures; oblique and horizontal fissure.

 The left lung has only two lobes (superior and inferior), divided by one oblique fissure. 

Each lung has three surfaces, an apex and a base. The surfaces of the lung are the costal, mediastinal and diaphragmatic surface.

FUNCTIONS

The main function of the respiratory system is pulmonary ventilation, which is the movement of air between the atmosphere and the lung by inspiration and expiration driven by the respiratory muscles. The respiratory system works as a whole to extract the oxygen from the inhaled air and eliminate the carbon dioxide from the body by exhalation. The upper respiratory mainly has an air-conducting function, while the lower respiratory tract serves both the conducting and respiratory functions. 

• Besides its main function to conduct the air to the lower respiratory tract, the upper respiratory also performs several other functions. As mentioned earlier, the nasal cavity and paranasal sinuses change the properties of the air by humidifying and warming it in orderto prepare it for the process of respiration. The air is also filtered from dust, pathogens and other particles by the nasal hair follicles and the ciliary epithelium.  
• The portion of the lower respiratory tract, starting from the respiratory bronchioles, is the place where gas exchange begins to occur.

CLINICAL ASPECTS of Respiratory system

• Upper respiratory tract infections

Upper respiratory tract infections are contagious infections that can be caused by a variety of bacteria and viruses. The most common causing agents are influenza virus (the flu), rhinoviruses and streptococcus bacteria. Depending on which part of the upper respiratory tract is affected, these infections may have different types, suchas rhinitis, sinusitis, pharyngitis, epiglottitis, laryngitis and others. 

The common cold is the most common type of upper respiratory tract infection. It is a viral infection that usually involves the nose and throat, but other parts can be affected as well. The symptoms usually include sore throat,‎ coughing, sneezing, runny nose, headache, and fever.

• Lower respiratory tract infections

Lower respiratory tract infections are infections that affect the parts of the respiratory tract below the vocal cords. These infections can affect the airways and manifest as bronchitis or bronchiolitis, or they can affect the lung alveoli and present as pneumonia. These can also occur in conjunction as bronchopneumonia. 

The most common cause of lower respiratory tract infections are bacteria, but they can also occur due to viruses, mycoplasma, rickettsiae and fungi. These agents invade the epithelial lining, causing inflammation, increased mucus secretion, and impaired mucociliary function. The inflammation and build-up of fluid in the lungs and airways may result in symptoms such as coughing, fever, sputum production, difficulty breathing or in severe cases, airway obstruction and impaired gas exchange.

PHYSIOLOGY OF RESPIRATORY SYSTEM

MECHANICS OF BREATHING

To take a breath in, the external intercostal muscles contract, moving the ribcage up and out. The diaphragm moves down at the same time, creating negative pressure within the thorax. The lungs are held to the thoracic wall by the pleural membranes, and so expand outwards as well. This creates negative pressure within the lungs, and so air rushes in through the upper and lower airways.

Expiration is mainly due to the natural elasticity of the lungs, which tend to collapse if they are not held against the thoracic wall. This is the mechanism behind lung collapse if there is air in the pleural space (pneumothorax).

PHYSIOLOGY OF GAS EXCHANGE

Each branch of the bronchial tree eventually sub-divides to form very narrow terminal bronchioles, which terminate in the alveoli. There are many millions of alveloi in each lung, and these are the areas responsible for gaseous exchange, presenting a massive surface area for exchange to occur over.

Each alveolus is very closely associated with a network of capillaries containing deoxygenated blood from the pulmonary artery. The capillary and alveolar walls are very thin, allowing rapid exchange of gases by passive diffusion along concentration gradients.
CO₂ moves into the alveolus as the concentration is much lower in the alveolus than in the blood, and O₂ moves out of the alveolus as the continuous flow of blood through the capillaries prevents saturation of the blood with O₂ and allows maximal transfer across the membrane.

Applied anatomy of stomach

              The stomach is a muscular organ located on the left side of the upper abdomen. The stomach receives food from the oesophagus. As food reaches the end of the oesophagus, it enters the stomach through a muscular valve called the lower oesophageal sphincter. The stomach secretes acid and enzymes that digest food. It acts as reservoir of food and helps in digestion of carbohydrates, proteins and fats.

Applied anatomy of stomach:

1. Gastro-oesophageal reflux: Stomach contents, including acid, can travel backward up the oesophagus. There may be no symptoms, or reflux may cause heartburn or coughing.
2. Gastro-oesophageal reflux disease (GERD): When symptoms of reflux become bothersome or occur frequently, they’re called GERD. Infrequently, GERD can cause serious problems of the oesophagus.
3. Dyspepsia: Another name for stomach upset or indigestion. Dyspepsia may be caused by almost any benign or serious condition that affects the stomach.
4. Gastric ulcer (stomach ulcer): An erosion in the lining of the stomach, often causing pain and/or bleeding. Gastric ulcers are most often caused by NSAIDs or H. pylori infection.
5. Peptic ulcer disease: Doctors consider ulcers in either the stomach or the duodenum (the first part of the small intestine) peptic ulcer disease.
6. Gastritis: Inflammation of the stomach, often causing nausea and/or pain. Gastritis can be caused by alcohol, certain medications, H. pylori infection, or other factors.
7. Stomach cancer: Gastric cancer is an uncommon form of cancer in the U.S. Adenocarcinoma and lymphoma make up most of the cases of stomach cancer.
8. Zollinger-Ellison syndrome (ZES): One or more tumors that secrete hormones that lead to increased acid production. Severe GERD and peptic ulcer disease result from this rare disorder.
9. Gastric varices: In people with severe liver disease, veins in the stomach may swell and bulge under increased pressure. Called varices, these veins are at high risk for bleeding, although less so than esophageal varices are.
10. Stomach bleeding: Gastritis, ulcers, or gastric cancers may bleed. Seeing blood or black material in vomit or stool is usually a medical emergency.
11. Gastroparesis (delayed gastric emptying): Nerve damage from diabetes or other conditions may impair the stomach’s muscle contractions. Nausea and vomiting are the usual symptoms.
12. Displacement of stomach : pancreatic and pseudocyst and abcess in omentum bursa can push the stomach anteriorly/ forward. This displacement is usually visible in lateral radiography/ CT scan.

Small intestine

              The small intestine is the longest part of the digestive system. It extends from the stomach (pylorus) to the large intestine (cecum) and consists of three parts: duodenum, jejunum and ileum. The main functions of the small intestine are to complete digestion of food and to absorb nutrients. 

It is divided into :–

1. An upper fixed part called the duodenum, which measures about 25 cm in length.
2. A lower mobile part forming a long-convoluted tube. Upper 2/5th of the mobile is known as jejunum
3. Lower 3/5th part is known as ileum

Structure of small intestine is adapted for digestion and absorption.

APPLIED ANATOMY OF SMALL INTESTINE

• Ulcer :is a defect of intestinal mucosa. Ulcers can appear in the stomach and/or duodenum, usually due to a bacterial infection of the pylorus of the stomach withhelicobacter pylori c .
• Diarrhoea is the frequent passage of unformed stool. in most cases, the diarrhoea is caused by microorganisms such as escherichia coli, salmonellaand shigella. 
• Obstructive disorders: including paralytic ileus, a hernia or volvulus are common but can become complicated.
• Infectious diseases:such as tapeworm, tropical sprue or giardiasis are rare but severe when left untreated. More common infections such as the adenovirus or salmonella are seen in the west.
• Neoplastic growths:may include gastrointestinal stromal tumors (GIST), lymphomas and sarcomas.
• Developmental, congenital or genetic conditionsinclude pyloric stenosis, duodenal atresia and gastroschisis. (Gastroschisis is a birth defect of the abdominal (belly) wall. The baby’s intestines are found outside of the baby’s body, exiting through a hole beside the belly button).
• Mal absorption – it is a failure of normal absorption of nutrients.

1. Generalized mal absorption- affect all classes of nutrients, usually result from small intestine disease, fat absorption is most affected.
2. Specific mal absorption- absorption of one type of nutrient is effected, eg. Lactose, vitamin b12

Causes:-

• Lack of solubilizing bile salts
• Deficiency of certain factors received from liver
• Gut mucosa- celiac disease

Symptoms :-

• Diarrhoea and weight loss
• Family history celiac disease, crohn ’s disease
• Abdominal pain

• Abdominal tuberculosis:It can effect the GI tract, peritoneum, lymph nodes of the small bowel mesentery or solid viscera (liver, spleen, pancreas).Site- terminal ileum, ileo ceacal region are the most common site.
• Other conditions or a miscellaneous mixture of diseases that can affect the small intestine include Crohn’s disease, coeliac disease, gastric dumping syndrome and irritable bowel syndrome .

large intestine

            The large intestine is a 1-to-1.5-meter continuation of the ileum, extending from the ileocecal junction to the anus. Most of the large intestine is located inside the abdominal cavity, with the last portion residing within the pelvic cavity. Some parts of it are intraperitoneal while others are retroperitoneal. 

The large intestine has several distinct anatomical characteristics; the omental appendices, teniae coli and haustra. Omental or epiploic appendages are fat filled pouches of peritoneum that are attached externally to the walls of the large intestine. Teniae coli are three longitudinal bands of smooth muscle located underneath the peritoneum that extend along certain sections of the large intestine. Their contractions facilitate the peristaltic action of the large intestine, propelling the fecal matter and forming the haustra. Haustra are sacculations that occur along the large intestine, providing it with its characteristic ‘baggy’ aspect. They are created by semilunar folds on the internal surface of the large intestine.

The structure of large intestine is very similar to that of small intestine except that its mucosa is completely devoid of villi.

Applied anatomy of large intestine

1. Diverticulosis :is a medical condition in which multiple sac-like protrusions called diverticula develop along the colon. Their highest frequency is within the sigmoid part. Diverticulosis has numerous risk factors, such as low fiber diet, physical inactivity, obesity and constipation. Diverticulosis is generally asymptomatic until the diverticula become inflamed (diverticulitis). This condition manifests with abdominal pain in the left iliac fossa, nausea, vomiting and low-grade fever. Uncomplicated diverticulitis is usually treated with oral antibiotics.
2. Diverticulitis :Pea-size pouches called diverticula sometimes form on weakened spots of the intestinal walls as a result of increased pressure; for example, while straining during defecation. They are most common in the sigmoid colon.People who have diverticula but mild or no symptoms are said to have the benign condition diverticulosis. Complications can occur in about 20% of people with diverticulosis, who will develop diverticulitis – an inflammation and infection of the diverticula. This tends to occur when bacteria have built up in diverticula blocked by waste.

Diverticular bleeding may occur, as well as chronic injury to the small blood vessels next to the diverticula and colonic obstruction.

1. Crohn’s diseaseis a chronic inflammatory bowel disease of unknown etiology which can affect any part of the alimentary tract, but most often the terminal ileum and colon. There are usually multiple inflammatory focuses leading to formation of multiple ulcers in the intestinal wall. The most common symptoms are fever, abdominal pain, diarrhoea, and weight loss. Crohn’s disease is diagnosed by endoscopic and radiographic examination of the abdomen and is usually treated with immunosuppressants
2. Lactose intolerance: People with lactose intolerance cannot digest dietary lactose. The undigested lactose ferments in the large intestine, producing gas, abdominal cramps, bloating and diarrhoea. Symptoms range from mild discomfort to severe pain. One of the gases produced by the bacterial fermentation of lactose in the colon is hydrogen, so people who have lactose intolerance exhale hydrogen. The hydrogen breath test can be used to help diagnose the condition (Argnani et al, 2008).
3. Coeliac disease:Coeliac disease is an intolerance to gluten, a protein found in wheat, barley and rye. If people with coeliac disease eat gluten, intestinal immune cells (T cells) release inflammatory mediators that cause a flattening of the intestinal mucosal lining, impairing the ability to digest and absorb foods. Symptoms range from mild to severe and include diarrhoea, abdominal pain, bloating and flatulence, indigestion and constipation; in severe cases the condition can lead to malnutrition.
4. Diarrhoea:is most commonly caused by gastroenteritis, norovirus or food poisoning but can also be due to food intolerances or allergies, irritable bowel syndrome, inflammatory bowel disease, coeliac disease and diverticular disease.

