Which of the following not true about alveolar lining?: (A) Type II cells make up 95% of the lining, (B) Type II cells contain lamellar inclusion bodies, (C) Type II cells secrete surfactant, (D) None of the above
Answer is A. The alveoli contain two types of epithelial cells. Type I cells are flat cells with large cytoplasmic extensions and are the primary lining cells of the alveoli, covering approximately 95% of the alveolar epithelial surface area. Type II cells (granular pneumocytes) are thicker and contain numerous lamellar inclusion bodies. A primary function of these cells is to secrete surfactant; however, they are also impoant in alveolar repair as well as other cellular physiology. Although these cells make up approximately 5% of the surface area, they represent approximately 60% of the epithelial cells in the alveoli. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 35.