The sacrum is part of the pelvis, while the coccyx is the lowest part of the spine. The sacrum forms part of the ring of the pelvis.

The spine is made up of many parts. It is supported by an upright row of stacked spine bones, called vertebrae. This column of bone starts under the skull and continues to the buttocks. All the vertebrae have flexible joints except those in the sacrum.

Anatomy examples:

• Bones and ligaments of the pelvis
• Sacrum and coccyx
• Sacroiliac joint of the pelvis