Lesser pelvis

The lesser pelvis (or true pelvis) is that part of the pelvic cavity which is situated below and behind the pelvic brim.

Its bony walls are more complete than those of the greater pelvis.

For convenience of description, it is divided into a pelvic inlet bounded by the superior circumference, and pelvic outlet bounded by the inferior circumference, and a cavity of the lesser pelvis.

Cavity
The cavity of the lesser pelvis is bounded in front and below by the pubic symphysis and the superior rami of the pubes; above and behind, by the pelvic surfaces of the sacrum and coccyx, which, curving forward above and below, contract the superior and inferior apertures of the cavity; laterally, by a broad, smooth, quadrangular area of bone, corresponding to the inner surfaces of the body and superior ramus of the ischium and that part of the ilium which is below the arcuate line.

From this description it will be seen that the cavity of the lesser pelvis is a short, curved canal, considerably deeper on its posterior than on its anterior wall.

It contains, in the fresh subject, the pelvic colon, rectum, bladder, and some of the organs of generation.

The rectum is placed at the back of the pelvis, in the curve of the sacrum and coccyx; the bladder is in front, behind the pubic symphysis.

In the female the uterus and vagina occupy the interval between these viscera.