|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
|On the medial side are the first four ribs with their corresponding Intercostales, and part of the Serratus anterior. On the lateral side, where the anterior and posterior walls converge, the space is narrow, and bounded by the humerus, the Coracobrachialis, and the Biceps brachii.|
Contents.It contains the axillary vessels, and the brachial plexus of nerves, with their branches, some branches of the intercostal nerves, and a large number of lymph glands, together with a quantity of fat and loose areolar tissue. The axillary artery and vein, with the brachial plexus of nerves, extend obliquely along the lateral boundary of the axilla, from its apex to its base, and are placed much nearer to the anterior than to the posterior wall, the vein lying to the thoracic side of the artery and partially concealing it. At the forepart of the axilla, in contact with the Pectorales, are the thoracic branches of the axillary artery, and along the lower margin of the Pectoralis minor the lateral thoracic artery extends to the side of the chest. At the back part, in contact with the lower margin of the Subscapularis, are the subscapular vessels and nerves; winding around the lateral border of this muscle are the scapular circumflex vessels; and, close to the neck of the humerus, the posterior humeral circumflex vessels and the axillary nerve curve backward to the shoulder. Along the medial or thoracic side no vessel of any importance exists, the upper part of the space being crossed merely by a few small branches from the highest thoracic artery. There are some important nerves, however, in this situation, viz., the long thoracic nerve, descending on the surface of the Serratus anterior, to which it is distributed; and the intercostobrachial nerve, perforating the upper and anterior part of this wall, and passing across the axilla to the medial side of the arm.
| The position and arrangement of the lymph glands are described on pages 699 and 700.|
1. The Axillary Artery
The axillary artery (Fig. 523), the continuation of the subclavian, commences at the outer border of the first rib, and ends at the lower border of the tendon of the Teres major, where it takes the name of brachial. Its direction varies with the position of the limb; thus the vessel is nearly straight when the arm is directed at right angles with the trunk, concave upward when the arm is elevated above this, and convex upward and lateralward when the arm lies by the side. At its origin the artery is very deeply situated, but near its termination is superficial, being covered only by the skin and fascia. To facilitate the description of the vessel it is divided into three portions; the first part lies above, the second behind, and the third below the Pectoralis minor.
Relations.The first portion of the axillary artery is covered anteriorly by the clavicular portion of the Pectoralis major and the coracoclavicular fascia, and is crossed by the lateral anterior thoracic nerve, and the thoracoacromial and cephalic veins; posterior to it are the first intercostal space, the corresponding Intercostalis externus, the first and second digitations of the Serratus anterior, and the long thoracic and medial anterior thoracic nerves, and the medial cord of the brachial plexus; on its lateral side is the brachial plexus, from which it is separated by a little areolar tissue; on its medial, or thoracic side, is the axillary vein which overlaps the artery. It is enclosed, together with the axillary vein and the brachial plexus, in a fibrous sheaththe axillary sheathcontinuous above with the deep cervical fascia.
| The second portion of the axillary artery is covered, anteriorly, by the Pectorales major and minor; posterior to it are the posterior cord of the brachial plexus, and some areolar tissue which intervenes between it and the Subscapularis; on the medial side is the axillary vein, separated from the artery by the medial cord of the brachial plexus and the medial anterior thoracic nerve; on the lateral side is the lateral cord of the brachial plexus. The brachial plexus thus surrounds the artery on three sides, and separates it from direct contact with the vein and adjacent muscles.|
| The third portion of the axillary artery extends from the lower border of the Pectoralis minor to the lower border of the tendon of the Teres major. In front, it is covered by the lower part of the Pectoralis major above, but only by the integument and fascia below; behind, it is in relation with the lower part of the Subscapularis, and the tendons of the Latissimus dorsi and Teres