476 



MYOLOGY 



The Tensor fasciae latae (Tensor fascice femoris) arises from the anterior part 

 of the outer lip of the iliac crest; from the outer surface of the anterior superior 

 iliac spine, and part of the outer border of the notch below it, between the Glutaeus 

 medius and Sartorius; and from the deep surface of the fascia lata. It is inserted 

 between the two layers of the iliotibial band of the fascia lata about the junction 

 of the middle and upper thirds of the thigh. 



The Piriformis is a flat muscle, pyramidal in shape, lying almost parallel with 

 the posterior margin of the Glutaeus medius. It is situated partly within the pelvis 

 against its posterior wall, 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 to 

 the grooves leading from the foramina : a few fibers also arise from the margin of 

 the greater sciatic foramen, and from the anterior surface of the sacrotuberous 

 ligament. The muscle passes out of the pelvis through the greater sciatic fora- 

 men, the upper part of which it fills', and is inserted by a rounded tendon into 

 the upper border of the greater trochanter behind, but often partly blended with, 

 the common tendon of the Obturator internus and Gemelli. 



Variations. It is frequently pierced by the common peroneal nerve and thus divided more or 

 less into two parts. It may be united with the Glutaeus medius, or send fibers to the Glutaeus 

 minimus or receive fibers from the Gemellus superior. It may have only one or two sacral attach- 

 ments or be inserted in to the capsule of the hip-joint. It may be absent. 



Ant. sup. iliac spine- 



Obturator canal 

 Lacunar ligament 

 Pubic tubercle 



Symphysis 

 pubis 



Transverse acelabular 

 ligament 



FIG. 435. The obturator membrane. 



Obturator Membrane (Fig. 435). The obturator membrane is a thin fibrous sheet, 

 which almost completely closes the obturator foramen. Its fibers are arranged 

 in interlacing bundles mainly transverse in direction; the uppermost bundle is 

 attached to the obturator tubercles and completes the obturator canal for the pas- 

 sage of the obturator vessels and nerve. The membrane is attached to the sharp 

 margin of the obturator foramen except at its lower lateral angle, where it is fixed 



