Epithelial Transport Mechanisms Practice Test

Cystic fibrosis disrupts the chloride channel CFTR, which also supports bicarbonate movement across epithelial surfaces. When CFTR is defective, chloride and bicarbonate secretion into luminal secretions falls. In the lungs, less chloride secretion means less water is drawn into the airway surface liquid, so mucus becomes abnormally thick and sticky, hindering mucociliary clearance and promoting infections. In the pancreas, bicarbonate-rich fluid is essential to neutralize stomach acid and provide the right environment for digestive enzymes; reduced bicarbonate secretion leads to ductal plugging and pancreatic exocrine insufficiency. So the best description is that CFTR dysfunction reduces both chloride and bicarbonate secretion, producing thick mucus in the lungs and pancreatic insufficiency.