Hip bone Hip bone The hip bone (os coxa, innominate bone, pelvic bone or coxal bone) is a large flat bone, constricted in the center and expanded above and below. In some vertebrates (including humans before puberty) it is composed of three parts: the ilium, ischium, and the pubis. The two hip bones join at the pubic symphysis and together with the sacrum and coccyx (the pelvic part of the spine) comprise the skeletal component of the pelvis – the pelvic girdle which surrounds the pelvic cavity. They are connected to the sacrum, which is part of the axial skeleton, at the
Squamous part of occipital bone The lower division of the cruciform eminence is prominent and is named the internal occipital crest; it bifurcates near the foramen magnum and gives attachment to the falx cerebelli. In the attached margin of this falx is the occipital sinus, which is sometimes duplicated. In the upper part of the internal occipital crest, a small depression is sometimes distinguishable; it is termed the vermian fossa since it is occupied by part of the vermis of the cerebellum. Transverse grooves, one on either side, extend from the internal occipital protuberance to the lateral angles of the bone; those grooves accommodate the