anatomy
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arterysupplyofupperlimb.pptxARTERIAL SUPPLY
OF UPPER LIMB
The arterial supply to the upper limb begins in the chest as the subclavian artery. The right subclavian artery arises from the brachiocephalic trunk, while the left subclavian branches directly off the arch of aorta.
When the subclavian arteries cross the lateral edge of the 1st rib, they enter the axilla, and are called axillary arteries.
IN THE AXILLA
The axillary artery passes through the axilla, just underneath the pectoralis minor muscle, enclosed in the axillary sheath.
At the level of the humeral surgical neck, the posterior and anterior circumflex humeral arteries arise. They circle posteriorly around the humerus to supply the shoulder region. The largest branch of the axillary artery also arises here – the subscapular artery.
The axillary artery becomes the brachial artery at the level of the teres major muscle.
Anteriorly
(i) Skin.
(ii) Superficial fascia
(iii) Deep fascia.
(iv) Clavicular part of the pectoralis major.
(v) Clavipectoral fascia with cephalic vein, lateral pectoral nerve, and thoracoacromial vessels.
Posteriorly
(i) First intercostal space with the external intercostal muscle.
(ii) First and second digitations of the serratus anterior with the nerve to serratus anterior.
(iii) Medial cord of brachial plexus with its medial pectoral
branch
laterally
Lateral and posterior cords of the brachial plexus.
Medially
Axillary vein
The first part of the axillary artery is enclosed (together with the brachial plexus) in the axillary sheath, derived from the prevertebral layer of deep cervical fascia.
Anteriorly
(i) Skin.
(ii) Superficial fascia.
(iii) Deep fascia.
(iv) Pectoralis major.
(v) Pectoralis minor
Posteriorly
(i) Posterior cord of brachial plexus.
(ii) subscapularis
Medially
(i) Medial cord of brachial plexus,
(ii) Medial pectoral nerve,
(iii) Axillary vein.
Laterally
Lateral cord of brachial plexus.
Anteriorly
(i) Skin.
(ii) Superficial fascia,
(iii) Deep fascia.
(iv) In the upper part there are the pectoralis major and medial root of the median nerve.
Posteriorly
(i) Radial nerve.
(ii) Axillary nerve in the upper part,
(iii) Subscapularis in the upper part,
(iv) Tendons of the latissimus dorsi and the teres major in the lower part.
Laterally
Coracobrachialis.
Musculocutaneous nerve in the upper part,
Lateral root of median nerve in the upper part,
Trunk of median nerve in the lower part.
Medially
(i) Axillary vein,
(ii) Medial cutaneous nerve of the forearm and ulnar nerve
(iii) Medial cutaneous nerve of arm
1st part:
Superior Thoracic artery
2nd part:
Acromiothoracic artery
Lateral Thoracic artery
3rd part:
Subscapular artery
Ant circumflex humeral artery
Post circumflex humeral artery
CLINICAL RELEVANCE: AXILLARY ARTERY ANEURYSM
An aneurysm is dilation of a blood vessel to more than twice its original size. Although rare, axillary artery aneurysms can occur as a result of atherosclerosis, thoracic outlet syndrome, or trauma.
The dilated portion of the axillary artery can compress the brachial plexus, producing neurological symptoms such as paraesthesia and muscle weakness.
The definitive treatment of an axillary artery aneurysm is surgical, and involves removing the aneurysm and reconstructing the vessel wall using a graft.
IN THE UPPER ARM
When the axillary artery reaches the lower border of the teres major, it becomes the brachial artery. The brachial artery is the main source of blood for the arm.
Immediately distal to the teres major, the brachial artery gives rise to the profunda brachii – the deep artery of the arm. It travels along the posterior surface of the humerus, running in the radial groove. It supplies structures in the posterior aspect of the arm (e.g the triceps brachii, and terminates by contributing to a network of vessels at the elbow joint.
