The mediastinum is the central compartment of the thoracic cavity, located between two pleural sacs. It contains most of the thoracic organs, and acts as a conduit for structures traversing the thorax on their way into the abdomen. Modern understanding of the mediastinum is that it is divided into two subsections - the superior mediastinum and the inferior mediastinum. Here, we shall focus solely on the anatomy of the anterior mediastinum, its borders, contents, and clinical correlations.
The anterior mediastinum is bordered by the mediastinal pleura, which is part of the parietal pleural membrane, the body of the sternum and the transversus thoracis muscles, and the pericardium. Its roof is continuous with the superior mediastinum at the level of the sternal angle, and its floor is the diaphragm.
This space contains no major structures, but rather loose connective tissue, fat, lymphatic vessels, lymph nodes, and branches of the internal thoracic vessels. In infants and children, the thymus extends inferiorly into the anterior mediastinum, but as people age and pass through puberty, the thymus is mostly replaced by adipose tissue.
The anterior mediastinum is a space with many important structures containing important clinical correlations. For example, the sternopericardial ligaments tether the pericardium to the sternum, and the thymus in infants and children provides maturation for T-cells to help the body’s immune system.
The thymus is known to repress the production of autoimmune cells, and so it’s an important structure within the anterior mediastinum. Its regression in adolescence potentially explains why some autoimmune diseases are more likely to manifest in adulthood.
The anterior mediastinum may also be affected in conditions such as pleural effusions, or the abnormal accumulation of fluid in the pleural cavity. An increase in the anterior mediastinum size may compress the trachea and cause stridor, a respiratory noise caused by the turbulent flow of air through an airway. In addition, it can interfere with the cardiovascular system, leading to dyspnea and/or chest pain.
The fat contained in the anterior mediastinum may also be a factor in certain diseases. Recent research has shown that increased adiposity may be associated with an increased risk of cardiovascular disease, type 2 diabetes, and other metabolic disorders. Excess fat may also lead to pulmonary diseases, such as obstructive sleep apnea and emphysema.
The anterior mediastinum is a complex space in the thorax, bordered by the mediastinal pleura, the body of the sternum and the transversus thoracis muscles, and the pericardium. It contains connective tissue, fat, lymphatic vessels, lymph nodes, internal thoracic vessels, thymus, and adipose tissue. It plays a significant role in many medical conditions, and its study is of utmost importance to medical professionals.
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