Answer
There are 12 pairs of thoracic vertebrae. They are attached to the 12 pairs of ribs and function to support the thorax which contains and protects the vital organs --the heart and the lungs.
The structure of the thoracic vertebrae includes the following distinguishing features:
The body is somewhat cordate (heart-shaped) in form and larger than those of cervical vertebrae but smaller that the more massive bodies of lumbar vertebrae. There are small smooth articular surfaces on the head for the attachment of ribs. A second set of articular surfaces --the transverse costal facets-- exist at end of each transverse process. These articular surfaces are found only on ribs vertebrae T1-T10. They do not exist on T11 and T12 vertebrae because ribs 11 and 12 articulate only with the bodies of those vertebrae,
Work Step by Step
The spinous processes of thoracic vertebrae are pointed downward.
In most thoracic costo-vertebral articulations, the rib inserts between vertebrae so that a rib articulates with the inferior costal facet of the upper vertebra and the superior costal facet of the vertebra below. There are, however, variations: vertebrae T1, T10, T11 and T12 have complete costal facets for ribs 1, and 10-12; these ribs articulate on vertebral bodies and not between vertebrae. . Vertebrae T11 and T12 have no transverse costal facets.
