Digestion, Absorption and Intestinal Secretion Flashcards Preview

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Flashcards in Digestion, Absorption and Intestinal Secretion Deck (28):

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


Where does fat breakdown occur?

small intestine


What does the hydrolysis of emulsified fats produce?

micelles (nanometre particles of lipid digestion)


What are micelles and how are they formed?

consist of 2 monoglycerides


What are the products of cholesterol breakdown by cholesterol esterase?

fatty acid and free cholesterol


Where is carbohydrate digestion facilitated in the small intestine?

conducted by brush border enzymes on the enterocytes


Where is peptide digestion facilitated in the small intestine?

conducted by brush border enzymes on the enterocytes


Describe lymphatic routes of nutrient transport

Only really used for lipid molecules too large to pass through into the capillary


Describe portal routes of nutrient transport

Carries molecules from the small intestine to the liver


Describe the different types of amino acid transporters

There are at least 5 types: three are sodium-independent transporters which are involved in the efflux of amino acids, whereas there are two sodium-dependent channels which are used for the uptake of amino acids


Describe what happens when amino acids are transported into an enterocyte

90% are transported across the basolateral membrane, 10% remain in the cell where they serve role in intracellular protein synthesis


Describe how micelles are absorbed in the small intestine

diffuse through to reach the brush border


Describe how fatty acids, cholesterol and phospholipids are absorbed in the small intestine

absorbed by free diffusion


Why may fat be taken up into the lymph circulation?

if they are too large to pass into the capillary