Pneumatocytes lines the

(Alveoli) (83-M. Kaul histology 3rd) (221- LB.Singh 5th)Respiratory system - Histology* Trachea - lined by pseudostratified ciliated columnar epithelium* Intrapulmonary Bronchus - lined by pseudostratified ciliated columnar epithelium* Terminal Bronchiole - lined by simple columnar epithelium* Respiratory Bronchiole - lined by cuboidal epithelium* Atria, alveolar ducts and alveoli - lined with squamous epitheliumALVEOLI - The main support of the alveoli is provided by elastic fibres* Majority of cells lining the alveoli are the squamous cells or type 1 pneumocytes. Few are larger cells or type II pneumocytes. Type II cells secrete the surfactant which lowers surface tension and prevents alveoli from collapsing* The exchange between the blood in the capillaries and air in the alveoli takes place through(a) Cytoplasm of endothelial cell of a capillary(b) Basement membrane of the capillary(c) Basement membrane of the alveolus(d) Cytoplasm of the epithelial cells of the alveolus* In CHF, heart failure cells are present in the sputum. These cells are the alveolar macrophages, containing hemosiderin of the red blood cells from the ruptured capillaries.