The pelvis consists of the sacrum (the triangular spinal bone below the lumbar vertebrae), coccyx, and two innominate or hip-bones. Each of the hip-bones, known also as the coxal or innominate bones, consists of three parts – ilium, ischium, and pubis – which are fused together. When you put your hands on your hips, they are resting on your illia. The hip-bones curve forwards to join at the symphysis pubis at the front.
The legs are connected to the pelvis by the hip joint. The head of the femur (thigh bone) fits inside a deep socket in the pelvis called the acetabulum to make the hip joint, which is a ball-and-socket joint.
In women, the pelvis is broader and shallower than in men, to facilitate childbirth.
Detailed anatomy of the pelvisThe pelvis is divided into two parts by a plane which extends from the upper margin or promontory of the sacrum to the upper margin of the articulation between the two pubic bones – i.e., the symphysis pubis. On the surface of each coxal bone a line may be traced from the sacral promontory to the symphysis pubis. This is called the iliopectineal line, and it helps to complete the circumference of the plane which divides the pelvis into two parts. The space above this plane lies mostly between the expanded iliac bones. It belongs to the abdomen proper and is known as the false (or lesser) pelvis. The space below the level of the sacral promontory and iliopectineal lines is called the true (or greater) pelvis, and certain descriptive terms are employed in connection with it. Thus the plane which separates it from the false pelvis is called the inlet or brim of the true pelvis. Its inferior circumference or outlet extends from the tip of the coccyx to the inferior border of the pubic symphysis, and from the one ischial tuberosity to the other.
In addition to the ligaments, muscles, blood vessels, and nerves which constitute the soft parts of the pelvis, there are certain organs, including the urinary bladder and rectum, that are present in both sexes, and others that are peculiar to each sex. The urinary bladder is located behind the symphysis pubis, and only rises out of the pelvis into the abdomen when considerably distended. The rectum, i.e. that part of the gastrointestinal tract which passes through the pelvis, lies on the front of the sacrum and coccyx, a short distance below which it terminates in the anus. The lower end of the rectum is supported by two muscles – the levatores ani – which surround it so completely as to form a floor or diaphragm for the pelvis.
Differences between the male and female pelvis
Related category• ANATOMY AND PHYSIOLOGY
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