Alveolar epithelium

Alveolar epithelium is a thin tissue layer that lines the alveoli in the lungs. It is composed of two types of cells: type I alveolar cells and type II alveolar cells. The alveolar epithelium plays a crucial role in gas exchange and maintaining the balance of fluids and electrolytes in the lungs.

Structure

The alveolar epithelium is composed of two types of cells. The type I alveolar cells are squamous, thin and cover about 95% of the alveolar surface area. They are involved in the process of gas exchange between the alveoli and the capillaries.

The type II alveolar cells are cuboidal and cover the remaining 5% of the alveolar surface area. They are responsible for the secretion of surfactant, a substance that reduces the surface tension in the alveoli and prevents them from collapsing.

Function

The primary function of the alveolar epithelium is to facilitate gas exchange. Oxygen from the air in the alveoli diffuses across the alveolar epithelium and into the capillaries, where it binds to hemoglobin in red blood cells. At the same time, carbon dioxide, a waste product of cellular metabolism, diffuses from the blood into the alveoli and is exhaled.

The alveolar epithelium also plays a role in maintaining the balance of fluids and electrolytes in the lungs. The type II alveolar cells secrete surfactant, which prevents the alveoli from collapsing and keeps them open for gas exchange.

Clinical significance

Damage to the alveolar epithelium can lead to a number of lung diseases, including pulmonary edema, acute respiratory distress syndrome (ARDS), and pulmonary fibrosis. In these conditions, the function of the alveolar epithelium is compromised, leading to impaired gas exchange and respiratory failure.