Digestion, Absorption and Intestinal Secretion Flashcards
What is the role of the parotid glands?
secrete serous saliva which is watery and rich in amylase
What is the role of the sublingual and submandibular glands?
produce a mixture of serous and mucus secretion which serves as an antimicrobial and a lubricant
How does amylase work?
breaks onw the alpha-1,4 glycolytic bonds in glycogen etc.
What do stomach secretions contain?
hydrochloric acid, pepsin, mucus, salts, water, intrinsic factor (critical for vit b12 absorption) and bicarbonate
How is gastric acid secretion stimulated?
driven by gastrin which is released by G cells in the antral part of the stomach in response to the presence of peptides. The release of gastrin stimulates CCKB receptors on parietal cells to produce acid as well as on ECL cells in the corpus to secrete histamine, which then stimulates parietal cells via the H2 receptor
How is gastric acid secretion inhibited?
somatostatin released by D cells which inhibits the G cells, ECL cells and parietal cells via SST2 receptors as well as reducing excitatory control via the vagus nerve to the cells.
Describe the role of pepsin in the stomach
secreted as pepsinogen by chief cells
Describe the composition of pancreatic secretions
rich in bicarbonate and contains trypsin inhibitor (to prevent premature activation in the pancreatic ducts)
What is the function of bile salts?
Bile salts are synthesised from cholesterol and promote the emulsification of fats into droplets
What is bile?
composition of bile acids formed from cholesterol
What happens to the bile after it has been produced?
secreted into the canaliculi of hepatocytes and travels in the liver ducts to the gall bladder where it is stored until stimulated for release
How is the release of bile stimulated?
by the presence of acetylcholine, gastrin or CCK
What is the sphincter of oddi and what is it’s function?
allows the flow of bile into the duodenum when opened, and when closed prevents this (when not stimulated)
What are bruner cells and where would you find them?
secrete bicarbonate rich mucus in the small intestine
What are peyer’s patches and where are they found?
an aggregate of lymphoid tissue in the large intestine