THE ANATOMY OF THE SPINE
A thorough knowledge of the anatomy of the spine, or the vertebral column/ backbone, is very essential to the diagnosis and treatment of patients with back pain. The adult spine (spinal column) typically consists of 26 vertebrae.They are distributed as follows:
- 7 cervical vertebrae: found in the neck region. (C1 - C7)
- 12 thoracic vertebrae: just posterior to the thoracic cavity. (T1 - T12)
- 5 lumbar vertebrae: lower back. (L1 - L5)
- 1 sacrum, which consists of five fused sacral vertebrae. (S1 - S5 fused)
- 1 coccyx, which consists of four fused coccygeal vertebrae.
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Note: During early development, the total number of vertebrae is 33. (Image provided by NIAMS)
The spine consists of bones (vertebrae) stacked one on top of the other. Between the bodies (main part of the vertebrae) are the intervertebral (between vertebrae) discs.
INTERVERTEBRAL DISCS:
The intervertebral discs are flexible plates of fibrocartilage located between adjacent vertebral bodies, which facilitates movement of the
spine and acts as shock absorbers.Each disc is comprised of an outer fibrous ring consisting of a connective tissue: fibrocartilage called the annulus fibrosus and an inner matrix: a pulpy, highly elastic substance called the nucleus pulposus.In standing or sitting, these discs are compressed and they are flattened, broadened, and bulge from their intervertebral spaces.
Each vertebra consists of a body from which an arch of bone arises. On each arch of the vertebra the re are articular processes that allows limited movement between adjacent vertebrae.Several functions of the spinal column include support, protection and locomotion. The cervical spine is the most mobile among the vertebral column while, the thoracic spine is less mobile because of the attachment of the ribs. The lumbar spine (lower back), on the other hand, is fairly mobile with the greatest movement occurring between the fifth lumbar vertebra (L5) and the first sacral vertebra (S1).Support of the spine:Surrounding ligaments and muscles supports the spine. The ligaments are responsible for the passive stability of the spine. Muscles of the back and the abdomen, on the other hand, are responsible for the active stability of the spine. Spinal Nerves:The arrangement of the spinal nerves in relation to the vertebrae is a major clinical importance. These spinal nerves arise from the spinal cord within the vertebral canal and exit through the intervertebral foramen.
There are eight cervical spinal nerves, twelve thoracic spinal nerves, five lumbar spinal nerves, and five sacral spinal
nerves.
C1 to C7 spinal nerves leave the spinal cord through the intervertebral foramen above the corresponding vertebra. Thus, protrusion of the disc between C5 and C6 affects the C6 spinal nerve root.
T1 and the rest of the spinal nerves exit from the intervertebral foramina beneath the vertebra from the same number. The T1 nerve root exits through the intervertebral foramen formed by T1 and T2 vertebrae. C8, on the other hand, exits below C7 (7th cervical vertebra). A protrusion of the disc between T1 and T2 vertebrae affects T1 spinal nerve root.
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Page Last Update
Wed Dec 06 2006 14:05:26 GMT-0800
