The bony chest surrounds the chest cavity (cavitas thoracis). It consists of the breastbone (sternum), the ribs (costae) and the thoracic spine, and protects the organs in the chest cavity. Its cross section appears oval from the outside but more bean-shaped from the inside where the spinal column (columna vertebralis) protrudes deep into the inside of the chest cavity.
When seen from the front, the chest appears to be cut away with the thoracic spine (vertebrae thoracicae) longer than the breastbone (sternum). The chest has a narrow upper opening (apertura thoracis superior), which is restricted by the first ribs (costae), the first thoracic vertebra and the breastbone manubrium (manubrium). This opening acts as a passage for arteries and veins to the head, throat and body wall together with the esophagus, windpipe and apex of the lung, and also in some cases to the thyroid gland.
A lower opening in the chest (apertura thoracis inferior), which is somewhat larger than the upper opening, is restricted by the 12th vertebra, the 10th to 12th ribs, the costal arch and the xyphoid process (processus xyphoideus) of the breastbone.
The chest finishes with the diaphragm (diaphragma), with openings for vessels and nerves. The diaphragm turns inwards and broadly upwards into the chest cavity so that the abdominal organs are also enclosed by the lower chest opening.
The 12 pairs of ribs which make up the chest consist of seven real pairs of ribs (costae verae) and five false ribs. The 8th to 10th pair of ribs make up the costal arch (arcus costalis), each being connected by cartilage to the pair of ribs above.
The last two pairs of ribs are not connected to the next higher ribs; they end freely between the muscles of the front or lateral abdomen wall. The intercostal spaces assist in breathing movement and are used to constrict or expand the chest.
Cartilage elements on each rib (cartilago costalis) connect the ribs
to the breastbone. The breastbone consists of three parts. The upper
part consists of the manubrium (manubrium), the middle part the sternum
body (corpus sterni), and the lower part the xyphoid process (processus
xyphoideus).
