Anatomy & Organs

Mediastinum – structure, function & diseases

Mediastinum

The mediastinum is a tissue space in the chest cavity that houses all of the chest organs except the lungs . The organs are stored within the mediastinum in connective tissue , which maintains its shape and, in addition to supporting, also takes on protective functions. The mediastinum is often of clinical relevance due to mediastinal tumors, which can move the mediastinal space, including the organs, into one half of the thorax .

What is the mediastinum?

Different systems with vital functions are located in the human chest. In addition to the heart , for example, the immunologically relevant thymus and the trachea are embedded in the chest cavity. The medical profession understands the mediastinum to be a tissue space in the thoracic cavity that houses all the thoracic organs with the exception of the lungs.

Literally translated, mediastinum means as much as middle skin space. The structure lies median within the thoracic cavity and is bounded on the ventral side by the sternum. The dorsal boundary is formed by the spinal column . The mediastinum is bordered laterally by the pleurae and the upper thoracic aperture is located cranially. The diaphragm is located caudal to the mediastinum and, like the lungs, is not part of the mediastinum. 

Anatomically, the thoracic cavity is divided into two distinct sections: an inferior tissue space and an upper tissue space. In addition to veins , arteries and nerves , the mediastinum is primarily home to the lymphatic system. Organs like the heart are also part of the structure.

Anatomy & Structure

Loose connective tissue lines the mediastinum and embeds all thoracic organs except the lungs. The upper mediastinum houses the thymus and vessels close to the heart such as the aortic arch or its branches, the pulmonary trunk or the superior vena cava. The trachea , esophagus , mediastinal, and tracheobronchial lymph nodes also lie in the upper mediastinum.The nerve structures of the upper area correspond to the phrenic nerve, the vagus nerve and the recurrent laryngeal nerve. As the so-called thoracic duct, the ductus thoracicus belongs to the lymphatic system. 

Between the arch of the aorta and the left pulmonary artery lies the so-called ‘aortopulmonary window’: a space that plays a role in radiology. The lower mediastinal space connects to the upper mediastinum. This inferior space is further divided into an anterior section between the sternum and pericardium , a middle section encircling the heart, and a posterior section located between the heart and the thoracic spine.

The posterior portion is home to the esophagus, aorta , and inferior vena cava, as well as the azygos vein, hemiazygos vein, and the neural structures of the vagus nerve . The origins of various neck muscles lie in the upper layer of the mediastinum. The organs lie in the deeper layers.

Function & Tasks

Most of the thoracic organs are located in the mediastinum. The main task of the structure is the protective function. The entire mediastinum is lined with connective tissue, which forms an ideal protective space for the vital thoracic structures. In the human body, connective tissue mainly performs supporting tasks and consists of comparatively few cells. Because of the large intercellular mass of connective tissue structures, connective tissue can maintain the shape of organs.

In the mediastinum, the lining of connective tissue primarily protects the organs from damage. For this purpose, there are different types of fibers in the intercellular substance. Fibers made from fibrillar proteins such as collagen form a tight meshwork that supports the organs.

 Between these fibers are strongly swelling proteoglycans that resist tensile forces and at the same time have a compression-dampening effect. In interaction, the fibrous meshwork and the proteoglycan buffer of the mediastinal connective tissue support and protect the breast organs. In addition, the mediastinal connective tissue serves as a water reservoir and also assumes important functions in the defense against disease.

While the structures of the thoracic cavity are already relatively shock-protected by the ribs , it is the connective tissue protection of the mediastinum that preserves the organ’s shape and location. This means that the organs in the thoracic cavity are essentially protected and secured in multiple ways. The ribs provide skeletal protection, while the mediastinum provides tissue protection. The multiple protection of the chest organs points to the vital necessity of organs such as the heart in the human body.

Diseases

In the clinic, the doctor is confronted with various diseases of the mediastinum every day. The most common of these are mediastinal tumors such as thymomas and lymphomas. Slightly less common are masses in the thoracic area that displace the mediastinum. A mediastinal displacement does not necessarily have to be associated with a mass, but can also be an indication of pneumothorax. To image the mediastinum, the doctor performs a mediastinoscopy .

Mediastinal tumors cause typical symptoms by locally displacing neighboring structures. Compression of the superior vena cava accompanied by hoarseness is a common sign of a tumor in the mediastinum. In this scenario, the tumor displaces the superior vena cava and the recurrent laryngeal nerve. Due to the displacement, the two structures are now jammed, so that circulatory disorders and nerve conduction disorders occur. Tumors of the mediastinum can also cause the symptom complex Horner’s syndrome and thus result in paralysis of the smooth muscles of the eye.

Due to the tissue displacement caused by the tumour, an elevated diaphragm can also occur, which is accompanied by increasing shortness of breath. This scenario is primarily caused by tumor-related compression of the trachea. 

Non-specific accompanying symptoms of a tissue-displacing mass within the mediastinum are cough and the general symptoms night sweats and fever . In the context of tumor diseases of the structure of the mediastinum, a mediastinal shift often occurs, which corresponds to a shift of the mediastinum that can be demonstrated radiologically. This shift shifts the mediastinal space and its organs into one of the halves of the thorax.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.