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Cervical vertebrae

This figure shows the structure of the cervical vertebrae. The left panel shows the location of the cervical vertebrae in green along the vertebral column. The middle panel shows the structure of a typical cervical vertebra and the right panel shows the superior and anterior view of the axis.
A typical cervical vertebra has a small body, a bifid spinous process, transverse processes that have a transverse foramen and are curved for spinal nerve passage. The atlas (C1 vertebra) does not have a body or spinous process. It consists of an anterior and a posterior arch and elongated transverse processes. The axis (C2 vertebra) has the upward projecting dens, which articulates with the anterior arch of the atlas.

Thoracic vertebrae

The bodies of the thoracic vertebrae    are larger than those of cervical vertebrae ( [link] ). The characteristic feature for a typical midthoracic vertebra is the spinous process, which is long and has a pronounced downward angle that causes it to overlap the next inferior vertebra. The superior articular processes of thoracic vertebrae face anteriorly and the inferior processes face posteriorly. These orientations are important determinants for the type and range of movements available to the thoracic region of the vertebral column.

Thoracic vertebrae have several additional articulation sites, each of which is called a facet    , where a rib is attached. Most thoracic vertebrae have two facets located on the lateral sides of the body, each of which is called a costal facet    (costal = “rib”). These are for articulation with the head (end) of a rib. An additional facet is located on the transverse process for articulation with the tubercle of a rib.

Thoracic vertebrae

This figure shows the structure of the thoracic vertebra. The left panel shows the vertebral column with the thoracic vertebrae highlighted in pink. The right panel shows the detailed structure of a single thoracic vertebra.
A typical thoracic vertebra is distinguished by the spinous process, which is long and projects downward to overlap the next inferior vertebra. It also has articulation sites (facets) on the vertebral body and a transverse process for rib attachment.

Rib articulation in thoracic vertebrae

This diagram shows how the thoracic vertebra connects to the angle of the rib. The major parts of the vertebra and the processes connecting the vertebra to the rib are labeled.
Thoracic vertebrae have superior and inferior articular facets on the vertebral body for articulation with the head of a rib, and a transverse process facet for articulation with the rib tubercle.

Lumbar vertebrae

Lumbar vertebrae carry the greatest amount of body weight and are thus characterized by the large size and thickness of the vertebral body ( [link] ). They have short transverse processes and a short, blunt spinous process that projects posteriorly. The articular processes are large, with the superior process facing backward and the inferior facing forward.

Lumbar vertebrae

This image shows the location and structure of the lumbar vertebrae. The left panel shows the location of the lumbar vertebrae (highlighted in green) along the vertebral column. The right panel shows the inferior articular process and the major parts are labeled.
Lumbar vertebrae are characterized by having a large, thick body and a short, rounded spinous process.

Sacrum and coccyx

The sacrum is a triangular-shaped bone that is thick and wide across its superior base where it is weight bearing and then tapers down to an inferior, non-weight bearing apex ( [link] ). It is formed by the fusion of five sacral vertebrae, a process that does not begin until after the age of 20. On the anterior surface of the older adult sacrum, the lines of vertebral fusion can be seen as four transverse ridges. On the posterior surface, running down the midline, is the median sacral crest    , a bumpy ridge that is the remnant of the fused spinous processes (median = “midline”; while medial = “toward, but not necessarily at, the midline”). Similarly, the fused transverse processes of the sacral vertebrae form the lateral sacral crest    .

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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