292 THE ARTICULATIONS, OR JOINTS 



The small or anterior sacrosciatic ligament (ligamentum sacrospinosum) (Figs. 

 239 and 240), much shorter and smaller than the preceding, is thin, triangular 

 in form, attached by its apex to the spine of the ischium, and internally, by its 

 broad base, to the lateral margin of the sacrum and coccyx, anterior to the attach- 

 ment of the great sacrosciatic ligament, with which its fibres are intermingled. 



ANT. SACROILIAC 

 LIGAMENT. 



-GREAT SACRO- 

 SCIATIC LIGA- 



POUPART'S >m ' * ^^f ~~" **&umm^i v^^^pa^menism ^f^mmi WENT. 



LIGAMENT 



SMALL SACRO- 

 SCIATIC LIGA- 

 MENT. 



GREAT SACRO- 

 SCIATIC LIGA- 

 MENT. 



Obturator 

 membrane. 



FIG. 240. Side view of pelvis, showing the greater and lesser sacrosciatic ligaments. 



Relations. Its deep surface is in relation with the Coccygeus muscle; its superficial surface 

 is covered by the great sacrosciatic ligament and crossed by the internal pudic vessels and 

 nerve. Its superior border forms the lower boundary of the great sacrosciatic foramen; its 

 inferior border, part of the lesser sacrosciatic foramen. 



These two ligaments convert the sacrosciatic notches into foramina. The superior or great 

 sacrosciatic foramen (foramen ischiadicum majus) (Figs. 239 and 240) is bounded, in front and 

 above, by the posterior border of the os innominatum; behind, by the great sacrosciatic ligament; 

 and below, by the lesser sacrosciatic ligament. It is partially filled in the recent state by the 

 Pyriformis muscle, which passes through it. Above this muscle the gluteal vessels and superior 

 gluteal nerve emerge from the pelvis, and, below it, the sciatic vessels and nerves, the internal 

 pudic vessels and nerve, the inferior gluteal nerve, and the nerves to the Obturator internus and 

 Quadratus femoris. The inferior or lesser sacrosciatic foramen (foramen ischiadicum minus') 

 (Figs. 239 and 240) is bounded, in front, by the tuber ischii; above, by the spine and lesser sacro- 

 sciatic ligament; behind, by the greater sacrosciatic ligament. It transmits the tendon of the 

 Obturator internus muscle, its nerve, and the internal pudic vessels and nerve. 



3. ARTICULATION OF THE SACRUM AND COCCYX (SYMPHYSIS SACROCOCCYGEA). 



This articulation is an amphiarthrodial joint, formed between the oval surface 

 at the apex of the sacrum and the base of the coccyx. It is analogous to the 

 joints between the bodies of the vertebrae. The ligaments are the 



Anterior Sacrococcygeal. Lateral Sacrococcygeal. 



Posterior Sacrococcygeal. Interposed Fibrocartilage. 



