Sternum
The sternum is a flat bone with a sword-like shape. It is located centrally at the front of the thorax. The rib cartilages are attached to it as an extension of the ribs.
Anatomy
The sternum is a flat, sword-shaped and slightly forward curved bone. The side of the sternum has several indentations (Incisurae costales).
The sternum can be divided into three main bony sections:
- Manubrium (Manubrium sterni)
- Body (Corpus sterni)
- Xiphoid process (Processus xiphoideus).
A notch (incisura jugularis) on the cranial edge of the manubrium is easily palpable through the skin.
The indentations Incisurae claviculares, on the right and left side of the Incisura jugulari, allow the connection to the respective clavicle.
The flat notch (Incisura costalis I) below is for the cartilaginous connection with the first rib.
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The other notches (Incisura costales II-VII) are for the cartilaginous connection with the ribs 2-7.
At the angulus sterni the manubrium is slightly bent backwards against the body of the sternum.
The xiphoid process is often cartilaginous and has no connection to a rib.
Manubrium sterni
The Manubrium sterni is also known as the manubrium. This part of the sternum is the widest. At the upper end there are two lateral notches, the incisurae claviculares. The two clavicles are attached to these indentations. Between the incisurae claviculares is the incisura jugularis. On each of the lateral edges one incisura costalis prima can be found.
The Manubrium sterni is connected to the Corpus sterni via the Angulus sterni. The Manubrium sterni and Corpus sterni are slightly angled towards each other. The second incisura costalis is located directly next to the angulus sterni.
Corpus sterni
The Corpus sterni, also called body, is longer and narrower than the Manubrium sterni. There are further indentations on the sides of the body. These are the incisurae claviculares for ribs two to seven. Whereby the Incisura claviculares of the second rib is next to the Angulus sterni as already mentioned.
Processus xiphoideus
Durch den Proc. xiphoideus (Schwertfortsatz) wird die Rückseite des Corpus sterni fortgesetzt. An ihm setzen keinerlei Rippen an. Seine Form ist sehr individuell und kann auch gespalten oder perforiert vorliegen.
Entwicklung
Die Verknöcherug des Sternums beginnt bereits im sechsten Embryolanmonat und dauert teilweise bis zum 25. Lebensjahr an. Dabei liegt der Proc. xiphoideus als letztes in einer knorpeligen Form vor. Das Brustbein entwickelt sich dabei aus zwei Organanlagen. Diese werden Sternalleisten genannt. Diese beiden verschmelzen von oben nach unten.
