Rib cage

The rib cage is an arrangement of bones in the thorax of all vertebrates except the lamprey and the frog. It is formed by the vertebral column, ribs, and sternum and encloses the heart and lungs. In humans, the rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral girdle (shoulder girdle), forming a core portion of the human skeleton. A typical human rib cage consists of 24 ribs, the sternum (with xiphoid process), costal cartilages, and the 12 thoracic vertebrae. Together with the skin and associated fascia and muscles, the rib cage makes up the thoracic wall and provides attachments for the muscles of the neck, thorax, upper abdomen, and back.

Ribs are described based on their location and connection with the sternum. Ribs that articulate directly with the sternum are called true ribs, whereas those that connect indirectly via cartilage are termed false ribs.

The terms true and false rib describe rib pairs that are directly or indirectly attached to the sternum. The phrase true rib (Latin: costae verae), or fixed rib, refers to the first seven, or vertebrosternal, rib pairs. The phrase false rib (Latin: costae spuriae), or vertebrochondral ribs refers to the eighth-to-twelfth pairs of ribs. The eighth-to-tenth pairs of ribs connect to the sternum indirectly via the costal cartilages of the ribs above them. Their elasticity allows ribcage movement for respiratory activity.

The phrase floating rib (Latin: costae fluitantes) refers to the two lowermost, the eleventh and twelfth, rib pairs; so-called because they are attached only to the vertebrae–and not to the sternum or cartilage of the sternum. These ribs are relatively small and delicate, and include a cartilaginous tip.

The spaces between the ribs are known as intercostal spaces; they contain the intercostal muscles, nerves, arteries, and veins.

Each rib consists of a head, neck, and a shaft, and they are numbered from top to bottom. The head of a rib is the end part closest to the spine with which it articulates. It is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two facets. The superior facet is smaller and articulates with the vertebra above, and the inferior facet articulates with the vertebra of the same number. The transverse process of a thoracic vertebra also articulates with the rib of the same number. The crest gives attachment to the intra-articular ligament. All ribs are attached posteriorly to the thoracic vertebrae.

This page was last edited on 15 May 2018, at 22:38.
Reference: https://en.wikipedia.org/wiki/Human_rib_cage under CC BY-SA license.

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