Brunner's glands secrete an alkaline product that helps achieve optimal pH for the activity of pancreatic enzymes. Where are these glands located?
(A)At the base of villi throughout the small intestine
(B)In he epithelium of the ampulla of vater
(C)In the mucosa and submucosa of the jejunum
(D)In the submucosa of the duodenum
(E)In the submucosa of the ileum
Answer: (D)In the submucosa of the duodenum