434 A MANUAL OF ANATOMY 



Relations — Superficial or Posterior. — Gluteus maximus. Deep or 

 Anterior. — Posterior surface of spine of ischium. 



On either side of the artery is a vena comes. The pudic nerve 

 Hes on the inner side, and the nerve to the obturator internus on 

 the outer side. 



Branches. — Muscular, to gluteus maximus, and sacral, which 

 pierces the great sacro-sciatic ligament, and ramifies over the 

 back of the lower end of the sacrum, where it anastomoses with 

 the coccygeal branch of the sciatic artery. 



The position of the second part of the internal pudic artery upon 

 the back of the spine of the ischium, which spine is about 4 inches 

 below the posterior superior iliac spine, is ascertained as follows : 

 the thigh being rotated inwards, draw a line from the upper border 

 of the great trochanter to the junction of the sacrum with the 

 coccyx, and take a point in this line at the junction of the inner 

 third and outer two-thirds. 



Relation of Structures on Back of Spine of Ischium. — The relation from 

 within outwards is as follows: (i) pudic nerve, (2) internal vena comes, 

 (3) second part of internal pudic artery, (4) external vena comes, and 

 (5) nerve to obturator internus muscle. 



Deep Nerves. Superior Gluteal Nerve. — ^This nerve arises from the 

 sacral plexus, more particularly from the dorsal divisions of the 

 descending branch of the fourth lumbar, the fifth lumbar, and the 

 first sacral nerves. It passes through the upper compartment of 

 the great sacro-sciatic foramen, above the pyriformis, with the 

 gluteal artery, and then beneath the gluteus medius, where it 

 divides into a small upper and large lower branch. The upper 

 branch accompanies the corresponding division of the deep part of 

 the gluteal artery along the upper border of the gluteus minimus, and 

 it supplies the gluteus medius. The lower branch passes outwards 

 over the centre of the gluteus minimus with the lower division of the 

 deep part of the gluteal artery. It supplies the gluteus medius 

 and gluteus minimus, and terminates by supplying the tensoi 

 fasciae femoris. 



Inferior Gluteal Nerve. — ^This nerve arises from the sacral plexus, 

 more particularly from the dorsal divisions of the fifth lumbar, and 

 first and second sacral nerves. It passes through the lower com-i 

 partment of the great sacro-sciatic foramen, below the^ pyriformis | 

 in close contact with the small sciatic nerve. It then divide;^ 

 into several branches which enter the deep surface of the gluteu: 

 maximus in its lower third. 



Nerve to Obturator Internus. — This nerve arises from the sacra, 

 plexus, more particularly from the ventral divisions of the fiftl' 

 lumbar, and first and second sacral nerves. It passes through th 

 lower compartment of the great sacro-sciatic foramen, below th 

 pyriformis, internal to the great sciatic nerve ; over the posterior sui 

 face of the spine of the ischium, where it lies to the outer side of th 

 internal pudic vessels ; and through the small sacro-sciatic foram(> 

 to the intrapelvic part of the obturator internus. At the 1o\m 



