part of part of Homo sapiens rib 1 scalene tubercle of first rib 2026-03-19T00:00:00Z A skeletal element projection on the superior surface of the first rib, situated between the groove for the subclavian vein anteriorly and the groove for the subclavian artery posteriorly, that serves as the insertion of the anterior scalene muscle. It is a prominent surgical landmark unique to the first rib. skeletal element projection David Osumi-Sutherland