Ischium Ischium The ischium () forms the lower and back part of the hip bone ("os coxae"). Situated below the ilium and behind the pubis, it is one of these three bones whose fusion creates the hip. The superior portion of this bone forms approximately one third of the acetabulum. The ischium is made up of three parts–the body, the superior ramus and the inferior ramus. The body contains a prominent spine, which serves as the origin for the superior gemellus muscle. The indentation inferior to the spine is the lesser sciatic notch. Continuing down the posterior side, the ischial tuberosity
Basilar part of occipital bone of the pharynx. On either side of the middle line the longus capitis and rectus capitis anterior are inserted, and immediately in front of the foramen magnum the anterior atlantooccipital membrane is attached. The "upper surface", constitutes the lower half of clivus, presents a broad, shallow groove which inclines upward and forward from the foramen magnum; it supports the medulla oblongata, and near the margin of the foramen magnum gives attachment to the tectorial membrane On the lateral margins of this surface are faint grooves for the inferior petrosal sinuses. Basilar part of occipital bone The basilar part of the