rib

rib one of the slender, elongated, curved bones that compose the chest cage in higher vertebrates. Ribs occur in pairs, and are found in most vertebrates; however, in some lower vertebrates, including fishes, they run along the entire length of the backbone. The ribs of the snake are used in locomotion. In the human there are 12 pairs of ribs. Each rib is connected to the vertebral column by strong ligaments. In the front, a flexible section of cartilage connects the rib to the sternum, or breastbone. Below the 7th rib, the 8th, 9th, and 10th ribs are not attached directly to the sternum, but to the cartilage of the 7th rib. The 11th and 12th pairs of ribs are not attached in front at all, and hence are known as floating ribs. Technically, these ribs do not "float," however, but are attached to the vertebral column in the rear and extend only part of the way around the chest. In birds and mammals, ribs enclose the lungs and heart and assist in the process of breathing. During inhalation the ribs move upward and farther apart, expanding the chest cavity. During exhalation their downward motion aids in expelling air from the lungs. See skeleton .

rib Part of the axial skeleton of vertebrates, related to the vertebral apophyses. Ribs develop at the myosepta skeletagenous septa junction, articulating with vertebral apophyses. There are two types of rib: dorsal ribs form at the myoseptum horizontal septum junction, ventral ribs form where the myoseptum intersects the connective tissue surrounding the coelom.

rib (rib) n. a curved strip of bone forming part of the skeleton of the thorax. There are 12 pairs of ribs. The head of each rib articulates with one of the 12 thoracic vertebrae of the backbone; the other end is attached to a costal cartilage. false r. any of the three pairs of ribs below the true ribs. Each is connected by its cartilage to the rib above it. floating r. any of the last two pairs of ribs, which end freely in the muscles of the body wall. true r. any of the first seven pairs of ribs, which are connected directly to the sternum by their costal cartilages. Anatomical name: costa.