Diameters of inferior aperture of lesser pelvis (female).
Muscles of the female perineum.
|Latin||apertura pelvis inferior|
|Anatomical terms of bone|
The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or pelvic outlet.
It has the following boundaries:
- anteriorly: the pubic arch
- laterally: the ischial tuberosities
- posterolaterally: the inferior margin of the sacrotuberous ligament
- posteriorly: the tip of the coccyx
These eminences are separated by three notches:
- one in front, the pubic arch, formed by the convergence of the inferior rami of the ischium and pubis on either side.
- The other notches, one on either side, are formed by the sacrum and coccyx behind, the ischium in front, and the ilium above; they are called the sciatic notches; in the natural state they are converted into foramina by the sacrotuberous and sacrospinous ligaments.
When the ligaments are in situ, the inferior aperture of the pelvis is lozenge-shaped, bounded as follows:
- in front, by the pubic arcuate ligament and the inferior rami of the pubes and ischia
- laterally, by the ischial tuberosities
- behind, by the sacrotuberous ligaments and the tip of the coccyx.