Final answer:
A rib that has a full facet superiorly and an inferior demifacet articulates with the corresponding thoracic vertebrae at both the full facet and demifacet, providing flexible support for the thoracic cage.
Step-by-step explanation:
The rib that has a full facet superiorly and an inferior demifacet is typically one of the ribs that articulate with the thoracic vertebrae. Each thoracic vertebra has superior and inferior articular facets on the vertebral body for articulation with the head of a rib. The superior articular facet of a vertebra meets the full facet of the corresponding rib's head, while the inferior articular facet, also known as a demifacet, accommodates the partial articulation with the head of the next rib.
For example, the head of rib 6 will articulately primarily with the full facet on the superior side of the T6 vertebra, and to a lesser extent, with the demifacet on the inferior side of the T5 vertebra. This allows the ribs to form a more flexible ribcage capable of expanding and contracting during respiration. These articulations provide structural support and facilitate the movement of the thoracic cage.