The coccyx is the distal end of the spinal column in human beings. It is the rudimentary tail of the mammals. Being the continuation of the sacrum, it curves inwardly as it tapers to a point. It is composed of four or five coccygeal vertebrae, which fuse together into one bone structure in adults.
The coccyx has the shape of an inverted pyramid, with its base facing upwards and the apex downwards. The vertebrae that form it are deprived of transverse process and spinous process. They have only bodies. On each side of the first coccygeal vertebra are the remnants of the superior articular processes in the form of small projections, which are called the coccygeal cornua. These extend upward to articulate with the sacral cornua.
The superior surface of the coccyx has a slight concave area, which articulates with the apex of the sacrum by means of the sacrococcygeal joint.
Below, anterior (A) and posterior (B) view of the coccyx.
