Combined Handbook 24-25 PDF

Module 1 – Unit 1.1 Superficial Dissection of the Upper Limb Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Complete the basic medical history she...

Module 1 – Unit 1.1 Superficial Dissection of the Upper Limb Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Complete the basic medical history sheet. 2. Identify the bones of the upper limb and their named parts on the skeleton. 3. Understand the innervation of the skin and the concept of dermatomes. 4. Understand the difference between superficial and deep fascia. 5. Describe the superficial veins of the upper limb. 8. Understand the clinical applications associated with the skin and superficial veins. 1 Summary 1. The bony landmarks of the upper limb are important points of attachment for muscles and tendons. They are important in the diagnosis of many musculoskeletal disorders. 2. The joints of the upper limb articulate to permit placing of the hand in a variety of positions in relation to the trunk. 3. The superficial veins in the upper limb arise from the dorsal venous arch of the hand. This arch forms two main veins: the cephalic and basilic veins. The median cubital vein connects these two veins at the cubital fossa, but variations are common. 4. The cephalic vein runs proximally towards the shoulder where it lies in the deltopectoral groove. It then pierces the clavipectoral fascia to join the axillary vein. The basilic vein pierces the deep fascia in mid-arm and joins the of the brachial artery to form the axillary vein. 5. The cutaneous (sensory) nerves are branches of the main nerves in the limb. 6. Deep to the skin, the muscles and other structures are enveloped in a layer of deep fascia. From this layer, intermuscular septa extend towards the bones, dividing the arm and forearm into anterior and posterior compartments. Donor Medical History and Cause of Death You should regard your donor as the first patient you will encounter in your medical education. As dissection progresses during the year, record anatomical variations, previous surgical procedures, and other pathology on the dissection findings sheets provided. Remember to do this for each dissection session. At the end of each module, write up a summary of the findings for that region. By the end of Lent Term, you should be in a position to determine a possible cause of death and any contributing pathological conditions. At the beginning of Easter Term, Prof Stephen Barclay, University Senior Lecturer in Palliative Care, will explain how doctors complete the Medical Certificate of the Cause of Death. He will also describe the different trajectories to death that people undergo, and the key aspects of the care we provide for people as they approach the end of their lives. You will then be told the cause of death that was officially recorded for your donor, as well as any known medical history. You will have the opportunity to have discussions in your table groups about this important topic. 2 Self-Directed Learning 1. Read: Bones of the upper limb 2. Read: Skin of upper limb 3. Read: Dermatomes of upper limb 4. Now study the following summary notes and diagrams: FIG.1 Skin Incisions A and B indicate the planes of transverse sections for FIG.2. FIG.2 Muscle Compartments (Transverse sections) Mid-arm (at A) Mid-forearm (at B) Key: h = humerus; r = radius; u = ulna; F = flexor & E = extensor compartments 1 = deep fascia; 2 = medial intermuscular septum; 3 = lateral intermuscular septum of arm 4 = lateral intermuscular septum of forearm; 5 = interosseous membrane 3 SKIN The skin is the largest organ in the body, comprising 16% of the body weight and with a surface area of around 1.8m2. It forms a barrier between body tissues and the environment, providing protection, thermoregulation and sensation. The skin consists of the epidermis and dermis. Although structurally consistent throughout the body, skin varies in thickness according to site and age. The epidermis is a physical and chemical barrier between the body and the exterior, while the dermis provides structural support. Deep to the dermis is a layer of loose connective tissue which is an important deposit of fat. You will study the cellular structure of the skin and it derivatives in histology. Innervation The area of dermis supplied by an individual spinal nerve is known as a dermatome. Knowledge of the dermatomes is important in order to diagnose problems associated with nerve-related disorders, peripheral nerve or spinal injuries, and to administer local anaesthesia. The nerves to the upper limb originate from five spinal root levels, extending from the 5th cervical (C5) to the 1st thoracic spinal nerves (T1). They form a network known as the brachial plexus, from which peripheral nerves emerge. This is described in detail in Unit 1.4. FIG.6 Dermatomes of the Upper Limb Key: AL = axial lines An axial line is the line of junction of two dermatomes supplied from discontinuous spinal cord levels. C = cervical spinal segment T = thoracic spinal segment FASCIA 5. Read: Fascia of arm Superficial Fascia This is composed of loose connective tissue and subcutaneous fat. Naturally thicker in women than in men, this is the layer which is built up when weight is gained. It exists in all areas but the fat is absent in some areas, notably the eyelids, scrotum and penis. It is not homogeneous as it may be differentiated into layers by fibrous tissue, as in the anterior abdominal wall where a fatty layer (Camper’s fascia) and a membranous layer (Scarpa’s fascia) exist. Deep Fascia 4 The deep or investing fascial layer is composed of collagen fibres, often arranged to respond to lines of stress. Over the limbs it can be seen as a tough white sheet of fibrous tissue which forms a non-elastic tight-fitting sleeve. This keeps underlying structures in position, and also assists venous and lymphatic return. Fascial processes extend downwards from the sleeve forming septa which in the case of limbs mark out a series of compartments containing separate muscle groups and bundles of vessels and nerves. Fascial compartments offer the benefit of limiting the spread of infection. SUPERFICIAL VEINS OF THE UPPER LIMB 6. Read: Veins of the upper limb 7. Read: Pectoral region and axilla 8. Read: Vessels of the dorsum of hand There are two main superficial veins in the upper limb: the cephalic and basilic veins. They form from an arch of veins on the dorsum of the hand, the dorsal venous arch, which receives blood from the fingers and hand. The cephalic vein begins on the lateral (radial) aspect of the hand, crosses the anatomical snuffbox and runs up the lateral aspect of the forearm and arm to lie in the deltopectoral groove (FIG.8). This vein is important for intravenous cannulation and venous access at the wrist and distal forearm because of its size and fairly constant position. It pierces the clavipectoral fascia to join the axillary vein. The basilic vein begins on the medial (ulnar) aspect of the wrist and runs up the forearm on the medial aspect of the cubital fossa. About midway between the elbow and shoulder, it pierces the deep fascia and joins the venae comitantes (accompanying veins) of the brachial artery to form the axillary vein. In the cubital fossa there is usually a connection between the cephalic and basilic veins, the median cubital vein. Many other communications may exist, with many variations. FIG.7 Superficial Veins of the Upper Limb Key: 1 = cephalic vein 2 = basilic vein 5  3 = median cubital vein 4 = dorsal venous arch FIG.8 The Deltopectoral Groove Key: C = clavicle; V = cephalic vein; Cp = clavipectoral space; Dp = deltopectoral groove Muscles: D = deltoid; P = pectoralis major B = biceps brachii 6 Clinical Applications Study the following clinical applications notes: 1) Langer’s lines Langer’s lines, also known as tension or cleavage lines, follow the orientation of collagen fibres in the dermis. They are of special interest to surgeons, as incisions made parallel to these lines heal more rapidly and produce neater scars. 2) Venepuncture and venous cannulation The median cubital vein is often used for venepuncture to take blood for diagnostic purposes. The cephalic vein in the forearm is a good vein for successful insertion of a cannula, as it is fairly large and has a constant position. 7  Module 1 – Unit 1.2 Compartments of the Arm Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Describe the landmarks and regions of the arm. 2. Understand the attachments and functions of the muscles of the anterior compartment. 3. Describe the boundaries and contents of the cubital fossa. 4. Describe the course and branches of the brachial artery. 5. Describe the course of the musculocutaneous, median, ulnar and radial nerves in the arm. 6. Understand the attachments and functions of the muscle in the posterior compartment. 7. Understand some common clinical applications associated with the arm. 8 Summary 1. The arm is the segment of the upper limb that lies between the shoulder and elbow joints. 2. The arm is divided into anterior and posterior muscular compartments by the medial and lateral intermuscular septa derived from the deep fascia, which merges with the periosteum of the humerus. 3. The anterior compartment contains three muscles which are supplied by the musculo- cutaneous nerve: biceps brachii, brachialis and coracobrachialis. 4. Biceps brachii has two heads: long and short, arising from the supraglenoid tubercle of the scapula and coracoid process respectively. They insert via a common tendon onto the radial tuberosity, and via an aponeurosis onto the deep fascia and the ulna. The most important actions of biceps brachii are supination of the forearm and elbow flexion. 5. Brachialis arises from the humeral shaft and inserts into the coronoid process of the ulna. It is the main elbow flexor. Coracobrachialis arises from the coracoid process of the scapula and inserts onto the humerus. It is an adductor and weak flexor of the glenohumeral joint. 6. Other structures in the anterior compartment include the median nerve and the brachial artery with its venae comitantes. On the medial aspect of the compartment are the ulnar nerve and medial cutaneous nerves of the arm and forearm. 7. The posterior compartment contains the triceps brachii muscle, which is supplied by branches of the radial nerve. 8. Triceps brachii has three heads: long, medial and lateral heads. Their common tendon is attached to the posterosuperior aspect of the olecranon. It extends the elbow. 9. Other structures in the posterior compartment include the radial nerve and the profunda brachii artery which run in the spiral groove of the humerus between the medial and lateral heads of triceps brachii. 9 Self-Directed Learning ANTERIOR COMPARTMENT OF THE ARM 1. Read Upper Limb Regions Landmarks (Introduction) followed by Anterior Regions (Introduction) on the same page. MUSCLES (all supplied by the musculocutaneous nerve) 2. Read anterior compartment of the arm. 3. Read arm flexor compartment muscles. 