The pubic bones are united to one another by a superior and an inferior pubic ligament, and by an interpubic disc of fibrocartilage.
The superior pubic ligament connects the pubic bones superiorly, and extends as far as the pubic tubercles.
The inferior (arcuate) pubic ligament is a thick, triangular arch of fibers, connecting the two pubic bones below, and forming the upper boundary of the pubic arch. Above, it is blended with the interpubic disc; laterally, it is attached to the inferior rami of the pubic bones; its base is free; and is separated from the perineal membrane (inferior fascia, of the urogenital diaphragm) by all opening through which the deep dorsal vein of the penis (or clitoris) enters the pelvis.
The interpubic disc connects the opposed surfaces of the pubic bones. Each of these surfaces is covered with a thin layer of hyaline cartilage firmly joined to the bone by a series of nipple-like processes which fit accurately into corresponding depressions on the osseous surface. These opposed cartilaginous surfaces are connected by a lamina of fibrocartilage, which varies in thickness in different subjects. It often contains a cavity in its interior, probably formed by the softening and absorption of the fibrocartilage, since it rarely appears before the tenth year of life and is not lined with synovial membrane. This cavity is usually limited to the upper and back part of the joint; it occasionally reaches the front, and may extend the entire length of the cartilage. When present it may be demonstrated by making a coronal section of the symphysis pubis near its posterior surface (fig. 547). In front the disc is strengthened by several superimposed layers of fibers, which pass obliquely from one bone to the other, decussating and forming an interlacement with the fibers of the external oblique aponeuroses and the medial tendons of origin of the recti abdominis.
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