Vertebrae in different regions of the spine have features that distinguish one from another. All cervical vertebrae are distinguished by foramina in their transverse processes that transmit the vertebral artery and associated sympathetic nerve plexus, and the vertebral vein. The spinous processes of C2-C7 are bifid and the transverse processes have anterior and posterior tubercles. The vertebral foramina are large to accommodate the large diameter of the cervical spinal cord and to permit extensive movement. The bodies of cervical vertebrae C3-C7 are longer in the lateral dimension than they are in the anterior-posterior dimension and the superior aspects are concave. This concavity is accentuated by lateral and posterolateral uncinate processes that articulate with a bevel on the body of the vertebra above. The first two cervical vertebrae are unique. The C1 vertebra is a ring of bone containing two lateral masses connected by anterior and posterior arches. The anterior arch displays a tubercle on its anterior aspect for attachment of the anterior longitudinal ligament and the longus capitis muscle. A facet on its posterior aspect articulates with the odontoid process of the axis. The posterior arch displays a posterior tubercle for muscle attachment and grooves on either side for the horizontal portion of the vertebral artery.
The distinguishing feature of the C2 vertebra is its odontoid process, or dens, which is the displaced body of the atlas. Each lateral mass of the axis has a superior articulating surface to receive the inferior articulating surface of the atlas, and an inferior articulating surface to meet the superior articulating process of C3. Its spinous process is large and bifid, being the attachment point for intrinsic muscles of the back, namely the semispinalis cervicis and the inferior oblique muscle of the suboccipital triangle. The spinous process of C7 is the first that can be palpated in the midline of the neck, earning the C7 vertebra the name vertebra prominens.
The bodies of thoracic vertebrae are heart shaped and the laminae are broad and flat. The thoracic spinous processes are long and slender and reach the level of the body of the vertebra below. The thoracic vertebrae have facets on their bodies for articulation with the heads of the ribs and facets on their transverse processes for articulation with the tubercles of the ribs.
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