Sacrospinous Ligament The structure indicated is the sacrospinous ligament. The sacrospinous ligament attaches at one end to the ischial spine, and at the other end to the lateral aspect of the sacrum and coccyx, lying deep to the sacrotuberous ligament. The sacrotuberous ligament runs from the sacrum to the ischial tuberosity. The sacrotuberous ligament converts the greater sciatic notch into the greater sciatic foramen. Likewise, it converts the lesser sciatic notch into the lesser sciatic foramen. Learn more about the bones of the pelvis in this tutorial.
Median Sacral Crest The structure indicated is the median sacral crest. The median sacral crest is located on the dorsal surface of the sacrum. The median sacral crest possesses three to four tubercles which are essentially the equivalent of the spinous processes of the upper sacral vertebrae. Either side of the median sacral crest on the dorsal surface of the sacrum, are the posterior sacral foramina (four pairs). Inferiorly, the sacrum forms two horns, or cornua, which articulate with the cornua of the coccyx. To learn more about the anatomy of the bones of the pelvis watch this video.
Sacrotuberous Ligament The structure indicated is the sacrotuberous ligament. The sacrotuberous ligament runs from the sacrum (sacro-) to the ischial tuberosity (-tuberous). The sacrotuberous ligament contains the coccygeal branch of the inferior gluteal artery. In combination with the sacrospinous ligament, the two ligaments serve to form two important foramina which allow structures to exit the pelvis: Greater sciatic foramen Lesser sciatic foramen The sacrospinous ligament runs from the sacrum and coccyx to the ischial spine. The greater sciatic foramen is formed by the sacrospinous ligament and the greater sciatic notch; the lesser sciatic foramen is formed by the sacrotuberous ligament …