THE SACRAL PLEXUS. 



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the lower limb, and is formed by the union of four large roots from 

 the lumbo-sacral cord and the first three sacral nerves. 



b. The superior gluteal nerve (fig. 150, sg) arises by two roots Superior 

 from the back of the lumbo-sacral cord and the first sacral s luteaL 

 nerve, and leaves the pelvis with the gluteal artery above the 



FIG. 150. DIAGRAM OP THE SACRAL PLEXUS, FROM BEHIND. 



LSC. Lumbo-sacral cord, formed by 

 the fifth lumbar nerve and a small 

 branch from the fourth. 



SI to SV. First to fifth sacral 

 nerves. 



Co. Coccygeal nerve. 



gs. Great sciatic nerve. 



ss. Small sciatic. 



p. Pudic. 



sg. Superior gluteal. 



ig. Inferior gluteal. 



py. Branch to pyriformis. 



oi. Nerve to obturator internus. 



q. Nerve to quadratus. 



v. Visceral branches of third and 

 fourth sacral nerves. 



la. Branch to levator ani. 



co. Branch to coccygeus. 



h. Haemorrhoidal or perinea! 

 branch of fourth sacral. 



pc. Perforating cutaneous. 



pyriformis for the supply of the muscles on the outer surface of 

 the ilium. 



c. The inferior gluteal (ig) is the nerve of the gluteus maximus. inferior 

 It springs from the back of the lumbo-sacral cord and first two luteaL 

 sacral nerves, and passes out below the pyriformis. 



d. The small sciatic (ss) is the cutaneous nerve of the back of the Small 



sciatic. 

 D D 2 



