The vertebrae (singular: vertebra) are those bones which 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.
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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 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.