In a preterm baby with Respiratory distress syndrome, which type of cell is deficiency?: (A) Type 1 alveolar cell, (B) Type 2 alveolar cell, (C) Alveolar capillary endothelial cells, (D) Bronchial mucosal epithelial cell
Answer is B. Cells in Alveolar Epithelial Lining- Type I pneumocytes-Gas exchange occurs across them. .Cover93%surface area of alveoli. Type II pneumocytes -synthesizesurfactant. Direct / indirect injury to type 2 cells lead to ARDS.Cover 5%surface area of Alveoli. When there is alveolar injury, type I cells degenerate and are replaced by type II cells. Type II cells are thus responsible for regeneration of epithelium. Type I and type II pneumocytes exist in a ratio of 1:1. Type III pneumocytesact as chemoreceptors.Cover 2% surface area of Alveoli.