4IO A MANUAL OF ANATOMY 



metacarpo-phalangeal ligaments are strong bands which are attached 

 above to the dorsal tubercle and palmar depression on either side 

 of the head of a metacarpal bone, and below to each side of the 

 base of a first phalanx, and also to the lateral margin of the palmar 

 fibrous plate. Each is connected with a deep expansion of a 

 digital process of the central division of the palmar fascia. The 

 palmar ligament takes the form of a fibrous plate. It is closely 

 attached at either side to the lateral ligaments, interiorly to the 

 palmar aspect of the base of the first phalanx, and superiorly, 

 where it is connected with the transverse metacarpal ligament, it 

 is slightly attached to the palmar aspect of the head of a metacarpal 

 bone, close above the articular cartilage. It increases the extent 

 of the phalangeal socket for the head of a metacarpal bone, and it 

 forms part of the tunnel for the passage of a pair of flexor tendons. 

 Its deep surface is lined by the synovial membrane of the joint. There 

 is no dorsal ligament, its place being taken by the extensor tendon. 



Each joint is provided with a synovial membrane, which is looser 

 in front than behind. 



Arterial Supply. — The digital arteries from the superficial palmar 

 arch, or the palmar interosseous from the deep palmar arch. 



Nerve-supply. — ^The deep division of the ulnar nerve. 



Movements. — The movements are flexion, extension, abduction, adduction, 

 and circumduction. Flexion is particularly free, and is combined with 

 adduction. Extension is associated with abduction, and dorsal flexion is 

 prevented by the palmar fibrous plates and flexor tendons. 



Metacarpo-phalangeal Joint of the Thumb. — ^The lateral liga- 

 ments of this joint are similar to those of the other joints, but there 

 is no palmar fibrous plate, its place being taken by two sesamoid 

 bones. Each of these bones resembles a split pea. The palmar 

 surface is convex, whilst the deep surface is almost flat and covered 

 by cartilage, to play upon a groove on the palmar surface of the 

 head of the first metacarpal bone. The two bones are united by 

 fibres which pass between their contiguous surfaces, and are related i 

 superficially to the tendon of the flexor longus pollicis. Interiorly j 

 they are connected by fibres with the palmar aspect of the base ofj 

 the first phalanx. At either side they are connected with the lateralf 

 ligaments, and posteriorly they are slightly connected with the head; 

 of the first metacarpal above the articular cartilage. The outeri; 

 sesamoid bone is closely associated with the superficial head of the i 

 flexor brevis pollicis, and the inner with the adductor obliquus;; 

 pollicis. The place of a dorsal ligament is taken by the tendonsf^ 

 of the extensor brevis, and extensor longus, pollicis. I 



Arterial Supply. — ^The arteria princeps pollicis of the radial. | 



Nerve-supply. — ^The median nerve. 1 



Movements. — Flexion, extension, and lateral movement, the latter onljji 

 when the joint is partially flexed. ( 



Interphalangeal Joints. — These belong to the class diarthrosisf 



and to the subdivision ginglymus. The ligaments are similar iff 



