The thoracic vertebrae are twelve in number. Compared to the cervical vertebrae, they are higher and thicker and they lack the transverse foramen in their transverse process. As the spinal column runs down towards the lumbar vertebrae, their bodies gradually increase in size as they get thicker. There is a concavity on the inferior and superior surface at the base of the vertebral arches; it is the vertebral notch; thus, the two adjacent vertebrae notches form the intervertebral foramen for the spinal nerve roots.
The arches of the thoracic vertebrae form an almost circular vertebral foramina, which is the orifice through which the spinal cord runs; however, it is smaller in diameter than the cervical vertebrae foramina. The transverse process of the thoracic vertebrae extends laterally and obliquely backwards, bearing a small costal facet which articulates with the tubercle of rib. Their spinous processes are long, three-sided, and pointing downwards. Those of the middle thoracic vertebrae fit one over the other, like tiles.
The posterolateral surface of each one of the thoracic verterae bears two facets; the superior costal facet and the inferior costal facet. The inferior facet of one vertebra joins the superior facet of the adjacent distal vertebra (the one below) to give shape to a complete articular facet, which is the site of articulation with the head of the rib. However, the body of the first thoracic vertebra is an exception, for it has a complete articular facet by itself for articulation with the head of the first rib on the superior part of the posterolateral surface, as well as a semifacet for articulation with the head of the second rib on the inferior part.
The tenth vertebra features one superior semifacet on the superior part of the body. Meanwhile, the bodies of the eleventh and twelfth vertebra each bears only one complete costal facet in the middle of each lateral surface.
Below, lateral view of a thoracic vertebra. Every part is labeled
Below, the eighth thoracic vertebra, superior view
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