214 MYOLOGY, OR ANATOMY OF MUSCULAR SYSTEM 



THE MUSCLES AND FASCLffi OF THE HANDS 



Fascia of the dorsum is a thin layer prolonged from the 

 posterior annular ligament and blending with the extensor 

 expansions over the fingers; deeper than this the interossei 

 are covered by thin aponeuroses. 



Fascia of the palm (volar aponeurosis) consists of a strong 

 central part and two lateral portions which cover the short 

 muscles of the thumb and little finger. The central portion 

 is the part commonly called the palmar fascia; it consists of 

 fibers mostly prolonged from the palmaris longus, some from 

 the annular ligament, thus forming two superficial layers 

 with vertical fibers, between which is the palmaris brevis 

 muscle; there is a deep layer of transverse fibers. Below, the 

 fascia divides into four processes to join the digital sheaths; 

 offsets are sent back to the deep transverse ligament at the 

 heads of the metacarpals, forming a short canal above each 

 finger for the flexors. Between the processes the transverse 

 layer of fascia covers the lumbrical muscles, digital vessels, 

 and nerves, passing over to the thumb and forefinger. At the 

 clefts of the fingers a transverse band is called the superficial 

 transverse ligament, or Gerdy's fibers. The interossei muscles 

 also have a separate fascia continued below into the deep 

 transverse ligament. 



The Muscles of the Dorsal Surface 



Extensor tendons already described. 



DEEP MUSCLES. Median Carpal Burass. As the super- 

 ficial and deep flexors and flexor longus pollicis enter the hollow 

 of the hand they are bound into one tube lined by synovial 

 tissue; a loose synovial sac is formed, passing up to the level 

 of the radiocarpal joint and prolonged down the inner tendons 

 to the digital sheath of the little finger, opening into it generally. 

 The sheath for the tendon of the thumb is generally separated 

 from the large sac by a sagittal septum behind the median 

 nerve; the bursa extends but a short distance on the index 

 and middle finger tendons. 



