The perineum forms the floor of the pelvis and, as the pelvic outlet, represents the perineal approach to the rectum. The perineal region extends from the inferior border of the pubic symphysis to the tip of the coccyx, and laterally to the inferior ramus of the pubis and the ischial tuberosity. The sacrotuberous ligaments complete the outline. The perineal region is diamond shaped and can be divided by a transverse line into an anterior triangle, the urogenital region, and a posterior triangle, the anal region. The line separating these two regions runs just behind the bulb of the urethra, or in the female behind the vagina. The line corresponds to the transverse septum of the perineal muscles (linea septi perinei). The midpoint of this line is the central point of the region (central point of the perineum). In the upright position and when sitting or lying with adducted legs the perineal region is hidden. Abduction of the legs brings the perineal region into view. For muscles and fasciae see Fig. 33, lymphatics Fig. 79. Anal region p. 268, urogenital region p. 270, central tendon of perineum p. 271.