The brachial artery descends down the arm immediately posterior to the median nerve. As it crosses the cubital fossa, underneath the brachialis muscle, the brachial artery terminates by bifurcating into the radial and ulnar arteries.
CLINICAL RELEVANCE: OCCLUSION OR LACERATION OF THE BRACHIAL ARTERY
The arm has relatively good anastomotic supply which protects it from temporary or partial occlusion of the brachial artery. However, if the artery is completely blocked, or severed, it is a medical emergency.
The resulting ischaemia of the forearm can cause necrosis and paralysis of the muscles in the forearm. The affected muscles are replaced to some degree by scar tissue, and shorten considerably. This can cause a characteristic flexion deformity, caused Volkmann’s contracture.
IN THE FOREARM
In the distal region of the cubital fossa, the brachial artery bifurcates into the radial artery and the ulnar artery. The radial artery supplies the posterior aspect of the forearm and the ulnar artery supplies the anterior aspect. The two arteries anastomose in the hand, by forming two arches, the superficial palmar arch, and the deep palmar arch.
IN THE HAND
The hand has a very good blood supply, with many anastomosing arteries, allowing the hand to be perfused when grasping or applying pressure. A good majority of these arteries are superficial, allowing for heat loss when needed. In the hand, the ulnar and radial arteries interconnect to form two arches, from which branches to the digits emerge.
Radial artery – contributes mainly to supply of the thumb and the lateral side of the index finger
Ulnar artery – contributes mainly to the supply of the rest of the digits, and the medial side of the index finger
The ulnar artery moves into the hand anteriorly to the flexor retinaculum, and laterally to the ulnar nerve. In the hand, it divides into two branches, the superficial palmar arch, and the deep palmar branch.
From the superficial palmar arch, common palmar digital arteries arise, supplying the digits. The superficial palmar arch then anastamoses with a branch of the radial artery. The superficial palmar arch is found anteriorly to the flexor tendons in the hand, deep to the palmar aponeurosis.
The radial artery enters the hand dorsally, crossing the floor of the anatomical snuffbox. It turns medially and moves between the heads of the adductor pollicis. The radial artery then anastamoses with the deep palmar branch of the ulnar artery, forming the deep palmar arch, which gives rise to five arteries supplying the digits.
Arterial supply to the hand, via the superficial and deep palmar arches
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VENOUS DRAINAGE OF UPPER LIMB
The venous system of the upper limb drains deoxygenated blood from the arm, forearm and hand. It can anatomically be divided into the superficial veins and the deep veins.
DORSAL VENOUS ARCH
Location- dorsum of hand.
Afferents-
3 dorsal metacarpal veins.
1 dorsal digital vein medial side of little finger.
1 dorsal digital vein lateral side of index finger.
2 dorsal digital vein of thumb.
Efferents-
Cephalic vein.
Basilic vein.
SUPERFICIAL VEINS
The major superficial veins of the upper limb are the cephalic and basilic veins. As their name suggests, they are located within the subcutaneous tissue of the upper limb.
The basilic vein originates from the dorsal venous network of the hand. It ascends the medial aspect of the upper limb. At the border of the teres major, the vein moves deep into the arm. Here, it combines with the brachial veins to form the axillary vein.
The cephalic vein arises from the dorsal venous network of the hand. It ascends the antero-lateral aspect of the upper limb, passing anteriorly at the elbow.
At the shoulder, the cephalic vein travels between the deltoid and pectoralis major muscles (known as the deltopectoral groove), and enters the axilla region via the clavipectoral triangle. Within the axilla, the cephalic vein terminates by joining the axillary vein.
At the elbow, the cephalic and basilic veins are connected by the median cubital vein.
DEEP VEINS
The deep veins of the upper limb are situated underneath the deep fascia.
They are paired veins that accompany and lie either side of an artery. The brachial veins are the largest in size, and are situated either side of the brachial artery. The pulsations of the brachial artery assists the venous return. Veins that are structured in this way are known as vena comitantes.
