Which of the following structures separates the right and left pleurae?
A.
Intercostal muscles
B.
Pleural cavity
C.
Mediastinum
D.
Diaphragm
The Correct Answer and Explanation is:
The correct answer is C. Mediastinum.
Explanation:
The mediastinum is the central compartment of the thoracic cavity, which separates the right and left pleural cavities. It is a crucial anatomical feature of the chest that helps organize and support the structures within the thorax.
Anatomy and Function of the Mediastinum
The mediastinum is located between the two pleural sacs and extends from the sternum (anteriorly) to the vertebral column (posteriorly), and from the thoracic inlet (superiorly) to the diaphragm (inferiorly). It is divided into several regions:
- Superior Mediastinum: Contains structures such as the trachea, esophagus, great vessels (aorta, superior vena cava), thymus gland, and major nerves (vagus nerves and phrenic nerves).
- Inferior Mediastinum: Further divided into three parts:
- Anterior Mediastinum: Contains connective tissue and fat, and in adults, it is relatively small.
- Middle Mediastinum: Houses the heart, pericardium, and major vessels (including the pulmonary arteries and veins).
- Posterior Mediastinum: Contains the descending aorta, esophagus, thoracic duct, and sympathetic trunk.
Role in Separating Pleurae
The pleural cavities are the spaces on either side of the mediastinum, lined by the pleurae. The right pleural cavity surrounds the right lung, while the left pleural cavity surrounds the left lung. These cavities are separated from each other by the mediastinum, which acts as a barrier that contains and protects the central thoracic organs. The mediastinum provides structural support and ensures that the lungs can expand and contract independently during respiration.
Other Structures
- Intercostal Muscles: These are located between the ribs and are primarily involved in the mechanics of breathing, but they do not separate the pleurae.
- Pleural Cavity: Refers to the space between the visceral and parietal pleurae of each lung; it is not a structure that separates the pleurae but rather a space within each pleural cavity.
- Diaphragm: This muscle separates the thoracic cavity from the abdominal cavity and aids in breathing but does not separate the pleural cavities.
In summary, the mediastinum is the anatomical structure that separates the right and left pleural cavities, playing a vital role in the organization and protection of thoracic organs.