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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
artery and the descending branch of the transverse cervical; the other is continued along the axillary border of the scapula, between the Teres major and minor, and at the dorsal surface of the inferior angle anastomoses with the descending branch of the transverse cervical. In addition to these, small branches are distributed to the back part of the Deltoideus and the long head of the Triceps brachii, anastomosing with an ascending branch of the a. profunda brachii.
  5. The posterior humeral circumflex artery (a. circumflexa humeri posterior; posterior circumflex artery) (Fig. 524) arises from the axillary artery at the lower border of the Subscapularis, and runs backward with the axillary nerve through the quadrangular space bounded by the Subscapularis and Teres minor above, the Teres major below, the long head of the Triceps brachii medially, and the surgical neck of the humerus laterally. It winds around the neck of the humerus and is distributed to the Deltoideus and shoulder-joint, anastomosing with the anterior humeral circumflex and profunda brachii.
  6. The anterior humeral circumflex artery (a. circumflexa humeri anterior; anterior circumflex artery) (Fig. 524), considerably smaller than the posterior, arises nearly opposite it, from the lateral side of the axillary artery. It runs horizontally, beneath the Coracobrachialis and short head of the Biceps brachii, in front of the neck of the humerus. On reaching the intertubercular sulcus, it gives off a branch which ascends in the sulcus to supply the head of the humerus and the shoulder-joint. The trunk of the vessel is then continued onward beneath the long head of the Biceps brachii and the Deltoideus, and anastomoses with the posterior humeral circumflex artery.

Peculiarities.—The branches of the axillary artery vary considerably in different subjects. Occasionally the subscapular, humeral circumflex, and profunda arteries arise from a common trunk, and when this occurs the branches of the brachial plexus surround this trunk instead of the main vessel. Sometimes the axillary artery divides into the radial and ulnar arteries, and occasionally it gives origin to the volar interosseous artery of the forearm.
 
4b. 2. The Brachial Artery
 
  
(A. Brachialis)


The brachial artery (Fig. 525) commences at the lower margin of the tendon of the Teres major, and, passing down the arm, ends about 1 cm. below the bend of the elbow, where it divides into the radial and ulnar arteries. At first the brachial artery lies medial to the humerus; but as it runs down the arm it gradually gets in front of the bone, and at the bend of the elbow it lies midway between its two epicondyles.

Relations.—The artery is superficial throughout its entire extent, being covered, in front, by the integument and the superficial and deep fasciæ; the lacertus fibrosus (bicipital fascia) lies in front of it opposite the elbow and separates it from the vena mediana cubiti; the median nerve crosses from its lateral to its medial side opposite the insertion of the Coracobrachialis. Behind, it is separated from the long head of the Triceps brachii by the radial nerve and a. profunda brachii. It then lies upon the medial head of the Triceps brachii, next upon the insertion of the Coracobrachialis, and lastly on the Brachialis. Laterally, it is in relation above with the median nerve and the Coracobrachialis, below with the Biceps brachii, the two muscles overlapping the artery to a considerable extent. Medially, its upper half is in relation with the medial antibrachial cutaneous and ulnar nerves, its lower half with the median nerve. The basilic vein lies on its medial side, but is separated from it in the lower part of the arm by the deep fascia. The artery is accompanied by two venæ comitantes, which lie in close contact with it, and are connected together at intervals by short transverse branches.

The Anticubital Fossa.—At the bend of the elbow the brachial artery sinks deeply into a triangular interval, the anticubital fossa. The base of the triangle is directed upward, and is represented by a line connecting the two epicondyles of the humerus; the sides are formed by the medial edge of the Brachioradialis and the lateral margin of the Pronator teres; the floor is formed by the Brachialis and Supinator. This space contains the brachial artery, with its accompanying veins; the radial and ulnar arteries; the median and radial nerves; and the tendon of the Biceps brachii. The brachial artery occupies the middle of the space, and

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