Ipneumocytter

Ipneumocytter, or pneumocytes, are specialized epithelial cells that line the alveoli in the lungs. They are divided into two main subtypes: type I pneumocytes (AT1) and type II pneumocytes (AT2). Together, they form the alveolar–capillary barrier essential for gas exchange and maintaining lung integrity.

Type I pneumocytes are extremely thin, large, and cover most of the alveolar surface. Their primary role is to facilitate gas exchange by providing a minimal diffusion distance between air and blood. They form extensive tight junctions with neighboring cells, contributing to the barrier that regulates fluid and solute movement. Type I cells have limited capacity to proliferate, so they rely on Type II cells to replenish them after injury.

Type II pneumocytes are cuboidal and more numerous in certain alveolar regions, especially at the edges of alveolar sacs. They produce and secrete pulmonary surfactant, a surface-active substance that lowers surface tension and prevents alveolar collapse during expiration. In addition to surfactant production, Type II cells proliferate readily and can differentiate into Type I cells as part of alveolar repair after injury.

Clinical relevance and development: Surfactant deficiency or dysfunction, common in preterm infants, leads to respiratory distress syndrome. In conditions such as acute respiratory distress syndrome (ARDS), alveolar epithelial damage involves pneumocytes, and repair processes often begin with Type II cells replacing damaged Type I cells. Ipneumocytter are central to lung physiology, development, and pathology.