NERVES 171 



three and part of the 4th nerves enter the sacral plexus, whilst 

 the lower part of the 4th, the 5th, and the coccygeal nerve 

 form a small plexus, ano-coccygeal, which lies on the pelvic 

 surface of the coccygeus. 



The ano-coccygeal plexus : formed as described above. 

 Branches : 

 Muscular to : 

 Coccygeus. 

 Levator ani. 

 Sphincter ani externus (usually called the perinea) 



branch of the 4th sacral). 

 Visceral. 

 Vesical. 

 Rectal. 



Vaginal (in female). 



Cutaneous : perforating cutaneous of 4th sacral to integu- 

 ment over coccyx. 



The SACRAL PLEXUS is formed by the lumbo-sacral cord 

 (p. 167), anterior primary branches of the upper three and 

 part of that of the 4th sacral nerves. Lies on anterior surface 

 of pyriformis, behind the sciatic and internal pudic arteries. 

 Branches : 

 Muscular: To pyriformis, from ist and and. 



To obturator internus and gemellus superior, 

 from 5th lumbar, ist and 2nd sacral, emerges 

 from pelvis through great sacro-sciatic foramen, 

 winds over ischial spine outside the internal pudic 

 artery, passes in through small sacro-sciatic 

 foramen to inner surface of muscle, having first 

 supplied superior gemellus. 



To quadratus femoris and gemellus inferior, 

 given off from lumbo-sacral cord and ist sacral, 

 passes anterior to gemelli and obturator internus 

 tendon to anterior surface of quadratus, giving 

 on its way a branch to gemellus inferior, and an 

 articular branch to the hip-joint. 



Superior gluteal : from lumbo-sacral cord and ist sacral, 

 passes out of great sacro-sciatic foramen, above the pyriformis, 

 with the gluteal vessels ; divides into a superior branch, which 

 passes between the two smaller glutei, supplying the medius, 

 and an inferior branch, supplying the gluteus minimus and the 

 tensor fasciae femoris. 



Pudic : comes off from the 2nd, 3rd, and 4th nerves, passes 

 out of great sacro-sciatic notch between pyriformis and 

 coccygeus internal to great sciatic nerve, winds over ischial 



