778 HUMAN ANATOMY. 



3. The Anastomotica Magna. — The anastomotica magna (a. coI!aterali& 

 ulnaris inferior) (Fig. 709) arises from the inner surface of the brachial artery, about 

 4 cm. (i^ in.) above its termination. It passes inward over the brachialis anticus 

 and beneath the median nerve, and, piercing the internal intermuscular septum, winds 

 around the inner border of the humerus and passes transversely across its posterioi 

 surface, just above the olecranal fossa. It anastomoses with the posterior ulnar recur- 

 rent and with both the superior and inferior profunda arteries, and also, by means of a 

 branch given off before it pierces the intermuscular septum, with the anterior ulnar 

 recurrent. 



Anastomoses around the Elbow. — The brachial artery forms rich anasto- 

 moses around the elbow-joint with both the radial and ulnar arteries by means of its 

 superior and inferior profunda branches and the anastomotica magna, abundant 

 opportunity being thus afforded for a collateral circulation to the forearm after ligation 

 of the brachial. Thus, the superior profunda anastomoses in front of the external 

 condyle of the humerus with the radial recurrent, and its medial collateral branch 

 anastomoses in the neighborhood of the olecranon process with the posterior inter- 

 osseous and the posterior ulnar recurrents. The inferior profunda also anastomoses 

 with the posterior ulnar recurrent behind the internal condyle, while the anastomotica 

 magna makes connections in front of the internal condyle with the anterior ulnar 

 recurrent; and posteriorly, with the posterior ulnar and the posterior interosseous 

 recurrents. 



THE ULNAR ARTERY. 



The ulnar artery (a. ulnaris) ( Figs. 710, 712) is the larger of the two terminal 

 branches of the brachial. It arises just below the bend of the elbow and passes at 

 first distally and inward, in a gentle curve, beneath the muscles which arise from the 

 internal condyle of the humerus, and at the junction of the upper and middle thirds 

 of the forearm assumes a more vertical direction. Arrived at the wrist, it passes over 

 the anterior annular ligament to the radial side of the pisiform bone and then passes 

 across the palmar surface of the hand, forming the siiperjicial palmar arch (arcus 

 volaris superficialis), whose convexity looks distally, and terminates opposite the 

 second intermetacarpal space by anastomosing with the superficial volar branch of 

 the radial. 



For convenience in description, the ulnar artery may be regarded as consisting 

 of three parts : (i) an antibrachial portion extending from the origin of the yessel to 

 the upper border of the anterior annular ligament, (2) a carpal portion resting upon 

 the annular ligament, and (3) a palmar portion in the hand. The course of the 

 lower two-thirds of the antibrachial portion may be represented by a line drawn from 

 the front of the internal condyle of the humerus to a point immediately to the radial 

 side of the pisiform bone, while the course of the upper third may be indicated by a 

 line drawn from the middle of the bend of the elbow to meet the first line at the 

 junction of its upper and middle thirds. The superficial palmar arch is on a leve^. 

 with the thumb when the digit is abducted to a position at right angles to the axis 

 of the hand. 



Relations. — The antibrachial portion of the ulnar in its upper third is cov- 

 ered by the pronator radii teres, the flexor carpi radialis, the palmaris longus, and the 

 flexor sublimis digitorum, and is crossed obliquely by the median nerve. Behind, it 

 rests upon the tendons of the brachialis anticus and upon the flexor profundus digi- 

 torum. In its lower two-thirds it is overlapped above by the flexor carpi ulnaris, but 

 below it lies entirely to the radial side of the tendon of that muscle, and is covered 

 only by the skin and fasciae. It rests upon the flexor profundus digitorum, and to its 

 radial side is the tendon of the flexor sublimis digitorum, while to its ulnar side it is in 

 close relation with the ulnar nerve, as well as with the tendon of the flexor carpi ulnaris. 



In its carpal portion it rests upon the anterior surface of the anterior annular 

 ligament, immediately to the radial side of the pisiform bone, and is covered by an 

 expansion from the tendon of the flexor carpi ulnaris. 



The palmar portion, in the upper part of its course, is covered by the palmaris 

 brevis and rests upon the flexor brevis minimi digiti. The superficial palmar arch, 

 as it passes radialwards, is crossed successively by the palmar branch of the ulnar 