4. Now study the following summary notes: i) Coracobrachialis This muscle originates from the coracoid process and inserts midway down the humerus on its medial aspect. It adducts the shoulder, enabling one to hold items under the arm. It is also a weak flexor of the shoulder joint. ii) Biceps brachii This muscle extends from the scapula to the radius, crossing both shoulder and elbow joints. The long head has a tendinous origin from the supraglenoid tubercle of the scapula within the cavity of the shoulder joint. It emerges in a sleeve of synovial tissue in the intertubercular (bicipital) groove of the humerus. The short head arises from the coracoid process, and joins the long head to form the belly of the muscle about midway down the arm. It inserts by a common tendon into the radial (bicipital) tuberosity. A fascial band, the bicipital aponeurosis, extends from the medial side of the tendon into the deep fascia of the medial forearm and onto the subcutaneous border of the ulna. The aponeurosis protects the underlying nerves and vessels, and helps biceps to flex the elbow more effectively. Biceps brachii is primarily a supinator of the forearm when the elbow is flexed, acting by pulling the radial tuberosity forwards. When the forearm is supinated, biceps is an important elbow flexor. At the shoulder joint, it acts to stabilise the humeral head within the glenoid and is a weak flexor. When dissecting, note that the musculocutaneous nerve passes deep to biceps and superficial to brachialis. Note also that the brachial artery and median nerve lie in a groove along the medial border of biceps. At the cubital fossa, the basilic vein and medial cutaneous nerve of the forearm are superficial to the bicipital aponeurosis, while the brachial artery and median nerve lie deep to it. iii) Brachialis This muscle lies deep to biceps, arising from the distal half of the anterior humeral shaft and the medial intermuscular septum. It converges distally to form a strong tendon that inserts into the coronoid process of the ulna. It is the main flexor of the elbow. CUBITAL FOSSA 5. Read cubital fossa roof. 6. Read cubital fossa contents and floor. 7. Now study the following summary notes and diagram: The cubital fossa is a triangular area anterior to the elbow. The base of the triangle is an imaginary line joining the two humeral epicondyles. Its sides are formed by pronator teres and brachioradialis and its apex is distal. The roof is the deep fascia of the forearm, and the floor is formed by brachialis and supinator. 10  FIG.1 The Cubital Fossa Key: 1 = biceps brachii 2 = pronator teres 3 = brachioradialis T = biceps tendon Ap = aponeurosis A = brachial artery N = median nerve R = radial nerve NERVES, ARTERIES AND VEINS All the nerves to the upper limb are derived from the brachial plexus, whose formation and branches are described in detail in Unit 1.4. All three muscles in the anterior compartment are supplied by the musculocutaneous nerve. 8. Read musculocutaneous nerve. 9. Read median nerve. 10. Read ulnar nerve. 11. Now study the following summary notes: Musculocutaneous nerve The musculocutaneous nerve arises from the lateral cord of the brachial plexus. It perforates and supplies coracobrachialis, then passes to the lateral aspect of the arm between biceps brachii and brachialis, both of which it supplies. Just above the elbow, it becomes cutaneous as the lateral cutaneous nerve of the forearm. Median nerve The median nerve is formed by two heads from the medial and lateral cords of the brachial plexus (see Session 4). It runs down the anteromedial aspect of the arm with the brachial artery. Midway along the arm, it crosses anterior to the brachial artery to lie medial to it. It does not give any branches in the arm. The following three nerves all arise from the medial cord of the brachial plexus. Ulnar nerve The ulnar nerve passes down the medial side of the axillary and brachial arteries to midway down the arm. It then inclines posteriorly to pierce the medial intermuscular septum and passes downwards to the groove between the olecranon and medial epicondyle. It does not give any branches in the arm. Medial cutaneous nerve of the arm This nerve pierces the deep fascia in the superior part of the arm to supply the skin on the anterior and medial aspects. Medial cutaneous nerve of the forearm This nerve pierces the deep fascia on the medial aspect of the arm with the basilic vein. It supplies skin over the inferior part of the arm, then passes into the medial side of the forearm. 11 12. Read brachial artery. 13. Read veins of the upper limb. 14. Now study the following summary notes and diagram: Brachial artery A continuation of the axillary artery, the brachial artery extends from the lower border of teres major to just distal to the elbow, at the level of the neck of the radius. It runs along the medial border of coracobrachialis and biceps brachii, accompanied by venae comitantes. It ends by dividing into the radial and ulnar arteries. In the proximal part of the arm, the brachial artery lies next to the ulnar nerve. In the distal part of the arm, the median nerve lies on its medial side. As it reaches the elbow, it runs deep to the bicipital aponeurosis, with the median nerve lying medially. Its branches include: the profunda brachii artery, which runs posterolaterally with the radial nerve in the spiral groove of the humerus; nutrient branches to the humerus; the superior ulnar collateral artery which accompanies the ulnar nerve; the inferior ulnar collateral artery, and muscular branches to coracobrachialis, brachialis, and biceps brachii. Deep veins These accompany the main arteries and are usually paired, the venae comitantes. They also communicate with the superficial veins. The radial and ulnar veins unite to form the brachial veins. After receiving tributaries which correspond to the branches of the brachial artery, they form the axillary vein at the lower border of teres major. They are also joined by the basilic vein which pierces the deep fascia at the level of the mid-arm. FIG.2 Transverse Section through Mid-arm Key: H = humerus Muscles: 1 = biceps brachii; 2 = brachialis; 3 = coracobrachialis 4, 5, 6 = medial, lateral and long heads of triceps brachii Nerves: mc = musculocutaneous; m = median; u = ulnar; r = radial Arteries: ba = brachial artery with venae comitantes; p = profunda brachii artery Veins: bv = basilic vein; c = cephalic vein 12 POSTERIOR COMPARTMENT OF THE ARM 15. Read Posterior Regions (Introduction). 16. Read posterior compartment of the arm. 17. Read arm extensor compartment muscles. 18. Read radial nerve. 19. Now study the following summary notes and diagram: The posterior compartment of the arm is occupied entirely by the triceps brachii muscle. Triceps brachii This muscle has three heads. The long head originates from the infraglenoid tubercle of the scapula. The lateral head arises from the lateral lip of the spiral groove, above the deltoid tuberosity of the humerus. These two heads converge and fuse into a tendon which is inserted into the posterosuperior aspect of the olecranon. The medial head arises on the medial aspect of the spiral groove of the humerus. In its upper part, it lies medial to the lateral head, with the radial nerve and profunda brachii artery running between them. Below the spiral groove, its origin widens to include the whole posterior surface of the humerus and both intermuscular septa. The medial head is thus the deepest of the three heads. Its fibres are inserted into the olecranon and the deep part of the tendon formed by the other two heads. Some fibres are also inserted into the capsule of the elbow joint. Triceps brachii is the extensor of the elbow joint. The long head plays a role in stabilising the shoulder joint, and also aids in extending it. FIG.3 The Triceps Brachii Key: Triceps brachii: 1 = long head; 2 = lateral head; 3 = medial (deep) head N = radial nerve and A = profunda brachii artery, in the spiral groove 13 Radial nerve The radial nerve arises from the posterior cord of the brachial plexus. It lies posterior to the axillary and brachial arteries, then winds between the lateral and medial heads of triceps in the spiral groove with the artery. The branches of the radial nerve to the three heads of triceps are characteristically given off at a level that is considerably proximal to the part that is innervated. The radial nerve also gives sensory branches which supply the posterior part of the arm and forearm, as well as the anterolateral aspect of the lower half of the arm. The nerve leaves the posterior compartment by piercing the lateral intermuscular septum to reach the cubital fossa, where it lies between brachialis and brachioradialis. The following diagram shows the distribution of the main branches of the radial nerve in the upper limb. The foreman muscles will be described in Unit 1.3. FIG.4 Distribution of the Radial Nerve Key: S = superficial branch and P = posterior interosseous nerve (deep branch) d = digital branches (radial three and a half fingers on the dorsum of the hand but not beyond the distal interphalangeal joints) Muscular branches: To triceps brachii: 1 = long head; 2 = lateral head; 3 = medial (deep) head (also supplies anconeus) 4 = brachioradialis; 5 = extensor carpi radialis longus; 6 = extensor carpi radialis brevis; 7 = supinator; 8 = extensor digitorum communis; 9 = extensor digiti minimi; 10 = extensor carpi ulnaris 11 = abductor pollicis longus; 12 = extensor pollicis brevis; 13 = extensor pollicis longus 14 = extensor indicis Note that the radial nerve also gives three cutaneous branches not shown in the above diagram. These are the posterior cutaneous nerve of the arm, lower lateral cutaneous nerve of the arm, and posterior cutaneous nerve of the forearm. 14 Clinical Applications Study the following clinical applications: 1) Ruptured biceps tendon Rupture of the proximal part of the biceps tendon account for over 90% of all biceps ruptures, and almost exclusively involve the long head. The retracted muscle “bunches up” in the arm, leading to a bulge, the Popeye muscle. Functional loss is minimal as the short head is intact. The injury is most commonly seen in individuals aged 40-60 with a history of shoulder problems, secondary to chronic wear and tear of the tendon. Younger individuals may rupture the biceps tendon after a fall, during heavy weightlifting or other sporting activities. Distal ruptures may occur at the insertion on the radial tuberosity. These are followed by reduced strength in forearm supination and elbow flexion, and require surgical repair. 2) Humeral shaft fractures Fractures of the humeral shaft may lead to radial nerve injury due to its location in the spiral groove. As branches of the radial nerve also supply the extensors of the wrist and fingers, injury will lead to wrist drop. In this condition, the patient cannot extend their wrist and the hand hangs flaccidly. However, over 90% of cases of radial nerve palsy associated with closed fractures will recover spontaneously. 3) Supracondylar fractures A supracondylar fracture of the humerus is a common childhood fracture. It is a fracture of the distal humerus proximal to the epicondyles and is usually caused by a fall on the outstretched hand. This type of fracture may be associated with serious complications including rupture or compression of the brachial artery and injury to the median nerve, as these structures lie anteriorly. Compression of the artery leading to a pulseless hand must be treated as an orthopaedic emergency. 