Physiology of the Small Intestine Flashcards
(47 cards)
Which glands the in duodenum produce mucus?
Brunner’s glands.
What 2 things cause secretion of water into the lumen of the intestine?
- The hypertonicity of the chyme.
- The intestinal epithelium secretes Na+, Cl-, and HCO3- into the lumen.
Water follows by osmosis.
Is there a large net loss or absorption of water from the small intestine?
Net absorption.
Where are Brunner’s glands located?
Duodenum
What is the main function of Motilin? How does it do this?
Stimulates migrating motor complexes (MMCs) via both the enteric and autonomic nervous systems.
List the 5 key intestinal hormones.
- Motilin
- VIP (vasoactive intestinal peptide)
- GIP (gastric inhibitory peptide)
- Cholecystokinin
- Secretin
What is the function of vasoactive intestinal peptide (VIP)?
Increases blood flow to the GI tract.
What are the 2 functions of gastric inhibitory peptide (GIP)?
- Inhibits gastric secretion.
2. Stimulates insulin secretion.
Which 2 hormones control pancreatic and biliary secretions?
Cholecystokinin and Secretin.
Secretin stimulates which organs to release which substances?
HCO3- from the pancreas, and bile from the liver.
What 2 things does Cholecystokinin stimulate?
Digestive enzyme secretion from the pancreas, and gallbladder contraction.
What are the main types of cells in the exocrine pancreas? What do they each secrete?
Acinar cells - secrete enzymes
Ductal cells - secrete bicarbonate
List the 5 main enzymes of the exocrine pancreas.
- Trypsin
- Chymotrypsin
- Carboxypeptidase
- Pancreatic amylase
- Lipases
Which enzymes of the exocrine pancreas are secreted in their inactive, precursor forms?
- Trypsin
- Chymotrypsin
- Carboxypeptidase
What is a zymogen?
A zymogen, also called a proenzyme, is an inactive precursor of an enzyme.
What activates inactive pancreatic digestive enzymes such as trypsinogen into active enzymes in the small intestine?
Enterokinase
Which enzyme turns CO2 and H2O into H+ and HCO3-?
Carbonic anhydrase
Other than Cholecystokinin, which other substance stimulates the secretion of pancreatic enzymes? What kind of substance is it?
Acetylcholine - a neurotransmitter.
Outline 7 steps of the digestion and absorption of fats in the small intestine.
- Fats (triglycerides) are emulsified by bile salts and phospholipids.
- Triglycerides are digested by pancreatic lipase to a monoglyceride and 2 fatty acids.
- The products are held in micelles, combined with bile salts and phospholipids.
- The micelles move next to the surface of the epithelial cells. When a micelle breaks down, the monoglycerides and fatty acids diffuse across the cell membrane.
- Once in the cell, the fatty acids and monoglycerides are reassembled into triglycerides.
- The triglycerides are packaged into chylomicrons.
- Chylomicrons leave the intestinal villus via its lymph vessel.
In the digestion of fats (triglycerides), what are they emulsified by?
Bile salts and phospholipids.
Pancreatic lipase turns triglycerides into what?
A monoglyceride and 2 free fatty acids.
What is the primary product in the breakdown of starch and glycogen?
Maltose.
How do glucose and galactose enter the luminal membrane of the intestinal epithelium?
Secondary active transport (SGLT1), coupled to Na+K+ATPase on the basolateral membrane.
How does fructose enter the luminal membrane of the intestinal epithelium?
Facilitated diffusion (GLUT5).
