The pleural cavity is a region within the chest that plays a significant role in respiration. It helps ensure the proper movement and protection of the lungs.
What is the Pleural Cavity?
The pleural cavity is a narrow, potential space located within the thoracic cavity, surrounding the lungs. This sealed compartment is formed by two layers of a smooth, thin membrane known as the pleura.
The outer layer, called the parietal pleura, lines the inner surface of the chest wall, including the ribs, diaphragm, and the mediastinum. The inner layer, known as the visceral pleura, adheres directly to the surface of the lung, extending into its fissures. These two layers are continuous with each other around the hilum. Between these two pleural layers lies a small amount of serous pleural fluid, typically only a few milliliters in a healthy adult.
The Organs Housed Within
The primary organs found within the pleural cavities are the lungs. There are two distinct pleural cavities, one for each lung, located on either side of the mediastinum. This separation is important because it means that events affecting one lung, such as a localized infection, do not necessarily spread to the other.
It is important to note that while other significant organs like the heart, esophagus, and major blood vessels are also present in the thoracic cavity, they are not located inside the pleural cavities. Instead, these structures are situated in the mediastinum, the central region of the chest that separates the two pleural sacs. The mediastinum is a distinct anatomical compartment containing a variety of tissues and organs, including the thymus and trachea, in addition to the heart and great vessels.
The Pleural Cavity’s Essential Role
The pleural cavity and the fluid it contains perform functions that support breathing. The thin layer of pleural fluid acts as a lubricant, allowing the two pleural layers to glide smoothly past each other with minimal friction during respiration. This lubrication enables the lungs to expand and contract freely as air moves in and out of the body.
The pleural cavity also plays a part in maintaining the inflated state of the lungs. There is a slightly negative pressure within this space compared to the atmospheric pressure. This pressure difference, along with the surface tension created by the pleural fluid, helps to keep the lungs expanded and closely associated with the chest wall. This mechanism ensures that as the chest wall moves during inhalation, the lungs are pulled along, facilitating effective airflow and preventing their collapse.