The sternum (or breast bone) is the most anterior bone of the thoracic cage. It has three portions, which may remain as three bones in early life:
Upper part of the sternum. It articulates with
- first and second costal cartilages
Articulates with body via a fibrocartilaginous joint. This is palpable externally as the angle of Louis, and is the point from which costal cartilages can be counted (the first rib is difficult to feel as it is largely buried beneath the clavicles) and is also the level of the disc between T4 and T5 vertebrae
Articulates with the manubrium above, the xiphoid process below and the 2nd to the 7th costal cartilages
A thin plate of hyaline cartilage at the lower end of the sternum that becomes calcified in adult life. The xiphisternal joint lies at the level of the body of the T9 vertebra.
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