If the intestines do not absorb fluids, the body can lose several litres of fluid per day, with consequences such as dehydration, loss of electrolytes (potassium and sodium ions) and increased risk of blood clotting. Large losses of potassium ions, for example, can cause cardiac arrest. The only absorption mechanism that is not disturbed by diarrhoea is glucose/sodium co-transport, which means people with diarrhoea can increase absorption of essential sodium and water in the presence of glucose.

If a person has diarrhoea, it is essential to quickly replenish fluids and electrolytes by administrating a solution containing the correct balance of glucose and electrolytes (for example, Dioralyte). Drinks such as lemonade or squash may not contain the correct balance.

If diarrhoea leads to acute hyponatraemia (serum sodium concentration <135mmol/L), this must be corrected promptly. Treatment may include the administration of hypertonic saline, but care must be taken to ensure that blood sodium levels are not allowed to increase too quickly, as this can cause a sudden shift of water in brain cells that may lead to the fatal complication central pontine myelinolysis (Rusoke-Dierich, 2018).

1. Constipation:Constipation is the infrequent and difficult or painful evacuation of faeces due to slow movement of hard, dry faeces. It may lead to abdominal distension and pain and, if left untreated, faecal impaction and GI obstruction. The condition can be due to irregular bowel habits, a diet low in fibre, and immobility. Certain medications, eating disorders and the overuse of laxatives may also cause – or compound – constipation. Including 20-60g of fibre/day in the diet and drinking one or two glasses of fluid with each meal may help to prevent constipation. Nurses need to bear in mind that constipation can indicate serious physiological disturbance or disease such as diverticulitis, obstruction due a tumour or paralytic ileus.
2. Bowel obstruction:A tumour, adhesions in the intestinal walls, foreign bodies or impacted faeces may cause the intestines to become partially or completely blocked and intestinal contents to back up. This may result in abdominal swelling, pain, cramps, vomiting and severe constipation or diarrhoea. Another cause of bowel obstruction is paralytic ileus, a dramatic slowing of the normal peristaltic movement of the intestines. Paralytic ileus can be caused by bacterial or fungal infections, mesenteric ischaemia, appendicitis, abdominal surgery and certain medications.
3. Inflammatory bowel disease: Inflammatory bowel disease (IBD) is uncontrolled inflammation and bowel injury in the large intestine resulting in severe discomfort, with symptoms such as abdominal cramps, bloating, gas, liquid motions and diarrhoea. Often there is a severe urgency to defecate and there may be anal/rectal discharge or bleeding. Severe IBD may result in loss of appetite, loss of weight and iron deficiency anaemia.

The two main types of IBD are Crohn’s disease and ulcerative colitis. While ulcerative colitis often manifests as continuous areas of inflammation and can usually be cured by removing the affected areas, Crohn’s disease tends to cause a patchy distribution of inflamed ulceration that can affect any part of the GI tract, but most commonly the terminal ileum, or the colon, making treatment and surgery more difficult.

1. Ulcerative colitis: is characterized by inflammation and ulceration in the lining of colon and rectum, and rectal urgency that can result in painful, bloody diarrhoea up to 20 times a day. Symptoms may come and go but 5-10% patients have constant symptoms. Perforation is a potential complication, since chronic inflammation and ulceration may weaken the intestine wall to such an extent that a hole may form. This is generally linked with toxic megacolon, an emergency condition where the colon loses all contractile function and gas builds up. Perforation can result in life-threatening peritonitis.

1. Malabsorption syndrome:covers a number of disorders in which the small intestine is unable to absorb enough of certain nutrients (proteins, fats, minerals, vitamins and/or carbohydrates) and fluids, resulting in deficiencies, malnutrition and wasting. In patients who have had more than 50% of the small intestine removed, nutrient absorption will be severely compromised.

1. Appendicitis: If the appendix becomes blocked it becomes inflamed, causing appendicitis. Obstruction causes a pressure build-up, which may compress the blood supply to the gut wall, resulting in ischaemic injury and bacterial infection. The classical symptom is acute pain beginning at the umbilicus and spreading to the right iliac fossa. Nausea, vomiting and possibly fever may ensue. If this is not treated, the appendix may rupture, causing dangerous peritonitis and allowing bacterial infection to rapidly spread through the peritoneal cavity, potentially leading to death within hours. Appendicitis is one of the commonest causes of acute abdominal pain.

1. Colorectal cancer :is the second most common cause of cancerdeath in the UK and may be signaled by constipation or diarrhea, cramping, abdominal pain and rectal bleeding – which may be either visible or hidden in the faeces (occult). Smoking, excessive alcohol consumption and a diet high in animal fat and proteins have been linked to an increased risk of colorectal cancer.
2. Salmonellosis: Salmonella bacteria can contaminate food and infect the intestine. Salmonella causes diarrhoea and stomach cramps, which usually resolve without treatment.Shigellosis: Shigella bacteria can contaminate food and infect the intestine. Symptoms include :

– Fever.

-Stomach cramps

-Diarrhoea, which may be bloody.

1. Traveler’s diarrhoea: Many different bacteria commonly contaminate water or food in developing countries.

1. Colon polyps: Polyps are growths inside the colon. Colon can often develop in after many years.

1. Colon cancer: Cancer of the colon affects more than 100,000 Americans each year. Most colon cancer is preventable through regular screening.

1. Rectal cancer: Colon and rectal cancer are similar in prognosis and treatment. Doctors often consider them together as colorectal cancer.

1. Constipation: Constipation is a condition in which patient may have fewer than three bowel movements a week; stools that are hard, dry, or lumpy; stools that are difficult or painful to pass; or a feeling that not all stool has passed.

1. Rectal prolapse: Part or all of the wall of the rectum can move out of position, sometimes coming out of the anus, when straining during a bowel movement.

1. Intussusception: Occurring mostly in children, the small intestine can collapse into itself like a telescope. It can become life-threatening if not treated.

MUSCLES OF UPPER LIMB are divided into

1.Muscles of pectoral region

2.Muscles of shoulder

2.1 Extrinsic muscles of the shoulder

2.2 Intrinsic muscles of the shoulder

3.Muscles of upper arm

4.Muscles of anterior compartment of forearm

5.Muscles of posterior compartment of forearm

6.Muscles of hand

1.MUSCLES OF PECTORAL REGION

The pectoral region is located on the anterior chest wall. It contains four muscles that exert a force on the upper limb:

1. Pectoralis major
2. Pectoralis minor
3. Serratus anterior
4. Subclavius
5. Pectoralis Major

• most superficial muscle in the pectoral region.
• It is large and fan shaped
• composed of a sternal head and a clavicular head:

Attachments: The distal attachment of both heads is into the intertubercular sulcus of the humerus

Origin:

• Clavicular head – originates from the anterior surface of the medial clavicle.
• Sternocostal head – originates from the anterior surface of the sternum, the superior six costal cartilages and the aponeurosis of the external oblique muscle.

Function: Adducts and medially rotates the upper limb and draws the scapula Antero inferiorly. The clavicular head also acts individually to flex the upper limb.

Innervation: Lateral and medial pectoral nerves.

2. Pectoralis Minor

The pectoralis minor lies underneath its larger counterpart muscle, pectoralis major. Both muscles form part of the anterior wall of the axilla region.

Attachments: 

• Originates from the 3rd-5th ribs
• inserts into the coracoid process of the scapula.

Function: Stabilises the scapula by drawing it Antero inferiorly against the thoracic wall.

Innervation: Medial pectoral nerve.

3. Serratus Anterior

• located more laterally in the chest wall and forms the medial border of the axilla region.

Attachments: 

• The muscle consists of several strips, which originate from the lateral aspects of ribs 1-8.
• They attach to the costal surface (rib facing) of the medial border of the scapula.

Function: Rotates the scapula, allowing the arm to be raised over 90 degrees. It also holds the scapula against the ribcage.

Innervation: Long thoracic nerve.

5. Subclavius

The subclavius is small muscle, which is located directly underneath the clavicle, running horizontally. It affords some minor protection to the underlying neurovascular structures (e.g., in cases of clavicular fracture or other trauma).

Attachments: Originates from the junction of the 1st rib and its costal cartilage, inserting into the inferior surface of the middle third of the clavicle.

Function: Anchors and depresses the clavicle.

Innervation: Nerve to subclavius.

2. MUSCLES OF SHOULDER

The muscles of the shoulder are associated with movements of the upper limb. They produce the characteristic shape of the shoulder, and can be divided into two groups:

Extrinsic – originate from the torso, and attach to the bones of the shoulder (clavicle, scapula or humerus).

Intrinsic – originate from the scapula and/or clavicle, and attach to the humerus.

EXTRINSIC MUSCLES

The extrinsic muscles of the shoulder originate from the trunk, and attach to the bones of the shoulder – the clavicle, scapula, or humerus. They are located in the back, and are also known as the superficial back muscles.

The muscles are organised into two layers – a superficial layer and a deep layer.

• Superficial

There are two superficial extrinsic muscles – the trapezius and latissimus dorsi.

1. Trapezius

• broad, flat, and triangular muscle.
• The muscles on each side form a trapezoid shape.
• most superficial of all the back muscles.

Attachments: Originates from the skull, nuchal ligament and the spinous processes of C7-T12. The fibres attach to the clavicle, acromion, and the scapula spine.

Innervation: Motor innervation is from the accessory nerve. It also receives proprioceptor fibres from C3 and C4 spinal nerves.

Actions: The upper fibres of the trapezius elevate the scapula and rotates it during abduction of the arm. The middle fibres retract the scapula and the lower fibres pull the scapula inferiorly.

b .Latissimus Dorsi

• originates from the lower part of the back, where it covers a wide area.

Attachments: Has a broad origin – arising from the spinous processes of T7-T12, iliac crest, thoracolumbar fascia and the inferior three ribs. The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus.

Innervation: Thoracodorsal nerve.

Actions: Extends, adducts, and medially rotates the upper limb.

Deep Muscles

There are three muscles in this group – the levator scapulae and the two rhomboids. They are situated in the upper back, underneath the trapezius.

1. Levator Scapula

The levator scapulae is a small strap-like muscle. It begins in the neck, and descends to attach to the scapula.

Attachments: Originates from the transverse processes of the C1-C4 vertebrae and attaches to the medial border of the scapula.

Innervation: Dorsal scapular nerve.

Actions: Elevates the scapula.

1. Rhomboids

There are two rhomboid muscles – major and minor. The rhomboid minor is situated superiorly to the major.

• Rhomboid Major
  • Attachments: Originates from the spinous processes of T2-T5 vertebrae. Attaches to the medial border of the scapula, between the scapula spine and inferior angle.
  • Innervation: Dorsal scapular nerve.
  • Actions: Retracts and rotates the scapula.

• Rhomboid Minor
  • Attachments: Originates from the spinous processes of C7-T1 vertebrae. Attaches to the medial border of the scapula, at the level of the spine of scapula.
  • Innervation: Dorsal scapular nerve.
  • Actions: Retracts and rotates the scapula.

INTRINSIC MUSCLES

• The intrinsic muscles (also known as the scapulohumeral group) originate from the scapula and/or clavicle, and attach to the humerus
• There are six muscles in this group – the deltoid, teres major, and the four rotator cuff muscles (supraspinatus, infraspinatus, subscapularis and teres minor).

1. Deltoid

The deltoid muscle is shaped like an inverted triangle. It can be divided into an anterior, middle and posterior part.

Attachments: Originate from the lateral third of the clavicle, the acromion and the spine of the scapula. It attaches to the deltoid tuberosity on the lateral aspect of the humerus.

Innervation: Axillary nerve.

Actions:

• • Anterior fibres – flexion and medial rotation.
  • Posterior fibres – extension and lateral rotation.
  • Middle fibres – the major abductor of the arm (takes over from the supraspinatus, which abducts the first 15 degrees).

1. Teres Major

The teres major forms the inferior border of the quadrangular space – the ‘gap’ that the axillary nerve and posterior circumflex humeral artery pass through to reach the posterior scapula region.

• Attachments: Originates from the posterior surface of the inferior angle of the scapula. It attaches to the medial lip of the intertubercular groove of the humerus.

• Innervation: Lower subscapular nerve.

• Actions: Adducts and extends at the shoulder, and medially rotates the arm.