4) Dislocation of the elbow This is the commonest dislocation in children, also as a result of a fall on the outstretched hand. In adults, it is the second most common dislocation after the shoulder. Posterior dislocation is the commonest from of elbow dislocation. The close proximity of the ulnar nerve as it runs posterior to the medial epicondyle increases the likelihood of entrapment in a posterior dislocation. The brachial artery and median nerve may also be injured, albeit less frequently. 15  Module 1 – Unit 1.3 Compartments of the Forearm Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Describe the attachments and functions of the muscles of the anterior compartment of the forearm. 2. Understand the course and branches of the brachial artery in the forearm. 3. Describe the course of the median and ulnar nerves with their branches in the forearm. 4. Describe the attachments and functions of the muscles of the posterior compartment of the forearm. 5. Describe the course of the radial nerve and its branches in the forearm. 6. Understand the concept of the carpal tunnel and its contents. 7. Understand the common clinical applications associated with the forearm. 16 Summary 1. The forearm is the segment of the upper limb that lies between the elbow and wrist joints. 2. The anterior compartment of the forearm comprises three layers of muscles: a. Superficial layer: pronator teres, flexor carpi radialis, palmaris longus and flexor carpi ulnaris. They are supplied by the median nerve, except for flexor carpi ulnaris, which is supplied by the ulnar nerve. b. Intermediate layer: flexor digitorum superficialis, supplied by the median nerve. c. Deep layer: flexor digitorum profundus, flexor pollicis longus and pronator quadratus. 3. They are supplied by the anterior interosseous branch of the median nerve, except for the ulnar part of flexor digitorum profundus which is supplied by the ulnar nerve. 4. The brachial artery divides into the radial and ulnar arteries. These run down the forearm and form the deep and superficial palmar arches in the hand respectively. 5. The median nerve enters the palm in the carpal tunnel deep to the flexor retinaculum. The long flexors of the fingers and thumb also run through this narrow space. 6. The ulnar nerve runs posterior to the medial epicondyle, passes between the heads of flexor carpi ulnaris, and divides into superficial and deep palmar branches in the hand. 7. In the posterior compartment, the superficial muscles are wrist extensors and forearm supinators, except for brachioradialis, which flexes the elbow with the forearm in a mid- prone position. Brachioradialis and extensor carpi radialis longus arise from the lateral supracondylar ridge and are supplied by the radial nerve. The other superficial muscles arise from the common extensor origin on the anterior aspect of the lateral epicondyle of the humerus, and are supplied by the posterior interosseous branch of the radial nerve. 8. The deep muscles are supinator and the long extensors of the thumb and index finger. They are all supplied by the posterior interosseous branch of the radial nerve. 9. The extensor retinaculum stretches from the distal part of the radius to the pisiform and triquetral. It is therefore unaffected by pronation and supination. 17 Self-Directed Learning ANTERIOR COMPARTMENT OF THE FOREARM 1. Read anterior compartments of the forearm 2. Read forearm superficial flexors 3. Read forearm deep flexors 4. Now study the following summary notes and diagram: MUSCLES (supplied by the median & ulnar nerves) The muscles are contained within the deep fascia which sends septa between them, and is attached posteriorly to the subcutaneous border of the ulna. They are described in three layers. FIG.1 Muscles of the Anterior Compartment of the Forearm Key: S, I, D = superficial, intermediate and deep layers of muscles H = humerus; R = radius; U = ulna S: 1 = pronator teres; 2 = flexor carpi radialis 3 = palmaris longus; 4 = flexor carpi ulnaris I: 5 = flexor digitorum superficialis D: 6 = pronator quadratus 7 = flexor pollicis longus 8 = flexor digitorum profundus SUPERFICIAL LAYER These 4 muscles arise from the common flexor origin (CFO) on the anterior aspect of the medial epicondyle of the humerus, from the overlying fascia and the septa between them. Pronator teres This muscle arises from the CFO and the distal part of the supracondylar ridge of the humerus. An additional deep origin comes from the medial aspect of the coronoid process of the ulna. It inserts into the maximum convexity of the radius at the midpoint of the lateral aspect of the bone and pronates the forearm. It is supplied by a branch of the median nerve. The median nerve passes between the two heads of the muscle, while the ulnar artery lies deep to both heads. The radial artery passes over its tendon of insertion. Flexor carpi radialis (FCR) This muscle arises from the CFO and inserts into the bases of the second and third metacarpals. Its tendon does not run in the carpal tunnel but in a separate compartment, lying in a groove in the trapezium. It is supplied by the median nerve. FCR works with flexor carpi ulnaris to flex the wrist, and with the radial extensors to abduct the wrist. It also assists in stabilising the wrist during powerful finger movements. Palmaris longus 18 When present, this muscle arises from the CFO and inserts into the palmar aponeurosis, with a superficial tendon which is adherent to the flexor retinaculum. It is supplied by the median nerve. It tenses the palmar fascia and flexes the wrist. Flexor carpi ulnaris (FCU) This muscle arises from the CFO and the medial margin of the olecranon process of the ulna. It has an aponeurosis that attaches to the upper two-thirds of the subcutaneous border of the ulna. Its tendon is attached to the pisiform, a sesamoid bone, with extensions to the hamate and the fifth metacarpal via the pisohamate and pisometacarpal ligaments respectively. There is also an attachment to the anterior aspect of the flexor retinaculum. It is supplied by the ulnar nerve which runs posterior to the medial epicondyle, between its two heads. It adducts and flexes the wrist. INTERMEDIATE LAYER Flexor digitorum superficialis (FDS) This muscle is described as having two heads. The humero-ulnar head arises from the anterior aspect of the medial epicondyle via the CFO, the coronoid process of the ulna, and the ulnar collateral ligament of the elbow joint. There is also an extended origin from the radius. Its four tendons run in a common sheath through the carpal tunnel (FIG.3.1). Over the proximal phalanx, each tendon divides into two slips (the decussation) to allow the tendon of flexor digitorum profundus (FDP) to pass through. The slips of each tendon then insert into radial and ulnar aspects of the base of the middle phalanx. FDS is a weak flexor of the elbow and a strong flexor of the wrist and fingers (excluding the distal interphalangeal joint). It is supplied by the median nerve. DEEP LAYER Flexor digitorum profundus (FDP) This muscle arises from the ulna and the adjacent interosseous membrane. Its tendons run deep in the carpal tunnel to each of the four fingers, inserting into the base of the terminal phalanges beyond the decussation of the FDS tendon. It is supplied by the median nerve (anterior interosseous branch) for the part supplying the radial two fingers, and the ulnar nerve for the ulnar two fingers. Its primary action is flexion of the distal interphalangeal joints, and secondarily, flexion of the proximal interphalangeal joints, the metacarpophalangeal joints, and the wrist. Flexor pollicis longus This muscle arises from the anterior surface of the distal radius proximal to pronator quadratus. It passes through the carpal tunnel (FIG.3.1) to insert into the base of the distal phalanx of the thumb. It is a strong flexor of the thumb and is supplied by the anterior interosseous branch of the median nerve. Pronator quadratus This is a square-shaped muscle that pronates the forearm. It arises from the anterior surfaces of the distal radius and ulna. It is a flat muscle whose fibres run from medial to lateral rather than proximal to distal. It is supplied by the terminal motor branch of the anterior interosseous branch of the median nerve. 19  FIG.2 The Carpal Tunnel Key: Distal to the wrist, the deep fascia is thickened anteriorly to form the flexor retinaculum. It attaches laterally to the tubercles of the scaphoid and trapezium, and medially to the pisiform and the hook of the hamate. T = trapezium; Td = trapezoid; C = capitate; H = hamate; FR = flexor retinaculum t = thenar eminence; h = hypothenar eminence; M = median nerve 1 = palmar cutaneous branch of median nerve; 2 = palmaris longus tendon; 3 = ulnar artery 4 = ulnar nerve; 5 = tendon of flexor carpi radialis (in a separate compartment) 6 = tendon of flexor pollicis longus; 7 = tendons of FDS; 8 = tendons of FDP POSTERIOR COMPARTMENT OF THE FOREARM 5. Read posterior compartment of the forearm 6. Read forearm superficial extensor layer 7. Read forearm deep extensor layer 8. Read anatomical snuffbox roof 9. Read anatomical snuffbox borders and floor 10. Now study the following summary notes and diagram: The superficial muscles are extensors and supinators, except brachioradialis and anconeus. Brachioradialis and extensor carpi radialis longus arise from the lateral supracondylar ridge, while the common extensor origin (CEO) on the anterior aspect of the lateral epicondyle gives attachment to extensors carpi radialis brevis, digitorum communis, digiti minimi and carpi ulnaris. SUPERFICIAL MUSCLES Anconeus This triangular muscle arises from the posterior aspect of the lateral epicondyle, and inserts onto the lateral aspect of the proximal ulna. It is supplied by the radial nerve, via its branch to the medial head of triceps. It extends the elbow and pulls the ulna posterolaterally in pronation. Brachioradialis This muscle arises from the upper two-thirds of the lateral supracondylar ridge of the humerus and inserts into the radial styloid process. It flexes the elbow in a position midway between supination and pronation. It is supplied by the radial nerve. 