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The vertebrae (singular: vertebra) are those bones which compose
the spine in vertebrates.
There are 33 vertebrae in humans, including the five that are fused
to form the sacrum and the four coccygeal
bones.
The 24 remaining are divided into:
- Seven cervical vertebrae.
- Twelve thoracic vertebrae.
- Five lumbar vertebrae.
General Structure
The anterior (front) of a vertebra is the vertebral body. In the spine, intervertebral discs separate adjacent vertebral bodies. Behind the
vertebral body, a vertebral foramen (hole) is formed by two pedicles
and two laminae. The spinal column runs through this
foramen. Two transverse processess and one spinous process are posterior
to (behind) the vertebral body. The spinous process comes out the back, one transverse process comes out the left, and one
on the right. The spinous processes of the cervical and lumbar regions can be felt through the skin. Superior
and inferior articular facets on each vertebra act to restrict
the range of movement possible.
Cervical vertebrae
These are generally small and delicate. Their spinous processes are short (with the exception of C7 which has the first
palpable spinous process), and often split. Numbered top-to-bottom from C1-C7, atlas (C1) and axis (C2), are the vertebrae
that allow the neck so much rotation.
Thoracic vertebrae
Their spinous processes point downwards, and are quite long. They have surfaces that articulate with the ribs. Some rotation can occur at the thoracic vertebrae, but
the ribs prevent much flexion.
Lumbar vertebrae
These are very heavily built, as they must support more weight from above them. They allow flexion and
extension, and sideways flexion, but not rotation.
See also
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