Understanding the spine

The spine is a linked column of bones running from the head down to the lower back. Bone segments form the column. One bone segment is called a vertebra, and multiple bone segments are vertebrae. Ligaments and muscles connect these vertebrae, and a disc separates most of the vertebrae and acts like a cushion to absorb shock along the spine. Each vertebra is numbered and grouped into 5 regions, namely:

Cervical region (C) – 7 cervical vertebrae
Thoracic region (T) – 12 thoracic vertebrae
Lumbar region (L) – 5 lumbar vertebrae
Sacral region (S) – 5 sacral vertebrae are fused together and known as the sacrum.
Coccygeal region – 3 to 5 coccygeal vertebrae fused together and known as the coccyx.

The spinal column contains the spinal cord, which is a bundle of nerves that carries motor and sensory signals back and forth between your body and your brain. Along the length of the spinal cord, 31 pairs of spinal nerves emerge through spaces between the vertebrae. There are 8 pairs of sensory nerve roots for the 7 cervical vertebrae, with each of the 12 thoracic, 5 lumbar, and 5 sacral vertebrae having one pair of spinal nerve roots; and finally one pair of coccygeal nerve roots, which supply a small area of the skin around the coccyx. Spinal nerves carry nerve impulses to and from the spinal cord through two nerve roots:

Sensory root: Carries sensory information from the body to the spinal cord.

Motor root: Carries impulses from the spinal cord to muscles to stimulate muscle movement.

Each spinal nerve runs from a specific vertebra in the spinal cord to a specific area of the body known as a myotome or dermatome. Myotomes refer to the various motor levels, while dermatomes refer to the various sensory levels. By noting the level where a person has weakness, paralysis, sensory loss, or other loss of function, determinations can be made as to where the spinal cord is damaged.