Sacrospinal ligament-the sacrospinal ligament connects the sacrum to the ischial spine. together with the sacrotuberous ligament, it converts the greater and lesser sciatic notches into greater and lesser sciatic foramina. however, it is not near the perineum-it is more important as a landmark that creates the greater and lesser sciatic foramina which helps to organize the structures exiting the pelvis. the bounderies of the perineum are as follows. anterior: pubic symphysis; anterolateral: ischiopubic rami; lateral: ischial tuberosities; posterolateral: sacrotuberous ligament; posterior: tip of the coccyx. these boundaries create two triangles in the perineum: the urogenital triangle and the anal triangle. the urogenital triangle is the anterior subdivision, bounded by the pubic symphysis, ischiopubic rami, and the posterior margin of the perineal membrane, which corresponds to an imaginary line between the two ischial tuberosities. the anal triangle is the posterior division of the perineum. it starts off where the urogenital triangle ends: at the posterior margin of the perineal membrane. then, it is bounded by the sacrotuberous ligament and the tip of the coccyx.its important to look at these triangles and orient yourself to them using the bones in your bone set-youll realize that the perineum is not contained in one flat plane; instead, the triangles are at angles to each other.
