Pelvic Walls

On looking laterally at the inside of the pelvis, the iliopecti-neal line is seen separating the abdominal from the pelvic portion. On the iliac or abdominal portion lie the iliacus and psoas muscles. Below the iliopectineal line anteriorly is the body of the pubis with the symphysis in the median line. The descending ramus of the pubis passes down to be continuous with the ramus of the ischium to the tuberosity. A short distance above the tuberosity is the spine of the ischium. Posteriorly are the five vertebrae of the sacrum and the four of the coccyx. Passing upward from the tuberosity of the ischium to the sacrum is the great sacro-sciatic ligament (ligamentum sacrotuberosum); passing backward from the spine of the ischium to the sacrum and coccyx is the lesser sacrosciatic ligament (ligamentum saerospinosunt). The large opening above the lesser sacrosciatic ligament is the great sacrosciatic foramen. Through it pass the pyriformis muscle, with the gluteal vessels and superior gluteal nerve above, and, below, 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 smaller opening below the lesser sacrosciatic ligament is the lesser sacrosciatic foramen, through which passes the tendon of the obturator internus, the nerve to it, and the internal pudic vessels and nerve. In front of these two foramina is a third, the obturator. It is closed by a membrane except at its upper inner portion, which gives exit to the obturator vessels and nerve. Attached to the inner surface of this membrane is the origin of the obturator internus muscle and to its outer surface the obturator externus (Fig. 441). Pelvic Floor. - The pelvic outlet is closed by two muscles, the levator ani and coccygeus. These on each side constitute the pelvic floor. The coccygeus is a comparatively small muscle passing from the spine of the ischium to the coccyx. The levator ani is the main muscle which supports and retains the pelvic and abdominal viscera in their normal positions. It arises from the "white line" - which is a thickening of the pelvic fascia extending from the posterior surface of the pubes in front to the spine of the ischium behind - and descends to be attached to the coccyx posteriorly, then around the lower portion of the rectum just above the external sphincter and, farther front, surrounds the vagina of the female or the prostate gland in the male. The part surrounding the prostate has been called the levator prostata. The anterior edge of the levator ani muscle reaches to the central tendon of the perineum (Fig. 442).

Fig. 441.   View of the pelvis from the inside.

Fig. 441. - View of the pelvis from the inside.

Pelvic Herniae

Hernial protrusions of the pelvic contents may occur through the upper portion of the obturator membrane, following the vessels and nerve. This is called an obturator hernia. The sac is usually to the medial or inner side of the vessels and nerve. It makes its appearance in Scarpa's triangle and is covered by the pectineus muscle. Death has frequently occurred in these cases from strangulation. Sciatic hernia is the name given to those forms in which the intestine escapes through the great sciatic notch, passing just above or just below the pyriformis muscle. Perineal hernia are those which work their way downward in other places. Thus the sac may push down between the rectum and bladder and bulge in the perineum. It may pass between the coccygeus and levator ani muscles or between the fibres of the latter and bulge into the ischiorectal fossa or forward into the labium of the female.