Axis (anatomy)

The Axis (pronounced: /ˈæksɪs/), in anatomy, refers to the second cervical vertebra of the spine, also known as C2. It is an essential part of the vertebral column and plays a crucial role in the rotation of the head and neck.

Etymology

The term "Axis" is derived from the Latin word 'axis', meaning 'axle' or 'pivot'. This is due to the pivotal role the Axis vertebra plays in the rotation of the head.

Structure

The Axis is unique in its structure compared to other vertebrae. It has a large bony prominence, known as the odontoid process or dens, which projects upwards. This dens fits into a hole in the first cervical vertebra, the Atlas, allowing for the rotation of the head.

Function

The primary function of the Axis is to support the head and allow for its rotation. It forms a pivot joint with the Atlas, which enables the head to turn from side to side.

Related Terms

Atlas: The first cervical vertebra with which the Axis forms a joint.
Cervical vertebrae: The seven vertebrae that make up the neck portion of the spine.
Vertebral column: The series of vertebrae extending from the skull to the bottom of the spine.
Odontoid process: A tooth-like projection from the upper part of the axis around which the atlas rotates.