Rib
in anatomy, one of the long curved bones which form the walls of the chest. They extend in an oblique direction from the vertebræ of the back to the sternum in front. There are usually 12 on each side; but in some rare cases 13 have been found, in others only 11.
They are distinguished into "true" and "false"; the former being the seven upper ribs, which are articulated to the sternum; the latter the five lower ones, which are not immediately attached to that bone. The use of the ribs is to cover and defend the lungs and heart; and their articulations with the vertebræ and sternum admitting of a slight motion, they assist in respiration. See ANATOMY: THORAX. In shipbuilding, one of the timbers of a ship, which have their base in the keel as a backbone, and serve to maintain generally the cavity of the vessel. In architecture, one of the curvilinear timbers to which, in an arched or covered plaster ceiling, the laths are nailed. In botany, the principal vein or nervure which proceeds from the petiole into the blade of a leaf. In mining, a pillar of coal left for the support of the roof of a mine.