20 Extensor carpi radialis longus and brevis (ECRL and ECRB) These two radial extensors of the wrist arise from the distal third of the lateral supracondylar ridge and the CEO respectively. Their tendons insert into the bases of the second and third metacarpals. ECRL is supplied by the radial nerve, while ECRB is supplied by its posterior interosseous branch. When acting with extensor carpi ulnaris, the wrist is neutrally extended. While acting with flexor carpi radialis, the wrist is pulled into radial deviation. Extensor digitorum communis (EDC) EDC is the main extensor at the finger joints, but in crossing the wrist, it also contributes to wrist extension. It inserts via four tendons which spread out onto the dorsum of the hand, passing to the index, middle, ring, and little fingers. The tendons run in a common compartment deep to the extensor retinaculum. As each tendon crosses the metacarpophalangeal joint, it forms a dorsal expansion which covers the proximal phalanx. This expansion is reinforced by the tendons of the corresponding interosseus and lumbrical muscles. Over the proximal interphalangeal joint, the tendon divides into three slips. The middle slip attaches to the base of the middle phalanx, while the outer two slips reunite to attach to the base of the distal phalanx. EDC is supplied by the posterior interosseous nerve. Extensor digiti minimi (EDM) This muscle arises from the CEO and inserts into the medial aspect of the dorsal expansion of the little finger. It supplements the extensor action of the EDC tendon to the little finger, which only joins EDM just proximal to the metacarpal head. It is supplied by the posterior interosseous nerve and extends the joints of the little finger. Extensor carpi ulnaris (ECU) This muscle arises from the CEO, with an additional proximal attachment to the subcutaneous border of the ulna. It inserts into the base of the fifth metacarpal. It extends or adducts the hand at the wrist, depending on whether it works with extensor carpi radialis longus and extensor carpi radialis brevis, or with flexor carpi ulnaris. It is supplied by the posterior interosseous nerve. FIG.3 The Extensor Retinaculum FIG.4 The Extensor Tendons (Dorsum of hand) (Transverse section at wrist) Key: FIG.3.2 shows the extensor retinaculum (E) and the disposition of the synovial sheaths of the extensor tendons in groups. Note that the extensor retinaculum is attached to the lateral margin of the distal radius and to the triquetral and pisiform bones medially. It is not attached to the ulna. FIG.3.3 is a transverse section across the wrist to show the extensor tendons. U = ulna; R = radius; d = dorsal (Lister’s) tubercle of the radius 1 = abductor pollicis longus (inferior in diagram) and extensor pollicis brevis 2 = extensor carpi radialis longus (more radial) and brevis; 3 = extensor pollicis longus 4 = four tendons of extensor digitorum communis and extensor indicis (deep) 5 = extensor digiti minimi; 6 = extensor carpi ulnaris 21 DEEP MUSCLES The deep muscles are all supplied by the posterior interosseous branch of the radial nerve. Supinator This muscle originates from the supinator crest of the ulna and the area just distal to the radial notch. More oblique superficial fibres originate from the posterior aspect of the lateral epicondyle, as well as from the lateral and annular ligaments of the elbow. It inserts into the lateral aspect of the proximal shaft of the radius. It supinates the pronated radius, but is weaker than biceps brachii. In a fully extended elbow, it is the prime mover for supination, which is much weaker in this position. The posterior interosseous nerve runs dorsally between its oblique and transverse fibres. The following three muscles form the borders of the anatomical snuffbox (FIG.3.5). Abductor pollicis longus (AbPL) This muscle originates from the proximal part of the dorsum of the ulna, the interosseous membrane, and the dorsum of the mid-portion of the radius. It inserts into the lateral aspect of the base of the thumb metacarpal. It abducts and extends the thumb metacarpal at the carpometacarpal joint. In crossing the wrist, it also abducts the hand at the wrist. Extensor pollicis brevis (EPB) This muscle originates on the dorsum of the radius distal to AbPL, with an additional origin from the adjacent part of the interosseous membrane. It inserts into the base of the proximal phalanx of the thumb. It does not have an extensor action on the IP joint of the thumb, but extends the thumb at both the metacarpophalangeal (MCP) and carpometacarpal (CMC) joints. Extensor pollicis longus (EPL) This muscle originates on the dorsum of the ulna distal to AbPL, with an additional origin from the adjacent part of the interosseous membrane. Its long tendon winds around the dorsal (Lister’s) tubercle of the radius, changing its direction to reach the thumb. EPL inserts into the dorsum of the base of the terminal phalanx of the thumb, thus extending both metacarpo-phalangeal and interphalangeal (IP) joints of the thumb. It is also a weak extensor of the wrist. FIG.5 The Anatomical Snuffbox Key: Tendons forming the boundaries: 1 = extensor pollicis longus 2 = extensor pollicis brevis 3 = abductor pollicis longus D = first dorsal interosseus muscle A = radial artery T = trapezium S = scaphoid Extensor indicis (EI) This muscle arises from the posterior aspect of the ulna, distal to the thumb extensors, and from the interosseous membrane. The EI tendon runs in the same compartment as the EDC deep to the extensor retinaculum (FIG.3), and crosses the EDC tendon to the index finger to lie on its medial (ulnar) side. It inserts into the dorsal expansion of the index finger. 22 Clinical Applications Study the following clinical applications: 1) Carpal tunnel syndrome This is a nerve entrapment syndrome caused by compression of the median nerve within the carpal tunnel. Affected individuals present with pain and paraesthesia in the distribution of the median nerve, with weakness of the muscles of the thenar eminence. Management includes the use of night splints to prevent wrist flexion, steroid injections and ultimately surgery to divide the flexor retinaculum. 2) Rupture of the extensor pollicis longus tendon Fractures of the distal radius may result in rupture of the tendon of extensor pollicis longus because of its association with the dorsal (Lister’s) tubercle. Patients are unable to extend the interphalangeal joint of the thumb. 3) Fracture of the scaphoid A fracture at the waist of the scaphoid is a common fracture caused by a fall onto the outstretched hand. As the scaphoid is palpable on the floor of the anatomical snuffbox, patients presenting to the Accident Department with snuffbox tenderness must be treated as a fracture by applying a plaster cast and X-raying again in 4 weeks. This is because an undisplaced fracture may not be visible at first and if untreated, may become displaced with avascular necrosis of the proximal fragment, as the blood supply to the scaphoid goes from distal to proximal. The follow-up X-ray will reveal a fracture as it heals. If the X-ray remains normal the cast can be removed. 4) Tennis and golfer’s elbow Patients with tennis elbow, or lateral epicondylitis, present with pain and tenderness over the common extensor origin, probably caused by overuse leading to a degenerative tear. Resisted wrist extension aggravates the pain. Non-operative management with rest and/or steroid injections is effective in the majority of cases. Golfer’s elbow is a similar inflammatory condition affecting the medial epicondyle, where the forearm flexors attach. 23  Module 1 – Unit 1.4 The Axilla, Brachial Plexus and Breast Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Describe the boundaries and contents of the axilla. 2. Describe the anatomy of the breast, its blood supply and lymphatic drainage. 3. Describe the courses of the axillary artery and vein. 4. Identify the regions of the body that drain to the axillary lymph nodes. 5. Understand the formation of the brachial plexus and describe its branches systematically. 6. Identify the muscles innervated by the different branches of the brachial plexus. 7. Describe the clinical presentations of injuries to different parts of the brachial plexus. 24 Summary 1. The axilla is a pyramidal space between the arm and lateral thoracic wall. It provides a passageway for the important nerves and vessels that supply the upper limb. 2. The brachial plexus is formed from the anterior primary rami of the lower four cervical spinal nerves (C5-C8) and the first thoracic spinal nerve (T1). 3. The roots of the brachial plexus form into three trunks: upper, middle and lower. Each trunk subdivides into an anterior and posterior division. 4. The anterior divisions from the upper and middle trunks form the lateral cord of the plexus; the anterior division of the lower trunk forms the medial cord; and the posterior divisions of all three trunks unite to form the posterior cord. 5. The divisions lie posterior to the clavicle, and the cords are named according to their relationship to the second part of the axillary artery, deep to pectoralis minor. 6. There are three branches from the roots, one branch from the upper trunk, three branches from the lateral cord, and five branches from each of the medial and posterior cords. 7. The brachial plexus supplies the motor and sensory innervation of the whole upper limb with two exceptions. Trapezius is supplied by the spinal accessory nerve, and an area of skin on the medial arm is supplied by the intercostobrachial nerve, which is the lateral cutaneous branch of the second intercostal nerve (T2). 8. The breast is intimately attached to pectoralis fascia over the anterior thoracic wall. It is divided into lobules by fibrous septa. Its lymphatic drainage is mainly into axillary but also internal thoracic channels. 25 Self-Directed Learning THE AXILLA 1. Read Anterior Regions (Introduction) 2. Read Axilla Walls and Base 3. Read Axilla Apex 4. Now study the following summary notes: The axilla is a fat-filled pyramidal space between the arm and lateral thoracic wall, bounded by anterior and posterior axillary folds. It communicates superiorly with the posterior triangle of the neck and contains neurovascular structures destined for the upper limb. Boundaries The floor of the axilla is formed by deep fascia, subcutaneous tissue and skin. The anterior wall is formed by pectoralis major and minor, subclavius (a small muscle connecting the upper border of the first rib and the inferior surface of the clavicle), and the clavipectoral fascia. The posterior wall extends lower and is formed by subscapularis, teres major and the tendon of latissimus dorsi winding around the latter. The medial wall is formed by serratus anterior, which originates from the outer surfaces of the upper eight ribs and inserts into the whole length of the medial border of the scapula. The lateral wall is the intertubercular or bicipital groove of the humerus. FIG.1 Exposing the Contents of the Axilla Key: c = coracoid process; P = pectoralis minor; A = axillary artery; V = axillary vein L, M = lateral and medial cords of the brachial plexus The posterior cord is hidden from view behind the axillary artery. 