Definition of Term

rib

(English) One of a series of long, thin bony rods articulating with the apophyses of the vertebrae and supporting the trunk musculature. The ventral ends are free. They consist of two types: the dorsal, epipleural or true ribs which arise from the transverse processes and lie in the transverse septum of the epaxial muscles (homologous to those in tetrapods) and the ventral, pleural, or pleuroperitoneal ribs which lie just outside of the body cavity. Pleural ribs are found in Elasmobranchii, pleural and dorsal ribs in Teleostomi; ribs are lacking in Holocephali. The intramuscular bones of the horizontal septum are homologous with dorsal ribs. Haemal ribs is a misnomer for the ventral ribs.

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