Perforating veins run between the deep and superficial veins of the upper limb, connecting the two systems.
CLINICAL RELEVANCE:
VENEPUNCTURE is the practice of obtaining intravenous access. This is usually for the purpose of providing intravenous therapy (e.g. fluids, medications) or for obtaining a blood sample.
The median cubital vein is a common site of venepuncture. It is a superficial vein that is located anteriorly to the cubital fossa region. It is thought to be fixed in place by perforating veins, which arise from the deep venous system and pierce the bicipital aponeurosis.
Its ease of access, fixed position and superficial position make the median cubital vein a good site for venepuncture in many individuals.
The lymphatic system functions to drain tissue fluid, plasma proteins and other cellular debris back into the blood stream, and is also involved in immune defence. Once this collection of substances enters the lymphatic vessels it is known as lymph; lymph is subsequently filtered by lymph nodes and directed into the venous system.
LYMPHATIC VESSELS
SUPERFICIAL LYMPHATIC VESSELS
The superficial lymphatic vessels of the upper limb initially arise from lymphatic plexuses in the skin of the hand, They then ascend up the arm, in close proximity to the major superficial veins:
The vessels shadowing the basilic vein go on to enter the cubital lymph nodes. These are found medially to the vein, and proximally to the medial epicondyle of the humerus. Vessels carrying on from these nodes then continue up the arm, terminating in the lateral axillary lymph nodes.
The vessels shadowing the cephalic vein generally cross the proximal part of the arm and shoulder to enter the apical axillary lymph nodes, though some exceptions instead enter the more superficial deltopectoral lymph nodes.
DEEP LYMPHATIC VESSELS
The deep lymphatic vessels of the upper limb follow the major deep veins (i.e. radial, ulnar and brachial veins), terminating in the humeral axillary lymph nodes. They function to drain lymph from joint capsules, periosteum, tendons and muscles. Some additional lymph nodes may be found along the ascending path of the deep vessels.
LYMPH NODES
The majority of the upper lymph nodes are located in the axilla. They can be divided anatomically into 5 groups:
Pectoral (anterior) – 3-5 nodes, located in the medial wall of the axilla. They receive lymph primarily from the anterior thoracic wall, including most of the breast.
Subscapular (posterior) – 6-7 nodes, located along the posterior axillary fold and subscapular blood vessels. They receive lymph from the posterior thoracic wall and scapular region.
Humeral (lateral) – 4-6 nodes, located in the lateral wall of the axilla, posterior to the axillary vein. They receive the majority of lymph drained from the upper limb.
Central – 3-4 large nodes, located near the base of the axilla (deep to pectoralis minor, close to the 2nd part of the axillary artery). They receive lymph via efferent vessels from the pectoral, subscapular and humeral axillary lymph node groups.
Apical – Located in the apex of the axilla, close to the axillary vein and 1st part of the axillary artery. They receive lymph from efferent vessels of the central axillary lymph nodes, therefore from all axillary lymph node groups. The apical axillary nodes also receive lymph from those lymphatic vessels accompanying the cephalic vein.
Efferent vessels from the apical axillary nodes travel through the cervico-axillary canal, before converging to form the subclavian lymphatic trunk. The right subclavian trunk continues to form the right lymphatic duct, and enters the right venous angle (junction of internal jugular and subclavian veins) directly. The left subclavian trunk drains directly into the thoracic duct.
CLINICAL RELEVANCE
ENLARGEMENT OF AXILLARY LYMPH NODES
Enlargement of these lymph nodes can have a number of either infectious or malignant causes:
Infection of the upper limb, resulting in lymphangitis (inflammation of lymphatic vessels, with tender, enlarged lymph nodes). The humeral group of lymph nodes is usually affected first, and red, warm and tender streaks are visible in the skin of the upper limb.
Infections of the pectoral region and breast.
Metastasis of breast cancers.
