Rib 4

The rib 4 (fourth rib is a true rib that articulates posteriorly with the thoracic vertebrae (T4) and anteriorly with the sternum via costal cartilage. The fourth rib is classified as a true rib, meaning it has a direct cartilaginous connection to the sternum.

Anatomically, the fourth rib has several key features:

• Head: The head of the rib articulates with the bodies of the T3 and T4 vertebrae.

• Neck: The neck is a flattened portion that extends laterally from the head.

• Tubercle: The tubercle is a small bump on the posterior surface of the rib, which articulates with the transverse process of the T4 vertebra.

• Body (shaft): The body is the main, curved part of the rib. It has a superior border, which is rounded and smooth, and an inferior border, which is sharp and contains the costal groove for the intercostal vessels and nerve.

• Costal cartilage: The anterior end of the rib connects to the sternum via costal cartilage, which provides flexibility to the thoracic cage.

The fourth rib also serves as an important landmark in thoracic anatomy. For instance, the horizontal fissure of the right lung typically meets the anterior thoracic wall at the level of the fourth rib