 Rotator Cuff Muscles

The rotator cuff muscles are a group of four muscles that originate from the scapula and attach to the humeral head. Collectively, the resting tone of these muscles acts to ‘pull’ the humeral head into the glenoid fossa. This gives the glenohumeral joint a lot of additional stability.

In addition to their collective function, the rotator cuff muscles also have their own individual actions.

1. Supraspinatus

Attachments: Originates from the supraspinous fossa of the scapula, attaches to the greater tubercle of the humerus.

Innervation: Suprascapular nerve.

Actions: Abducts the arm 0-15^o, and assists deltoid for 15-90^o

1. Infraspinatus

Attachments: Originates from the infraspinous fossa of the scapula, attaches to the greater tubercle of the humerus.

Innervation: Suprascapular nerve.

Actions: Laterally rotates the arm.

1. Subscapularis

Attachments: Originates from the subscapular fossa, on the costal surface of the scapula. It attaches to the lesser tubercle of the humerus.

Innervation: Upper and lower subscapular nerves.

Actions: Medially rotates the arm.

1. Teres Minor

Attachments: Originates from the posterior surface of the scapula, adjacent to its lateral border. It attaches to the greater tubercle of the humerus.

Innervation: Axillary nerve.

Actions: Laterally rotates the arm.

3.MUSCLES OF UPPER ARM

The upper arm is located between the shoulder joint and elbow joint. It contains four muscles – three in the anterior compartment (biceps brachii, brachialis, coracobrachialis), and one in the posterior compartment (triceps brachii).

• Anterior Compartment

-There are three muscles located in the anterior compartment of the upper arm – biceps brachii, coracobrachialis and brachialis.

-They are all innervated by the musculocutaneous nerve. A good memory aid for this is BBC – biceps, brachialis, coracobrachialis.

Arterial supply to the anterior compartment of the upper arm is via muscular branches of the brachial artery.

1. Biceps Brachii

-The biceps brachii is a two-headed muscle. Although the majority of the muscle mass is located anteriorly to the humerus, it has no attachment to the bone itself.

As the tendon of biceps brachii enters the forearm, a connective tissue sheet is given off – the bicipital aponeurosis. This forms the roof of the cubital fossa and blends with the deep fascia of the anterior forearm.

Attachments: Long head originates from the supraglenoid tubercle of the scapula, and the short head originates from the coracoid process of the scapula. Both heads insert distally into the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis.

Function: Supination of the forearm. It also flexes the arm at the elbow and at the shoulder.

Innervation: Musculocutaneous nerve. The bicep tendon reflex tests spinal cord segment C6.

1. Coracobrachialis

-The coracobrachialis muscle lies deep to the biceps brachii in the arm.

Attachments: Originates from the coracoid process of the scapula. The muscle passes through the axilla, and attaches the medial side of the humeral shaft, at the level of the deltoid tubercle.

Function: Flexion of the arm at the shoulder, and weak adduction.

Innervation: Musculocutaneous nerve.

1. Brachialis

The brachialis muscle lies deep to the biceps brachii, and is found more distally than the other muscles of the arm. It forms the floor of the cubital fossa.

Attachments: Originates from the medial and lateral surfaces of the humeral shaft and inserts into the ulnar tuberosity, just distal to the elbow joint.

Function: Flexion at the elbow.

Innervation: Musculocutaneous nerve, with contributions from the radial nerve.

• Posterior Compartment

-The posterior compartment of the upper arm contains the triceps brachii muscle, which has three heads. The medial head lies deeper than the other two, which cover it.

Arterial supply to the posterior compartment of the upper arm is via the profunda brachii artery.

1. Triceps Brachii

Attachments: Long head – originates from the infraglenoid tubercle. Lateral head – originates from the humerus, superior to the radial groove. Medial head – originates from the humerus, inferior to the radial groove. Distally, the heads converge onto one tendon and insert into the olecranon of the ulna.

Function: Extension of the arm at the elbow.

Innervation: Radial nerve. A tap on the triceps tendon tests spinal segment C7.

Note: In some individuals, the long head of the triceps brachii is innervated by the axillary nerve.

• THE MUSCLES IN THE ANTERIOR COMPARTMENT OF THE FOREARM

The muscles in the anterior compartment of the forearm are organized into three layers:

Superficial: flexor carpi ulnaris, palmaris longus, flexor carpi radialis, pronator teres.

Intermediate: flexor digitorum superficialis.

Deep: flexor pollicis longus, flexor digitorum profundus and pronator quadratus.

This muscle group is associated with pronation of the forearm, flexion of the wrist and flexion of the fingers.

They are mostly innervated by the median nerve (except for the flexor carpi ulnaris and medial half of flexor digitorum profundus, which are innervated by the ulnar nerve), and they recieve arterial supply from the ulnar artery and radial artery.

1. Superficial Compartment

The superficial muscles in the anterior compartment are the flexor carpi ulnaris, palmaris longus, flexor carpi radialis and pronator teres.

They all originate from a common tendon, which arises from the medial epicondyle of the humerus.

1. Flexor Carpi Ulnaris

Attachments: 

The flexor carpi ulnaris has two origins. The humeral head originates from the medial epicondyle of the humerus with the other superficial flexors, whilst the ulnar head originates from the olecranon of the ulnar.

The muscle tendon passes into the wrist and attaches to the pisiform bone, hook of hamate, and base of the 5th metacarpal

Actions: Flexion and adduction at the wrist.

Innervation: Ulnar nerve.

1. Palmaris Longus

This muscle is absent in about 15% of the population.

Attachments: Originates from the medial epicondyle, attaches to the flexor retinaculum of the wrist.

Actions: Flexion at the wrist.

Innervation: Median nerve.

1. Flexor Carpi Radialis

Attachments: Originates from the medial epicondyle, attaches to the base of metacarpals II and III.

Actions: Flexion and abduction at the wrist.

Innervation: Median nerve.

1. Pronator Teres

The lateral border of the pronator teres forms the medial border of the cubital fossa, an anatomical triangle located over the elbow.

Attachments: It has two origins, one from the medial epicondyle, and the other from the coronoid process of the ulna. It attaches laterally to the mid-shaft of the radius.

Actions: Pronation of the forearm.

Innervation: Median nerve.

Intermediate Compartment

1. Flexor digitorum superficialis

• only muscle of the intermediate compartment. It can sometimes be classed as a superficial muscle, but in most individuals, it lies between the deep and superficial muscle layers.
• The muscle is a good anatomical landmark in the forearm – the median nerveand ulnar artery pass between its two heads, and then travel posteriorly.

Attachments: It has two heads – one originates from the medial epicondyle of the humerus, the other from the radius. The muscle splits into four tendons at the wrist, which travel through the carpal tunnel, and attaches to the middle phalanges of the four fingers.

Actions: Flexes the metacarpophalangeal joints and proximal interphalangeal joints at the 4 fingers, and flexes at the wrist.

Innervation: Median nerve.

Deep Compartment

There are three muscles in the deep anterior forearm:

-Flexor digitorum profundus

-Flexor pollicis longus,

– Pronator quadratus.

1. Flexor Digitorum Profundus

Attachments: Originates from the ulna and associated interosseous membrane. At the wrist, it splits into four tendons, that pass through the carpal tunnel and attach to the distal phalanges of the four fingers.

Actions: It is the only muscle that can flex the distal interphalangeal joints of the fingers. It also flexes at metacarpophalangeal joints and at the wrist.

Innervation: The medial half (acts on the little and ring fingers) is innervated by the ulnar nerve. The lateral half (acts on the middle and index fingers) is innervated by the anterior interosseous branch of the median nerve.

1. Flexor Pollicis Longus

This muscle lies laterally to the FDP.

Attachments: Originates from the anterior surface of the radius and surrounding interosseous membrane. Attaches to the base of the distal phalanx of the thumb.

Actions:  Flexes the interphalangeal joint and metacarpophalangeal joint of the thumb.

Innervation: Median nerve (anterior interosseous branch).

1. Pronator Quadratus

A square shaped muscle found deep to the tendons of the FDP and FPL.

Attachments: Originates from the anterior surface of the ulna and attaches to the anterior surface of the radius.

Actions: Pronates the forearm.

Innervation: Median nerve (anterior interosseous branch).

6. MUSCLES IN THE POSTERIOR COMPARTMENT OF THE FOREARM

The muscles in the posterior compartment of the forearm are commonly known as the extensor muscles. The general function of these muscles is to produce extension at the wrist and fingers. They are all innervated by the radial nerve.

Anatomically, the muscles in this compartment can be divided into two layers; deep and superficial. These two layers are separated by a layer of fascia.

Superficial Muscles

The superficial layer of the posterior forearm contains seven muscles. Four of these muscles – extensor carpi radialis brevis, extensor digitorum, extensor carpi ulnaris and extensor digitiminimi share a common tendinous origin at the lateral epicondyle.

1. Brachioradialis

The brachioradialis is a paradoxical muscle. Its origin and innervation are characteristic of an extensor muscle, but it is actually a flexor at the elbow.

The muscle is most visible when the forearm is half pronated, and flexing at the elbow against resistance.

In the distal forearm, the radial artery and nerve are sandwiched between the brachioradialis and the deep flexor muscles.

Attachments: Originates from the proximal aspect of the lateral supracondylar ridge of humerus, and attaches to the distal end of the radius, just before the radial styloid process.

Actions: Flexes at the elbow.

Innervation: Radial nerve

1. Extensor Carpi Radialis Longus and Brevis

The extensor carpi radialis muscles are situated on the lateral aspect of the posterior forearm. Due to their position, they are able to produce abduction as well as extension at the wrist.

Attachments: The ECRL originates from the supracondylar ridge, while the ECRB originates from the lateral epicondyle. Their tendons attach to metacarpal bones II and III.

Actions: Extends and abducts the wrist.

Innervation: Radial nerve.

1. Extensor Digitorum Communis

The extensor digitorum is the main extensor of the fingers. To test the function of the muscle, the forearm is pronated, and the fingers extended against resistance.

Attachments: Originates from the lateral epicondyle. The tendon continues into in the distal part of the forearm, where it splits into four, and inserts into the extensor hood of each finger.

Actions: Extends medial four fingers at the MCP and IP joints.

Innervation: Radial nerve (deep branch).

1. Extensor DigitiMinimi

The extensor digitiminimi is thought to originate from the extensor digitorum muscle. In some people, these two muscles are fused together. Anatomically, the extensor digitiminimi lies medially to the extensor digitorum.

Attachments: Originates from the lateral epicondyle of the humerus. It attaches, with the extensor digitorum tendon, into the extensor hood of the little finger.

Actions: Extends the little finger, and contributes to extension at the wrist.

Innervation: Radial nerve (deep branch).

1. Extensor Carpi Ulnaris

The extensor carpi ulnaris is located on the medial aspect of the posterior forearm. Due to its position, it is able to produce adduction as well as extension at the wrist.

Attachments: Originates from the lateral epicondyle of the humerus, and attaches to the base of metacarpal V.

Actions: Extension and adduction of wrist.

Innervation: Radial nerve (deep branch).

1. Anconeus

The anconeus is situated medially and superiorly in the extensor compartment of the forearm. It is blended with the fibres of the triceps brachii, and the two muscles can be indistinguishable.

Attachments: Originates from the lateral epicondyle, and attaches to the posterior and lateral part of the olecranon.

Actions: Extends and stablises the elbow joint. Abducts the ulna during pronation of the forearm.

Innervation: Radial nerve.

Deep Muscles

There are five muscles in the deep compartment of the posterior forearm – the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis.

With the exception of the supinator, these muscles act on the thumb and the index finger.

1. Supinator

The supinator lies in the floor of the cubital fossa. It has two heads, which the deep branch of the radial nerve passes between.

Attachments: It has two heads of origin. One originates from the lateral epicondyle of the humerus, the other from the posterior surface of the ulna. They insert together into the posterior surface of the radius.

Actions: Supinates the forearm.

Innervation: Radial nerve (deep branch).

1. Abductor Pollicis Longus

The abductor pollicis longus is situated immediately distal to the supinator muscle. In the hand, its tendon contributes to the lateral border of the anatomical snuffbox.

Attachments: Originates from the interosseous membrane and the adjacent posterior surfaces of the radius and ulna. It attaches to the lateral side of the base of metacarpal I.

