J058 THE NERVE SYSTEM 



The gluteal cutaneous branches (nri. clunium inferiores [laterales]), two or three 

 in number, turn upward around the lower border of the Gluteus maximus to 

 supply the skin covering the lower and outer part of that muscle. 



The perineal cutaneous branches (rami perineales) are distributed to the skin at 

 the upper and inner side of the thigh, on its posterior aspect. One branch, 

 longer than the rest, the inferior pudendal or long scrotal nerve (Fig. 776), curves 

 forward below the ischial tuberosity, pierces the fascia lata, and runs forward 

 beneath the superficial fascia of the perineum to be distributed to the skin of the 

 scrotum in the male and the labium ma jus in the female, communicating with the 

 superficial perineal and inferior hemorrhoidal nerves. 



The femoral cutaneous branches consist of numerous descending filaments 

 derived from both sides of the nerve, and are distributed to the back and inner 

 sides of the thigh, to the skin covering the popliteal space, and to the upper part 

 of the leg. 



The Great Sciatic Nerve (n. ischiadicus) (Figs. 774 and 776) supplies nearly 

 the whole of the integument of the leg, the muscles of the back of the thigh, and 

 those of the leg and foot. It is the largest nerve cord in the body, measuring 

 three-quarters of an inch in breadth, and is the continuation of the flattened band 

 of the sacral plexus. It passes out of the pelvis through the great sacrosciatic 

 foramen, below the Pyriformis muscle. It descends between the great trochanter 

 of the femur and the tuberosity of the ischium, along the back part of the thigh, to 

 about its lower third, where it divides into two large branches, the internal popliteal 

 ortibial and external popliteal or peroneal nerves (Fig. 776). This division may take 

 place at any point between the sacral plexus and the lower third of the thigh. 

 When the division occurs at the plexus (in 10 per cent, of cases) the two nerves 

 descend together side by side; or they may be separated, at their commencement, 

 by the interposition of part or the whole of the Pyriformis muscle. 



As the nerve descends along the back of the thigh, it rests upon the posterior 

 surface of the ischium, the nerve of the Quadra tus femoris and the External 

 rotator muscles of the thigh, in company with the small sciatic nerve and artery, 

 and is covered by the Gluteus maximus; lower down, it lies upon the Adductor 

 magnus, and is covered by the long head of the Biceps. 



The branches of the nerve, before its division, are articular and muscular. 



The articular branches (rami articulares) arise from the upper part of the nerve ; 

 they supply the hip-joint, perforating the posterior part of its fibrous capsule. 

 These branches are sometimes derived directly from the sacral plexus. 



The muscular branches (rami musculares) are distributed to the flexors of the leg 

 viz., the Biceps, Semitendinosus, and Semimembranosus, and to the Adductor 

 magnus. The nerve to the short head of the Biceps comes from the external 

 popliteal part of the great sciatic, while the other muscular branches arise from the 

 internal popliteal portion, as may be seen in those cases where the two popliteal 

 nerves emerge separately on the buttock. 



The Internal Popliteal or Tibial Nerve (n. tibialis} (Figs. 774 and 776), the larger 

 of the two terminal branches of the great sciatic, arises from the anterior primary 

 branches of the last two lumbar and first three sacral nerves. It descends along 

 the back part of the thigh, through the middle of the popliteal space, to the lower 

 part of the Popliteus muscle, where it passes with the artery beneath the arch of 

 the Soleus and becomes the posterior tibial. It is overlapped by the Hamstring 

 muscles above, and then becomes more superficial, and lies to the outer side of, 

 and some distance from, the popliteal vessels; opposite the knee-joint it is in close 

 relation with the vessels, and crosses to the inner side of the artery. Below, it 

 is overlapped by the Gastrocnemius. 



The branches of this nerve are the articular and muscular, and a cutaneous branch, 

 the communicans tibialis. 



