ULNAR 535 



interosseous niemltrane below, the i)l)li(|iK' liganu'iit above, and tlie ubia internally, 

 and, emerging at the back of the forearm between the extensor ossis metacarpi 

 })oIlicis and the supinator l»revis, under cover of the superficial extensors of the 

 forearm, descends between the superficial and the deej) muscles, crossing in this 

 course the extensor ossis metacarpi pollicis, the extensor primi internodii pollicis, 

 the extensor secundi internodii pollicis, and the indicator (fig. 353). It anasto- 

 moses at the lower border of this muscle with the anterior interosseous, or with the 

 l>osterior Ijranch of the anterior interosseous which here, as above described, has 

 l)erforated the interosseous membrane. It is separated from the nerve of the same 

 name at first V)y the radius and supinator brevis and on the back of the forearm by 

 the extensores secundi internodii pollicis and indicis. 



It gives off the following l)ranches: — (i) The interosseous recurrent, or pos- 

 terior interosseous recurrent (fig. 353), arises from the posterior interosseous as 

 tlie latter emerges from l)eneath the supinator brevis. It runs upwards between 

 the anconeus and supinator brevis, usually under cover of the former, to the inter- 

 val l)etween the external condyle and the olecranon, where it anastomoses Avith the 

 superior profunda, anastomotica magna, radial recurrent, and posterior ulnar 

 recurrent arteries, and gives i>ranches to the retiform plexus over the olecra- 

 non — the rete olecrani. (ii) Muscular branches are given off to the superficial 

 and deep extensor muscles, (iii; Articular branches enter the back of the 

 wrist-joint. 



4. The muscular branches of the ulnar artery supply the contiguous 

 nuiscles, and are varial»le in numl)er, origin, and distribution. 



5. The nutrient artery of the ulna may be given of? from the main trunk of 

 the ulnar artery, or from one of its muscular branches, or from the anterior inter- 

 osseous artery. 



6. The posterior ulnar carpal comes of? from the ulnar artery a little above 

 the anterior annular ligament, and, winding inwards round the end of the vilna 

 (»r the internal lateral ligament of the wrist, beneath the flexor carpi ulnaris, 

 ramifies on the l)ack of the carpus beneath the extensor tendons. It forms by 

 its anastomosis with the posterior radial carpal and with the pjosterior branch of 

 the anterior interosseous and with the posterior interosseous arteries, a plexus or 

 rete, the so-called posterior carpal arch. The branches given off from this plexus 

 or arch are described with the posterior carpal branch of the radial arterv (page 

 541). 



7. The anterior ulnar carpal is a small branch given off from the ulnar arterv 

 opposite the car})us. It passes lieneath the flexor profundus digitorum to anasto- 

 mose with the anterior radial carjjal, with terminal twigs of the anterior branch of 

 the anterior interosseous, and with recurrent branches from the deep palmar arch, 

 forming an anastomotic arch across the front of the carpus — the so-called anterior 

 carpal arch or rete. 



II. Relations of the Ulnar Artery at the Wrist 



The ulnar artery at the wrist may be said to extend from the upper to the 

 lower border of the anterior aimular ligament. It here lies immediately to the 

 radial side of the pisiform bone, and to the ulnar side of the hook of the unciform, 

 the two bones forming for the vessel a protecting channel, which is further converted 

 into a short canal by the expansion of the flexor carjn ulnaris passing from the 

 ])isiform to the hook of the unciform. The ulnar nerve in this situation is imme- 

 diately to the ulnar side of the arterv. 



Relations. — In front it has. in addition to the expansion aliove menticnied. 

 the skin and superficial fascia; below, it rests on the annular ligament; inter- 

 nally are the ulnar nerve and })isitorm bone: externally, the hook of the unci- 

 form. 



The ulnar artery gives off no named branch in this part of its course. 