1 = musculocutaneous nerve; 2 = median nerve; 3 = radial nerve; 4 = ulnar nerve Contents 5. Read Vessels & nerves of axilla 6. Read Axillary & brachial arteries 26 7. Read Veins of upper limb 8. Read Lymph vessels & nodes of upper limb 9. Now study the following summary notes: The axillary artery is the continuation of the subclavian artery at the outer border of the first rib. It ends by becoming the brachial artery at the lower border of teres major. Branches include the subscapular artery which passes backwards to form part of the important scapular anastomosis, the anterior and posterior circumflex humeral arteries, which anastomose around the surgical neck of the humerus and supply the shoulder joint and deltoid, as well as branches which supply the pectoral muscles, breast and chest wall. The axillary vein is formed by the venae comitantes of the brachial artery and the basilic vein. It receives the cephalic vein which pierces the clavipectoral fascia. The axillary lymph nodes receive lymph from the upper limb, breast, and the abdominal wall above the umbilicus. The cords and branches of the brachial plexus are described on the following pages. FIG.2 Boundaries of the Axilla (Transverse section) Key: Bones: H = humerus; S = scapula Muscles: 1, 2 = pectoralis major and minor; 3 = long head of biceps brachii; 4 = tendon of latissimus dorsi 5 = subscapularis; 6 = serratus anterior Contents: A, V = axillary artery and vein L = lymph node The black dots represent the lateral, medial and posterior cords of the brachial plexus. THE BRACHIAL PLEXUS 10. Read Nerve plexuses 11. Read Brachial plexus (supraclavicular part) 12. Read Brachial plexus 13. Read Axillary nerve 14. Read Median nerve (same page as Unit 1.2) 15. Read Ulnar nerve (same page as Unit 1.2) 16. Read Radial nerve (same page as Unit 1.2) 17. Read Upper limb cutaneous nerve supply (Brachial plexus section) 18. Now study the following summary notes: 27 The brachial plexus is formed by the union and subsequent division of the anterior primary rami of the lower four cervical and part of the anterior ramus of the first thoracic nerves (C5 to T1). These are the five roots, which emerge between scalenus anterior and medius in the neck. The roots unite to form three trunks, which cross the posterior triangle of the neck. The upper two roots (C5, 6) form the upper trunk, the C7 root continues as the middle trunk, and the lower two roots (C8, T1) form the lower trunk. Each trunk divides into anterior and posterior divisions at the apex of the axilla. The cords are formed in the following way, and are named according to their relationship to the second part of the axillary artery deep to pectoralis minor: the anterior divisions from the upper and middle trunks form the lateral cord, the anterior division of the lower trunk forms the medial cord, and all the posterior divisions unite to form the posterior cord. The branches from the cords are related to the third, most distal part of the axillary artery. FIG.3 The Brachial Plexus The branches of the brachial plexus are numbered consecutively and described below The posterior divisions and posterior cord are shown in grey in the diagram. 28 Branches from the Roots The roots lie deep to the prevertebral fascia behind scalenus anterior. There are 3 branches: 1. The dorsal scapular nerve (C5), which supplies levator scapulae and the rhomboid muscles. Levator scapulae assists the upper fibres of trapezius in elevating the scapula. The rhomboids act together in retracting the shoulders. 2. The nerve to subclavius (C5, 6), which comes off at the junction of C5 and C6. 3. The long thoracic nerve (C5, 6, 7), which supplies serratus anterior. It protracts the scapula and acts with trapezius to rotate the scapula in abduction of the shoulder. Branch from the Upper Trunk The trunks lie in the floor of the posterior triangle of the neck. There is only one branch: 4. The suprascapular nerve (C5, 6), which supplies supraspinatus and infraspinatus. The divisions occur at the apex of the axilla, behind the clavicle. There are no branches. Branches from the Cords There are 3 branches from the lateral cord: 5. The lateral pectoral nerve (C5, 6, 7), which pierces the clavipectoral fascia to reach the deep surface of pectoralis major. 6. The musculocutaneous nerve, which supplies the 3 muscles of the anterior compartment of the arm (see Unit 1.2) and terminates as the lateral cutaneous nerve of the forearm. 7. The lateral head of the median nerve. (See detailed description below.) There are 5 branches from the medial cord: 8. The medial pectoral nerve (C8, T1), which passes between the axillary artery and vein to supply pectoralis minor. It continues on to supply pectoralis major. 9. The medial cutaneous nerve of the arm (T1), which gives sensory supply to the skin of the medial side of the arm as far as the medial epicondyle. 10. The medial cutaneous nerve of the forearm (C8, T1), which gives sensory supply to the skin of the lower part of the arm and the medial side of the forearm. 11. The medial head of the median nerve. (See detailed description below.) 12. The ulnar nerve. (See detailed description below.) There are 5 branches from the posterior cord: 13. The upper subscapular nerve (C6), which supplies the upper part of subscapularis. 14. The thoracodorsal nerve (C6, 7, 8), which supplies the latissimus dorsi muscle. 15. The lower subscapular nerve (C6, 7), which supplies the lower part of subscapularis and teres major. 16. The axillary nerve (C5, 6), which supplies teres minor and deltoid. It passes posteriorly inferior to the shoulder joint and is closely related to the surgical neck of the humerus. It supplies the shoulder joint and the skin over the lateral part of the deltoid. 17. The radial nerve. (See detailed description below.) 29 Ulnar Nerve (C8, T1) The ulnar nerve runs on the medial aspect of the arm close to coracobrachialis. It pierces the medial intermuscular septum to lie posteriorly in the groove between the olecranon and medial epicondyle. It then enters the anterior compartment of the forearm by passing between the two heads of flexor carpi ulnaris (FCU), which it supplies. It also supplies the ulnar half of flexor digitorum profundus. The palmar cutaneous branch arises near the mid-forearm and supplies the skin of the medial side of the palm. The dorsal cutaneous branch winds round the ulna deep to FCU to supply the ulnar one and a half fingers on their dorsal aspects. The main nerve runs with the ulnar artery to the wrist and divides into a superficial branch and a deep motor branch. The superficial branch supplies the palmaris brevis muscle and the skin of the ulnar one and a half fingers via two digital branches; while the deep terminal branch runs into the palm to supply the small muscles of the hypothenar eminence (flexor digiti minimi, abductor digiti minimi and opponens digiti minimi), all the palmar and dorsal interossei, and the ulnar two lumbricals. It ends by supplying adductor pollicis. FIG.4 Distribution of the Ulnar Nerve Key: 1 = to flexor carpi ulnaris 2 = to ulnar half of flexor digitorum profundus 3 = dorsal cutaneous branch 4 = palmar cutaneous branch S = superficial branch in the hand D = deep branch in the hand, supplying 5 = hypothenar muscles (abductor, flexor, and opponens digiti minimi) 6 = ulnar two lumbricals 7 = all palmar and dorsal interossei 8 = adductor pollicis Median Nerve (C5-T1) The median nerve forms from two “heads” from the lateral and medial cords. It runs down the anteromedial aspect of the arm with the brachial artery. Midway along the arm, it crosses anterior to the artery to lie medially, reaching the cubital fossa. Passing between the heads of pronator teres, the median nerve descends through the forearm between flexor digitorum superficialis (FDS) and flexor digitorum profundus, before emerging lateral to FDS to become superficial proximal to the wrist. It gives branches to palmaris longus, and flexor carpi radialis. Proximal to the carpal tunnel, it gives the palmar cutaneous branch to supply the skin over the thenar eminence and enters the hand by passing deep to the flexor retinaculum. It then gives a recurrent muscular branch to the thenar muscles (flexor pollicis brevis, abductor pollicis brevis and opponens pollicis) and divides into digital branches to supply the thumb, index, middle and radial half of the ring fingers. The anterior interosseous branch arises after the median nerve has pierced pronator teres and passes distally on the interosseous membrane. It supplies flexor pollicis longus, the radial half of flexor digitorum profundus and ends in pronator quadratus. 30 FIG.5 Distribution of the Median Nerve Key: Muscular branches: 1 = pronator teres 2 = flexor digitorum superficialis 3 = palmaris longus 4 = flexor carpi radialis A = anterior interosseous nerve, supplying 5 = flexor digitorum profundus 6 = flexor pollicis longus 7 = pronator quadrates Branches to the hand: 8 = palmar cutaneous branch 9 = thenar muscles (abductor pollicis brevis, opponens pollicis, flexor pollicis brevis) 10 = radial two lumbricals d = digital branches to radial three and a half fingers Radial Nerve (C5-T1) The radial nerve supplies triceps brachii in the posterior compartment of the arm. It runs with the profunda brachii artery in the spiral groove, perforates the lateral intermuscular septum, and passes anteriorly to divide into a superficial branch and a deep branch, which passes between the two heads of supinator to emerge as the posterior interosseous nerve. The superficial branch lies deep to brachioradialis and lateral to the radial artery. Distally, it passes deep to the brachioradialis tendon, curves round the lateral side of the radius and pierces the deep fascia to divide into terminal digital branches. These supply the skin on the radial half of the dorsum of the hand, and the dorsal aspects of the thumb, index, middle and radial half of the ring fingers, but not beyond the distal interphalangeal joints. The deep branch, the posterior interosseous nerve, supplies the extensors of the wrist and fingers and supinator. The distribution of the radial nerve was shown in F IG.4 of Unit 1.2. THE BREAST 19. Read Breasts 20. Read Pectoral region and breast 21. Read Subcutaneous layer of thorax 22. Now study the following summary notes: The breast is a nutritional organ producing milk in the lactating female. It is also a secondary sexual characteristic in the adult female. It is composed of fat, connective tissue and glandular elements. The latter are arranged into 15 to 20 lobules each opening independently onto the surface of the nipple. Interlobular connective tissue is lax to allow for expansion of the glandular elements in pregnancy. The breast tissue is enclosed within anterior and posterior leaves of body wall fascia. Posteriorly there is a connection to the deep fascia overlying pectoralis major which can give some support to the dependent breast. Although the breast can vary both in size and shape, it is generally attached from the second to the sixth ribs, extending laterally from the lateral sternal edge to the mid-axillary line. 31 There is often an extension of breast tissue into the axilla, known as the axillary tail. In the adult male and young adult female, the nipple is at the level of the fourth intercostal space. Innervation of the breast is by the fourth to sixth intercostal nerves. The nipple is innervated by the fourth intercostal nerve, and sensory stimulation is an important part of the suckling reflex. However, secretory control of the breast is principally hormonal. Blood supply to the breast is via the axillary, intercostal and internal thoracic arteries, with venous drainage by the associated corresponding veins. Lymphatic drainage follows the veins. About 75% of drainage is into the axillary nodes. There are usually 20-30 nodes divided into groups according to location. The anterior or pectoral, posterior or subscapular and lateral groups drain into the central nodes lying within the axillary fat. Lymph then drains to the apical nodes which lie at the apex of the axilla at the lateral border of the first rib. These drain into the subclavian lymph trunk which drains into the thoracic duct on the left, and the right lymphatic duct on the right. 