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

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