first rib I
first rib [I][TA]
atypical rib having a single facet on its head, for articulation with the T1 vertebra, and the broadest, shortest and most sharply curved shaft; it also bears two transverse grooves on its superior surface for the subclavian vessels, separated by the scalene tubercle and ridge.
Synonym(s): costa prima [I] [TA]
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