32 Clinical Applications Study the following clinical applications: 1) Erb’s palsy This is caused by an injury to the upper trunk (C5, 6) of the brachial plexus, from excessive downward traction on the upper limb during a difficult delivery, or motorcycle accidents. Shoulder abduction, elbow flexion and supination are affected, leading to the waiter’s tip sign, i.e. the arm hangs by the side with a pronated forearm and the palm facing posteriorly. 2) Klumpke’s palsy This is caused by an injury to the lower fibres (T1) of the brachial plexus. This can result from hyperabduction of the shoulder as in a breech delivery or grasping an object while falling. This results in wasting of the intrinsic muscles of the hand. 3) Median nerve injury Low (distal) lesions of the median nerve may be a result of carpal tunnel syndrome (see Unit 1.3). Patients with high (proximal) lesions of the median nerve will present with additional symptoms: inability to flex the index and middle fingers and distal phalanx of the thumb; weakness and wasting of the muscles of the thenar eminence; inability to oppose and abduct the thumb with impairment of precision grip; and ulnar deviation at the wrist. 4) Ulnar nerve injury The characteristic sign of a low (distal) ulnar nerve lesion is a claw hand, with extension of the metacarpophalangeal joints and flexion of the interphalangeal joints of the ring and little fingers. This is due to paralysis of the interossei and lumbrical muscles (see Unit 1.6). The index and middle fingers are relatively unaffected as their lumbricals are supplied by the median nerve. In a high (proximal) ulnar nerve lesion at or above the elbow, there is less deformity but greater functional disability as the ulnar branches to flexor digitorum profundus are also lost. This is the ulnar paradox. 5) Radial nerve injury A patient with a radial nerve injury typically presents with wrist drop, i.e. an inability to extend the wrist, fingers and thumb. Lesions of the radial nerve also cause weakness of the power grip, which depends on the synergistic contraction of both flexors and extensors. Wrist drop in association with loss of active elbow extension suggests a more proximal injury, e.g. in the axilla. Saturday night palsy results when an inebriated person has fallen asleep with their arm across the back of a chair! 6) Breast cancer This is the commonest cancer in women in the UK and worldwide. Knowledge of the lymphatic drainage of the breast is essential in surgical treatment, hence axillary palpation is crucial. Biopsy of the sentinel node, the first lymph node or group of nodes draining the cancer, is used to determine the type and extent of treatment. Cancer of the male breast is rare. Surgical removal of axillary nodes (axillary clearance) may result in injury to the long thoracic nerve, leading to paralysis of serratus anterior and a winged scapula. Axillary clearance may lead to lymphoedema, especially when combined with radiotherapy. 33  Module 1 – Unit 1.5 The Pectoral Girdle and Vertebral Column Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Know how the upper limb interacts with the trunk and axial skeleton. 2. Understand the articulations of the pectoral girdle and the scapulothoracic articulation. 3. Describe the superficial back muscles and their role in moving the scapula and upper limb. 4. Identify the principal parts of the vertebral column and its movements. 5. Identify the components of a typical vertebra and the regional differences. 6. Understand the path of the exiting spinal nerve. 7. Understand the common clinical applications associated with the pectoral girdle. 34 Summary 1. The pectoral girdle connects the upper limb to the axial skeleton. It consists of the scapula and clavicle with their associated joints. The joints of the pectoral girdle may be considered in two groups: anatomical (sternoclavicular, acromioclavicular and glenohumeral joints) and physiological (scapulothoracic articulation). 2. Movements occurring at the glenohumeral (shoulder) joint consist of flexion, extension, abduction, adduction, medial and lateral rotation. However, little if any movement occurs at the glenohumeral joint without accompanying movements of the scapula. 3. Movements of the scapula include (a) elevation and depression, (b) rotation, (c) lateral or anterior movement (protraction), and (d) medial or posterior movement (retraction). Scapular elevation, as in shrugging the shoulders, is produced by the upper fibres of trapezius and the levator scapulae. Depression is usually achieved by gravity. 4. During movement, the acromion is kept away from the chest wall by the clavicle, which acts as a strut. The lateral end of the clavicle travels in an arc around the sternoclavicular joint, which acts as a pivot. The medial border of the scapula is held against the chest and travels in the arc of the chest wall. Movement at the acromioclavicular joint is continuous, and the clavicle must be free to rotate around its longitudinal axis. 5. The vertebral column is made up of vertebrae which articulate with each other. A typical vertebra has a body, two pedicles, two laminae, a spinous process and two transverse processes. Regional vertebrae have different characteristics. The combination of flexibility and control in the vertebral column is brought about by the intervertebral joints, discs, supporting muscles and strong ligaments. 6. The spinal cord is protected by the vertebral column, and its emerging nerve roots exit through the intervertebral foramina. It terminates in the conus medullaris and becomes the cauda equina at the lower border of L1. The dural sac terminates at S2. 35 Self-Directed Learning THE PECTORAL GIRDLE The pectoral girdle connects the upper limb to the axial skeleton and comprises the scapula and clavicle with their interposing joints: two anatomical joints (sternoclavicular and acromioclavicular joints), and a physiological joint, the scapulothoracic articulation. They assist the movement of the glenohumeral joint and contribute greatly to mobility of the shoulder region. 1. Read about the joints of the clavicle. 2. Read about the internal and external structure of the glenohumeral joint. 3. Read about the deltoid and scapular regions 4. Read Scapular muscles. 5. Now study the summary notes and diagram: Sternoclavicular Joint This is a synovial joint between the medial end of the clavicle and the clavicular notch of the manubrium, together with the adjacent superior aspect of the first costal cartilage. The joint contains a fibrocartilaginous intra-articular disc that divides it into two separate synovial cavities. Elevation and depression of the pectoral girdle involves a rocking motion of the medial end of the clavicle on the disc. Protraction and retraction of the pectoral girdle is accomplished by a rocking motion of the medial end of the clavicle and the disc, as a unit, on the manubrium. Acromioclavicular Joint This small synovial joint permits a small degree of motion about all three potential axes. The movement around the mediolateral axis is called rotation, and is particularly important during normal elevation of the upper limb. Rotation at the acromioclavicular joint accounts for about half of the ‘glenoid-up’ rotation of the scapula relative to the chest wall. Glenohumeral Joint The glenohumeral (shoulder) joint is a synovial ball-and-socket joint. The surface area of the humeral head is three times that of the glenoid fossa, whose margins are extended by a fibrocartilaginous labrum to provide stability. The capsule is attached at the margins of the anatomical neck, and is lax inferiorly to allow abduction. It is strengthened by the coracohumeral ligament and three anterior glenohumeral ligaments. Movements occur in 3 planes: flexion/extension, abduction/adduction, medial/lateral rotation. Circumduction is a combination of flexion, extension, abduction and adduction, resulting in a circular movement. Prime movers are deltoid, pectoralis major, latissimus dorsi, teres major and coracobrachialis. The rotator cuff muscles (supraspinatus, infraspinatus, teres minor and subscapularis) hold the humeral head within the glenoid, giving strength and dynamic stability. FIG.1 The Shoulder Joint (Sagittal section) Key: Dashed lines indicate the synovial membrane. C = coracoid process; A = acromion CAL = coracoacromial ligament; G = glenoid cavity GL = glenoid labrum; AC = articular capsule B1 = subacromial bursa; B2 = subscapular bursa Muscles: 1 = supraspinatus; 2 = infraspinatus; 3 = teres minor 4 = subscapularis; 5 = long head of biceps 36 Abduction is initiated by supraspinatus and continued by the lateral fibres of deltoid. The only true adductor is coracobrachialis, but pectoralis major, latissimus dorsi, and teres major can also adduct the abducted shoulder. Infraspinatus and teres minor laterally rotate, while medial rotation is by subscapularis and teres major, as well as latissimus dorsi and pectoralis major. Important neighbouring structures include the brachial plexus, axillary artery and vein, as well as the axillary nerve and circumflex humeral artery around the surgical neck of the humerus. Deltoid Deltoid is a powerful multipennate muscle with a broad origin from the spine of the scapula, acromion and clavicle. The scapular origin is by means of an aponeurosis at the inferior lip of its crest, while fleshy fibres originate from the lateral edge of the acromion and the anterior surface of the lateral third of the clavicle. Multiple tendons form within the muscle and converge onto the prominent V- shaped deltoid tuberosity above the midshaft of the humerus. Its lateral fibres produce abduction at the glenohumeral joint; anterior fibres cause medial rotation and flexion; and posterior fibres produce lateral rotation and extension. It is supplied by the axillary nerve from the posterior cord of the brachial plexus. Scapulothoracic Articulation The scapula moves in different planes to produce a combination of movements leading to protraction or retraction. For everyday activities, scapulothoracic motion provides only 15 degrees of internal rotation. This articulation allows increased shoulder movement beyond the initial 120 degrees provided by the glenohumeral joint. Coordinated movement of the scapulathoracic and glenohumeral joints has been termed the scapulothoracic rhythm. Scapulothoracic movement may be independent of any motion of the upper limb, e.g. shrugging the shoulders, although it usually forms part of a coordinated movement of the upper limb. For example, flexion or abduction of the glenohumeral joint involves both elevation of the scapula relative to the thoracic wall and active rotation so that the glenoid fossa faces more superiorly. MUSCLES CONNECTING THE TRUNK TO THE SCAPULA Trapezius is described in detail in The Triangles of the Neck (Module 2, Unit 2.1). 