Albany Medical College Virtual Anatomy Lab

Pelvis and Perineum: Module 1 - Page 2 of 5

Now, add the muscles and ligaments that form the lateral walls and define the apertures of the pelvic cavity.

Add the piriformis, which originates from the anterior surface of the sacrum and passes through the greater sciatic foramen.
Add the obturator internus muscle, which lines the internal surface of the obturator foramen and exits through the lesser sciatic foramen.
Add the sacrotuberous ligament, which extends from the sacrum to the ischial tuberosity.
Add the sacrospinous ligament, which runs from the sacrum and coccyx to the ischial spine. This ligament helps divide the greater and lesser sciatic notches into their respective foramina.
Add the right hemipelvis to visualize the relationships of these structures in a complete pelvic context.
Rotate the 3D model to examine each item thoroughly, and identify the apertures of the pelvic wall.

These include the greater sciatic foramen, the lesser sciatic foramen and the obturator canal.
In the image below, observe the structures that pass through these apertures.
Pelvic capetures

The lesser sciatic foramen is the primary entry for neurovascular structures entering the perineum (e.g. pudendal nerve and internal pudendal vessels). The greater sciatic foramen and obturator canal primarily allow communication between the pelvic cavity and the gluteal region of the lower limb.