Lateral view, superior surface

  Lateral view, inferior surface

A facet is a flat or nearly flat surface on a bone.  A demifacet is actually half of a facet and is where part of the head of the rib or part of the costal cartilage articulates and these are usually found on ribs 2 through 9.  The superior demifacet of the body of the vertebra receives the head of the rib with the same number as the vertebra of interest.  For example, rib 5 articulates with thoracic vertebra 5 at its superior demifacet.  The inferior demifacet of the body of the vertebra receives the head of the rib with a number greater than the number of the vertebra.  For example, rib 5 articulates with thoracic vertebra 4 at is inferior demifacet.  Instead of a single facet for the costal cartilage of rib 7 on the body of the sternum, there may a demifacet on the inferior end of the body of the sternum as well as one on the xiphoid process.  These demifacets articulate with the costal cartilage of rib 7.

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