Upper Limb 2 Nerves, Vessels and Lymph Learning Objectives 1. Describe the anatomy of the brachial plexus from its origin in the neck to its terminal branches. 2. Describe the course of neurovascular structures lying in close relation to the bones and joints of the upper limb. Identify those that are at risk of injury and predict what the functional effects of such injury might be. 3. Describe the sensory innervation to the upper limb. 4. Describe the origin, course and distribution of the major arteries and their branches that supply the shoulder, arm, forearm and hand. Identify common sites of injury. Palpate pulse points. 5. Describe the course of the main veins of the upper limb. Identify the common sites of venous access and describe their key anatomical relations 6. Describe the anatomy of the axillary lymph nodes. Explain their importance in the lymphatic drainage of the breast and upper limb, and in the spread of tumours. NERVES- Upper Limb • Brachial plexus • Extensor compartment • Flexor compartment • Hand • Dermatome distribution/Sensory innervation Brachial Plexus Nerves to the upper limb originate at the levels C5 to T1. The exit the spine as roots, join together in communal fascial sheaths to form trunks, reorganise themselves at the axillary artery into an anterior and posterior division. The anterior division supplies the flexors in the anterior compartment of the upper limb, the posterior division supplies the extensors in the posterior compartment of the upper limb. The organisation of the nerves then changes into 3 cords- lateral, medial, posterior. The lateral and medial cords supply the anterior (flexor) compartment. The posterior cord supplies the posterior (extensor) compartment. The cords give rise to the named nerves supplying motor and sensory innervation. Anterior division- lateral and medial cords ARM The lateral and medial cords lie anterior to the axillary artery. The musculocutaneous, median and ulnar nerves come from these two cords and pass down through the anterior compartment of the arm to supply the flexors NECK Posterior division- posterior cord ARM The posterior cord sits posterior to the axillary artery. The radial and axillary nerves come from this cord and pass down through the posterior compartment of the arm to supply the extensors NECK Upper Limb Dermatomes Lateral Shoulder (Regimental Badge) Radial forearm, thumb, forefinger Medial forearm, middle finger Ulnar forearm, little and ring fingers Medial arm Axilla (deodorant) C5 C6 C7 C8 T1 T2 Flexion of the arm- Musculocutaneous nerve All motor and sensory functions in the flexor compartment of the arm are supplied by the musculocutaneous nerve. The nerve passes with the brachial artery in a fascial plane that lies between brachialis and biceps brachii, sending off branches superior and inferior to innervate the muscles either side of it. Muscles involved in flexion of the arm are biceps brachii, brachialis, corocobrachialis. Dermatome is C5/6 Arm with biceps brachii cut and reflected showing: NCB- nerve to corocobrachialis NBB- nerve to biceps brachii NB- nerve to brachialis LCNF- lateral cutaneous nerve to the forearm MN- median nerve Flexion of the wrist and hand - Ulna nerve The ulna nerve passes straight through the arm to innervate the flexors of the forearm and medial hand. The ulna nerve passes medial to the medial epicondyle (‘funny bone’) supplying flexor carpi ulnaris, and the medial part of the muscle bulk of flexor digitorum profundus. It passes into the hand through Guyons canal under the hook of the hamate to innervate the medial two fingers and most of the intrinsic muscles of the hand. Damage gives rise the distinctive ‘ulnar claw’. Dermatome is C8, T1 Ulnar claw Ulnar nerve supply involved in ‘hitting your funny bone’ Flexion of the wrist and hand- Median nerve The median nerve passes through the centre of the cubital fossa to supply the superficial flexors of the wrist and fingers. It passes into the hand under the flexor retinaculum in the carpal tunnel. 80% of the nerve fibres are sensory nerves carrying information from the palm, thumb, index, middle and lateral half of the ring finger back to the brain. It can be compressed at the wrist ‘carpal tunnel syndrome’. Dermatomes C6/7 Median nerve To Hand To Head Cubital fossa showing median nerve with brachial artery Ulnar and radial sensory distribution Extensors- Axillary nerve The axillary nerve passes from the posterior division of the brachial plexus behind the humerus to supply deltoid and teres minor muscles. The area immediately over the deltoid known as the ‘regimental badge’ is used to test for sensory muscle damage in a shoulder dislocation. Dermatome C5/6 Extensors- Radial nerve The radial nerve comes off the posterior division of the brachial plexus to pass behind the humerus and curves around it in the ‘spiral groove’- a distinct groove visible on the humeral bone. It supplies triceps in the arm, and the extensors of the forearm. It passes through the cubital fossa lateral to the median nerve and passes into the extensor compartment of the forearm. It supplies sensory information from the entire posterior of the arm and the lateral part of the dorsum of the hand. Dermatome C5/6/7/8/T1 Sensory distribution in the hand Red- ulnar Yellow- median Blue- radial Nerve Dance https://www.youtube.com/watch?v=ZXLhwF2ptl0 (fun version) Upper Limb Myotomes Abduct the Shoulder Adduct the Shoulder Flex the Arm Extend the Arm C5 C6,7,8 C5,6 C7,8 Supinate Pronate Flex and Extend the Wrist Flex and Extend the Fingers C5,6 C7,8 C6,7 C7,8 Vessels ArteriesSubclavian, Scapular branches, Axillary, Brachial, Radial, Ulnar VeinsCephalic, Basilic, Median cubital, Subclavian