Bronchioles of the lung: anatomy and function
Pleural cavity and pleura
The pleura refers to the serous membrane that lines the pleural cavity and is attached to the lungs and chest wall.
- Each lung is enveloped in its own double-membrane pleural sac.
- The inner membrane of the sac adheres to the outer surface of the lung and is called the visceral pleura.
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- The outer membrane is called the parietal pleura and is an extension of the visceral pleura, which doubles back on itself at the hilum (hilus) and runs along the surfaces of the rib cage, diaphragm, and mediastinum.
- Both pleurae are serous membranes, which secrete a thin layer of watery pleural fluid into the pleural cavity that separates them.
- An open space does not normally exist in the pleural cavity because the pleural fluid loosely attaches the two membranes. During breathing movements, this slippery seal allows the two membranes to slide past one another. The pleurae also form a barrier that helps protect the lungs from infections that can occur elsewhere in the thoracic cavity.