Actions: Abducts the thumb.

Innervation: Radial nerve (posterior interosseous branch).

1. Extensor Pollicis Brevis

The extensor pollicis brevis can be found medially and deep to the abductor pollicis longus. In the hand, its tendon contributes to the lateral border of the anatomical snuffbox.

Attachments: Originates from the posterior surface of the radius and interosseous membrane. It attaches to the base of the proximal phalanx of the thumb.

Actions: Extends at the metacarpophalangeal and carpometacarpal joints of the thumb.

Innervation: Radial nerve (posterior interosseous branch).

1. Extensor Pollicis Longus

The extensor pollicis longus muscle has a larger muscle belly than the EPB. Its tendon travels medially to the dorsal tubercle at the wrist, using the tubercle as a ‘pulley’ to increase the force exerted.

The tendon of the extensor pollicis longus forms the medial border of the anatomical snuffbox in the hand.

Attachments: Originates from the posterior surface of the ulna and interosseous membrane. It attaches to the distal phalanx of the thumb.

Actions: Extends all joints of the thumb: carpometacarpal, metacarpophalangeal and interphalangeal.

Innervation: Radial nerve (posterior interosseous branch).

1. Extensor Indicis Proprius

This muscle allows the index finger to be independent of the other fingers during extension.

Attachments: Originates from the posterior surface of the ulna and interosseous membrane, distal to the extensor pollicis longus. Attaches to the extensor hood of the index finger.

Actions: Extends the index finger.

Innervation: Radial nerve (posterior interosseous branch).

7. MUSCLES OF THE HAND

Muscles acting on the hand can be divided into two groups: extrinsic and intrinsic muscles.

The extrinsic muscles are located in the anterior and posterior compartments of the forearm. They control crude movements and produce a forceful grip.

The intrinsic muscles of the hand are located within the hand itself. They are responsible for the fine motor functions of the hand.

INTRINSIC MUSCLES OF HAND

These include the adductor pollicis, palmaris brevis, interossei, lumbricals, thenar and hypothenar muscles.

Thenar Muscles

The thenar muscles are three short muscles located at the base of the thumb. The muscle bellies produce a bulge, known as the thenar eminence. They are responsible for the fine movements of the thumb.

The median nerve innervates all the thenar muscles

.

1. Opponens Pollicis

The opponens pollicis is the largest of the thenar muscles, and lies underneath the other two.

Attachments: Originates from the tubercle of the trapezium, and the associated flexor retinaculum. It inserts into the lateral margin of the metacarpal of the thumb (i.e. the first metacarpal).

Actions: Opposes the thumb, by medially rotating and flexing the metacarpal on the trapezium.

Innervation: Median nerve.

1. Abductor Pollicis Brevis

This muscle is found anteriorly to the opponens pollicis and proximal to the flexor pollicis brevis.

Attachments: Originates from the tubercles of the scaphoid and trapezium, and from the associated flexor retinaculum. Attaches to lateral side of proximal phalanx of the thumb.

Actions: Abducts the thumb.

Innervation: Median nerve.

1. Flexor Pollicis Brevis

The most distal of the thenar muscles.

Attachments: Originates from the tubercle of the trapezium and from the associated flexor retinaculum. Attaches to the base of the proximal phalanx of the thumb.

Actions: Flexes the metacarpophalangeal (MCP) joint of the thumb.

Innervation: Median nerve. The deep head is innervated by the deep branch of the ulnar nerve.

Hypothenar Muscles

The hypothenar muscles produce the hypothenar eminence – a muscular protrusion on the medial side of the palm, at the base of the little finger. These muscles are similar to the thenar muscles in both name and organisation.

The ulnar nerve innervates the muscles of the hypothenar eminence.

1. OpponensDigitiMinimi

The opponens digit minimi lies deep to the other hypothenar muscles.

Attachments: Originates from the hook of hamate and associated flexor retinaculum, inserts into the medial margin of metacarpal V.

Actions: It rotates the metacarpal of the little finger towards the palm, producing opposition.

Innervation: Ulnar nerve.

1. Abductor DigitiMinimi

The most superficial of the hypothenar muscles.

Attachments: Originates from the pisiform and the tendon of the flexor carpi ulnaris. It attaches to the base of the proximal phalanx of the little finger.

Actions: Abducts the little finger.

Innervation: Ulnar nerve.

1. Flexor DigitiMinimi Brevis

This muscle lies laterally to the abductor digitiminimi.

Attachments: Originates from the hook of hamate and adjacent flexor retinaculum, and inserts into the base of the proximal phalanx of the little finger.

Actions: Flexes the MCP joint of the little finger.

Innervation: Ulnar nerve.

Muscles of the Lower Limb

1. Fascia lata

2.Muscles of gluteal region

3.Muscles of the thigh

3.1 Anterior compartment of thigh

3.2 Muscles medial compartment of thigh

3.3 Muscles in the posterior compartment of thigh

4.Muscles of leg

4.1 muscles in the anterior compartment of leg

4.2 muscles in the lateral compartment of leg

4.3muscles in the posterior compartment of leg

5.muscles of foot

1.THE FASCIA LATA

Fascia is a sheet or band of fibrous tissue lying deep to the skin. It lines, invests, and separates structures within the body. There are three main types of fascia:

• Superficial fascia – blends with the reticular layer beneath the dermis.
• Deep fascia – envelopes muscles, bones, and neurovascular structures.
• Visceral fascia – provides membranous investments that suspend organs within their cavities.

Anatomical Structure 

The fascia lata is a deep fascial investment of the musculature of the thigh, and is analogous to a strong, extensible, and elasticated stocking. It begins proximally around the iliac crest and inguinal ligament and ends distal to the bony prominences of the tibia.

An ovoid hiatus known as the saphenous opening is present in the fascia lata just inferior to the inguinal ligament. The opening serves as an entry point for efferent lymphatic vessels and the great saphenous vein, draining into superficial inguinal lymph nodes and the femoral vein respectively.

• Anatomical Relations

1. Iliotibial Tract (ITT)

The iliotibial tract (sometimes known as the iliotibial band or IT band) is a longitudinal thickening of the fascia lata, which is strengthened superoposteriorly by fibres from the gluteus maximus.

It is located laterally in the thigh, extending from the iliac tubercle to the lateral tibial condyle. The ITT has three main functions:

Movement – acts as an extensor, abductor and lateral rotator of the hip, with an additional role in providing lateral stabilisation to the knee joint.

Muscular sheath – forms a sheath around the tensor fascia lata muscle.

1. Tensor Fascia Lata (TFL)

The tensor fascia lata is a gluteal muscle that acts as a flexor, abductor, and internal rotator of the hip. Its name, however, is derived from its additional role in tensing the fascia lata. It is innervated by the superior gluteal nerve, like gluteus medius and minimus, but is located more anterolaterally than the other gluteal muscles.

The muscle originates from the iliac crest and descends inferiorly to the superolateral thigh. At the junction of the middle and upper thirds of the thigh, it inserts into the anterior aspect of the iliotibial tract. When stimulated, the tensor fasciae lata tautens the iliotibial band and braces the knee, especially when the opposite foot is lifted.

The property of TFL tightening the fascia lata is analogous to hoisting an elastic stocking up the thigh. When the fascia lata is pulled taut, it forces muscles in the anterior and posterior compartments closer to towards the femur. Contraction within each compartment centralises muscle weight and limits outward expansion, which in turn reduces the overall force required for movement at the hip joint.

Attachments

-Proximal

The fascia lata arises from multiple superior attachments around the pelvis and hip region:

Posterior – sacrum and coccyx.

Lateral – iliac crest.

Anterior – inguinal ligament, superior pubic rami.

Medial – inferior ischiopubic rami, ischial tuberosity, sacrotuberous ligament.

The fascia lata is also continuous with other regions of deep and superficial fascia at its superior aspect. The deep iliac fascia descends from the thoracic region at the diaphragm, covers the entire iliacus and psoas regions, and blends with the fascia lata superiorly.

The deep layer of the superficial fascia of the abdominal wall (Scarpa’s fascia) blends with the fascia lata just below the inguinal ligament.

Lateral

The lateral thickening of fascia lata forms the iliotibial tract and receives tendon insertions superiorly from gluteus maximus and tensor fascia lata. The widened band of fibres descends the lateral thigh and attaches to the lateral tibial condyle on the anterolateral (Gerdy) tubercle.

Inferior

The fascia lata ends at the knee joint where it then becomes the deep fascia of the leg (the crural fascia). Attachments are made at bony prominences around the knee including the femoral and tibial condyles, patella, head of fibula and the tibial tuberosity.

Central

The deep aspect of fascia lata produces three intermuscular septa which attach centrally to the femur. The lateral septum joins to the lateral lip of the linea aspera and the medial and anterior septa attach to the medial lip. These attachments then continue along the whole length of the femur to include the supracondylar lines.

2. Muscles of the Gluteal Region

The gluteal region is an anatomical area located posteriorly to the pelvic girdle, at the proximal end of the femur. The muscles in this region move the lower limb at the hip joint.

The muscles of the gluteal region can be broadly divided into two groups:

Superficial abductors and extenders – group of large muscles that abduct and extend the femur. Includes the gluteus maximus, gluteus medius, gluteus minimus and tensor fascia lata.

-Deep lateral rotators – group of smaller muscles that mainly act to laterally rotate the femur. Includes the quadratus femoris, piriformis, gemellus superior, gemellus inferior and obturator internus.

The arterial supply to these muscles is mostly via the superior and inferior gluteal arteries – branches of the internal iliac artery. Venous drainage follows the arterial supply.

In this article, we shall examine the two groups of gluteal muscles – their attachments, innervations and actions. We shall also look at the clinical consequence of gluteal muscle disorders.

• The Superficial Muscles

The superficial muscles in the gluteal region consist of the three glutei and the tensor fascia lata. They mainly act to abduct and extend the lower limb at the hip joint.

1. Gluteus Maximus

The gluteus maximus is the largest of the gluteal muscles. It is also the most superficial, producing the shape of the buttocks.

Attachments: Originates from the gluteal (posterior) surface of the ilium, sacrum and coccyx. It slopes across the buttock at a 45 degree angle, then inserts into the iliotibial tract and the gluteal tuberosity of the femur.

Actions: It is the main extensor of the thigh, and assists with lateral rotation. However, it is only used when force is required, such as running or climbing.

Innervation: Inferior gluteal nerve.

1. Gluteus Medius

The gluteus medius muscle is fan-shaped and lies between to the gluteus maximus and the minimus. It is similar in shape and function to the gluteus minimus.

Attachments: Originates from the gluteal surface of the ilium and inserts into the lateral surface of the greater trochanter.

Actions: Abducts and medially rotates the lower limb. During locomotion, it secures the pelvis, preventing pelvic drop of the opposite limb. (Note: the posterior fibres of the gluteus medius are also thought to produce a small amount of lateral rotation).

Innervation: Superior gluteal nerve.

1. Gluteus Minimus

The gluteus minimus is the deepest and smallest of the superficial gluteal muscles. It is similar in shape and function to the gluteus medius.

Attachments: Originates from the ilium and converges to form a tendon, inserting to the anterior side of the greater trochanter.

Actions: Abducts and medially rotates the lower limb. During locomotion, it secures the pelvis, preventing pelvic drop of the opposite limb.

Innervation: Superior gluteal nerve.

1. Tensor Fascia Lata

Tensor fasciae lata is a small superficial muscle which lies towards the anterior edge of the iliac crest. It functions to tighten the fascia lata, and so abducts and medially rotates the lower limb.

Attachments: Originates from the anterior iliac crest, attaching to the anterior superior iliac spine (ASIS). It inserts into the iliotibial tract, which itself attaches to the lateral condyle of the tibia.

Actions: Assists the gluteus medius and minimus in abduction and medial rotation of the lower limb. It also plays a supportive role in the gait cycle.

Innervation: Superior gluteal nerve.

• The Deep Muscles

The deep gluteal muscles are a set of smaller muscles, located underneath the gluteus minimus. The general action of these muscles is to laterally rotate the lower limb. They also stabilise the hip joint by ‘pulling’ the femoral head into the acetabulum of the pelvis.

1. Piriformis

The piriformis muscle is a key landmark in the gluteal region. It is the most superior of the deep muscles.

