Pelvis (or Os Coxa)

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 protects abdominal organs such as the bladder, rectum and, in women, the uterus. The pelvis is made up of three hip bones, which are joined by rigid sacroilac joints to the sacrum at the back. The hip bones curve forward to join the pubic symphysis at the front. The symphysis pubis is a cartilaginous union between both sides of the pelvis anteriorly. It is significant during childbirth as it is capable of stretching to permit delivery. Attached to the pelvis are muscles of the abdominal wall, the buttocks, the lower back, and the insides and backs of the thighs. Each innominate bone is made up of three fused bones: the ilium, the ischium, and the pubis. Together they form the acetabulum which is a cup-like depression ball and socket joint. The ilium is the uppermost and largest and consists of a wide, flattened plate with a long curved ridge (called the "iliac crest") along its border. The pubis is the smallest pelvic bone. It extends forward from the ischium and around to the pubis symphysis, where it is joined to the other pubic bone by a tough, fibrous tissue. These three bones meet to form a cup-shaped cavity that make up the socket of the hip joint. 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. These and other differences give testimony to the fact that childbirth is a feat of nature indeed.