I am going to answer the sample USMLE Step 1 Questions with Explanation. These questions are available at USMLE.org
Q-A 45-year-old woman is recovering from acute respiratory distress syndrome secondary to gallstone pancreatitis. A drawing of the alveolar wall is shown.
Which of the following labeled cells will most likely proliferate and reestablish the injured epithelial layer in this patient?
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Answer and Explanation
This patient has suffered from acute respiratory distress syndrome (ARDS), which involves damage to the alveolar epithelial layer. The question refers to which cell type in the alveolar wall is most likely responsible for proliferating and reestablishing the injured epithelial layer. The type II pneumocytes are the cells most likely to proliferate and restore the injured epithelial layer. These cuboidal cells are located in the corners of alveoli and have two main functions: (1) producing surfactant, which reduces alveolar surface tension, and (2) serving as progenitor cells for the alveolar epithelium. After injury, type II pneumocytes proliferate and can differentiate into type I pneumocytes to restore the epithelial layer.
The correct answer is D