Attachments: Originates from the anterior surface of the sacrum. It then travels infero-laterally, through the greater sciatic foramen, to insert into the greater trochanter of the femur.

Actions: Lateral rotation and abduction.

Innervation: Nerve to piriformis.

1. Obturator Internus

The obturator internus forms the lateral walls of the pelvic cavity. In some texts, the obturator internus and the gemelli muscles are considered as one muscle – the triceps coxae.

Attachments: Originates from the pubis and ischium at the obturator foramen. It travels through the lesser sciatic foramen, and attaches to the greater trochanter of the femur.

Actions: Lateral rotation and abduction.

Innervation: Nerve to obturator internus.

1. The Gemelli – Superior and Inferior

The gemelli are two narrow and triangular muscles. They are separated by the obturator internus tendon.

Attachments: The superior gemellus muscle originates from the ischial spine, the inferior from the ischial tuberosity. They both attach to the greater trochanter of the femur.

Actions: Lateral rotation and abduction.

Innervation: The superior gemellus muscle is innervated by the nerve to obturator internus, the inferior gemellus is innervated by the nerve to quadratus femoris.

1. Quadratus Femoris

The quadratus femoris is a flat, square-shaped muscle. It is the most inferior of the deep gluteal muscles, located below the gemelli and obturator internus.

Attachments: It originates from the lateral side of the ischial tuberosity, and attaches to the quadrate tuberosity on the intertrochanteric crest.

Actions: Lateral rotation.

Innervation: Nerve to quadratus femoris.

3. MUSCLES OF THIGH

Muscles in the Anterior Compartment of the Thigh

The musculature of the thigh can be split into three sections; anterior, medial and posterior. Each compartment has a distinct innervation and function.

The muscles in the anterior compartment of the thigh are innervated by the femoral nerve (L2-L4), and as a general rule, act to extend the leg at the knee joint.

There are three major muscles in the anterior thigh – the pectineus, sartorius and quadriceps femoris.

In addition to these, the end of the iliopsoas muscle passes into the anterior compartment.

1. Iliopsoas

The iliopsoas is actually two muscles, the psoas major and the iliacus. They originate in different areas, but come together to form a tendon, hence why they are commonly referred to as one muscle.

Unlike many of the anterior thigh muscles, the iliopsoas does not extend the leg at the knee joint.

Attachments: The psoas major originates from the lumbar vertebrae, and the iliacus originates from the iliac fossa of the pelvis. They insert together onto the lesser trochanter of the femur.

Actions: Flexes the thigh at the hip joint.

Innervation: The psoas major is innervated by anterior rami of L1-3, while the iliacus is innervated by the femoral nerve.

1. Quadriceps Femoris

The quadriceps femoris consists of four individual muscles; three vastus muscles and the rectus femoris. They form the main bulk of the thigh, and collectively are one of the most powerful muscles in the body.

The muscles that form the quadriceps femoris unite proximal to the knee and attach to the patella via the quadriceps tendon. In turn, the patella is attached to the tibia by the patella ligament. The quadriceps femoris is the main extensor of the knee.

1. Vastus Lateralis

Proximal attachment: Originates from the greater trochanter and the lateral lip of linea aspera.

Actions: Extends the knee joint and stabilises the patella.

Innervation: Femoral nerve.

Vastus Intermedius

Proximal attachment: Anterior and lateral surfaces of the femoral shaft.

Actions: Extends the knee joint and stabilises the patella.

Innervation: Femoral nerve.

1. Vastus Medialis

Proximal attachment: The intertrochanteric line and medial lip of the linea aspera.

Actions: Extends the knee joint and stabilises the patella, particularly due to its horizontal fibres at the distal end.

Innervation: Femoral nerve.

1. Rectus Femoris

Attachments: Originates from the anterior inferior iliac spine and the area of the ilium immediately superior to the acetabulum. It runs straight down the leg and attaches to the patella via the quadriceps femoris tendon.

Actions: The only muscle of the quadriceps to cross both the hip and knee joints. It flexes the thigh at the hip joint, and extends at the knee joint.

Innervation: Femoral nerve.

1. Sartorius

The sartorius is the longest muscle in the body. It is long and thin, running across the thigh in a inferomedial direction. The sartorius is positioned more superficially than the other muscles in the leg.

Attachments: Originates from the anterior superior iliac spine, and attaches to the superior, medial surface of the tibia.

Actions: At the hip joint, it is a flexor, abductor and lateral rotator. At the knee joint, it is also a flexor.

Innervation: Femoral nerve.

1. Pectineus

The pectineus muscle is a flat muscle that forms the base of the femoral triangle. It has a dual innervation, and thus can be considered a transitional muscle between the anterior thigh and medial thigh compartments.

Attachments: It originates from the pectineal line on the anterior surface of the pelvis, and attaches to the pectineal line on the posterior side of the femur, just inferior to the lesser trochanter.

Actions: Adduction and flexion at the hip joint.

Innervation: Femoral nerve. May also receive a branch from the obturator nerve.

Muscles in the Medial Compartment of the Thigh

The muscles in the medial compartment of the thigh are collectively known as the hip adductors. There are five muscles in this group; gracilis, obturator externus, adductor brevis, adductor longus and adductor magnus.

All the medial thigh muscles are innervated by the obturator nerve, which arises from the lumbar plexus. Arterial supply is via the obturator artery.

Muscles of the Medial Thigh :

1. Adductor Magnus

The adductor magnus is the largest muscle in the medial compartment. It lies posteriorly to the other muscles.

Functionally, the muscle can be divided into two parts; the adductor part, and the hamstring part.

Attachments

Adductor part – Originates from the inferior rami of the pubis and the rami of ischium, attaching to the linea aspera of the femur.

Hamstring part – Originates from the ischial tuberosity and attaches to the adductor tubercle and medial supracondylar line of the femur.

Actions: They both adduct the thigh. The adductor component also flexes the thigh, with the hamstring portion extending the thigh.

Innervation: Adductor part is innervated by the obturator nerve (L2-L4), the hamstring part is innervated by the tibial component of the sciatic nerve (L4-S3).

1. Adductor Longus

The adductor longus is a large, flat muscle. It partially covers the adductor brevis and magnus. The muscle forms the medial border of the femoral triangle.

Attachments: Originates from the pubis, and expands into a fan shape, attaching broadly to the linea aspera of the femur

Actions: Adduction of the thigh.

Innervation: Obturator nerve (L2-L4).

Adductor Brevis

The adductor brevis is a short muscle, lying underneath the adductor longus.

It lies in between the anterior and posterior divisions of the obturator nerve. Therefore, it can be used as an anatomical landmark to identify the aforementioned branches.

Attachments: Originates from the body of pubis and inferior pubic rami. It attaches to the linea aspera on the posterior surface of the femur, proximal to the adductor longus.

Actions: Adduction of the thigh.

Innervation: Obturator nerve (L2-L4).

1. Obturator Externus

This is one of the smaller muscles of the medial thigh, and it is located most superiorly.

Attachments: It originates from the membrane of the obturator foramen, and adjacent bone. It passes under the neck of femur, attaching to the posterior aspect of the greater trochanter.

Actions: Adduction and lateral rotation of the thigh.

Innervation: Obturator nerve (L2-L4).

1. Gracilis

The gracilis is the most superficial and medial of the muscles in this compartment. It crosses at both the hip and knee joints. It is sometimes transplanted into the hand or forearm to replace a damaged muscle.

Attachments: It originates from the inferior rami of the pubis, and the body of the pubis. Descending almost vertically down the leg, it attaches to the medial surface of the tibia, between the tendons of the sartorius (anteriorly) and the semitendinosus (posteriorly).

Actions: Adduction of the thigh at the hip, and flexion of the leg at the knee.

Innervation: Obturator nerve (L2-L4).

• Muscles in the Posterior Compartment of the Thigh

The muscles in the posterior compartment of the thigh are collectively known as the hamstrings. They consist of the biceps femoris, semitendinosus and semimembranosus, which form prominent tendons medially and laterally at the back of the knee.

As group, these muscles act to extend at the hip, and flex at the knee. They are innervated by the sciatic nerve (L4-S3).

Muscles in the Posterior Compartment

The muscles located within the posterior compartment of the thigh are the biceps femoris, semitendinosus and semimembranosus.

1. Biceps Femoris

Like the biceps brachii in the arm, the biceps femoris muscle has two heads – a long head and a short head.

It is the most lateral of the muscles in the posterior thigh – the common tendon of the two heads can be felt laterally at the posterior knee.

Attachments: The long head originates from the ischial tuberosity of the pelvis. The short head originates from the linea aspera on posterior surface of the femur. Together, the heads form a tendon, which inserts into the head of the fibula.

Actions: Main action is flexion at the knee. It also extends the thigh at the hip, and laterally rotates at the hip and knee.

Innervation: Long head innervated by the tibial part of the sciatic nerve, whereas the short head is innervated by the common fibular part of the sciatic nerve.

1. Semitendinosus

The semitendinosus is a largely tendinous muscle. It lies medially to the biceps femoris, and covers the majority of the semimembranosus.

Attachments: It originates from the ischial tuberosity of the pelvis, and attaches to the medial surface of the tibia.

Actions: Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.

Innervation: Tibial part of the sciatic nerve.

1. Semimembranosus

The semimembranosus muscle is flattened and broad. It is located underneath the semitendinosus.

Attachments: It originates from the ischial tuberosity, but does so more superiorly than the semitendinosus and biceps femoris. It attaches to the medial tibial condyle.

Actions: Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.

Innervation: Tibial part of the sciatic nerve.

4. MUSCLES OF THE LEG

Muscles in the Anterior Compartment of the Leg

There are four muscles in the anterior compartment of the leg: tibialis anterior, extensor digitorum longus, extensor hallucis longus and fibularis tertius.

Collectively, they act to dorsiflex and invert the foot at the ankle joint.  The extensor digitorum longus and extensor hallucis longus also extend the toes. The muscles in this compartment are innervated by the deep fibular nerve (L4-S1), and blood is supplied via the anterior tibial artery.

1. Tibialis Anterior

The tibialis anterior muscle is located alongside the lateral surface of the tibia.

It is the strongest dorsiflexor of the foot.

To test the power of the tibialis anterior, the patient can be asked to stand on their heels.

Attachments: Originates from the lateral surface of the tibia, attaches to the medial cuneiform and the base of metatarsal I.

Actions: Dorsiflexion and inversion of the foot.

Innervation: Deep fibular nerve.

1. Extensor Digitorum Longus

The extensor digitorum longus lies lateral and deep to the tibialis anterior. The tendons of the EDL can be palpated on the dorsal surface of the foot.

Attachments: Originates from the lateral condyle of the tibia and the medial surface of the fibula. The fibres converge into a tendon, which travels to the dorsal surface of the foot. The tendon splits into four, each inserting onto a toe.

Actions: Extension of the lateral four toes, and dorsiflexion of the foot.

Innervation: Deep fibular nerve.

1. Extensor Hallucis Longus

The extensor hallucis longus is located deep to the EDL and TA.

Attachments: Originates from the medial surface of the fibular shaft.  The tendon crosses anterior to the ankle joint and attaches to the base of the distal phalanx of the great toe.

Action: Extension of the great toe and dorsiflexion of the foot.

Innervation: Deep fibular nerve.

1. Fibularis Tertius

The fibularis tertius muscles arises from the most inferior part of the EDL. It is not present in all individuals and is considered by some texts as a part of the extensor digitorum longus.

Attachments: Originates with the extensor digitorum longus from the medial surface of the fibula. The tendon descends with the EDL, until they reach the dorsal surface of the foot. The fibularis tertius tendon then diverges and attaches to metatarsal V.

Actions: Eversion and dorsiflexion of the foot.

Innervation: Deep fibular nerve.

• Muscles in the Lateral Compartment of the Leg

There are two muscles in the lateral compartment of the leg; the fibularis longus and brevis (also known as peroneal longus and brevis).

The common function of the muscles is eversion – turning the sole of the foot outwards. They are both innervated by the superficial fibular nerve. 

Fig 1.0 – Muscles of the lateral leg; fibularis longus and brevis

1. Fibularis longus

Larger and more superficial muscle within the compartment.

Attachments

The fibularis longus originates from the superior and lateral surface of the fibula and the lateral tibial condyle.

