Bone · Chest

Ninth rib

A false rib whose cartilage joins the eighth's, continuing the linked chain that forms the costal margin. It is noticeably shorter and more sharply angled than the ribs above. Its lower border gives attachment to the costal fibres of the diaphragm inside the cage and to external oblique and latissimus dorsi outside it. The tip of the ninth costal cartilage is a standard surface landmark, marking the point where the outer edge of rectus abdominis crosses the costal margin.