The breastbone is a flat bone. It consists of the manubrium (manubrium), the sternum body (corpus sterni) and the xyphoid process (processus xiphoideus), which can differ in shape. In young age, the three elements of the chest are separated by fibrocartilage zones.
Between the manubium and the sternum body is the angulus sterni, which can ossify to symphysis manubriosternalis in later years. Here the manubrium is somewhat kinked against the sternum body and is thus easily palpable.
The 2nd pair of ribs is on a level with the angulus sterni; with the 1st pair of ribs being concealed by the collarbone (clavicula), the angulus sterni is used as orientation guide for the thorax (chest) and for auscultation of the heart (auskultation).
Between the sternum body and the xyphoid process, there is another cartilage connection called the synchondrosis xiphisternalis. The xyphoid process, still separated in youngsters by a cartilage growth groove, can be either fork-shaped, leaf-shaped or perforated. In advanced age it forms a solid bony connection with the sternum body, which lets the xyphoid process kink inwards or outwards, depending on the state of curvature of the abdomen wall at this point in time.
The breastbone is somewhat shorter in women than in men. The lateral edge is notched, with incisures for the ribs (incisurae costales). The chest contains hematogenic bone marrow. The flat nature of the bone and the fact that it is covered with muscles makes it particularly ideal for bone-marrow puncture (sternal puncture).
Please click on the image below for a 3D view of the sternum.
Please click on the image below for an animation of the sternum.
