g04 



A MANUAL OF ANATOMY 



Nerve-supply. — Probably the hypogastric branch of the iho- 

 hypogastric, inguinal, and pudic nerves. 



Movements. — Very slight separation is allowed at this joint, due 



to yielding of the connecting 

 structures. This is most ap- 

 parent during pregnancy and 

 parturition. 



Great Sacro-sciatic Foramen. 

 — ^This foramen is formed by the 

 great sciatic notch, the spine of 

 the ischium, the great sacro- 

 sciatic ligament, and the small 

 sacro-sciatic ligament. For its 

 compartments, and the struc- 

 tures which pass through them, 

 see p, 429. 



SmaH Sacro-sciatic Foramen. 

 — This foramen is formed by 

 Fig. 379.-VERTICAL Section of the the small sciatic notch, the 

 Symphysis Pubis. spme of the ischium, the great 



sacro-sciatic ligament, and the 

 small sacro-sciatic ligament. For the structures which pass 

 through it, see Gluteal Region. 



Obturator Membrane and Ob.urator Canal. 



The obturator membrane, also called the thyroid membrane, is 



attached to the circumference of the obturator foramen, except 

 superiorly opposite the obturator groove, which it converts into 

 a fibro-osseous canal for the passage of the obturator vessels 

 and nerve. In this situation it is joined posteriorly by the parietal 

 pelvic fascia. Its fibres are arranged in an irregular, decussating 

 manner. Its posterior or pelvic surface is closely covered by the 

 obturator internus muscle. The anterior or femoral surface is in 

 like manner covered by the obturator externus muscle, and "at its 

 circumference there is an arterial loop, formed by the external and 

 internal terminal branches of the obturator artery. 



The obturator canal is a fibro-osseous canal, which is situated 

 above the upper border of the obturator membrane. Its upper 

 boundary, which represents the osseous element, is formed by the 

 obturator groove on the inferior surface of the superior pubic 

 ramus, the direction of the groove being downwards, forwards, and 

 inwards. The lower boundary, which represents the fibrous element, 

 is formed by the junction of the parietal pelvic fascia with the upper 

 border of the obturator membrane over the upper border of the 

 obturator internus. The canal transmits the obturator vessels and 

 obturator nerve, the nerve being above the artery. 



