By Mike Crystal • Updated Mar 24, 2022
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Our thorax houses 12 pairs of ribs that shield vital organs like the heart and lungs. Anatomists number ribs from the top (rib 1) to the bottom (rib 12), and each pair exhibits distinguishing characteristics that make identification straightforward.
Rib 1 is the shortest and flattest of the series, featuring a single articular facet for attachment to the thoracic vertebrae. Ribs 2–10 typically have two articular facets. Rib 2 also bears a roughened ridge on its superior surface where the serratus anterior muscle inserts. Ribs 11 and 12 lack a neck and possess only one articular facet each, making them distinct from the upper ribs.
Ribs 1–7 are “true” ribs that connect directly to the sternum via costal cartilages. Ribs 8–10 are “false” ribs; they attach to the cartilage of the rib above them rather than the sternum. Ribs 11 and 12 are “floating” ribs, as they have no anterior attachment.
