The pelvis creates the basin of the lower abdominal cavity. It is formed by three separate bones which become fused: the ilium, the ischium, and the pubis. The ilium is the broad, wing-like segment which features the wide, slightly concave surfaces of the back and sides of the pelvic girdle. The ischium forms the smaller, lower, portion which bears the weight of the body while sitting. The pubis creates an archway in the front of the basin which allows the urethra, blood vessels, and nerves to pass through the pelvic girdle to the external genitalia and lower body. The pelvis articulates with the sacrum in the back (and thereby connects to the rest of the vertebral column) and to the legs through the ball- and-socket joint formed by the two acetabula of the pelvis and the head of each femur. Research Pelvis