The fibres converge into a tendon, which descends into the foot, posterior to the lateral malleolus.

The tendon crosses under the foot, and attaches to the bones on the medial side, namely the medial cuneiform and base of metatarsal I.

Actions: Eversion and plantarflexion of the foot. Also supports the lateral and transverse arches of the foot.

Innervation: Superficial fibular (peroneal) nerve, L4-S1.

1. Fibularis Brevis

The fibularis brevis muscles is deeper and shorter than the fibularis longus.

Attachments:

Originates from the inferolateral surface of the fibular shaft. The muscle belly forms a tendon, which descends with the fibularis longus into the foot.

It travels posteriorly to the lateral malleolus, passing over the calcaneus and the cuboidal bones.

The tendon then attaches to a tubercle on metatarsal V.

Actions: Eversion of the foot.

Innervation: Superficial fibular (peroneal) nerve, L4-S1.

• Muscles in the Posterior Compartment of the Leg

The posterior compartment of the leg contains seven muscles, organised into two layers – superficial and deep. The two layers are separated by a band of fascia.

Collectively, the muscles in this area plantarflex and invert the foot. They are innervated by the tibial nerve, a terminal branch of the sciatic nerve.

Superficial Muscles

The superficial muscles form the characteristic ‘calf’ shape of the posterior leg. They all insert into the calcaneus of the foot (the heel bone), via the calcaneal tendon. The calcaneal reflex tests spinal roots S1-S2.

To minimise friction during movement, there are two bursae (fluid filled sacs) associated with the calcaneal tendon:

1. Subcutaneous calcaneal bursa – lies between the skin and the calcaneal tendon.
2. Deep bursa of the calcaneal tendon – lies between the tendon and the calcaneus.

1. Gastrocnemius

The gastrocnemius is the most superficial of all the muscles in the posterior leg. It has two heads – medial and lateral, which converge to form a single muscle belly.

Attachments: The lateral head originates from the lateral femoral condyle, and medial head from the medial femoral condyle. The fibres converge, and form a single muscle belly. In the lower part of the leg, the muscle belly combines with the soleus to from the calcaneal tendon, with inserts onto the calcaneus (the heel bone).

Actions: It plantarflexes at the ankle joint, and because it crosses the knee, it is a flexor there.

Innervation: Tibial nerve.

1. Plantaris

The plantaris is a small muscle with a long tendon, which can be mistaken for a nerve as it descends down the leg. It is absent in 10% of people.

Attachments: Originates from the lateral supracondylar line of the femur. The muscle descends medially, condensing into a tendon that runs down the leg, between the gastrocnemius and soleus. The tendon blends with the calcaneal tendon.

Actions: It plantarflexes at the ankle joint, and because it crosses the knee, it is a flexor there. It is not a vital muscle for these movements.

Innervation: Tibial nerve.

1. Soleus

The soleus is located deep to the gastrocnemius. It is large and flat, named soleus due to its resemblance of a sole – a flat fish.

Attachments: Originates from the soleal line of the tibia and proximal fibular area. The muscle narrows in the lower part of the leg, and joins the calcaneal tendon.

Actions: Plantarflexes the foot at the ankle joint.

Innervation: Tibial Nerve.

Deep Muscles

There are four muscles in the deep compartment of the posterior leg. One muscle, the popliteus, acts only on the knee joint. The remaining three muscles (tibialis posterior, flexor hallucis longus and flexor digitorum longus) act on the ankle and foot. 

Fig – Muscles in the deep layer of the posterior leg.

1. Popliteus

The popliteus is located superiorly in the leg. It lies behind the knee joint, forming the base of the popliteal fossa.

There is a bursa (fluid filled sac) that lies between the popliteal tendon and the posterior surface of the knee joint. It is called the popliteus bursa.

Attachments: Originates from the lateral condyle of the femur and the posterior horn of the lateral meniscus. From there, it runs inferomedially towards the tibia and inserts above the origin of the soleus muscle.

Actions: Laterally rotates the femur on the tibia – ‘unlocking’ the knee joint so that flexion can occur.

Innervation: Tibial nerve.

1. Tibialis Posterior

The tibialis posterior is the deepest out of the four muscles. It lies between the flexor digitorum longus and the flexor hallucis longus.

Attachments: Originates from the interosseous membrane between the tibia and fibula, and posterior surfaces of the two bones. The tendon enters the foot posterior to the medial malleolus, and attaches to the plantar surfaces of the medial tarsal bones.

Actions: Inverts and plantarflexes the foot, maintains the medial arch of the foot.

Innervation: Tibial nerve.

1. Flexor Digitorum Longus

The FDL is (surprisingly) a smaller muscle than the flexor hallucis longus. It is located medially in the posterior leg.

Attachments: Originates from the medial surface of the tibia, attaches to the plantar surfaces of the lateral four digits.

Actions: Flexes the lateral four toes.

Innervation: Tibial nerve.

1. Flexor Hallucis Longus

The flexor hallucis longus muscle is found on the lateral side of leg. This is slightly counter-intuitive, as it is opposite the great toe, which it acts on.

Attachments: Originates from the posterior surface of the fibula, attaches to the plantar surface of the phalanx of the great toe.

Actions: Flexes the great toe.

Innervation: Tibial nerve.

5.    MUSCLES OF THE FOOT

The muscles acting on the foot can be divided into two distinct groups; extrinsic and intrinsic muscles.

1. Extrinsicmuscles arise from the anterior, posterior and lateral compartments of the leg. They are mainly responsible for actions such as eversion, inversion, plantarflexion and dorsiflexion of the foot.
2. Intrinsicmuscles are located within the foot and are responsible for the fine motor actions of the foot, for example movement of individual digits.

• Dorsal Aspect

Whilst many of the extrinsic muscles attach to the dorsum of the foot, there are only two intrinsic muscles located in this compartment – the extensor digitorum brevis, and the extensor hallucis brevis.

1. Extensor Digitorum Brevis

The extensor digitorum brevis muscle lies deep to the tendon of the extensor digitorum longus.

Attachments: Originates from the calcaneus, the interosseous talocalcaneal ligament and the inferior extensor retinaculum. It attaches to proximal phalanx of the great toe and the long extensor tendons of toes 2-4.

Actions: Aids the extensor digitorum longus in extending the medial four toes at the metatarsophalangeal and interphalangeal joints.

Innervation: Deep fibular nerve.

1. Extensor Hallucis Brevis

The extensor hallucis brevis muscle is medial to extensor digitorum longus and lateral to extensor hallucis longus.

Attachments: Originates from the calcaneus, the interosseous talocalcaneal ligament and the inferior extensor retinaculum. It attaches to the base of the proximal phalanx of the great toe.

Actions: Aids the extensor hallucis longus in extending the great toe at the metatarsophalangeal joint.

Innervation: Deep fibular nerve.

• Plantar Aspect

There are 10 intrinsic muscles located in the sole of the foot. They act collectively to stabilise the arches of the foot, and individually to control movement of the digits.

All the muscles are innervated either by the medial plantar nerve or the lateral plantar nerve, which are both branches of the tibial nerve.

The muscles of the plantar aspect are described in four layers (superficial to deep).

First Layer :

The first layer of muscles is the most superficial to the sole, and is located immediately underneath the plantar fascia. There are three muscles in this layer.

1. Abductor Hallucis

The abductor hallucis muscle is located on the medial side of the sole, where it contributes to a small soft tissue bulge.

Attachments: Originates from the medial tubercle of the calcaneus, the flexor retinaculum and the plantar aponeurosis. It attaches to the medial base of the proximal phalanx of the great toe.

Actions: Abducts and flexes the great toe.

Innervation: Medial plantar nerve.

1. Flexor Digitorum Brevis

The flexor digitorum brevis muscle is located laterally to the abductor hallucis. It sits in the centre of the sole, sandwiched between the plantar aponeurosis and the tendons of flexor digitorum longus.

Attachments: Originates from the medial tubercle of the calcaneus and the plantar aponeurosis. It attaches to the middle phalanges of the lateral four digits.

Actions: Flexes the lateral four digits at the proximal interphalangeal joints.

Innervation: Medial plantar nerve.

1. Abductor DigitiMinimi

The abductor digitiminimi muscle is located on the lateral side of the foot. It is homologous with the abductor digitiminimi of the hand.

Attachments: Originates from the medial and lateral tubercles of the calcaneus and the plantar aponeurosis. It attaches to the lateral base of the proximal phalanx of the 5th digit.

Actions: Abducts and flexes the 5th digit.

Innervation: Lateral plantar nerve.

Second Layer

The second layer contains two muscles – the quadratus plantae, and the lumbricals. In addition, the tendons of the flexor digitorum longus (an extrinsic muscle of the foot) pass through this layer.

1. Quadratus Plantae

The quadratus plantae muscle is located superior to the flexor digitorum longus tendons. It is separated from the first layer of muscles by the lateral plantar vessels and nerve.

Attachments: Originates from the medial and lateral plantar surface of the calcaneus. It attaches to the tendons of flexor digitorum longus.

Actions: Assists flexor digitorum longus in flexing the lateral four digits.

Innervation: Lateral plantar nerve.

1. Lumbricals

There are four lumbrical muscles in the foot. They are each located medial to their respective tendon of the flexor digitorum longus.

Attachments: Originates from the tendons of flexor digitorum longus. Attaches to the extensor hoods of the lateral four digits.

Actions: Flexes at the metatarsophalangeal joints, while extending the interphalangeal joints.

Innervation: The most medial lumbrical is innervated by the medial plantar nerve. The remaining three are innervated by the lateral plantar nerve.

Third Layer

The third layer contains three muscles. The flexor hallucis brevis and adductor hallucis are associated with movements of the great toe. The remaining muscle, the flexor digitiminimi brevis, moves the little toe.

1. Flexor Hallucis Brevis

The flexor hallucis brevis muscle is located on the medial side of the foot. It originates from two places on the sole of the foot.

Attachments: Originates from the plantar surfaces of the cuboid and lateral cuneiforms, and from the tendon of the posterior tibialis tendon. Attaches to the base of the proximal phalanx of the great toe.

Actions: Flexes the proximal phalanx of the great toe at the metatarsophalangeal joint.

Innervation: Medial plantar nerve.

1. Adductor Hallucis

The adductor hallucis muscle is located laterally to the flexor hallucis brevis. It consists of an oblique and transverse head.

Attachments: The oblique head originates from the bases of the 2nd, 3rd and 4th metatarsals. The transverse head originates from the plantar ligaments of the metatarsophalangeal joints. Both heads attach to the lateral base of the proximal phalanx of the great toe.

Actions: Adduct the great toe. Assists in forming the transverse arch of the foot.

Innervation: Deep branch of lateral plantar nerve.

1. Flexor DigitiMinimi Brevis

The flexor digitiminimi brevis muscle is located on the lateral side of the foot, underneath the metatarsal of the little toe. It resembles the interossei in structure.

Attachments: Originates from the base of the fifth metatarsal. Attaches to the base of the proximal phalanx of the fifth digit.

Actions: Flexes the proximal phalanx of the fifth digit.

Innervation: Superficial branch of lateral plantar nerve.

Fourth Layer

The plantar and dorsal interossei comprise the fourth and final plantar muscle layer.  The plantar interossei have a unipennate morphology, while the dorsal interossei are bipennate.

1. Plantar Interossei

There are three plantar interossei, which are located between the metatarsals. Each arises from a single metatarsal.

Attachments: Originates from the medial side of metatarsals three to five. Attaches to the medial sides of the phalanges of digits three to five.

Actions: Adduct digits three to five and flex the metatarsophalangeal joints.

Innervation: Lateral plantar nerve.

1. Dorsal Interossei

There are four dorsal interossei, which are located between the metatarsals. Each arises from two metatarsals.

Attachments: Originates from the sides of metatarsals one to five. The first muscle attaches to the medial side of the proximal phalanx of the second digit. The second to fourth interossei attach to the lateral sides of the proximal phalanxes of digits two to four.

Actions: Abduct digits two to four and flex the metatarsophalangeal joints.

Innervation: Lateral plantar nerve.

MUSCLES OF THE ABDOMEN

The Anterolateral Abdominal Wall

The abdominal wall encloses the abdominal cavity and can be divided into anterolateral and posterior sections.

