This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Which of the following exocrine glandular ducts are not obstructed in cystic fibrosis: 
Select and explain. 
A. Pancreas, B. Lung, C. Sweat gland, D. All of above
C: Sweat gland
Answer: C: Sweat gland 
Explanation: Answer C. Sweat glandMost CF patients have 3 distinct abnormal characteristics:The ducts of the mucus-secreting glands are obstructed due to an increase in viscosity of these secretions leading to glandular dilatation and destruction.CF patients are prone to chronic bacterial colonization and infections.The sweat glands are not obstructed in CF patients because in serous glands such as sweat glands there are abnormal concentrations of inorganic ions, rather than glandular obstruction with thick mucus.The quantitative pilocarpine iontophoresis sweat test is a uniformly accepted method for diagnosing CF. The sweat gland ducts must be patent for this test.Obstruction of airways leads to bronchiectasis and atelectasis; pancreatic duct obstruction leads to pancreatitis and malabsorption; and plugging of bile ducts leads to obstructive jaundice.