Full Bones of the Pelvis and Lower Back (Posterior View) Description
[Continued from above] . . . vertebrae above them. At the base of the lower spine is a large triangular bone called the sacrum. Its narrow lower part joins the coccyx, or tail bone. The sides of the sacrum are connected to the iliums (the largest bones forming the pelvis). The iliac crest forms the prominence of the hip. The pelvis is a ring of bones in the lower trunk of the body, which is bounded by the coccyx (tail bone) and the hip bones. The pelvis is made up of three hip bones, which are joined by rigid sacroiliac joints to the sacrum at the back. The hip bones curve forward to join the pubic symphysis at the front. It is significant during childbirth as it is capable of stretching to permit delivery.
There are many structural differences between the male and the female pelvis, most of which reflect the role of childbirth in the female. The male pelvis is larger and smaller inside with the pubis symphysis deeper and longer. The female, on the other hand, has a much more delicate, less prominent pelvis that is wider inside and the pubis symphysis shallow and shorter.
Muscles from the abdominal wall, buttocks, the lower back, and the insides and back of the thighs are all attached to the pelvis.