Lower GI II Flashcards
______ hydrolyzes starch to form sugars
Amylase
Amylase is secreted by glands in the _______ as well as by the ______
mouth, pancreas
Starch is hydrolyzed to ________
disaccharides
Disaccharides are broken down to __________
monosaccharides
the breakdown of disaccharides occurs in _______ of _________
brush border of small intestine
Monosaccharides are absorbed by _________
enterocytes
The absorption of monosaccharides by enterocytes involves
energy-dependent mediator-specific carriers: Na+-dependent sugar glucose transporter-1 (SGLT-1)
Digestion of proteins begins in the ______
stomach
Proteins are hydrolyzed to
peptides
Digestion of proteins occurs through action of ______ (activated form of ______)
Pepsin (activated form of pepsinogen)
The digestion of proteins requires _____ environment of stomach, why?
proteins. Activation of pepsinogen to pepsin occurs in acidic enviroments
Polypeptide breakdown to peptides also occurs in the ______ and also occurs in the _______
stomach, small intestine
Polypeptide breakdown to peptides in the small intestine involves what enzymes secreted by the ______?
Secreted by the pancreas
- Trypsin
- Chymotrypsin
- Elastase
- Carboxypeptidase
Activation of pancreatic proteolytic enzymes is initiated by ______ (______) secreted by ___________
Enteropeptidase (enterokinase)
secreted by Duodenal enterocytes
Breakdown of oligopeptides to amino acids occurs in the
intestinal brush border
Transport of amino acids into enterocytes is via
carrier mediated process
Digestion of lipids begins in the _____
small intestine
Lipids enter the small intestine as _______
triglyceride droplets
________ emulsifies triglyceride droplets into smaller droplets and releases fatty acids and glycerol
pancreatic lipase
Fatty acids and glycerol combine with bile salts to form
micelles (2 nm in diameter)
Micelles can transport
- Fatty acids
- monoglycerides
- glycerol
- phospholipids
- cholesterol
- Vitamin A
- Vitamin K
_______ splits cholesterol into cholesterol and fatty acids
pancreatic lipid esterase
pancreatic lipid esterase splits cholesterol esters into
cholesterol and fatty acids
Micelles are _______ absorbed across ______ apical plasma membrane
passively, enterocyte
what is required for micelles to be passively absorbed across enterocyte apical plasma membrane
Requires fatty acid binding proteins (FABPs) in apical membrane
monoglycerides and glycerol are reesterified in the enterocyte ______ to form ______
SER, Triglycerides
The reesterification of monoglycerides and glycerol in the enterocyte SER requires _______ and _____ , which are found in
Acyl-CoA synthetase and acyltransferase
- found in membranes of enterocyte SER
Triglycerides recombine with proteins (from RER) to form ________
chylomicrons
Digestion of carbohydrates begin in the _______
mouth
Triglycerides recombine with proteins (from RER) to form
Chylomicrons
Chylomicrons are enclosed within membranes in __________, these membranes fuse to the plasma membrane and allow
Golgi Apparatus, exocytosis
Chylomicrons enter intercellular spaces and are taken up by __________ ________
central lacteals
Central lacteals are blind endings of lymphatic vessels within _______ that forms the content of the intercellular spaces within the _____
Lamina propria, villi
Lacteals dump into the large _____ _______ (_____ _____) that carry lymph form the gut tract
lymphatic network (cisterna chyli)
After being taken up by the central lacteals chylomicrons will later enter the blood via the
lymph ducts that enter the subclavian veins
Proteins and carbohydrates enter the blood vessels in the villi and are transported to the liver via the _____ ____ _____
hepatic portal system
Secretory activities of the GI tract are largely controlled by various _______ that, in turn, are under the influence of the contents of the GI tract.
hormones
Cholecystokinin site of secretion and in response of
- Upper intestinal mucosa (duodenum)
- Secreted in response to gastric contents
Targets and effects of cholecystokinin
- Acts on pyloric sphincter to slow down emptying of stomach
- Stimulates bile release from gallbladder
- Stimulates secretion of pancreatic enzymes
- Competitive inhibitor of gastrins.
Site of secretion of gastrin
pyloric-antral portion of stomach
Targets and effects of Gastrin
- Stimulates HCl production by gastric parietal ells
- Promotes growth of gastric mucosa
- Stimulates gastric motility
- Stimulates release of insulin by pancreatic beta cells
Site of Secretin secretion
- Epithelial cells of duodenum
- Stimulated by acid contents of stomach
Targets and effects of Secretin
- Enhances release of insulin by pancreatic Beta Cells
- Stimulates bicarbonate secretion by pancreas
The epithelium of the anus is ________ epithelium
stratified squamous epithelium
Skeletal muscle returns in the anal canal as the
external anal sphincter
What is the difference between internal and external hemorrhoids
internal are part of the internal hemorrhoidal plexus, which is internal to the internal anal sphincter and external hemorrhoidal plexus that is external to the external anal sphincter
What are hemorrhoids
Veins connecting the internal and external hemorrhoidal plexuses can become dilated and bulge the mucosa
