Final answer:
The costal facets of the thoracic vertebrae are specialized articulation sites for rib attachment and movement. They enable the connection of the ribs, which form the thoracic cage, protecting vital organs and assisting in breathing.
Step-by-step explanation:
The costal facets of the thoracic vertebrae are articulation sites for connecting with the ribs. These facets include the superior and inferior articular facets on the vertebral body, which articulate with the head of a rib, and a facet on the transverse process for articulation with the rib's tubercle. The costal facets enable the attachment and movement of the ribs, which play a crucial role in protecting the thoracic cavity and aiding in respiration.
Each rib is a curved, flattened bone, and they are numbered 1-12 corresponding to the T1-T12 thoracic vertebrae. The ribs articulate posteriorly with the thoracic vertebrae and most attach anteriorly via their costal cartilages to the sternum.
The thoracic cage, which includes the ribs, sternum, thoracic vertebrae, and costal cartilages, encases and safeguards the organs of the thoracic cavity, such as the heart and lungs. It also provides an attachment point for muscles involved in breathing and upper limb support.