Alveolarepitel

Alveolarepitel refers to the epithelial cells that line the alveoli, the tiny air sacs in the lungs responsible for gas exchange. These cells form a thin barrier crucial for the diffusion of oxygen into the bloodstream and carbon dioxide out of the bloodstream. There are two main types of alveolar epithelial cells, known as pneumocytes.

Type I pneumocytes are extremely thin and flat cells, covering about 95% of the alveolar surface. Their primary role is to facilitate gas exchange due to their minimal thickness. They are highly susceptible to injury and are not capable of cell division.

Type II pneumocytes are cuboidal cells scattered among the type I cells. They are larger and fewer in number, making up about 5% of the alveolar surface. Type II pneumocytes have a critical function in producing and secreting pulmonary surfactant, a substance that reduces surface tension within the alveoli, preventing them from collapsing during exhalation. They also play a role in repairing the alveolar epithelium and can differentiate into type I pneumocytes when needed. The alveolar epithelium, along with the capillary endothelium, forms the respiratory membrane, the functional unit of gas exchange in the lungs.