Vertebral Column Saint Louis MO

The vertebral column (spine) consists of 26 vertebrae bones (See Table 1 ). It provides support for the head and trunk of the body, protection for the spinal cord, and connecting points for the ribs and muscles.

TABLE 1 Bones of the Vertebral Column Vertebra Body Spinous Process Transverse Process Vertebral Process Cervical C1 (atlas) none, bony ring none with transverse foramen large; lightbulb-shaped C2 (axis) relatively small; with dens (odontoid process) bifid with transverse foramen large; heart-shaped C3-C6 relatively small; oval bifid with transverse foramen large; triangular C7 (vertebra prominens) relatively small; oval prominently long; not bifid with transverse foramen large; triangular Thoracic T1-T10 C2-C7, heart-shaped; 2 facets or demifacets for articulating with rib head long; points down with facets for articulating with rib tubercle circular T11-T12 larger than C2-C7, heart-shaped; 1 demifacets for articulating with rib head long; points down no facets for rib joints circular Lumbar L1–L5 largest of all vertebrae; kidney- shaped short, thick; points horizontally Sacrum 5 fused S1-S5 fusion of 5 vertebrae forms a triangular bone fuse to become the median sacral crest becomes the lateral sacral crest becomes sacral canal Coccyx 4 fused

A typical vertebra has the following characteristics (see Figure 1 ).

• The body (centrum) is the disc-shaped, anterior portion that gives strength to the bone.
  
  

  Figure 1 The four regions of the vertebral column.

• The vertebral arch is a bony ring behind the vertebral body. The opening in the ring is the vertebral foramen, the passageway for the spinal cord. The vertebral canal is the continuous passageway formed by the vertebral foramina of successive vertebrae.

• The pedicles and the laminae form the anterior and posterior sides, respectively, of the vertebral arch.

• Seven processes project from the vertebral arch:

  • A spinous process projects posteriorly from the vertebral arch. Muscle and ligaments attach here.

  • Two transverse processes project from the vertebral arch, one from each side, at each of the junctures of the pedicles and laminae. Muscles and ligaments attach here. Each transverse process of cervical vertebrae contains a transverse foramen through which blood vessels pass to the brain.

  • Two superior articular processes project from the superior surface of the vertebral arch, one from each of the pediclelamina junctions. These processes articulate (form joints) with the preceding vertebrae.

  • Two inferior articular processes project from the inferior surface of the vertebral arch, one from each of the pediclelamina junctions. These processes articulate (form joints) with the following vertebra.

• The intervertebral foramina are notches in the superior and inferior surfaces of each pedicle of the vertebral arch. Adjacent notches of successive vertebrae form a passage for nerves that leave the spinal cord and emerge outside the vertebral column.

• Intervertebral discs separate adjacent vertebrae. Each disc consists of an outer ring of fibrocartilage (annulus fibrosus) surrounding a semifluid cushion (nucleus pulposus) that provides elasticity and compressibility.

The vertebral column is divided into four regions, each region contributing to the alternating concave and convex curves of the spine (see Figure 1 ). As the vertebrae progress down the column, their bodies get more massive, enabling them to bear more weight. The sacrum is a triangular bone below the last lumbar vertebra (see Figure 1 ). It is formed by the fusion of five vertebrae (S₁-S₅).

The coccyx, formed by four fused vertebrae, is a small triangle-shaped bone that attaches to the bottom of the sacrum (see Figure 1 ).

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