Key Relationships in the Upper Limb This list contains some of the key relationships that will help you identify structures in the lab. They are organized by dissection assignment as defined in the syllabus. Page numbers refer to Grant s Dissector (15 th edition). Note: This list is by no means comprehensive! Pectoral Region (pp. 28-30) The Deltopectoral groove runs between the Deltoid and Pectoralis major muscles and ends at the Deltopectoral triangle where it abuts the Clavicle. The Cephalic vein runs along the groove and travels through the triangle to drain into the axillary vein. The Deltoid branch of the thoracoacromial artery can also be found in the deltopectoral groove. The Medial pectoral nerve pierces the Pectoralis minor muscle to reach the deep surface of Pectoralis major, while the Lateral pectoral nerve runs over the medial border of pectoralis minor with the Pectoral branch of the thoracoacromial artery. Occasionally the medial pectoral nerve will split and you will see multiple branches piecing the pectoralis minor. The Lateral thoracic artery can often be seen running together with the Long thoracic nerve. They emerge from deep to the lateral border of Pectoralis minor and run on the superficial surface of Serratus anterior. Axilla & Subscapular Region (pp. 30-34) The Lateral and Medial trunks of the brachial plexus lie anterior to the Axillary artery while the Posterior trunk is behind it. The Posterior circumflex humeral artery and the Axillary nerve run together through the Quadrangular space to emerge in the posterior shoulder deep to the Deltoid. The quadrangular space is bounded laterally by the humerus, medially by the Long head of Triceps brachii, superiorly by Teres minor, and inferiorly by Teres major. The Thoracodorsal artery and nerve (middle subscapular nerve) usually run together onto Latissimus dorsi. The Radial nerve exits the axilla with Profunda brachii (deep artery of the arm/deep brachial artery) by passing through the Triangular interval (inferior to the quadrangular space). This space is bounded superiorly by Teres major, laterally by the Long head of triceps brachii, and medially by the humerus. The Subscapular nerves lie on the surface of the Subscapularis muscle. Ansa pectoralis (a connection between the lateral and medial pectoral nerves may be seen passing anterior to the axillary artery. 1
The posterior wall of the axilla is formed superiorly by the Subscapularis muscle and inferiorly by Teres major and Latissimus dorsi. Define the borders of these muscles to understand relationships with the shoulder. The Lateral and Medial cords of the brachial plexus form an M anterior to the Axillary artery. The lateral leg of the M is the Musculocutaneous nerve (can be seen almost immediately diving into the Coracobrachialis muscle), the middle portion is the Median nerve and the medial leg is the Ulnar nerve. Brachium & Cubital Fossa (pp. 34-39) Coracobrachialis and the short head of Biceps brachii attach together to the Coracoid process of the scapula. Coracobrachialis is the more medial of the two. The Musculocutaneous nerve dives into the Coracobrachialis muscle and then runs between Biceps brachii and Brachialis. Its superficial branch (Lateral antebrachial cutaneous nerve) emerges from the lateral side. The Brachial artery and Median nerve run together in the Medial intermuscular septum of the arm. The Ulnar nerve and Superior ulnar collateral artery run together passing just posterior to the Medial epicondyle of the humerus. The inferior ulnar collateral artery passes anterior to the med The Bicipital aponeurosis overlies the Brachial artery and Median nerve in the cubital fossa and fans out to merge with the antebrachial fascia covering the flexor muscle mass of the forearm. The Brachial artery typically divides into the Radial and Ulnar arteries in the cubital fossa, but a high bifurcation may also occur. Profunda brachii and the Radial nerve exit the axilla through the Triangular interval and run along the posterior surface of the humerus in the Radial groove. The Lateral head of triceps brachii arises superior and lateral to the groove while the Medial head arises inferior and medial to the groove. Anterior Forearm (pp. 40-46) The muscles of the flexor region of the forearm can be divided into three layers: superficial, intermediate, and deep. o The superficial layer contains (from lateral to medial) the Pronator teres, Flexor carpi radialis, Palmaris longus, and Flexor carpi ulnaris muscles all arising from the Common flexor tendon on the medial epicondyle of the humerus (as does part of Flexor digitorum superficialis). o The intermediate layer contains the Flexor digitorum superficialis muscle. 2
o The deep layer contains the Flexor digitorum profundus, Flexor pollicis longus, and Pronator quadratus muscles. The Median n. runs between the two heads of the Pronator teres muscle [superficial (humeral) and deep (ulnar)]. The Ulnar a. runs deep to the Deep head of the pronator teres muscle. The Ulnar a. and Median n. pass deep to the tendinous arch of the Flexor digitorum superficialis muscle. The tendinous arch is the free portion of the Flexor digitiorum superficialis tendon between its origins on the radius and on the humerus and ulna. The Radial a. passes superficial to the anterior compartment muscles of the forearm, but runs deep to the Brachioradialis muscle for a time. Distally (proximal to the wrist), the four tendons of the Flexor digitorum superficialis muscle lie between the Median n. (lateral) and the Ulnar a. and n. (medial). The Radial recurrent a. and the Radial n. (or the Superficial and Deep branches of the radial n. depending on where it divides) runs in the plane between the Brachioradialis and Brachialis muscles. o The Superficial