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M01.05.002 Anterior Mediastinum
The mediastinum is the central compartment of the thoracic cavity, situated between the two pleural sacs. It plays a crucial role in housing most thoracic organs and serves as a conduit for structures traversing the thorax en route to the abdomen.
Anatomical Division of the Mediastinum
The mediastinum is divided into two parts by an imaginary line drawn from the sternal angle (junction of the manubrium and sternal body) to the T4 vertebra:
| Division | Boundaries | Subdivisions |
|---|---|---|
| Superior Mediastinum | Extends upwards to the superior thoracic aperture. | None |
| Inferior Mediastinum | Extends downwards to the diaphragm. | Anterior, Middle, and Posterior |
In this guide, we focus on the anterior mediastinum, examining its borders, contents, and clinical significance.
Anatomy of the Anterior Mediastinum
Borders of the Anterior Mediastinum
| Border | Structure |
|---|---|
| Lateral | Mediastinal pleura (parietal pleural membrane). |
| Anterior | Body of the sternum and transversus thoracis muscles. |
| Posterior | Pericardium. |
| Roof | Continuous with the superior mediastinum at the sternal angle. |
| Floor | Diaphragm. |
Contents of the Anterior Mediastinum
The anterior mediastinum contains no major organs. Its components include:
- Loose connective tissue: Includes sternopericardial ligaments (connecting the pericardium to the sternum).
- Fat tissue.
- Lymphatic structures:
- Lymphatic vessels.
- Lymph nodes.
- Branches of internal thoracic vessels.
- Thymus gland in children:
- Extends into the anterior mediastinum during infancy and childhood.
- Recedes and is replaced by adipose tissue after puberty.
Clinical Relevance
- Thymomas: Tumors of the thymus, often located in the anterior mediastinum. These can compress nearby structures, causing symptoms such as chest pain or shortness of breath.
- Mediastinitis: Inflammation of mediastinal tissues, which can result from infections or trauma.
- Lymphadenopathy: Enlarged lymph nodes in the anterior mediastinum can be indicative of malignancies, infections, or systemic diseases.
Key Points to Remember
- The mediastinum is a central compartment divided into superior and inferior parts.
- The anterior mediastinum, part of the inferior mediastinum, houses connective tissue, fat, lymph nodes, and branches of internal thoracic vessels.
- The thymus is prominent in infants and children but recedes by adulthood.
- Understanding the mediastinum’s anatomy is critical for recognizing pathological conditions like thymomas and lymphadenopathy.
References for Further Study
- TeachMeSeries Ltd. (2024). Anatomy of the Mediastinum. Accessed from TeachMeAnatomy.