Answer :
The gastrointestinal system has two classes of such cells, the islets of Langerhans in the pancreas and the enteroendocrine cells in the mucosal epithelium of the stomach and intestine.
Answer: Mucous cells: secrete an alkaline mucus that protects the epithelium against shear stress and acid.
Parietal cells: secrete hydrochloric acid.
Chief cells: secrete pepsin, a proteolytic enzyme.
Explanation: