The anterior mediastinum is the frontmost part of the mediastinum, which is a collection of structures found between the head and the abdomen. There are two more divisions, the middle mediastinum located in the middle and the posterior mediastinum located in the rear. The anterior mediastinum is of narrow build at its front section, but begins to widen a bit as it travels downward.
As part of one of the body's chambers known as the thoracic cavity, or chest cavity, the mediastinum is where organs such as the windpipe, or trachea, the heart and the esophagus are located. It is situated between the right and left sections of the pleural cavity, which surrounds the lungs. There are two portions of the mediastinum: the upper portion, which is called the superior mediastinum, and the lower portion.
Specifically, the anterior mediastinum forms part of the mediastinum's lower portion. Like the two other divisions, the anterior mediastinum contains some components of the body, such as some loose connective tissue and lymphatic vessels, two or three lymph nodes, and some branches of the internal thoracic artery. In infants and children, this interpleural space also contains the thymus — a two-lobed glandular organ known for generating T cells. The organ, however, begins to atrophy as one grows older, leaving only the lower end at adulthood.
The anterior mediastinum has four major boundaries. The front is bound by the sternum, which is the long flat T-shaped plate that connects the ribs. Also binding the space anteriorly is a fibrous plate called the transversus thoracis muscle as well as three of the costal cartilages, which allow the ribs to move forward. The costal cartilages that border the anterior mediastinum are the fifth, sixth and seventh ones on the left-hand side. At the back of the anterior mediastinum is the pericardium, which is a thick enclosure that contains the heart. The structure's lateral boundary consists of the pleural cavity.
Located behind the anterior mediastinum are the middle mediastinum and the posterior mediastinum. The middle mediastinum is the broadest of the three sections. It consists of the pericardium and the enclosure's contents such as the heart, the pulmonary veins and arteries, the ascending aorta, and the phrenic nerves. Behind the middle mediastinum is the posterior mediastinum, which is described as a triangular space. It contains part of the descending aorta, the veins that run at the sides of the thoracic vertebral column, and the vagus and splanchnic nerves.