AXILLARY LYMPH NODE DISSECTION
Removal and analysis of the axillary lymph nodes is often a vital tool for the staging of breast cancers. Interruption of lymphatic drainage from the upper limb can however result in lymphoedema, a condition whereby accumulated lymph in the subcutaneous tissue leads to painful swelling of the upper limb.
During this procedure there is also a risk of damage to either of the long thoracic nerve (potentially causing a winged scapula deformity), or the thoracodorsal nerve.
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BRACHIAL PLEXUS
The nerves entering the upper limb
provide the following important functions:
Sensory innervation to skin & deep structures (e.g. joints)
Motor innervation to the muscles
Influence over the diameters of the blood vessels by the sympathetic vasomotor nerves
Sympathetic secretomotor supply to the sweat glands.
At the root of the neck, the nerves form
Brachial plexus
Nerve fibers derived from different segments of the spinal cord arranged and distributed efficiently in various parts of the upper limb.
Most nerves in the upper limb arise from the brachial plexus, a major nerve network supplying the upper limb; it begins in the neck and extends into the axilla.
Almost
all branches
of the brachial plexus
arise in the axilla
(after the plexus
has crossed the 1st rib).
The brachial plexus is formed by:
union of the anterior rami of the
last 4 cervical (C5-C8) & first thoracic (T1) nerves
which constitute the roots of the brachial plexus.
Originates in the neck, passes laterally and inferiorly over rib I, and enters the axilla.
The parts of the brachial plexus, from medial to lateral, are roots, trunks, divisions, and cords.
All major nerves that innervate the upper limb originate from the brachial plexus, mostly from the cords.
The brachial plexus is a network of nerve fibres that supplies the skin and musculature of the upper limb. It begins in the root of the neck, passes through the axilla, and enters the upper arm.
The brachial plexus is divided into five parts; roots, trunks, divisions, cords and branches (a good mnemonic for this is Read That Damn Cadaver Book). There are no functional differences between these divisions – they are simply used to aid explanation of the brachial plexus.
ROOTS
The ‘roots’ refer the beginning of the brachial plexus. They are formed by the spinal nerves C5, C6, C7, C8 and T1.
At each vertebral level, paired spinal nerves arise. They leave the spinal cord via the intervertebral foramina of the vertebral column.
Each nerve then divides into anterior and posterior nerve fibres. The roots of the brachial plexus are formed by the ant divisions of spinal nerves C5-T1
After their formation, these nerves pass between the ant and med scalene muscles to enter the base of the neck.
TRUNKS
At the base of the neck, the roots of the brachial plexus converge, forming three trunks. These structures are named by their anatomical position:
Superior trunk: A combination of C5 and C6 roots.
Middle trunk: A continuation of C7.
Inferior trunk: A combination of C8 and T1 roots.
The trunks begin to move laterally, crossing the posterior triangle of the neck.
DIVISIONS
Within the posterior triangle of the neck, each trunk divides into two branches. One division travels anteriorly (toward the front of the body) and the other posteriorly (towards the back of the body). Thus, they are known as the anterior and posterior divisions.
We now have three anterior and three posterior nerve fibres. These divisions leave the posterior triangle and pass into the axilla region. They recombine in the next part of the brachial plexus.
The lateral cord is formed by:
The anterior division of the superior trunk
The anterior division of the middle trunk
The posterior cord is formed by:
The posterior division of the superior trunk
The posterior division of the middle trunk
The posterior division of the inferior trunk
The medial cord is formed by:
The anterior division of the inferior trunk.
The cords give rise to the major branches of the brachial plexus.
CORDS
Once the anterior and posterior divisions have entered the axilla, they combine together to form three nerves. These nerves are named by their position relative to the axillary artery.
MAJOR BRANCHES
In the axilla and the proximal aspect of the upper limb, the three cords give rise to five major branches. These nerves continue into the upper limb to provide innervation to the muscles and skin present. In this section, we shall concentrate on these five nerves.
