Ribs (Left)

Description

The ribs are one of the two groups of bones of the thoracic cage, the other being the sternum. They are all flat bones and articulate:

- posteriorly, with the thoracic vertebrae at the costovertebral joints;

- anteriorly, with their corresponding costal cartilages at costochondral joints.

From superior to inferior, the ribs and their costal cartilages are numbered one to twelve and adjacent ribs are separated from each other by intercostal spaces. For classification purposes, the ribs can be arbitrarily divided into three groups:

- true ribs, which consist of the first to seventh ribs;

- false ribs, which consist of the eighth to tenth ribs;

- floating ribs, which consist of the eleventh and twelfth ribs.

The ribs can also be classified based on whether they are typical or atypical. The atypical ribs are the first, second, tenth, eleventh and twelfth ribs, while all other ribs are classified as typical. The atypical ribs are classified as such because they have at least one of the following features that typical ribs do not have:

- only one articular facet on their head;

- no neck or tubercle;

- have extra bony features that typical ribs do not have (e.g., the grooves for subclavian artery and vein on the first rib, and the tuberosity for serratus anterior muscle on the second rib).