The vertebral column is divided into five sections: cervical (7 in number), thoracic (12), lumbar (5), sacral (4-6 but fused in the adult form to form sacrum), and coccygeal (3-5, also often fused in adult. The bodies of the cervical, thoracic and lumbar vertebrae increase in size from the head toward the feet. The numbers of each type of vertebra may vary slightly from the number given.
These are the smallest weight-supporting vertebrae. The coccygeal and terminal sacral vertebrae are smaller, but they support no weight. The cervical vertebrae are particularly recognizable due to:
- There are foramen on the transverse process. These foramina transmit the vertebral arteries that help supply blood and therefore oxygen to the brain.
- The spinous processes are often bifurcated (forked).
- The body is oval in shape with the long axis in the transverse direction
- The articular processes (between vertebrae) are nearly flat.
Thoracic Vertebrae are easy to recognize, because:
- They have facets for the articulation of the ribs. These articulations are also called costal pits.
- The articular processes (between vertebrae) are parallel to each other, vertical and flat (except for the 12th, which has a lumbar vertebra-type process on the inferior surface). These are articular processes face dorsally.
- Most of the spinous processes are long, pointed caudally, and tend to overlap the spinous process on the subjacent (next, below) vertebra.
- There is no transverse foramen.
Lumbar vertebrae are the largest of the movable vertebrae because they carry the most weight. In addition:
- The processes for articulation with the other vertebra are angled, vertical and curved to interlock with each other, giving a much stronger intervertebral articulation.
- The spinous processes are short and blunt.
- Lumbar vertebra have no rib facets.
- Lumbar vertebrae have no transverse foramina.