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Physiology Respiratory System bd8cccb2

Production of Surfactant is by:

A
Alveolar macrophages
B
Type I Pneumocytes
C
Type II Pneumocytes
D
Clara cells
High-Yield Explanation
Ans. C Type II PneumocytesRef: Guytotty 11th ed pg. 474,* The smaller type II pneumocytes are often more numerous than type I pneumocytes, but they contribute less than 10% of the surface area.* They are rounded cells which protrude from the alveolar surface, particularly at the angles between alveolar profiles.* In the human lung they are often associated with interalveolar pores of Kohn. Their cytoplasm contains numerous characteristic secretory lamellar bodies, which they can recycle.* Ultra structurally, the lamellar bodies are comprised of concentric whorls of phospholipid-rich membrane, the precursors of alveolar surfactant.* "Surfactant is stored in lamellar bodies and secreted in the form of tubular myelin (unrelated to myelin of the nervous system) by type II pneumocytes. It is recycled by type II pneumocytes, or cleared (phagocytosed) by alveolar macrophages.* Clara cells of the bronchiolar epithelium serve as progenitor cells. They are non-ciliated cuboidal epithelial cells in terminal bronchioles.

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