6. Read Upper limb muscles from the spine 7. Read Extrinsic muscles: 1st layer 8. Read Extrinsic muscles: 2nd layer 9. Now study the summary notes: Rhomboid Major and Minor The rhomboids arise from the inferior aspect of the ligamentum nuchae and the spines of the upper thoracic vertebrae. From this origin the muscle fibres pass inferolaterally to reach their insertion on vertebral border of the scapula from the root of its spine down to its inferior angle. The highest fibres that may be visualised are rhomboid minor; the bulk of the muscle sheet is rhomboid major. Both are innervated by the dorsal scapular nerve. They retract and, to a lesser extent, elevate the scapula. Levator Scapulae Levator scapulae arises from C1-C4 and inserts along the vertebral border of the scapula from its superior angle to the root of its spine. It is innervated by branches of the 3rd and 4th cervical anterior rami, as well as a branch from the dorsal scapular nerve. As its name suggests, levator scapulae contributes to elevation of the scapula and simultaneously pulls it forward. 37 Serratus Anterior This muscle arises from the outer surfaces of the upper 8 or 9 ribs, along the anterior axillary line. The digitations from ribs 1 and 2 insert on the ventral surface of the scapula along a narrow strip immediately adjacent to its vertebral border. This insertion passes all the way from the superior angle to near the inferior angle of the scapula. The ventral surface of the inferior angle itself receives the insertion of the remaining digitations. It is supplied by the long thoracic nerve. Pectoralis Minor Pectoralis minor is a true muscle of the upper limb and is innervated by the brachial plexus, specifically the medial pectoral nerve. It typically arises from the anterior surfaces of the third, fourth and fifth ribs in the vicinity of their costochondral junctions. The muscle fibres pass superolaterally, converging on a tendon that inserts into the medial lip of the coracoid crest near its tip. Pectoralis minor pulls the scapula inferomedially. MUSCLES CONNECTING THE TRUNK TO THE HUMERUS 10. Read Upper limb muscles from thorax 11. Now study the summary notes: Pectoralis Major This muscle arises by a clavicular head from the medial half of the anterior surface of the clavicle, and a sternocostal head from the anterior surface of the sternum, upper six costal cartilages and the upper part of the external oblique aponeurosis. The clavicular head is supplied by the lateral pectoral nerve, and the sternocostal head by the medial pectoral nerve. The fibres of the sternocostal head converge on a flat tendon that inserts onto the lateral lip of the bicipital groove of the humerus. The fibres of the clavicular head insert onto the anterior surface of this tendon. Both portions of the muscle adduct and medially rotate the arm at the glenohumeral joint, but the clavicular head is also a major flexor of the arm. With the upper limb fixed in abduction, pectoralis major is also an accessory muscle of respiration. Latissimus Dorsi Latissimus dorsi arises from the posterior region of the iliac crest and via an aponeurosis from the vertebral spines inferior to T6. The fibres converge on a flat tendon that inserts into the floor of the bicipital groove of the humerus near the crest of the lesser tuberosity. The latissimus dorsi and its tendon undergo a 180-degree twist prior to reaching the humerus so that fibres arising from the ilium actually insert most proximally, whereas those arising from midthoracic vertebrae insert most distally. The latissimus dorsi is an adductor, medial rotator, and extensor of the arm. It is important in all movements requiring powerful extension of the arm and is innervated by the thoracodorsal nerve. THE VERTEBRAL COLUMN 12. Read Arrangement of the vertebral column. 13. Read Curvatures of the vertebral column. 14. Read Structure and supply of a vertebra. 15. Read Joints of vertebral bodies. 16. Read Structure of an intervertebral disc 17. Read Joints of vertebral arches 18. Read Accessory ligaments 19. Read Lumbosacral & sacrococcygeal joints 20. Now study the summary notes and diagrams: The vertebral column is composed of cervical, thoracic, lumbar, and sacral vertebrae. There are usually 7 cervical, 12 thoracic and 5 lumbar vertebrae. The sacrum comprises 5 fused vertebrae and 38 the coccyx is formed from 3-4 fused vertebrae. Viewed posteriorly, the vertebral column appears to run vertically down from the back of the head to the natal cleft. Viewed laterally, there are the primary and secondary curvatures, which vary with age and pathology. The primary curvature is found in embryonic life, is concave forwards and involves the whole vertebral column. After birth, the cervical curvature becomes concave posteriorly to support the head. With walking, the lumbar curvature becomes concave posteriorly. These are the secondary curvatures. The thoracic and sacral regions retain the primary curvature. Structure of a Typical Vertebra Each vertebra consists of an anterior body and a posterior neural arch, which encloses the vertebral foramen, forming a canal for the spinal cord. The spinous process protrudes posteriorly and the transverse processes extend laterally. The laminae lie between these processes while the pedicles lie between the transverse processes and the body. At the junction of the laminae and pedicles, there are two superior and two inferior articular facets. These form synovial joints with the corresponding facets on the vertebrae above and below respectively. The superior and inferior edges of the pedicles are notched. The notches from two contiguous vertebrae form the intervertebral foramen for the spinal nerves to pass. FIG.2 A Typical Thoracic Vertebra Key: (articular facets in grey) 1 = body; 2 = pedicle, 3 = lamina 4 = transverse process; 5 = spinous process 6 = superior articular facet 7 = vertebral foramen 8 = spinal nerve in intervertebral foramen NB. A typical thoracic vertebra has articular facets on the transverse processes and demifacets on the sides of the bodies for the ribs. Cervical (C3-6) Thoracic (T2-9) Lumbar (L1-5) Foramen large, triangular circular small, triangular Body small demifacets for ribs large and thick uncovertebral processes Spinous bifid Long and points thick and oblong in process downwards shape Transverse anterior & posterior tubercles articular facet for large and protrudes process foramen transversarium ribs laterally Facets on oblique plane on arc of a circle interlocking, vertical and sagittal Movements* flexion, extension, lateral rotation, limited by flexion, extension and flexion and rotation thoracic cage lateral flexion *While only limited movements occur between adjacent vertebrae, the total range of movement in the vertebral column is considerable. The movements listed in this table are the main ones that occur in the different regions. 39 Intervertebral Joints Synovial joints are formed between the inferior articular facets of one vertebra and the superior articular facets of the vertebra below. These are strengthened by ligaments, which connect the tips and base of the spinous processes (supraspinous and interspinous), the transverse processes (intertransverse), and the laminae (ligamentum flavum). There are also capsular ligaments of the joints between the articular facets. Two ligaments connect the vertebral bodies and support the intervertebral disc: the anterior and posterior longitudinal ligaments. FIG.3 Ligaments of the Vertebral Column (Sagittal section) Key: (bone in grey) Parts of the vertebra: B = body; P = pedicle; L = lamina; S = spinous process Parts of intervertebral disc: A = annulus fibrosus; N = nucleus pulposus Ligaments: 1 = anterior longitudinal ligament; 2 = posterior longitudinal ligament 3 = ligamentum flavum; 4 = interspinous ligament; 5 = supraspinous ligament THE SPINAL CORD 21. Read Walls of the vertebral canal 22. Read Dimensions of the vertebral canal 23. Read Epidural space 24. Read Meninges & subarachnoid space 25. Read Position of spinal cord 26. Read Spinal cord and its blood supply 27. Read Structure of spinal cord 28. Read Spinal nerves 29. Read Nerve roots 30. Read Position of nerve roots 31. Read Posterior (dorsal) rami 32. Read Intervertebral foramina: walls of a foramen 33. Read Intervertebral foramina: contents of a foramen 34. Now study the summary notes : 40 The spinal cord begins at the level of the foramen magnum of the skull and ends at the lower border of L1, where it tapers to a cone-shaped ending, the conus medullaris. A stalk of pia mater, the filum terminale, attaches it to the end of the dural sac at S2. All the roots of the spinal nerves from L2 to the lowest coccygeal nerve pass caudal to the conus to exit at their respective intervertebral foramina. This mass of roots is known as the cauda equina. The Spinal Nerves The spinal nerve roots emerge from the ventral and dorsal aspects of the spinal cord as the ventral (or anterior) motor, and dorsal (or posterior) sensory nerve roots. At each level the two roots join to form a mixed spinal nerve in the intervertebral foramen. Each nerve takes with it, for a short distance, a covering of all three meningeal layers, i.e. pia, arachnoid and dura mater. As the nerve emerges from the intervertebral foramen, the coverings fuse with the epineurium of the nerve root. Note that there are 8 cervical nerve roots and only 7 cervical vertebrae. Therefore, the C7 nerve root emerges above the C7 vertebra, and the C8 nerve root emerges below it. Distal to C7, the nerve roots emerge below each of the corresponding vertebra. Meningeal Spaces The spinal epidural space lies between the dura mater and vertebral periosteum, containing loose connective tissue, venous plexuses and lymphatics. The subarachnoid space contains cerebrospinal fluid (CSF), bathing the brain and spinal cord. In the adult, it extends to the termination of the lumbar cistern, at the level of the second sacral vertebra. When lumbar puncture is performed to withdraw a sample of CSF for diagnostic purposes, the needle is inserted at the L3/4 or L4/5 spaces, avoiding the spinal cord which terminates at L1. 41 Clinical Applications Study the following clinical applications: 1) Clavicular fractures These are common injuries that occur in young active males or in elderly individuals, as a result of direct trauma to the shoulder, e.g. a fall directly on the shoulder. The force is transmitted through the clavicle from the acromioclavicular to the sternoclavicular joint. 2) Acromioclavicular dislocation This joint can be disrupted by a direct blow e.g. playing rugby or coming off a motorbike. It generally causes little disability but produces a palpable and visible swelling over the joint. 3) Glenohumeral dislocation The glenohumeral joint has an extensive range of movement but poor stability. It is the most commonly dislocated large joint, with anteroinferior dislocations being commonest. The head of the humerus comes to lie anteriorly under the coracoid process. Recurrent dislocation is common in this joint. Damage to the axillary nerve may occur, resulting in paralysis of deltoid and loss of sensation in the ‘regimental badge’ area of the arm. 4) Rupture of the rotator cuff Degenerative rupture of the rotator cuff leads to difficulty in initiating abduction. The patient may compensate for this by leaning over to the affected side, so that gravity assists abduction before deltoid can act. 5) Scapular fractures and scapulothoracic disorders Scapular fractures are rare and usually the result of a high energy, blunt force trauma. The ipsilateral upper limb is adducted and protected from movement. Disorders of the scapulothoracic articulation will affect the function of the glenohumeral joint, presenting as posterior shoulder pain, rotator cuff bursitis or tendinitis secondary to impingement. 