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Feb 27 2011, 5:52 PM EST (current) AndyC
Feb 27 2011, 5:52 PM EST AndyC 488 words added

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Regional Characteristics of Vertebrae


First cervical vertebra (atlas)
  • Supports the skull ; thus its name. According to Greek mythology, Atlas supported Earth on his shoulders.
  • Is the widest of the cervical vertebrae.
  • Has no body and no spine but consists of anterior and posterior arches and paired transverse processes.
  • Articulates superiorly with the occipital condyles of the skull to form the atlanto-occipital joints and inferiorly with the axis to form the atlantoaxial joints.
Second cervical vertebra (axis)
  • Has the smallest transverse process.
  • Is characterised by the dens (odontoid process) , which projects superiorly from the body of the axis and articulates with the anterior arch of the atlas , thus forming the pivot around which the atlas rotates. It is supported by the cruciform, apical, and alar ligaments and the tectorial membrane.
Third to sixth cervical vertebrae
  • Are typical cervical vertebrae and have short spinous processes and transverse processes with anterior and posterior tubercles and transverse foramina for the vertebral vessels.

Seventh cervical vertebra (C7)
  • Is called the vertebra prominens because it has a long spinous process that is nearly horizontal, ends in a single tubercle (not bifid), and forms a visible protrusion.
  • Provides an attachment site for the ligamentum nuchae, supraspinous ligaments, and numerous back muscles.
Thoracic vertebrae
  • Have costal facets; the superior costal facet on the body articulates with the head of the corresponding rib, whereas the inferior facet articulates with the subjacent rib (just below).
  • Have a transverse process that articulates with the tubercle of the corresponding rib.
  • Have the typical thoracic vertebrae , which are the second to the eighth thoracic vertebrae.
Lumbar vertebrae
  • Are distinguished by their large bodies, sturdy laminae, and absence of costal facets. The fifth lumbar vertebra has the largest body of the vertebrae.
  • Are characterized by a strong, massive transverse process and have mamillary and accessory processes.

Sacrum
  • Is a large, triangular, wedge-shaped bone composed of five fused sacral vertebrae .
  • Has four pairs of foramina for the exit of the ventral and dorsal primary rami of the first four sacral nerves.
  • Forms the posterior part of the pelvis and provides strength and stability to the pelvis .
  • Is characterised by the following structures:
    • Promontory: the prominent anterior edge of the first sacral vertebra (S1).
    • Ala: the superior and lateral part of the sacrum, which is formed by the fused transverse processes and fused costal processes of the first sacral vertebra.
    • Median sacral crest: formed by the fused spinous processes.
    • Sacral hiatus: formed by the failure of the laminae of vertebra S5 to fuse. It is used for the administration of caudal (extradural) anesthesia .
    • Sacral cornu or horn: formed by the pedicles of the fifth sacral vertebra. It is an important landmark for locating the sacral hiatus.

Coccyx
  • Is a wedge-shaped bone formed by the union of the four coccygeal vertebrae.
  • Provides attachment for the coccygeus and levator ani muscles.


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