THE GLUTEAL REGION 519 



tendon which is inserted into the oblique line which traverses the outer surface 

 of the great trochanter. 



Relations. By its superficial surface, with the Gluteus maximus behind, the Tensor fasciae 

 femoris and deep fascia in front; by its deep surface, with the Gluteus minimus and the gluteal 

 vessels and superior gluteal nerve. Its anterior border is blended with the Gluteus minimus. 

 Its posterior border lies parallel to the Pyriformis, the gluteal vessels intervening. 



A synovia! bursa (bursa trochanterica m. glutaei medii anterior} separates the tendon of the 

 muscle from the summit of the great trochanter. There is frequently a bursa (bursa trochan- 

 terica m. glutaei medii posterior) between the tendons of the Gluteus medius and Pyriformis. 



This muscle should now be divided near its insertion and turned upward, when the Gluteus 

 minimus will be exposed. 



The Gluteus minimus (in. glutaeus minimus) (Fig. 387), the smallest of the 

 three Glutei, is placed immediately beneath the preceding. It is fan-shaped, 

 arising from the outer surface of the ilium, between the middle and inferior 

 curved lines, and behind, from the margin of the great sacrosciatic notch; the 

 fibres converge to the deep surface of a radiated aponeurosis, which, terminating 

 in a tendon, is inserted into an impression on the anterior border of the great 

 trochanter. 



Relations. By its superficial surface, with the Gluteus medius and the gluteal vessels and 

 superior gluteal nerve; by its deep surface, with the ilium, the reflected tendon of the Rectus 

 fernoris, and the capsular ligament of the hip-joint. Its anterior margin is blended with the 

 Gluteus medius; its posterior margin is in contact and sometimes joined with the tendon of 

 the Pyriformis. There is a synovial bursa (bursa m. glutaei minimi) between the tendon of the 

 Gluteus minimus and the great trochanter. 



The Pyrifonnis (m. piriformis) (Figs. 387 and 388) is a flat muscle, pyramidal 

 in shape, lying almost parallel with the posterior margin of the Gluteus medius. 

 It is situated partly within the pelvis at its posterior part and partly at the back of 

 the hip-joint. It arises from the front of the sacrum by three fleshy digitations 

 attached to the portions of bone between the first, second, third, and fourth 

 anterior sacral foramina, and also from the grooves leading from the foramina; 

 a few fibres also arise from the margin of the great sacrosciatic foramen and from 

 the anterior surface of the great sacrosciatic ligament. The muscle passes out 

 of the pelvis through the great sacrosciatic foramen, the upper part of which it 

 fills, and is inserted by a rounded tendon into the inner side of the upper border 

 of the great trochanter, behind, but often partly blended with, the tendon of the 

 Obturator iriternus and Gemelli muscles. 



Relations. By its deep surface, within the pelvis, with the rectum (especially on the left 

 side), the sacral plexus of nerves, and the branches of the internal iliac vessels; external to the 

 pelvis, with the posterior surface of the ischium and the capsular ligament of the hip-joint; by 

 its superficial surface, within the pelvis, with the sacrum, and external to it, with the Gluteus 

 maximus; by its upper border, with the Gluteus medius, from which it is separated by the gluteal 

 vessels and superior gluteal nerve; by its Imcer border, with the Gemellus superior and Coccygeus, 

 the sciatic vessels and nerves, the internal pudic vessels and nerve, and muscular branches from 

 the sacral plexus, passing from the pelvis in the interval between the two muscles. 



The Obturator Membrane (membrana obturatoria) (Fig. 240) is a thin layer of interlacing 

 fibres which closes almost completely the obturator foramen. It is attached, externally, to 

 the margin of the foramen; internally, to the posterior surface of the ischiopubic ramus, below 

 and internal to the margin of the foramen. It presents at its upper and outer parts a small 

 canal, obturator canal (canalis obturatorius) for the passage of the obturator vessels and nerve. 

 Both obturator muscles are connected with this membrane. 



There is usually a bursa (bursa m. piriformis) between the tendon of the Pyriformis and the 

 ilium. 



Dissection. The next muscle, as well as the origin of the Pyriformis, can only be seen when 

 the pelvis is divided and the viscera removed. 



