The Sacrum and Coccyx

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At the lower portion of the spinal column, under the last lumbar vertebra are two other spinal bones: the sacrum and the coccyx, or tailbone. The sacrum consists of five bones naturally fused together forming a triangle, and the coccyx consists of four smaller naturally attached bones.

The sacrum and coccyx do not look like the other vertebrae. The sacrum is triangular in shape and the coccyx is attached to the lower end of this triangle. The nerve roots originating from these areas control the actions of the pelvic organs and buttock muscles