The tailbone
Coccyx · os coccygis
The small curved tip at the bottom of your spine, all that's left of a tail.
What it does
The tailbone is three to five tiny vertebrae fused together under the sacrum. It is an anchor for some of the muscles and ligaments of the pelvic floor and the buttock. When you sit and lean back, it also takes part of your weight.
Surprising fact
Human embryos have a visible tail for a few weeks early in development before it is reabsorbed, leaving the coccyx behind.
Why it matters
Falling straight onto your bottom can bruise or crack the tailbone, and because you sit on it, the pain can linger for weeks. A cushion with a cut-out helps.
Nearby
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Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.