782 * HUMAN ANATOMY. 



{cc} The anterior terminal branch passes either over or beneath the pronator quadratus, 

 and terminates usually by anastomosing with branches of the anterior radial and ulnar carpal 

 and with the p.ilmar recurrent arteries. Occasionally it anastomoses directly with the "super- 

 ficial palmar arch. 



[dd ) The posterior terminal branch is larger than the anterior. It perforates the inter- 

 osseous membrane, anastomoses with the posterior interrosseous arterj-, and terminates in 

 branches which anastomose witli the posterior radial and ulnar carpals to form the dorsal carpal 

 net- work. 



Variations. — The anterior interosseous artery may arise from the radial, and it may form 

 anastomoses below with the radial or with both the radial and ulnar. The relations which it 

 sometimes possesses with the superficial palmar arch w ill be considered later, 



The median artery is occasionally of considerable size and frequently arises from the 

 common interosseous. Its relations to the superficial palmar arch will also be considered 

 later (page 785). 



d. The Posterior Interosseous Artery. — The posterior interosseous (a. inter- 

 ossea dorsalis) (Fig. 715) passes backward between the radius and ulna, above the 

 concave upper margin of the interrosseous membrane. It thus reaches the posterior 

 portion of the forearm and turns abruptly downward between the superficial and deep 

 layers of the extensor muscles, and breaks up at the wrist into branches which anas- 

 tomose with the posterior radial and ulnar carpals and Mith the posterior terminal 

 branch of the anterior interosseous, assisting in the formation of the dorsal carpal 

 net-work. 



Just as' it reaches the posterior surface of the foiearm it gives off a posterior 

 interosseous recurrent branch (a. interossea recurrens), which ascends between the 

 anconeus and the supinator brevis to the posterior surface of the external condyle of 

 the humerus, where it anastomoses with the superior profunda and the anastomotica 

 magna. In its course down the arm the posterior interosseous gives branches to the 

 extensor muscles, and, through the dorsal carpal net-work, it takes part in the supply 

 of the articulations of the wrist and carpus. 



4. The Ulnar Nutrient Artery. — The nutrient branch for the ulna arises 

 from the upper third of the ulnar artery or from one of its muscular branches, or 

 from the anterior interosseous. It enters the nutrient foramen • situated upon the 

 anterior surface of the bone, near its outer border. 



5. The Posterior Ulnar Carpal Artery. — The posterior ulnar carpal (ramus 

 carpeus dorsalis) (Fig. 715) is small. It arises from the inner surface of the ulnar 

 artery, just above the pisiform bone, and winds inward beneath the tendon of the 

 flexor carpi ulnaris to the back of the carpus, where it anastomoses with the posterior 

 radial carpal and the posterior interosseous to form the dorsal carpal net-work. 



6. The Anterior Ulnar Carpal Artery. — The anterior ulnar carpal (ramus 

 carpeus volaris) (Fig. 712) is also small. It arises from the ulnar artery, just above 

 the upper border of the anterior annular ligament, and passes outward upon the car- 

 pal ligaments and beneath the long flexor tendons to anastomose with the anterior 

 radial carpal and anterior interosseous to form the anterior carpal net-work. 



7 and 8. The Deep Palmar Arteries. — The deep palmar branches (rami 

 volares profundi) (Fig. 712) are given off from the ulnar artery, just after it has 

 entered the palm. The superior brai7ch arises just after the ulnar artery has passed 

 the pisiform bone, and passes dorsally in the interval between the flexor brevis minimi 

 digiti and the abductor minimi digit!. It then perforates the opponens minimi digiti, 

 and terminates by inosculating with the deep palmar arch. 



The inferior branch arises just as the ulnar artery is bending to pass trans- 

 versely across the palm. It passes dorsally between the flexor brevis minimi digiti 

 and the long flexor tendon for the little finger, and terminates by inosculating with 

 the deep palmar arch, near the superior branch. 



Frequently one or other of these branches, more usually the superior one, is 

 lacking, and only one communication between the ulnar and the deep palmar arch 

 exists. In their passage dorsally, both arteries give off branches to the adjacent 

 muscles. 



