Spine Diagrams

The human spine consists of 33 vertebrae:

• 7 Cervical vertebra (C1-C7)
• 12 Thoracic vertebra (T1-T12)
• 5 Lumbar vertebra (L1-L5)
• The sacrum and coccyx are made up of 9 fused vertebrae

Each vertebra is attached to the one above and below it by ligaments and muscles. They are separated from the vertebra above and below it by an intervertebral disc. Two vertebra and the disc between them make up a motion segment.

Each vertebra is made up of:

• Spinous process: the part of the spine you can feel through your skin
• Lamina: The laminae form the walls of the spinal canal has four projections called articular processes
  • Two superior processes extending from the upper border,one on each side
  • Two inferior processes extending from the lower border, one on each side

• Facet joints

Formed by the overlapping of the projections from the lamina. The upper projection of one lamina (superior articular process) is overlapped by the lower projection (inferior articular process) of the adjacent vertebra and together form the facet joint.

There is a facet joint on each side of the spine at every level.

• Intervertebral Disc

The structure that separates two vertebra

Consists of:

• Nucleus, the jelly-like center. Under pressure, the nucleus pushes the vertebra apart
• Annulus, a fibrous ring that attaches to the vertebrae has high water content

A normal disc is so strong that it can be damaged only by extreme forces. A normal, healthy disc is one of the best parts of the spine.

• Foramen

An opening between the pedicles of the vertebrae through which nerve roots exit off the spinal cord.

• Spinal canal

Contains the spinal cord from the brain stem to the upper lumbar spine.

There is no spinal cord in the lower lumbar spine. At the L1 level, the spinal cord terminates as the conus medullaris.

A bundle of nerves called the cauda equina (meaning horse's tail) branch off the conus medullaris. These nerve roots are suspended in the fluid-filled dural sac.