6) Degenerative changes in the spine Vertical forces through the spine with rotational flexion-extension movements in the upright posture produce significant arthritic degenerative changes in the facet joints and intervertebral discs. These are more likely to occur in the lumbar spine. An abnormal increase in the thoracic curvature is a kyphosis; an abnormal increase in extension of the lumbar or cervical curvature is a lordosis; and an abnormal lateral curve is a scoliosis. 7) Prolapsed intervertebral disc The water content of an intervertebral disc is greater in the morning, and reduces with activity as body weight is applied to the disc during the day. The body is thus slightly shorter towards the evening. When the anulus fibrosus degenerates and ruptures, the nucleus pulposus protrudes through it and puts pressure on the cord or nerve roots. This is a prolapsed intervertebral disc, which occurs most commonly in the lower lumbar region, causing compression of the nerve root of the level below, as the nerve at the level of the disc has already emerged above the disc. Thus, an L4/5 disc prolapse will compress the L5 nerve root. This does not usually apply higher up in the vertebral column. 8) Developmental defects Incomplete fusion of the posterior elements of the vertebra may result in spina bifida. This is commonest in the lower lumbar region, and the meninges, spinal cord and roots may herniate through the defect posteriorly, resulting in severe neurological deficits. 42  Module 1 – Unit 1.6 The Hand and Joints of the Upper Limb Learning Outcomes On completing this Unit and the practical session in the Dissection Room, the annexe station activities and the applied anatomy seminar, you should be able to: 1. Describe the structure and function of the glenohumeral joint: type, articular surfaces, ligaments, movements and relations. 2. Describe the structure and function of the elbow joint: type, articular surfaces, ligaments, movements and relations 3. Describe the structure and function of the wrist joint: type, articular surfaces, ligaments, movements and relations. 4. Describe the courses of the median, ulnar and radial nerves, and their autonomous areas in the hand. 5. Name and describe the attachments and functions of the intrinsic muscles of the hand. 6. Describe the special features of the deep fascia of the hand. 7. Understand the clinical applications associated with the upper limb joints and the hand. 43 Summary 1. The bones of the upper limb articulate at the shoulder, elbow, wrist, hand, fingers and thumb. These joints enable the hand to be placed in a wide variety of positions relative to the trunk in order to fulfil its prehensile function. 2. The shoulder is a highly mobile, synovial ball-and-socket joint. Stability is enhanced by capsular thickenings, the glenoid labrum, muscles and ligaments. 3. The elbow is a stable synovial hinge joint with a limited range of motion to control hand position. Forearm supination and pronation results from three radioulnar articulations. 4. The wrist or radiocarpal joint is a mobile synovial ellipsoid joint. Of the joints in the hand, the first carpometacarpal joint at the thumb is a unique saddle-shaped joint that permits a wide range of movements, especially opposition. 5. The palmar aponeurosis is the deep fascia of the palm. It is attached proximally to the flexor retinaculum. Distally it divides into four slips which blend with the fibrous flexor sheaths of the fingers. 6. The muscles of the hand are in three groups: (a) muscles of the thumb forming the thenar eminence; (b) muscles of the little finger forming the hypothenar eminences; and (c) the deep palmar muscles comprising adductor pollicis, lumbricals and interossei. 7. The lumbricals arise from the tendons of flexor digitorum profundus to insert into the radial margins of the dorsal extensor expansions. The palmar and dorsal interossei arise from the metacarpal shafts, adducting and abducting the fingers. In conjunction with the lumbricals, they flex the metacarpophalangeal joints and extend the interphalangeal joints. 8. The autonomous zones are important for testing the integrity of the radial, ulnar and median nerves in the hand. 44 Self-Directed Learning BONES OF THE UPPER LIMB 1. Read Bony Landmarks of the Upper Limb 2. Read Bones of the Upper Limb 3. Familiarise yourself with the bones of the upper limbs, their landmarks and key muscle attachments: a. Clavicle b. Scapula c. Humerus d. Radius and Ulna e. Carpal bones f. Metacarpals and Phalanges 4. Now study the following summary notes: Clavicle The clavicle articulates with the manubrium and laterally with the acromion of the scapula to form the sternoclavicular and acromioclavicular joints respectively. It provides attachments for muscles from the spine, e.g. trapezius, and upper limb muscles, e.g. the deltoid. Scapula This flat, triangular bone is attached to the thorax and vertebral column by a number of stabilising muscles, providing a platform for the arm to hang from the shoulder. At rest, its medial border lies parallel to the vertebral column. Posteriorly, the spine separates the supraspinous and infraspinous fossae. The acromion is a superolateral prolongation of the spine and articulates with the lateral end of the clavicle to form the acromioclavicular joint. The subscapular fossa lies anteriorly. Laterally, the glenoid fossa articulates with the humeral head at the glenohumeral joint. Above this is the beak-like coracoid process. Humerus The head of this long bone articulates with the glenoid fossa of the scapula. The anatomical neck separates the head from the greater and lesser tuberosities, which provide attachment for the rotator cuff muscles. The tendon of the long head of biceps lies in the intertubercular groove. The surgical neck separates the proximal end from the humeral shaft. The spiral groove on the posterior aspect of the shaft houses the radial nerve and profunda brachii artery. Distally, the medial and lateral supracondylar ridges continue into the medial and lateral condyles. Their tips form the medial and lateral epicondyles. At the elbow joint, the trochlea articulates with the trochlear notch of the ulna and the capitulum with the head of the radius. Anteriorly, the coronoid fossa accepts the coronoid process of the ulna during elbow flexion. Posteriorly, the olecranon fossa accepts the olecranon during elbow extension. Radius and Ulna The two long bones of the forearm articulate with each other proximally and distally. The interosseous membrane connects them throughout the length of their shafts. The radius has a proximal head which articulates with the capitulum of the humerus and the radial fossa of the ulna. The biceps tendon inserts into the radial tuberosity. The shaft has a lateral area of maximum convexity for the insertion of pronator teres. Distally, the lateral aspect of the shaft extends into a projection known as the styloid process. Posteriorly is a groove for the extensor pollicis longus 45 tendon, with the dorsal (Lister’s) tubercle on the radial side. A notch articulates with the ulna to form the distal radio-ulnar joint. The ulna is shaped proximally to articulate precisely with the trochlea of the humerus. The coronoid process and olecranon articulate with the corresponding fossae of the humerus. The shaft has a subcutaneous border and a sharp margin for the interosseous membrane. Distally, the shaft expands to form the head, with a small styloid process. On the lateral aspect is a convex articulating surface that articulates with the distal radius in supination and pronation. Carpus The carpus consists of eight carpal bones arranged in two rows. The proximal row comprises the scaphoid, lunate, triquetral and pisiform, while the distal row comprises the trapezium, trapezoid, capitate and hamate. Minimal movement occurs between these bones, which are connected to each other by intercarpal ligaments that give the carpus its stability. Metacarpals The five metacarpals are long bones that form the skeleton of the hand. Each consists of a base, shaft and head. Minimal movement occurs between carpus and metacarpals, except for the saddle-shaped first carpometacarpal joint which allows free thumb movements. The shafts are joined by transverse metacarpal ligaments, and the palmar and dorsal interossei, allowing abduction and adduction of the fingers at the condyloid metacarpophalangeal joints. Phalanges These are small bones with a base, shaft and head, with three (proximal, middle and distal) in each digit and two in the thumb. The interphalangeal joints are hinge joints, allowing flexion and extension, which are controlled by the finger flexors, extensors, and the small muscles of the hand. They are stabilised by radial and ulnar collateral ligaments. JOINTS OF THE UPPER LIMB 5. Revise the Acromioclavicular and Glenohumeral joints covered in Session 5 6. Read Elbow joint internal structure followed by Elbow joint external structure 7. Read Wrist & Intercarpal Joints a. You may wish to read the Ligaments of the Wrist Complex 8. Now study the following summary notes: The acromioclavicular and glenohumeral joints were described in Unit 1.5. Elbow Joint The elbow is a synovial hinge joint. The radial head articulates with the ulna in supination and pronation, and slides on the capitulum of the humerus in flexion and extension. The capsule is attached to the margins of the articular surfaces but is lax anteriorly and posteriorly to permit full flexion and extension. The epicondyles are extracapsular. Stability is maintained by the congruous articular surfaces of the trochlea and trochlear fossa. It is also enhanced by medial and lateral collateral ligaments and the anular ligament around the radial neck. Movements are primarily flexion and extension by brachialis and biceps anteriorly and triceps posteriorly. Forearm supination and pronation occur at the superior and inferior radio-ulnar joints. The former communicates with the elbow joint. Important relations include the median nerve and brachial artery anteriorly, the ulnar nerve posteromedially, and the radial nerve anterolaterally. The radial nerve perforates the lateral intermuscular septum just proximal to the elbow and winds around the radial neck before dividing into its main superficial branch and deep posterior interosseous branch. 46  FIG.1 The Elbow Joint (Anterior view) Key: H = humerus; C = capitulum; T = trochlea R = radius; U = ulna N = ulnar nerve behind medial epicondyle Ligaments: 1 = lateral collateral ligament 2 = anular ligament (around neck of radius) 3 = medial collateral ligament Dashed lines indicate the attachment of the articular capsule. Wrist Joint The wrist is a synovial ellipsoid joint. The concave distal surface of the radius articulates with the convex proximal surfaces of the scaphoid and lunate. The head of the ulna is separated from the triquetral bone by a triangular fibrocartilaginous disc, which is attached to the edge of the ulnar notch of the radius and the base of the styloid process of the ulna. It separates the wrist joint from the distal radioulnar joint. The c