The thorax is the skeleton of the chest, housing the lungs, the heart and other significant organs. The opening on the upper part of the thorax, often referred to by surgeons as the thoracic outlet, allows passage for the esophagus, trachea, important ducts, nerves and vessels. The inferior thoracic aperture is virtually sealed by a muscle called the thoracic diaphragm. The region between the ribs is called the intercostal space, mostly containing muscles that help in respiration. The collective rib movement is responsible for about 25% of the respiratory effort while the other 75% is shouldered by the diaphragm.
The sternum is composed largely of cancellous bone that contains red bone marrow. During respiration, a fibrocartilaginous joint between the manubrium and the sternum makes subtle movements. The xiphoid process also has this joint with the body of the sternum. One good thing to remember is that all ribs form synovial joints with the thoracic vertebrae known as the costovertebral joint. Ribs 2 – 9 form a synovial joint with a demifacet of the upper and lower vertebral body, to add to this, the tubercle of the rib meets with the cartilaginous facet at the tip of the lower vertebrae. What’s unique with ribs 1, 10, 11 and 12 are unique because instead of joining with 2 vertebrae, it joins with only one.
Interestingly though, the ribs can be classified into true ribs and false ribs. Ribs 1 -7 meet directly with the body of the sternum and are being referred to as the true ribs. Ribs 8 – 10 indirectly meet with the body of the sternum; they meet with the use of a cartilage and ribs 11 – 12 or the floating ribs end in the muscular abdominal wall. Ribs 8 – 12 are called the false ribs.
The thoracic wall receives its blood supply from three main sources namely the axillary, subclavian and the aorta.
Because the thorax is housing relatively large body organs, it is the second largest hollow space of the body in order to accommodate the important organs. If the opening on the upper part of the thorax is closed by the thoracic diaphragm, the thoracic cavity’s floor is separated from the abdominal cavity by the diaphragm, the muscle for breathing.
A buzz of activities is happening within the thorax as it houses two of the most important organs in the body. A unique harmony of the bones and the muscles allows for the ribs to expand in time of inhalation and relaxes during exhalation. The diaphragm also helps in the breathing effort and serves as the gateway between the abdominal and thoracic cavity. Understanding the anatomy of the thorax is another step in our thirst of knowledge to understand the wonders of the human body.