Upper arm

Published on 17/03/2015 by admin

Filed under Basic Science

Last modified 17/03/2015

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 5 (1 votes)

This article have been viewed 4864 times

CHAPTER 47 Upper arm

SKIN AND SOFT TISSUE

SKIN

Cutaneous vascular supply

The blood supply to the skin of the upper arm can be divided into three regions with separate supply: the deltoid region, supplied by musculocutaneous perforators, and the medial and lateral regions, supplied by fasciocutaneous perforators (Cormack & Lamberty 1994; Salmon 1994) (Fig. 47.1, Fig. 47.2).

The deltoid region is supplied by the posterior circumflex humeral artery (p. 817) via musculocutaneous perforators. After the posterior circumflex humeral artery passes through the quadrangular space (p. 814) it gives off a descending branch, which runs down to the deltoid insertion and the overlying skin, and an ascending branch which passes superiorly towards the acromion, pierces the edge of deltoid and the deep fascia to fan out and supply the overlying skin.

The medial side of the upper arm is supplied by five or six fasciocutaneous perforators which arise from the brachial artery, the superior ulnar collateral artery and, if present, the single artery to biceps. These perforators pass along the medial intermuscular septum to spread out in the deep fascia and anastomose with perforating vessels superiorly and inferiorly and from the lateral side. There are virtually no musculocutaneous perforators through biceps or triceps.

The lateral side of the upper arm below deltoid is supplied by perforating vessels from the middle collateral and radial collateral arteries (the terminating bifurcation of the profunda brachii). The middle collateral artery sends perforators to the skin via the lateral intermuscular septum between brachioradialis and triceps, while the radial collateral artery gives off cutaneous perforators via the intermuscular septum between brachialis and brachioradialis. These cutaneous vessels anastomose with those from the medial side.

SOFT TISSUE

Brachial fascia

Brachial fascia, the deep fascia of the upper arm, is continuous with the fascia covering deltoid and pectoralis major: it forms a thin, loose sheath for muscles of the upper arm, and sends septa between them. It is thin over biceps, but thicker over triceps and the humeral epicondyles, and is strengthened by fibrous aponeuroses from pectoralis major and latissimus dorsi medially and from deltoid laterally. Strong medial and lateral intermuscular septa extend from it on each side.

The lateral intermuscular septum extends distally from the lateral lip of the intertubercular sulcus of the humerus along the lateral supracondylar ridge to the lateral epicondyle, and blends with the tendon of deltoid. It gives attachment to triceps behind, and brachialis, brachioradialis and extensor carpi radialis longus in front. It is perforated in the middle third by the radial nerve and the radial collateral branch of the profunda brachii artery. The thicker medial intermuscular septum extends from the medial lip of the intertubercular sulcus, distal to teres major, along the medial supracondylar ridge to the medial epicondyle, and blends with the tendon of coracobrachialis. It gives attachment to triceps behind, and brachialis in front. It is perforated by the ulnar nerve, superior ulnar collateral artery, and the posterior branch of the inferior ulnar collateral artery. At the elbow, the brachial fascia is attached to the epicondyles of the humerus and the olecranon of the ulna, and is continuous with the antebrachial fascia. Medially, just below the middle of the upper arm, it is traversed by the basilic vein and lymphatic vessels and, at various levels, branches of the brachial cutaneous nerves.

Together, the lateral and medial intermuscular septa of the upper arm divide the upper arm into anterior and posterior compartments.

MUSCLES

The muscles of the upper arm are coracobrachialis, which acts only on the shoulder joint; biceps and triceps, which cross both shoulder and elbow joints; and brachialis, which acts only at the elbow joint (Fig. 47.2, Fig. 47.3).

ANTERIOR COMPARTMENT

Coracobrachialis

Biceps brachii

Attachments

Biceps brachii derives its name from its two proximally attached parts or ‘heads’ (Fig. 46.20). The short head arises by a thick flattened tendon from the coracoid apex, together with coracobrachialis. The long head starts within the capsule of the shoulder joint as a long narrow tendon, running from the supraglenoid tubercle of the scapula at the apex of the glenoidal cavity, where it is continuous with the glenoidal labrum (p. 805). The tendon of the long head, enclosed in a double tubular sheath (an extension of the synovial membrane of the joint capsule), arches over the humeral head, emerges from the joint behind the transverse humeral ligament, and descends in the intertubercular sulcus, where it is retained by the transverse humeral ligament and a fibrous expansion from the tendon of pectoralis major. The two tendons lead into elongated bellies that, although closely applied, can be separated to within 7 cm or so of the elbow joint. At this joint they end in a flattened tendon, which is attached to the rough posterior area of the radial tuberosity; a bursa separates the tendon from the smooth anterior area of the tuberosity. As it approaches the radius, the tendon spirals, its anterior surface becoming lateral before being applied to the tuberosity. The tendon has a broad medial expansion, the bicipital aponeurosis, which descends medially across the brachial artery to fuse with deep fascia over the origins of the flexor muscles of the forearm (Fig. 47.5). The tendon can be split without difficulty as far as the tuberosity, whence it can be confirmed that its anterior and posterior layers receive fibres from the short and long heads, respectively.

In 10% of cases, a third head arises from the superomedial part of brachialis and is attached to the bicipital aponeurosis and medial side of the tendon of insertion. It usually lies behind the brachial artery, but it may consist of two slips, which descend in front of and behind the artery. Less often, other slips may spring from the lateral aspect of the humerus or intertubercular sulcus.

Brachialis

Attachments

Buy Membership for Basic Science Category to continue reading. Learn more here