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coccyx
anatomy
Also known as: tailbone
- Also called:
- tailbone
- Related Topics:
- human skeleton
- vertebral column
- vestigial structure
- caudal vertebra
- On the Web:
- Healthdirect - Tailbone (coccyx) pain and injury (Jan. 25, 2025)
coccyx, curved, semiflexible lower end of the backbone (vertebral column) in apes and humans, representing a vestigial tail. It is composed of three to five successively smaller caudal (coccygeal) vertebrae. The first is a relatively well-defined vertebra and connects with the sacrum; the last is represented by a small nodule of bone. The spinal cord ends above the coccyx. In early adulthood the coccygeal vertebrae fuse with each other; in later life the coccyx may fuse with the sacrum. A corresponding structure in other vertebrates, such as birds, may also be called a coccyx.