Covering Cells

Covering cells are specialized cells that line the surface of the alveoli of the lungs. They play a key role in the gas exchange that occurs in the lungs.

There are two main types of alveolocytes:

1. Alveolocytes type 1 (covering cells type I) are thin flat cells through which gas exchange occurs between the air in the alveoli and the blood in the pulmonary capillaries. They cover about 95% of the surface of the alveoli.

2. Alveolocytes type 2 (covering cells type II) are cubic cells that produce surfactant - a surface-active substance that reduces the surface tension in the alveoli, preventing them from collapsing.

Thus, covering cells play a critical role in the functioning of the respiratory system, providing gas exchange and maintaining the structure of the lungs.