There are 12 pairs of ribs, one on each side. All twelve of them articulate with the vertebral column. The first seven ribs connect directly to the sternum via cartilage processes (cartilago costalis) and are called true ribs (costae verae). The remaining lower five pairs of ribs are called false ribs (costae spuriae). The 11th and 12th ribs (costae fluctuantes) do not connect with the cartilaginous arch.
The 3rd to 10th ribs have a typical shape. The wedge-shaped head of the rib (caput costae) has two articular surfaces (facies articulares capitis costae). The tubercle of the rib (tuberculum costae) has one articular surface (facies articularis tuberculi costae). The intercostal vein, artery, and nerve (V-A-N) run in close proximity to the costal groove (sulcus costae). An invagination facilitates contact with the rib cartilage at the ventral end of the body of the rib (corpus costae).
The 1st, 2nd, 11th, and 12th ribs have an atypical rib structure. The 1st rib (costa prima) is hidden under the clavicle and is not palpable. It is broad, stumpy, with the strongest curving, and has only one articular surface on the head. The 2nd rib (costa secunda) is the first palpable rib. It displays only an outline of the costal groove (sulcus costae) and the tuberosity for serratus anterior (tuberositas musculi serrati anterioris) – the origin of the serratus anterior muscle (musculus serratus anterior). The heads of the 11th and 12th ribs have only one articular surface. They do not connect with the costal arch and have no tubercle (tuberculum costae).