Sex differences in human physiology pelvis is, in general, different between the human female and male skeleton. It differs both in overall shape and structure. The female pelvis, adapted for gestation and childbirth, is less high, but proportionately wider and more circular than in the male; its sacrum—the triangular bone at the upper posterior of the pelvic cavity, serving as base of the spine—is also wider. The female pelvis is tilted anteriorly, often resulting in the more sway-backed appearance. In the female, the acetabula, the concave surfaces to which the balls of the femurs attach via ligaments, are located farther apart, which increases the distance
Sacrum of the first piece of the coccyx, and this transmits the anterior division of the fifth sacral nerve. The thin lower half of the lateral surface gives attachment to the sacrotuberous and sacrospinous ligaments, to some fibers of the gluteus maximus at the back and to the coccygeus in the front. The sacrum articulates with four bones: Rotation of the sacrum superiorly and anteriorly whilst the coccyx moves posteriorly relative to the ilium is sometimes called "nutation" (from the Latin term nutatio which means "nodding") and the reverse, postero-inferior motion of the sacrum relative to the ilium whilst the coccyx