branch of the radial n. runs along the deep surface of the Brachioradialis muscle and will emerge from its posterior side. o The Radial a. joins the Superficial branch of the radial n. for a time, but continues downwards and can be seen at the wrist medial to the Abductor pollicis longus tendon before diving deep to it to run within the anatomical snuff box. o The Deep branch of the radial n. dives deep to the Supinator muscle. The Ulnar a. (after emerging from the medial border of the Flexor digitorum superficialis muscle) meets up with the Ulnar n. to run between the Flexor digitorum profundus the Flexor carpi ulnaris muscles in the distal forearm. At the wrist, they pass on the lateral side of the Pisiform bone. The Anterior interosseus a. (branch of the Common interosseus a. of the Ulnar a.) runs with the Anterior interosseus n. (branch of the Median n.) on the anterior surface of the Interosseus membrane between the Flexor pollicis longus and Flexor digitorum profundus muscles. o They both pass deep to the Pronator quadratus muscle. The Anterior ulnar recurrent a. anastomoses with the Inferior ulnar collateral a. while the Posterior ulnar recurrent a. anastomoses with the Superior ulnar collateral a. o The Anterior ulnar recurrent a. runs upwards on the medial side of the Brachialis muscle. 3
o The Posterior ulnar recurrent a. will run medially and upwards, running with the Ulnar n. Dorsal compartment muscles that can be seen in anterior view: o The Abductor pollicis longus tendon can be seen on the anterior surface of the wrist at its lateral boundary. o Part of the Supinator muscle can be seen when the Brachioradialis muscle is retracted. o The Brachioradialis muscle is seen in anterior view on the forearm (forming the lateral margin of the cubital fossa). Posterior Forearm (pp. 53-57) The muscles of the extensor region of the forearm can be divided into two layers: superficial and deep. o The superficial layer contains (from lateral to medial) the Brachioradialis, Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, and Extensor carpi ulnaris muscles. Of these, Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, and Extensor carpi ulnaris arise from the Common extensor tendon on the lateral epicondyle. o The deep layer contains (from lateral to medial more or less) the Supinator, Abductor pollicis longus, Extensor pollicis brevis, Extensor pollicis longus, Extensor indicis muscles. From lateral to medial the Abductor pollicis longus, Extensor pollicis brevis, and Extensor pollicis longus emerge from the interval between the Extensor carpi radialis brevis and Extensor digitorum muscles. The tendons of Abductor pollicis longus and Extensor pollicis brevis together cross the superficial surfaces of the tendons of Extensor carpi radialis brevis and Extensor carpi radialis longus. The tendon of Extensor pollicis longus crosses the tendons of the two radial extensors but more inferiorly towards their insertions on the metacarpal bases. The anterior border of the Anatomical snuffbox is formed by the Abductor pollicis longus and the Extensor pollicis brevis tendons. The posterior border is formed by the tendon of the Extensor pollicis longus. The Radial a. can be seen coursing through the Anatomical snuffbox before it dives between the two heads of the First dorsal interosseus muscle. When the Deep branch of the radial n. emerges from the inferior surface of the Supinator muscle, it changes its name to the Posterior interosseus n. 4
The Posterior interosseus n. (continuation of the Deep branch of the radial n. runs with the Posterior interosseus a. (branch of the Common interosseus a. of the Ulnar a.). Part of the Flexor carpi ulnaris muscle (a muscle of the ventral compartment) can be seen on the lateral side of the dorsum of the forearm. Hand (pp. 46-52) The Palmaris brevis muscle overlies the hypothenar eminence. The Superficial branch of the ulnar a. and the Superficial branch of the ulnar n. are deep to the Palmaris brevis muscle, but superficial to the hypothenar muscles. The main contribution to the Superficial palmar arch is the Superficial branch of the ulnar a. It is also formed from the Superficial palmar branch of the radial a which passes through the thenar muscles.. The Superficial palmar arch lies immediately deep to the Palmar aponeurosis. The Motor recurrent branch of the median n. runs superficial to the Flexor pollicis brevis muscle and then dives between the Flexor pollicis brevis and Abductor pollicis brevis muscles. The Opponens pollicis muscle lies deep to the Flexor pollicis brevis and Abductor pollicis brevis muscles. Similarly, the Opponens digiti minimi muscle lies deep to the Flexor digiti minimi brevis and Abductor digiti minimi muscles. The tendons of the Flexor digitorum superficialis muscle splits around those of the Flexor digitorum profundus muscle, which lies deep to it. The Lumbricals arise from the tendons of the Flexor digitorum profundus muscle. The Deep branch of the ulnar a. (aka deep palmar branch) and Deep branch of the ulnar n. pass between the proximal attachments of the Flexor digiti minimi brevis and Abductor digiti minimi muscles and then pierce the Opponens digiti minimi muscle. The main contribution to the Deep palmar arch is from the Radial a., which enters the palm by diving between the two heads of the First dorsal interosseus muscle and then running between the two heads of the Adductor pollicis muscle. The Deep plamar arch also receives a contribution from the Deep branch of the ulnar a. The Deep palmar arch lies deep to the Flexor digitorum profundus tendons and the Lumbricals. The Adductor pollicis muscle lies deep to the tendons of the Flexor digitorum profundus muscle, the Lumbricals, and the Flexor pollicis brevis muscle. 5