Anatomy of the Spine

The spine is both relatively simple and amazingly complex. It consists of 33 vertebrae, or backbones, stacked atop one another, from the tailbone to the base of the skull.

The spine, also known as the spinal column, gives shape to the torso and allows us to walk upright. It also protects the spinal cord, one component of the central nervous system. In this sense, it is easy to see the purpose and usefulness of the spine.

However, when even one component of one vertebra is off by a minuscule amount, it can cause debilitating back pain and even affect other parts of the body such as the arms, the legs, the bladder or the bowels. 

Each vertebra has a number of parts:

  • The vertebral body acts as the main structure of the spinal column, carrying about 80 percent of the body’s weight while standing. Attached to the top is a vertebral disc, which serves as a shock absorber. 
  • Two pedicles jut out from the vertebral body toward the rear. The pedicles help encase the spinal cord and act as a bridge between the vertebral body and the rest of the vertebra.
  • The lamina is attached to the pedicles and completes the circle of protection around the spinal cord. 
  • Attached to the lamina are a number of bony processes, to which attaches muscles or ligaments that connect vertebrae above and below.
  • Each vertebra is also attached to the vertabrae above and below it at the pedicles. These connections are called facet (pronounced fuh-SET) joints.
  • Finally, in the middle, flanked by the vertebral body, pedicles and lamina, is a hollow space called the spinal canal, through which runs the spinal cord.
The spine is also broken down into regions. Click on each region to learn more about it.

Cervical Spine

The cervical spine is more commonly known as the neck. Its vertebrae are numbered c1, at the base of the skull, to c7, above the shoulders. The first two vertebrae, c1 and c2, are known as the atlas and the axis, respectively. The nerve roots branching off of the spinal cord along the cervical spine serve:

  • The head and neck
  • The shoulders
  • The diaphragm
  • The arms
  • The hands

Problems with vertebrae or nerve roots in the cervical spine may translate to problems with those parts of the body. 

Thoracic Spine

The thoracic spine is the largest region of the spine, with 12 vertebrae. It begins at the shoulders and below the neck at the vertebra numbered t1 and ends just above the lower back at t12. One of the main functions of the 12 thoracic spine vertebrae is to provide attachment to the 24 ribs (two to a vertebra, one each side). A large number of muscles also attach at the thoracic spine. The thoracic spine is less flexible than either the cervical or lumbar regions, and therefore less likely to develop conditions such as stenosis or herniated discs. 

Lumbar Spine

The lower back, also known as the lumbar spine, consists of five vertebrae, numbered l1–at the top, where the thoracic spine ends–through l5, just above the sacrum. The lumbar spine is both strong and flexible, with a natural curve toward the belly called kyphosis.

Sacral Spine

The sacrum, or sacral spine, is a series of five vertebrae–s1 through s5–that are fused together into one wedge-shaped piece of bone. The sacrum forms the back part of the pelvis. At the bottom of the sacrum is another series of fused bones called the coccyx, or tailbone. Often sciatica develops where the lumbar spine meets the sacrum.