Musculocutaneous Nerve
Roots: C5, C6, C7.
Motor Functions: Innervates the brachialis, biceps brachii and coracobrachialis muscles.
Sensory Functions: Gives off the lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm, and a small lateral portion of the posterior forearm.
Axillary Nerve
Roots: C5 and C6.
Motor Functions: Innervates the teres minor and deltoid muscles.
Sensory Functions: Gives off the superior lateral cutaneous nerve of arm, which innervates the inferior region of the deltoid (“regimental badge area”).
Median Nerve
Roots: C6 – T1. (Also contains fibres from C5 in some individuals).
Motor Functions: Innervates most of the flexor muscles in the forearm, the thenar muscles, and the two lateral lumbricals that move the index and middle fingers.
Sensory Functions: Gives off the palmar cutaneous branch, which innervates the lateral part of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.
Radial Nerve
Roots: C5-C8 and T1.
Motor Functions: Innervates the triceps brachii, and the extensor muscles in the posterior compartment of the forearm.
Sensory Functions: Innervates the posterior aspect of the arm and forearm, and the posterior, lateral aspect of the hand.
Ulnar Nerve
Roots: C8 and T1.
Motor Functions: Innervates the muscles of the hand (apart from the thenar muscles and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum profundus.
Sensory Functions: Innervates the anterior and posterior surfaces of the medial one and half fingers, and associated palm area.
| Roots | Trunks | Lateral cord | Medial cord | Posterior cord |
| Dorsal scapular nerve Long thoracic nerve | Suprascapular nerve Nerve to subclavius | Lateral pectoral nerve | Medial pectoral nerve Medial cutaneous nerve of arm Medial cutaneous nerve of forearm | Superior subscapular nerve Thoracodorsal nerve Inferior subscapular nerve |
MINOR BRANCHES
In addition to the five major branches of the brachial plexus, there are a number of smaller nerves that arise. They do so from all five parts of the brachial plexus, and are listed below:
Clinical Relevance: Injury to the Brachial Plexus
An intact brachial plexus is vital for the normal function of the upper limb. There are two major types of injuries that can affect the brachial plexus. An upper brachial plexus injury affects the superior roots, and a lower brachial plexus injury affects the inferior roots.
Upper Brachial Plexus Injury – Erb’s Palsy
Erb’s palsy commonly occurs where there is excessive increase in the angle between the neck and shoulder – this stretches (or can even tear) the nerve roots, causing damage. It can occur as a result of a difficult birth or shoulder trauma.
The waiters’ tip position, characteristic of Erb’s palsy.
Nerves affected: Nerves derived from solely C5 or C6 roots; musculocutaneous, axillary, suprascapular and nerve to subclavius.
MUSCLES PARALYSED: Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor.
MOTOR FUNCTIONS: The following movements are lost or greatly weakened – abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder.
SENSORY FUNCTIONS: Loss of sensation down lateral side of arm, which covers the sensory innervation of the axillary and musculocutaneous nerves.
The affected limb hangs limply, medially rotated by the unopposed action of pectoralis major. The forearm is pronated due to the loss of biceps brachii. This is position is known as ‘waiter’s tip’, and is characteristic of Erb’s palsy.
LOWER BRACHIAL PLEXUS INJURY – KLUMPKE PALSY
A lower brachial plexus injury results from excessive abduction of the arm (e.g person catching a branch as they fall from a tree). It has a much lower incidence than Erb’s palsy.
Nerves affected: Nerves derived from the T1 root – ulna and median nerves.
Muscles paralysed: All the small muscles of the hand (the flexors muscles in the forearm are supplied by the ulna and median nerves, but are innervated by different roots).
Sensory functions: Loss of sensation along medial side of arm.
The metacarpophalangeal joints are hyperextended, and the interphalangeal joints are flexed. This gives the hand a clawed appearance.
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