Subclavian artery and scapular blood supply The left subclavian artery comes directly off the arch of the aorta. On the right hand side the brachiocephalic artery comes off the arch of the aorta, giving rise to the right carotid artery and the right subclavian artery. The first vessel to come off the subclavian is the internal thoracic (mammary) artery. This descends along the chest wall to supply the anterior portion of the ribcage and the mammary gland. The scapula is supplied the via the thyrocervical trunk, with the suprascapular branch passing posteriorly through the suprascapular notch to supply supraspinatus and infraspinatus muscles, and the artery to subscapularis passing anterior. These blood vessels anastamose (join up) to form a circuit around the scapula Thyrocervical trunk Brachiocephalic artery Internal thoracic (mammary) artery Right subclavian artery Blood supply to the scapula Axillary artery The axillary artery is a continuation of the subclavian artery. It starts at the lateral border of the first rib and ends at the lower border of teres major where it becomes the brachial artery. It gives rise to branches supplying the acromion, the shoulder joint capsule and the circumflex humeral artery which wraps around the neck of the humerus. Circumflex humeral artery Right axillary artery Brachial artery The brachial artery is a continuation of the axillary artery. It begins at the lower border of teres major and is the main blood supply to the anterior (flexor) compartment of the arm. The profunda brachii artery passes posteriorly into the extensor compartment of the arm to supply triceps Radial and Ulnar arteries At the elbow the brachial artery divides into the radial artery which follows the radial bone, and the ulnar artery which follows the ulna bone. The radial pulse is felt at the wrist before the artery passes posterior to the thumb on the dorsum of the hand to pass back through into the palm of the hand between the muscles in the first webspace between the thumb and the forefinger to form the deep palmar arch. The ulna artery passes directly into the hand underneath the bony hook of the hamate carpal bone. This forms the superficial palmar arch. The deep and superficial palmar arches anastomose to form a circuit in the hand. Pulse point Radial Deep palmar arch Ulnar Superficial palmar arch Pulse taking exercise https://www.youtube.com/watch?v=yP672n9U1Ew Work with a partner to find a pulse at Axilla Brachial Cubital Radial Ulna https://www.youtube.com/watch?v=0BSv4iN8T2E Work with a partner to perform Allens test Subclavian vein The left and right subclavian veins drain into the brachiocephalic trunks on each side. The brachiocephalic veins both drain into the superior vena cava which drains into the right atrium of the heart. The subclavian veins become the brachiocephalic veins at the point where the jugular vein joins, draining the head. The vein sits superior to the subclavian artery, travelling in the same fascial sheath. It is often used for inserting a ‘central line’ a cannula that is inserted into the subclavian vein that then travels through the brachiocephalic trunk and into the right atrium. This line is used to deliver large quantities of fluid and/or drugs directly into the circulatory system. Positioning of a central line inserted into the right subclavian vein Cephalic and Basilic veins The cephalic and basilica veins drain the arm. The basilic vein drains into the brachial vein. The cephalic vein travels in a groove formed between the deltoid and pectoralis major muscles called the deltopectoral groove. It drains directly into the subclavian vein just inferior to the clavicle. The median cubital vein runs between them at the elbow and is an often used site for drawing blood. The venous return in the hand is found on the dorsum. This is because veins are easily compressed and so they would not function on the palm of the hand, particularly in 4 footed animals. LYMPH The lymph nodes in the axilla drain the arm and most of the breast. They travel with the blood vessels and drain particular parts of the breast. For this reason they are key in the diagnosis and treatment of breast cancer. In the early stages of a tumour in the breast the lymph node draining that area will become enlarged, but the rest of the lymph will remain normal. The affected node is called a ‘sentinel’ node. Radioactive dye is injected into the lump which will track back to the sentinel node. Both the cancerous lump and the associated lymph node can be removed without the necessity for a mastectomy. This appreciation of the anatomy of the lymph draining the breast has revolutionised the care of breast cancer which has the highest incidence of any cancer, affecting 1 in 8 women in the UK. Learning Objectives Nerves: Describe the anatomy of the brachial plexus from its origin in the neck to its terminal branches. Describe the course of neurovascular structures lying in close relation to the bones and joints of the upper limb. Identify those that are at risk of injury and predict what the functional effects of such injury might be. Describe the sensory innervation to the upper limb. Vasculature: Arteries- Describe the origin, course and distribution of the major arteries and their branches that supply the shoulder, arm, forearm and hand. Identify common sites of injury and pulse points. Veins- Describe the course of the main veins of the upper limb. Identify the common sites of venous access and describe their key anatomical relations Lymph: Describe the anatomy of the axillary lymph nodes and explain their importance in the lymphatic drainage of the breast and upper limb, and in the spread of tumours.