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In Depth: Bones

The pelvis forms the base of the spine as well as the socket of the hip joint. The pelvic bones include the hip bones, sacrum, and coccyx.

The hip bones are composed of three sets of bones that fuse together as we grow older. Each set is nearly symmetrical across the body’s midline. The parts of the hip bone are:

  • Ilium: The largest part of the hip bone. The crests of the ilia are what people typically consider their hips as they typically can be felt at the waist.
  • Pubis: This is at the front of the hip bone closest to the genitals.
  • Ischium: Below the ilium and next to the pubis, this circular bone creates the lowermost portion of the hip bone. This is where the femur meets the pelvis to create the hip joint.

The sacrum is a triangular bone that appears wedged into the rear section of the pelvis. It is made up of five fused vertebral bones. The male sacrum is taller and narrower than a female’s. The sacrum is connected to the tailbone, or coccyx, which is made of several fused vertebral bones at the base of the spine.

A man’s pelvic bones are typically smaller and narrower than a woman’s. The pubic arch, or space at the base of the pelvis, is also smaller than a woman’s.

The opening at the base of the pelvis, the obturator foramen, creates the ball-and-socket hip joint with the femur, the large bone of the leg. This joint and its ability to rotate in many angles is one of many pieces of anatomy that allows humans to walk.

The spine, or vertebral column, is a tower of bone that consists of 24 irregularly shaped bones along with the nine fused bones in the sacrum and coccyx. The spine largely determines posture. It also houses and protects the spinal cord, which is the body’s major nerve center.

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