The
vertebrae (
singular: vertebra) are the bones that compose the
spine.
There are 33 of them 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.
A diagram of a thoracic vertebra, notice the articulations for the ribs.
The
anterior (front) of a vertebra is the
vertebral body. In the spine,
intervertebral discs separate adjacent vertebral bodies.
Behind the vertebral body, a vetebral
foramen[?] (hole) is formed by two
pedicles and two
laminae. The
spinal column runs through 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.
These are generally small and delicate. Their spinous processes are short, 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.
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.
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.