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
Squamous part of temporal bone attached to it some fibers of the masseter. The lateral surface is convex and subcutaneous; the medial is concave, and affords attachment to the masseter. The anterior end is deeply serrated and articulates with the zygomatic bone. The posterior end is connected to the squamous part by two roots, the anterior and posterior roots. The posterior root, a prolongation of the upper border, is strongly marked; it runs backward above the external auditory meatus, and is continuous with the temporal line. The anterior root, continuous with the lower border, is short but broad and strong; it is directed medialward and