160 



HUMAN ANATOMY. 



PYRIFORMIS. Origin, from the anterior surface of the sa- 

 crum, between the first to the fourth anterior sacral foramen, and 

 from the margin of the great sacro-sciatic foramen, and from 

 the anterior aspect of the great sacro-sciatic ligament ; insertion, 

 into the upper border of the great tro- 

 chanter, with the tendon of the obtu- 

 rator internus ; action, rotates femur 

 outward ; nerve, obturator. 



OBTURATOR INTERNUS. Origin, 

 from the inner side of the obturator 

 foramen and the internal surface of 

 obturator membrane and the anterior 

 and external wall of the pelvis it passes 

 out of the pelvis through the lesser 

 sacro-sciatic notch and receives the ten- 

 dons of the gemelli muscles ; insertion, 

 into the upper border of the great tro- 

 chanter in front of the pyriformis ; 

 action, rotates the thigh outward ; 

 nerves, branches from the sacral plexus. 

 GEMELLI consist of two muscles 

 gemellus superior and gemellus in- 

 ferior. 



GEMELLUS SUPERIOR. Origin, 

 from the outer aspect of the spine of 

 the ischium ; insertion, into the tendon 

 of the obturator internus. 



GEMELLUS LNFERIOR. Origin, 



from the outer border of tuberosity of 

 the ischium ; insertion, into the lower 

 portion of the tendon of the obturator 

 internus ; action, rotates the thigh out- 

 ward ; nerves, branches of the sacral 

 plexus. 



QUADRATUS FEMORIS. - - Origin, 

 from the external border of the tuber- 

 osity of the ischium ; insertion, into the 

 upper part of the linea quadrati, on 

 the posterior aspect of the trochanter 



major; action, rotates the thigh outward; nerves, branches of 

 the sacral plexus. 



OBTURATOR EXTERNUS. Origin, from the inner two-thirds 

 of the anterior aspect of the obturator membrane and the tendi- 

 nous arch covering the canal for the obturator vessels and nerves, 

 and the descending ramus of the pubis and the ascending ramus 



FIG. 101. 



Posterior femoral re- 

 gion: 1, gluteus medius; 

 2, gluteus maximus; 3, 

 vastus externus; 4, bi- 

 ceps; 6, semi-tendinosis; 

 7, semi-membranosis; 8, 

 gracilis. 



