Ischium Posteriorly the ramus forms a large swelling, the tuberosity of the ischium, where the hamstrings originate. The inferior ramus of the ischium (ascending ramus) is the thin, flattened part of the ischium, which ascends from the superior ramus, and joins the inferior ramus of the pubis—the junction being indicated in the adult by a raised line. The outer surface is uneven for the origin of the obturator externus and some of the fibers of the adductor magnus; its inner surface forms part of the anterior wall of the pelvis. Its medial border is thick, rough, slightly everted, forms part of
Parietal bone granulations (Pacchionian bodies). In the groove is the internal opening of the parietal foramen when that aperture exists. The parietal bone is ossified in membrane from a single center, which appears at the parietal eminence about the eighth week of fetal life. Ossification gradually extends in a radial manner from the center toward the margins of the bone; the angles are consequently the parts last formed, and it is here that the fontanelles exist. Occasionally the parietal bone is divided into two parts, upper and lower, by an antero-posterior suture. In non-human vertebrates, the parietal bones typically form the rear