• The abdominal wall Forms a firm, yet flexible boundary which keeps the abdominal viscera in the abdominal cavity and assists the viscera in maintaining their anatomical position against gravity.
• Protects the abdominal viscera from injury.
• Assists in forceful expiration by pushing the abdominal viscera upwards.
• Iinvolved in any action (coughing, vomiting, defecation) that increases intra-abdominal pressure.

The anterolateral abdominal wall consists of four main layers (external to internal):

1. Skin
2. Superficial fascia
3. Muscles and associated fascia
4. Parietal peritoneum.

Superficial Fascia

The superficial fascia is connective tissue. The composition of this layer depends on its location:

Above the umbilicus – a single sheet of connective tissue. It is continuous with the superficial fascia in other regions of the body.

Below the umbilicus – divided into two layers; the fatty superficial layer (Camper’s fascia) and the membranous deep layer (Scarpa’s fascia).

The superficial vessels and nerves run between these two layers of fascia.

• Muscles of the Abdominal Wall

The muscles of the anterolateral abdominal wall can be divided into two main groups:

1. Flat muscles– three flat muscles, situated laterally on either side of the abdomen.
2. Vertical muscles– two vertical muscles, situated near the mid-line of the body.

1. Flat Muscles

There are three flat muscles located laterally in the abdominal wall, stacked upon one another. Their fibres run in differing directions and cross each other – strengthening the wall and decreasing the risk of abdominal contents herniating through the wall.

In the anteromedial aspect of the abdominal wall, each flat muscle forms an aponeurosis (a broad, flat tendon), which covers the vertical rectus abdominis muscle. The aponeuroses of all the flat muscles become entwined in the midline, forming the Linea alba (a fibrous structure that extends from the xiphoid process of the sternum to the pubic symphysis).

1. External Oblique

The external oblique is the largest and most superficial flat muscle in the abdominal wall. Its fibres run inferomedially.

Attachments: Originates from ribs 5-12, and inserts into the iliac crest and pubic tubercle.

Functions: Contralateral rotation of the torso.

Innervation: Thoracoabdominal nerves (T7-T11) and subcostal nerve (T12).

Internal Oblique

The internal oblique lies deep to the external oblique. It is smaller and thinner in structure, with its fibres running superomedially (perpendicular to the fibres of the external oblique).

Attachments: Originates from the inguinal ligament, iliac crest and lumbodorsal fascia, and inserts into ribs 10-12.

Functions: Bilateral contraction compresses the abdomen, while unilateral contraction ipsilaterally rotates the torso.

Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.

1. Transversus Abdominis

The transversus abdominis is the deepest of the flat muscles, with transversely running fibres. Deep to this muscle is a well-formed layer of fascia, known as the transversalis fascia.

Attachments: Originates from the inguinal ligament, costal cartilages 7-12, the iliac crest and thoracolumbar fascia. Inserts into the conjoint tendon, xiphoid process, linea alba and the pubic crest.

Functions: Compression of abdominal contents.

Innervation: Thoracoabdominal nerves (T7-T11), subcostal nerve (T12) and branches of the lumbar plexus.

Vertical Muscles

There are two vertical muscles located in the midline of the anterolateral abdominal wall – the rectus abdominis and pyramidalis.

1. Rectus Abdominis

The rectus abdominis is long, paired muscle, found either side of the midline in the abdominal wall. It is split into two by the linea alba. The lateral borders of the muscles create a surface marking known as the linea semilunaris.

At several places, the muscle is intersected by fibrous strips, known as tendinous intersections. The tendinous intersections and the linea alba give rise to the ‘six pack’ seen in individuals with a well-developed rectus abdominis.

Attachments: Originates from the crest of the pubis, before inserting into the xiphoid process of the sternum and the costal cartilage of ribs 5-7.

Functions: As well as assisting the flat muscles in compressing the abdominal viscera, the rectus abdominis also stabilises the pelvis during walking, and depresses the ribs.

Innervation: Thoracoabdominal nerves (T7-T11).

1. Pyramidalis

This is a small triangular muscle, found superficially to the rectus abdominis. It is located inferiorly, with its base on the pubis bone, and the apex of the triangle attached to the linea alba.

Attachments: Originates from the pubic crest and pubic symphysis before inserting into the linea alba.

Functions: It acts to tense the linea alba.

Innervation: Subcostal nerve (T12).

• Rectus Sheath

The rectus sheath is formed by the aponeurosis of the three flat muscles and encloses the rectus abdominus and pyramidalis muscles. It has an anterior and posterior wall for most of its length:

-The anterior wall is formed by the aponeurosis of the external oblique, and of half of the   internal oblique.

-The posterior wall is formed by the aponeurosis of half the internal oblique and of the        transversus abdominis.

Approximately midway between the umbilicus and the pubic symphysis, all the aponeurosis move to the anterior wall of the rectus sheath. At this point, there is no posterior wall to the sheath; the rectus abdominis is in direct contact with the transversalis fascia.

The demarcation point where the posterior layer of the rectus sheath ends is the arcuate line.

• The Posterior Abdominal Wall

The posterior abdominal wall is a complex region of anatomy. It is formed by the lumbar vertebrae, pelvic girdle, posterior abdominal muscles and their associated fascia. Major vessels, nerves and organs are located on the inner surface of the posterior abdominal wall.

• Posterior Abdominal Muscles

There are five muscles in the posterior abdominal wall: the iliacus, psoas major, psoas minor, quadratus lumborum and the diaphragm. We shall look at the attachments, actions and innervation of these muscles in more detail.

 The quadratus lumborum of the posterior abdominal wall.

1. Quadratus Lumborum

The quadratus lumborum muscle is located laterally in the posterior abdominal wall. It is a thick muscular sheet which is quadrilateral in shape. The muscle is positioned superficially to the psoas major.

Attachments: It originates from the iliac crest and iliolumbar ligament. The fibres travel superomedially, inserting onto the transverse processes of L1 – L4 and the inferior border of the 12^th rib.

Actions: Extension and lateral flexion of the vertebral column. It also fixes the 12th rib during inspiration, so that the contraction of diaphragm is not wasted.

Innervation: Anterior rami of T12- L4 nerves.

1. Psoas Major

The psoas major is located near the midline of the posterior abdominal wall, immediately lateral to the lumbar vertebrae.

Attachments: Originates from the transverse processes and vertebral bodies of T12 – L5. It then moves inferiorly and laterally, running deep to the inguinal ligament, and attaching to the lesser trochanter of the femur.

Actions: Flexion of the thigh at the hip and lateral flexion of the vertebral column.

Innervation: Anterior rami of L1 – L3 nerves.

 Muscles of the posterior abdominal wall.

1. Psoas Minor

The psoas minor muscle is only present in 60% of the population. It is located anterior to the psoas major.

Attachments: Originates from the vertebral bodies of T12 and L1 and attaches to a ridge on the superior ramus of the pubic bone, known as the pectineal line.

Actions: Flexion of the vertebral column.

Innervation: Anterior rami of the L1 spinal nerve.

1. Iliacus

The iliacus muscle is a fan-shaped muscle that is situated inferiorly on the posterior abdominal wall. It combines with the psoas major to form the iliopsoas – the major flexor of the thigh.

Attachments: Originates from surface of the iliac fossa and anterior inferior iliac spine. Its fibres combine with the tendon of the psoas major, inserting into the lesser trochanter of the femur.

Actions: Flexion and lateral rotation of the thigh at the hip joint.

Innervation: Femoral nerve (L2 – L4).

1. Diaphragm

The posterior aspect of the diaphragm is considered to be part of the posterior abdominal wall. 

• Fascia of the Posterior Abdominal Wall

A layer of fascia (sheet of connective tissue) lies between the parietal peritoneum and the muscles of the posterior abdominal wall. This fascia is continuous with the transversalis fascia of the anterolateral abdominal wall.

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1. Psoas Fascia

The psoas fascia covers the psoas major muscle. It is attached to the lumbar vertebrae medially, continuous with the thoracolumbar fascia laterally and continuous with the iliac fascia inferiorly.

– Thoracolumbar fascia

The thoracolumbar fascia consists of the three layers; posterior, middle and anterior. Muscles are enclosed between these layers:

– Quadratus lumborum – between the anterior and middle layers.

– Deep back muscles – between the middle and posterior layers.

The posterior layer extends between the 12^th rib and the iliac crest posteriorly. Laterally the fascia meets the internal oblique and transversus abdominus muscles, but not the external oblique. As it forms these attachments it covers the latissimus dorsi.

The anterior layer attaches to the anterior aspect of the transverse processes of the lumbar vertebrae, the 12th rib and the iliac crest. Laterally the fascia is continuous with the aponeurotic origin of the transversus abdominis muscle. Superiorly the fascia thickens to become the lateral arcuate ligament, which joins the iliolumbar ligaments inferiorly.

MUSCLES OF BACK

The Superficial Back Muscles:

The muscles of the back can be divided into three groups – superficial, intermediate and deep.

Superficial – associated with movements of the shoulder.

Intermediate – associated with movements of the thoracic cage.

Deep – associated with movements of the vertebral column.

The deep muscles develop embryologically in the back, and are thus described as intrinsic muscles. The superficial and intermediate muscles do not develop in the back, and are classified as extrinsic muscles.

This article is about the anatomy of the superficial back muscles – their attachments, innervations and functions.

The superficial back muscles are situated underneath the skin and superficial fascia. They originate from the vertebral column and attach to the bones of the shoulder – the clavicle, scapula and humerus. All these muscles are therefore associated with movements of the upper limb.

The muscles in this group are the trapezius, latissimus dorsi, levator scapulae and the rhomboids. The trapezius and the latissimus dorsi lie the most superficially, with the trapezius covering the rhomboids and levator scapulae.

1. Trapezius

The trapezius is a broad, flat and triangular muscle. The muscles on each side form a trapezoid shape. It is the most superficial of all the back muscles.

Attachments: Originates from the skull, ligamentum nuchae and the spinous processes of C7-T12. The fibres attach to the clavicle, acromion and the scapula spine.

Innervation: Motor innervation is from the accessory nerve. It also receives proprioceptor fibres from C3 and C4 spinal nerves.

Actions: The upper fibres of the trapezius elevates the scapula and rotates it during abduction of the arm. The middle fibres retract the scapula and the lower fibres pull the scapula inferiorly.

1. Latissimus Dorsi

The latissimus dorsi originates from the lower part of the back, where it covers a wide area.

Attachments: Has a broad origin – arising from the spinous processes of T6-T12, thoracolumbar fascia, iliac crest, and the inferior three ribs. The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus.

Innervation: Thoracodorsal nerve.

Actions: Extends, adducts and medially rotates the upper limb.

1. Levator Scapulae

The levator scapulae is a small strap-like muscle. It begins in the neck, and descends to attach to the scapula.

Attachments: Originates from the transverse processes of the C1-C4 vertebrae and attaches to the medial border of the scapula.

Innervation: Dorsal scapular nerve.

Actions: Elevates the scapula.

Rhomboids

There are two rhomboid muscles – major and minor.

The rhomboid minor is situated superiorly to the major.

1. 1 Rhomboid Major

Attachments: Originates from the spinous processes of T2-T5 vertebrae. Attaches to the medial border of the scapula, between the scapula spine and inferior angle.

Innervation: Dorsal scapular nerve.

Actions: Retracts and rotates the scapula.

d.2 Rhomboid Minor

Attachments: Originates from the spinous processes of C7-T1 vertebrae. Attaches to the medial border of the scapula, at the level of the spine of scapula.

Innervation: Dorsal scapular nerve.

Actions: Retracts and rotates the scapula.

• The Intermediate Back Muscles

The muscles of the back can be divided into three groups – superficial, intermediate and intrinsic:

Superficial – associated with movements of the shoulder.

Intermediate – associated with movements of the thoracic cage.

Deep – associated with movements of the vertebral column.

The intermediate group contains two muscles – the serratus posterior superior and serratus posterior inferior. These muscles run from the vertebral column to the ribcage, and assist with elevating and depressing the ribs. They are thought to have a slight respiratory function.

The serratus posterior inferior.

1. Serratus Posterior Superior

The serratus posterior superior is a thin, rectangular shaped muscle. It lies deep to the rhomboid muscles on the upper back.

