Coccyx

Study entry

Parts

Small triangular bone, usually four fused rudimentary coccygeal vertebrae (sometimes one more or one fewer). Co1 is the largest and widest, with short transverse processes and rudimentary articular processes, the coccygeal cornua. Remnant of the embryonic tail.

Joints

Sacrococcygeal (with the apex of the sacrum; the coccygeal cornua with the sacral cornua). With age, Co1 often fuses to the sacrum.

Clinical

It does not bear weight when standing; when sitting, it flexes slightly forward. It gives attachment to part of the gluteus maximus, the coccygeus and the anococcygeal ligament.

Source: cap. 2, «Vértebras: cóccix»

Other structures in this region

• Typical cervical vertebra (C3–C6)
• Atlas (C1)
• Axis (C2)
• Vertebra prominens (C7)
• Typical thoracic vertebra (T1–T12)
• Typical lumbar vertebra (L1–L5)
• Sacrum