OS pubis

The bone which, although distinct in early life, in adult life unites with the ilium and ischium to form the pelvis. It is of an irregular shape, and is divided into a body or horizontal ramus, an ascending ramus, and a descending ramus. The outer extremity of the body forms about one-fifth of the acetabulum, and the inner unites in the middle line with the corresponding portion of the bone of the opposite side, forming the symphysis pubis. The junction of the articulating and superior surfaces is termed the angle, and somewhat external to this is a tubercle, projecting forward, the portion between the two being the spine. The portion of the bone which descends downward and outward from the body to unite with the ischium forms the descending ramus, and that pa ing backward to unite with the ilium and ischium in the acetabulum forms the ascending ramus. On the upper surface is the commencement of the i leo pectineal line. The descending ramus unites with the ascending ramus of the ischium to form the inner and lower part of the obturator foramen.