218 



MUSCLES OF THE UPPER LIMB. 



closely round the tendon of the deep flexor, and are reunited by their 

 margins behind it : the two portions of the tendon thereafter separating, 

 pass to be inserted one on each side into a ridge at the middle of the lateral 

 border of the second phalanx. A large synovial bursa loosely invests the 

 tendons of both the superficial and deep flexors of the fingers behind the 

 annular ligament, extending downwards into the palm of the hand. In the 

 little finger it approaches the synovial lining of the sheath, and in the 

 thumb it usually communicates with it. 



Fig. 180. 



Fig. 180. METACARPAL AND PHALANGEAL BONES OF Two FINGERS, WITH THE TENDONS 



AND THEIR ACCESSORY STRUCTURES. ^ 



In A, the tendons of the flexor muscles are bound to the finger by the fibrous bands 

 or retinaeula. In B, these bands have been removed, as well as the synovial capsules and 

 vincula accessoria : 1, raetacarpal bone ; 2, tendon of the flexor sublimis ; 3, tendon of 

 the flexor profundus ; *, perforation of the sublimis by the profundus tendon ; 4, tendon 

 of the extensor digitorum communis ; 5, one of the lumbricales muscles ; 6, one of the 

 interosseous muscles. 



The sheaths of the flexor tendons, by which they are bound down to the 

 fingers, are formed opposite the first and second phalanges by strong ten- 

 dinous bands of transverse fibres (ligamenta vagiualia) attached to the 

 rough margins of the palmar surfaces of the phalanges. Opposite the joints, 

 flexion is secured by the substitution for those bands of a thin membrane, 

 strengthened by oblique decussating fibres. The tendinous sheath has a 

 synovial lining, which is simple in front, but posteriorly dips between the 

 tendons. A few slender and loose bands (viucula accessoria tendinum, 

 vincula vasculosa) extend from the floor of the sheath to the deep surface 

 of both tendons. Behind each tendon, near its insertion, is a short mem- 

 branous structure (ligamentum breve), which fixes the tendon to the front 

 of the phalanx situated above that into which it is inserted. 



Superiorly, the flexor sublimis is concealed by the other muscles of the superficial 

 get, and is crossed near the radius by the radial artery ; it rests on the flexor pollicis 

 longus and flexor profundus, separated from the latter by the median nerve and the 

 ulnar artery. In the palm of the hand, its tendons are covered by the palmar fascia, 

 the superficial palmar arterial arch, and the branches of the median nerve ; and they 

 lie in front of the accompanying tendons of the flexor profundus. 



A muscular slip is frequently given from this muscle to the flexor profundus, or to 

 the flexor longus pollicis. The tendon for the little finger is sometimes wanting. 



The deep-seated muscles, on the anterior surface of the forearm, are the 

 flexor profundus, flexor pollicis longup, and pronator qnadratus. 



