About type II pneumocytes, which is not TRUE?
Correct Answer: Lamellar bodies are formed
Description: Type II pneumocytes are epithelial cells present in the alveolar surface, their cytoplasm exhibits lamellar bodies.They have many functions the most impoant is production of surfactant.Surfactant are produced by exocytosis and not endocytosis. Pneumocytes: Alveolar surface is formed by two types of epithelial cells, pneumocytes I and pneumocytes II.Type II pneumocytes are specialised cells within the alveoli of the lungs. There are as many type II as type I pneumocytes within the alveoli, but type II cells only constitute 1-5% of the alveolar surface area as they are cuboidal rather than squamous in shape. Type I pneumocytes are simple squamous epithelial cells responsible for gas exchange in the alveoli and cover a majority of the alveolar surface area. They are connected to each other by tight junctions. Type II pneumocytes are specialised cells within the alveoli of the lungs, they are adapted to produce surfactant. Their cytoplasm exhibits apical secretory granules termed lamellar bodies. These are released continuously by exocytosis onto the epithelial cell surface. The lamellar bodies contain the phospholipid component of surfactant. They occupy the thick poion of the alveolar-capillary complex. Functions: The main function of type II cells is secretion of the lung surfactant. They paicipate in clearance and in repair by proliferating and migrating to damage areas. Type II cells are able to divide and to differentiate into type I cells. They paicipate in defense responses by expressing various receptors (in paicular, Toll-like receptors). Type II cells are involved in the lung cytokine/chemokine network by secreting and responding to an array of cytokines and chemokines. They regulate transmigration of monocytes across epithelial layer and possibly paicipate in T cell activation. Ref: Color Atlas & Text of Pulmonary Pathology, edited by Philip T. Cagle, 2nd Edition, Page 11.
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