The pelvis contains the bladder, the rectum, and the internal genital organs. The bladder lies anteriorly close against the pubic bones, the rectum posteriorly close against the sacrum (see Section VI.), and the internal genital organs between the two. They are all covered superiorly by peritoneum.

Bladder

The bladder is a hollow organ with muscular walls capable of great distension. When empty and contracted, it lies entirely in the pelvis just behind the symphysis pubis; when distended, it rises above the pelvis into the abdominal cavity. Superiorly it is covered by peritoneum reflected from the anterior abdominal wall and the sides of the pelvis, and is in relation with the coils of the small intestine. The under surface lies on the symphysis pubis and the bodies of the pubic bones; externally it is in contact with the levator ani and obturator internus muscles on each side. Posteriorly it is separated from the rectum by the uterus and vagina in the female, and the seminal vesicles in the male. The lower part of the bladder only moves in position very slightly; during distension the side and upper walls expand and rise into the abdominal cavity. In the posterior wall of the bladder are the openings of the two ureters and the urethra. The three openings form an equilateral triangle with the apex downwards and the sides are about 1 inch long.