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The pleura is a membrane that surrounds the lungs of mammals. Presumably, the phrase means that the surface of the pleura was found to be normal in an examination.
The skin surface is not large enough for big creatures such as humans; therefore we have structures in our lungs that greatly increase the surface area.
When fully stretched out, the surface area of the lungs is estimated to be about the size of a tennis court, roughly 70 square meters (750 square feet). This large surface area is essential for efficient gas exchange, allowing oxygen to enter the bloodstream and carbon dioxide to be expelled. The extensive branching of the bronchi and alveoli contributes to this expansive area, maximizing the lungs' functionality.
If the surface area of the organism is small, then there is no problem with getting all the oxygen needed. If the surface area of the organism is large, therefore a special respiratory surface is needed. An example is lungs, gills. The ratio of surface area to volume in a small organism is greater than the ratio in a large organism.
Alveolar sac and alveoli
The most numerous cells in the lungs are the alveolar epithelial cells, specifically the type I alveolar cells which make up about 95% of the alveolar surface area. These cells are responsible for gas exchange and maintaining the structural integrity of the alveoli.
lungs
function of alveolar macrophagesThe function of alveolar macrophage in the lungs is to remove dust particles and other debris from alveolar spaces. -SheshiAveolar macrophages work to break up surfactanct in the aveoli which exists to decrease surface tension in the lungs. If there is a disorder where the macrophage does not function correctly, such as in PAP, the surfactant will not be broken up and decreased ventilation will occur resulting in less oxygen delivery.
the natural tendency for the lungs to recoil and the surface tension of the alveolar fluid
Pulmonary alveolar proteinosis (PAP) is a rare disease of the lungs.
Intra-alveolar surface tension is caused by the presence of fluid lining the alveoli, mainly composed of surfactant molecules. Surfactant helps reduce surface tension by lowering the cohesive forces between water molecules, preventing alveolar collapse during exhalation and allowing for efficient gas exchange in the lungs.
Pulmonary surfactant...see link for more information.
Surfactant is produced by the type II alveolar cells in the lungs. These cells secrete surfactant which helps lower surface tension in the alveoli, preventing collapse and facilitating gas exchange.
Interfering with the cohesiveness of water molecules, thereby reducing the surface tension of alveolar fluid.
Type 1 alveolar cells
An alveolar dead space is the volume of air in the alveoli of the lungs which does not partake in gas exchange.