Pneumocyte

The pneumocytes, also called alveolar or Alveolozyten are specialized cells that are found in the lungs and lining the alveoli. A distinction pneumocytes type I and type II alveolar epithelial cells are all connected to each other via tight junctions. The two types differ in part considerably in their number, of them clad surface and its function.

Pneumozyt Type I

Type I pneumocytes are incapable of division, differentiated cells and have a flat, about 0.2 micron thick cell body. Form together with the capillary endothelium, and a common, fused basal lamina of blood - air barrier in the lung. Although they make up only about 40 % of the total number of pneumocytes, they paper 90-95% of Alveolenoberfläche. Around the flattened nucleus have type I pneumocytes, some cell organelles are found in the cell remote from the core sections of microtubules and microfilaments.

Pneumozyt type II

The type II pneumocytes, also called niche cells are much smaller and cover with about 5% of the alveolar walls a much smaller area. Their number, however, exceeds that of type I pneumocytes, moreover, they are rich in cell organelles. Because these cubic cells constructed protrude further microscopic observation in the lumen of the alveoli and larger effect than the flat type I cells, they are sometimes misleadingly called the " large " refers to alveolar epithelial cells.

While the very flat type I pneumocytes are to form a very thin blood-air barrier, it is the task of the type II cells to produce the surfactant. Surfactant consists of lipids (mainly lecithin derivatives, phospholipids ) and proteins, is in the Type - II cell in vesicles ( lamellar bodies ) are stored, and secreted by exocytosis. This material covers the inside of the alveolar wall and the surface tension to such an extent that collapse of the alveoli is inhibited. The cells are also mitotically active, and can thus damaged type I pneumocytes replaced by cell proliferation and differentiation.

Mucin-1, a human gene that is associated with type II pneumocytes, has been identified as tumor markers in lung cancer.