Spine

The Spine, or backbone, is made up of a column of bones called vertebrae (so it’s also called the vertebral column). In general each consists of a bony body in the front, a pair of arches surrounding a canal, down which passes the spinal cord carrying signals between the body and the brain, and a projection called a spine at the back - which is what we feel as a series of bumps when we run our fingers down someone's spine. From each side there is a bony projection called a transverse process, and projections of bone above and below called articular processes which form joints called facet joints with the neighbouring vertebrae. The nerves leading to and from the spinal cord do so via spaces called intervertebral foramina. The vertebrae are separated from one another by discs made of fibrocartilage between the bony bodies, which act as shock absorbers (except the bottom nine which make up the sacrum and coccyx. Here they are fused together). Each vertebra is joined to the next by strong ligaments, providing great stability, and the spine as a whole is supported by a number of muscles.

There are some variations in the general structure and function of the vertebrae from the top to the bottom of the spine: the first vertebra at the top, called the Atlas, has no body in order to allow nodding of the head, which rests on it. The second vertebra, called the axis, has a projection called the odontoid peg pointing upwards: when we turn our heads from side to side we’re moving around this peg. There are five more vertebrae between the skull and the start of the chest, called cervical vertebrae, which have relatively small bony bodies and mobile joints to allow neck movement.

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