Lumbricals 273 



olecranon heads the ulnar nerve enters the fore-arm, and in that same 

 interval is the anastomosis between the inferior profunda and posterior 

 ulnar recurrent, over the internal lateral ligament of the elbow. 



The flexor profundus digitorum is a bulky muscle arising from 

 the upper two-thirds of the inner and anterior surfaces of the ulna, and 

 from the adjacent part of the interosseous membrane. Its four tendons 

 pass through those of the flexor sublimis, opposite the first phalanges, 

 and are inserted into the bases of the ungual phalanges. The nerve- 

 supply for its outer part is the anterior interosseous of the median, 

 and, for the inner part, the ulnar. 



Relations. Superficial to it are the flexors sublimis digitorum and 

 carpi ulnaris, the median and ulnar nerves, and the ulnar artery. The 

 flexor longus pollicis lies along its outer side, and in the deep and 

 narrow crevice between these muscles run the anterior interosseous 

 nerve and artery. On its inner aspect is the flexor carpi ulnaris. 



The lumbricals arise from the tendons of the deep flexor in the 

 palm, and pass into the radial side of the common extensor tendons. 

 These muscles are much used by the piano-forte player. They extend 

 the first phalanx, and flex the second and third phalanges. The two 

 outer are associated with the tendons of that part of the deep flexor 

 which is supplied by the anterior interosseous nerve of the median, 

 and consequently derive their nerve-supply from digital branches of 

 the median, whilst the two inner are supplied by the ulnar nerve, which 

 has already supplied the inner part of the deep flexor, from which 

 come the tendons for the ring and'little fingers. 



When the lumbricals are paralysed the metacarpal phalanges are 

 drawn backwards and the middle and terminal phalanges are flexed 

 into the palm. 



i, metacarpal bone ; 2, tendons of flex, sublimis and, 3, profundus, bound down by fibrous 

 sheath ; 4, extensor communis ; 5, lumbrical muscle ; 6, interosseous muscle. 



The flexor longus pollicis arises from the front of the radius 

 between the flexor sublimis and the pronator quadratus, and from the 

 adjoining part of the interosseous membrane. Its tendon passes over 

 the square pronator, under the annular ligament, and between the 

 heads of the flexor brevis pollicis, to be inserted into the base of the 

 ungual phalanx of the thumb. Its nerve is the anterior interosseous. 



Superficial to it are the flexors carpi radialis and sublimis digitorum, 

 and the radial artery. Its ulnar border is separated from the flexor 

 profundus by the anterior interosseous nerve and artery. 



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