Attachments: Originates from the lower part of the ligamentum nuchae, and the cervical and thoracic spines (usually C7 – T3). The fibres pass in an inferolateral direction, attaching to ribs 2-5.

Innervation: Intercostal nerves.

Actions: Elevates ribs 2-5.

1. Serratus Posterior Inferior

The serratus posterior inferior is broad and strong. It lies underneath the latissimus dorsi.

Attachments: Originates from the thoracic and lumbar spines (usually T11 – L3). The fibres pass in a superolateral direction, attaching to ribs 9-12.

Innervation: Intercostal nerves.

Actions: Depresses ribs 9-12.

• The Intrinsic Back Muscles

The muscles of the back can be divided into three groups – superficial, intermediate and intrinsic.

Superficial – associated with movements of the shoulder.

Intermediate – associated with movements of the thoracic cage.

Deep – associated with movements of the vertebral column.

1. Splenius Capitis

Attachments: Originates from the lower aspect of the ligamentum nuchae, and the spinous processes of C7 – T3/4 vertebrae. The fibres ascend, attaching to the mastoid process and the occipital bone of the skull.

Innervation: Posterior rami of spinal nerves C3 and C4.

Actions: Rotate head to the same side.

1. Splenius Cervicis

Attachments: Originates from the spinous processes of T3-T6 vertebae. The fibres ascend, attaching to the transverse processes of C1-3/4.

Innervation: Posterior rami of the lower cervical spinal nerves.

Actions: Rotate head to the same side.

The splenius muscles, located with the superficial layer of intrinsic back muscles.

• Intermediate

There are three intermediate intrinsic back muscles – the iliocostalis, longissimus and spinalis. Together these muscles form a column, known as the erector spinae.

The erector spinae is situated posterolaterally to spinal column, between the vertebral spinous processes and the costal angle of the ribs.

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1. Iliocostalis

The iliocostalis muscle is located laterally within the erector spinae. It is associated with the ribs, and can be divided into three parts – lumborum, thoracis, and cervicis.

Attachments: Arises from the common tendinous origin, and attaches to the costal angle of the ribs and the cervical transverse processes.

Innervation: Posterior rami of the spinal nerves.

Actions: Acts unilaterally to laterally flex the vertebral column. Acts bilaterally to extend the vertebral column and head.

1. Longissimus

The longissimus muscle is situated between the iliocostalis and spinalis. It is the largest of the three columns. It can be divided into three parts – thoracic, cervicis and capitis.

Attachments: Arises from the common tendinous origin, and attaches to the lower ribs, the transverse processes of C2 – T12, and the mastoid process of the skull.

Innervation: Posterior rami of the spinal nerves.

Actions: Acts unilaterally to laterally flex the vertebral column. Acts bilaterally to extend the vertebral column and head.

1. Spinalis

The spinalis muscle is located medially within the erector spinae. It is the smallest of the three muscle columns. It can be divided into the thoracic, cervicis and capitis (although the cervicis part is absent in some individuals).

Attachments: Arises from the common tendinous origin, and attaches to the spinous processes of C2, T1-T8 and the occipital bone of the skull.

Innervation: Posterior rami of the spinal nerves.

Actions: Acts unilaterally to laterally flex the vertebral column. Acts bilaterally to extend the vertebral column and head.

Deep

The deep intrinsic muscles are located underneath the erector spinae, and are known collectively as the transversospinalis. They are a group of short muscles, associated with the transverse and spinous processes of the vertebral column.

There are three major muscles in this group – the semispinalis, multifidus and rotatores.

1. Semispinalis

The semispinalis is the most superficial of the deep intrinsic muscles. Much like the intermediate muscles, it can be divided by its superior attachments into thoracic, cervicis and capitis.

Attachments: Originates from the transverse processes of C4-T10. The fibres ascend 4-6 vertebral segments, attaching to the spinous processes of C2-T4, and to the occipital bone of the skull.

Innervation: Posterior rami of the spinal nerves.

Actions: Extends and contralaterally rotates the head and vertebral column.

1. Multifidus

The multifidus is located underneath the semispinalis muscle. It is best developed in the lumbar area.

Attachments: Has a broad origin – arises from the sacrum, posterior iliac spine, common tendinous origin of the erector spinae, mamillary processes of lumbar vertebrae, transverse processes of T1-T3 and articular processes of C4-C7. The fibres ascend 2-4 vertebral segments, attaching the spinous processes of the vertebrae.

Innervation: Posterior rami of the spinal nerves.

Actions: Stablises the vertebral column.

1. Rotatores

The rotatores are most prominant in the thoracic region

Attachments: Originates from the vertebral transverse processes. The fibres ascend, and attach to the lamina and spinous processes of the immediately superior vertebrae.

Innervation: Posterior rami of the spinal nerves.

Actions: Stablises the vertebral column, and has a proprioceptive function.

• Minor Deep Intrinsic Muscles:

1. Interspinales: Spans between adjacent spinous processes. Acts to stablise the vertebral column.
2. Intertranversari– Spans between adjacent transverse processes. Acts to stablise the vertebral column.
3. Levatorescostarum– Originates from the transverse processes of C7-T11, and attaches to the rib immediately below. Acts to elevate the ribs.

capillaries

• Capillaries (capillus ~ little hair) are the smallest of blood vessels whose primary function is exchange of substances between the blood and interstitial fluid.
• Capillaries form an extensive network, approximately 10 billion in number.
• Total surface area of capillaries is estimated to be 500 to 700sq mts.
• Internal diameter of capillary is 4 to 9 µm, total thickness of capillary is about 0.5 µm, Because of the above characteristics, these thin-walled vessels are referred to as exchange vessels.
• Body tissues with high metabolic requirements, such as muscles, the brain, the liver, the kidneys, and the nervous system, use more O2 and nutrients and thus have extensive capillary networks.
• Tissues with lower metabolic requirements, such as tendons and ligaments, contain fewer capillaries.
• Capillaries are absent in a few tissues, such as all covering and lining epithelia, the cornea and lens of the eye, and cartilage.
• Throughout the body, capillaries function as part of a capillary bed, a network of 10–100 capillaries that arises from a single metarteriole. In most parts of the body, blood can flow through a capillary network from an arteriole into a venule.
• Typically, blood flows intermittently through capillaries due to alternating contraction and relaxation of the smooth muscle of metarterioles and the precapillary sphincters, which may occur 5 to 10 times per minute, is called vasomotion.

microcirculation

• The flow of blood from a metarteriole through capillaries and into a postcapillary venule is called the microcirculation.
• It consists of;
  • Arteriole
  • Capillary
  • Venule

types of capillaries

functions of capillaries

• Diffusion
• Pinocytosis
• Filtration and Reabsorption

DIFFUSION

• The most important method of capillary exchange is simple diffusion. Many substances, such as oxygen , carbon dioxide, glucose, amino acids, and hormones, enter and leave capillaries by simple diffusion.
• Since, O2 and nutrients normally are present in higher concentrations in blood, they diffuse down their concentration gradients into interstitial fluid and then into body cells.
• CO2 and other wastes released by body cells are present in higher concentrations in interstitial fluid, so they diffuse into blood.
• Water-soluble substances such as glucose and amino acids pass across capillary walls through intercellular clefts or fenestrations.
• Lipid-soluble materials, such as O2, CO2, and steroid hormones, may pass across capillary walls directly through the lipid bilayer of endothelial cell plasma membranes.
• In sinusoids, the intercellular clefts are so large that they allow even proteins and blood cells to pass through their walls.
• For example, hepatocytes (liver cells) synthesize and release many plasma proteins, such as fibrinogen (the main clotting protein) and albumin, which then diffuse into the bloodstream through sinusoids. In red bone marrow, blood cells are formed (hemopoiesis) and then enter the bloodstream through sinusoids.
• In contrast to sinusoids are the capillaries of the brain. Most areas of the brain contain continuous capillaries; however, these capillaries are very “tight.” The endothelial cells of most brain capillaries are sealed together by tight junctions. The resulting blockade to movement of materials into and out of brain capillaries is known as the blood – brain barrier.
• In brain areas that lack the blood – brain barrier, for example, the hypothalamus, pineal gland, and pituitary gland, here materials undergo capillary exchange more freely.

PINOCYTOSIS / TRANSCYTOSIS

• A small quantity of material crosses capillary walls by pinocytosis / transcytosis. In this process, substances in blood plasma become enclosed within tiny pinocytic vesicles that first enter endothelial cells by endocytosis, then move across the cell and exit on the other side by exocytosis.
• This method of transport is important mainly for large, lipid-insoluble molecules that cannot cross capillary walls in any other way.
• For example, the hormone insulin (a small protein) enters the bloodstream by transcytosis, and certain antibodies (also proteins) pass from the maternal circulation into the fetal circulation by transcytosis.

FILTRATION AND REABSORPTION (BULK FLOW)

• Bulk flow is a passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction.
• Bulk flow occurs from an area of higher pressure to an area of lower pressure, and it continues as long as a pressure difference exists.
• Diffusion is more important for solute exchange between blood and interstitial fluid, but bulk flow is more important for regulation of the relative volumes of blood and interstitial fluid.
  • Pressure – driven movement of fluid and solutes from blood capillaries into interstitial fluid is called filtration.
  • Pressure – driven movement from interstitial fluid into blood capillaries is called reabsorption.
• Two pressures that promote filtration are:
  • Blood hydrostatic pressure (BHP)
  • Interstitial fluid osmotic pressure.

VARIOUS TERMS USED IN CAPILLARY EXCHANGE

• Blood hydrostatic pressure (BHP): Blood hydrostatic pressure is the pressure, that water in blood plasma exerts against blood vessel walls. It is about 35 mmHg at the arterial end of a capillary, and about 16 mmHg at the capillary’s venous end, this pressure generated by the pumping action of the heart. BHP “pushes” fluid out of capillaries into interstitial fluid.
• Interstitial fluid hydrostatic pressure (IFHP): The opposing pressure of the interstitial fluid, called interstitial fluid hydrostatic pressure (IFHP), “pushes” fluid from interstitial spaces back into capillaries, IFHP is close to zero hence assumed 0 mmHg all along the capillaries.
• Blood colloid osmotic pressure (BCOP): It is a force caused by the colloidal suspension of the large proteins in plasma that averages 26 mmHg in most capillaries. The effect of BCOP is to “pull” fluid from interstitial spaces into capillaries.
• Interstitial fluid osmotic pressure (IFOP):Opposing BCOP is interstitial fluid osmotic pressure (IFOP), which “pulls” fluid out of capillaries into interstitial fluid. Normally, IFOP is very small 0.1–5 mmHg because only tiny amounts of protein are present in interstitial fluid.
• Net Filteration Pressure: The net filtration pressure is the pressure which determines the movement of fluid between capillaries and interstitial fluid.

STARLING’S LAW OF THE CAPILLARIES: 

• The volume of fluid and solutes reabsorbed normally is almost as large as the volume filtered. This near equilibrium is known as Starling’s law of the capillaries.
• Every day about 20 liters of fluid filter out of capillaries in tissues throughout the body. Of this fluid, 17 liters are reabsorbed and 3 liters enter lymphatic capillaries (excluding filtration during urine formation).

Effects of heat on Capillary Permiability

• Heat applied on body surface causes vasodilation and increase in blood flow to that area.
• Carries oxygen, nutrients, antibodies and leukocytes to that area aiding in the healing process.
• Relives pain, relaxes muscles, reduces tissue swelling and decreases joint swelling.
• Action of Pañcakarmaprocedures can be explained on the basis of capillary physiology.
• Any hot or warm aid applied to skin will cause capillary dilation. This phenomenon can be applied to Abhyaṅga– warm Sneha (fat) applied on the skin enters the dilated capillaries into the interstitial fluid.
• Applying heat in the form of Svedana– increased body temperature – vasodilation – increased blood flow through the area- necessary oxygen and nutrient supply to the cell and excretion of waste products.
• Water and fat soluble drugs administered through Basti can easily be absorbed through colon by simple or passive diffusion into capillaries.
• It has been approximately calculated as 22% of total dilatation of cerebral capillaries caused by the facial efferent stimulation will lead to 150% of total blood flow forcing more transfusion of Nasyamedicaments through olfactory pathway into brain tissue.