THE MUSCLES OF THE BUTTOCK. 



417 



medius, by fleshy fibres, from the dorsum ilii between the 

 gluteal lines (Fig. 369, p. 415). 



This muscle is fan-shaped and its fibres converge to the 

 of the greater tro- 

 chanter, to be inserted 

 into the anterior sur- 

 face of the trochanter, 

 and sometimes also 

 into the front part of 

 the superior border 

 (Figs. 361, p. 407, 

 and 373). It is also 

 inserted into the cap- 

 sule of the hip-joint. 

 A bursa is placed 

 deep to the tendon in 



Prrmf nf fVio (TY-onfov Pudendal nerve 



ront oi tne greater Nerve to obturator 

 trochanter. interims 



Nerve -Supply. 



The superior gluteal 

 nerve from the sacral 

 plexus (L. 4. 5. S. 1.). 



Actions. The mus- 

 cle is primarily an ab- 

 ductor of the thigh. Its 

 anterior fibres in addition 

 produce medial rotation 

 and its posterior fibres 

 lateral rotation of the 

 limb. 



anterior and inferior 

 antero-superior angle 



GRACILIS 

 ADDUCTOR MAGNUS 



HAMSTRING MUSCLES 

 (biceps) 



Superior gluteal nerve 



GLUT.EUS MEDIUS (cut) 

 __ Inferior gluteal nerve 



PlRIFORMIS 



OBTURATOR INTERNUS 

 AND GEMELLI 

 OBTURATOR EXTERXUS 



UADRATUS FEMORI3 



Sciatic nerve 

 (and subdivisions) 



Posterior cutaneous 

 'nerve of thigh 



GLUT^US MAXIMUS 

 (insertion) 



ADDUCTOR MAGNUS 



FIG. 372. THE MUSCLES AND NERVES OF THE RIGHT BUTTOCK. 



The glutseus maximus is reflected ; and the glutaeus medius is cut, in part, to 

 show the glutaeus minimus. 



Glutseus minimus 

 (insertion) 

 Piriformis 

 (insertion) 



M. Piriformis. 

 The piriformis is 



one of the few mus- 

 cles connecting the 

 lower limb to the 

 axial skeleton. It arises (1) within the pelvis from the roots of the vertebral 

 arches of the second, third, and fourth sacral vertebrae, and from the adjacent 

 part of the bone lateral to the anterior sacral foramina. Passing out through 

 the greater sciatic foramen, it receives an origin from (2) the upper margin of the 



greater sciatic notch 



Obturator internus and gemelli (insertion) ^s^tf^B^^^ of the ilium, and (3) 



the pelvic surface of 

 the sacro-tuberous 

 ligament. 



In the buttock it 

 forms a rounded ten- 

 don, which is inserted 

 into a facet on the 

 superior border and 

 medial aspect- of the 

 greater trochanter of 

 the femur (Figs. 370, 

 p. 416, and 373). 



FIG. 373. MUSCLE-ATTACHMENTS TO THE PROXIMAL ASPECT OF THE GREATER T-L _ wlVv,-YYiia af 



TROCHANTER OF THE LEFT FEMUR. lhe . P mloimls > 



its origin, covers part 



of the inner surface of the posterior wall of the pelvis minor. In the buttock 

 it is covered by the glutseus maximus, and lies behind the capsule of the hip-joint, 

 between the glutseus medius and superior gemellus. 



Nerve -Supply. Branches direct from the anterior rami of the first and second sacral 

 nerves. 



28 



Obturator externus 

 (insertion) 



