GI physio Flashcards
function of the GI system
Ingest food and liquid with nutrients
digest large molecules in ingested food into absorbable molecular forms
absorption of nutrients from the gut
metabolic transform of fuel molecules
detox of foreign substance (liver)
Elimination of metabolic end product secreted by the liver
immune function
where does GI tissue start to have the same structure
From the mid-esophagus all the way down
what does the surface of microvilli of the GI contain
Brush border
how fast does the intestinal epithelial cells turn over
17 billion new cells each day
complete turnover
complete turnover every 5 days
what is the vein associated with GI tissue
Hepatic portal vein
what is the roll of lymph vessels in the GI tract
transport breakdown products for recycling
what is the roll of muscles and nerves of the GI
peristallic movements
what does the brush border do to breakdown food
Contains enzymes
what are the 5 basic
Carbs Proteins Fats Vitamins Minerals
what is the intermediate product of carbs
Maltose
what breaks up polysaccharides
Amylase
what breaks up triglycerides
Lipase
where does Amylase come rom
Saliva and pancreas
what does the breakdown of carbs lead to
Disaccharide maltose
mix of short branched chains of glucose molecules
what breaks down maltose an ingested sucrose and lactose
enzymes located on the apical membranes of small intestine epithelial cells (brush border)
where are most ingested carbs digested and absorbed
first 20% of small intestin
what are the steps of carbohydrate breakdown in the lumen to be absorbed into the intestinal epithelial cells
Polysaccharides broken into maltose via pancreatic amylase
brush border enzymes break maltose and ingested disaccharised into monsaccharides(fructose, glucose, galactose
how does Fructose get into the interstinal epithelial cells
GLUT5
how does Glucose and galactose get intot he intestinal epithelium
SGLT, cotransported with Na
how does Fructose, Glucose and Galactose get into the interstitial fluid
Via GLUT2
what keeps Na out of the cell after SGLT cotransports it in
Na/K ATPase
what are the enzymes invovled in breaking down complex carbs into monosaccharides
DIgestive Enzymes (amylase) Ectoenzymes (lactase)
what breaks down proteins in the stomach
PEpsin
what breaks down proteins in the small intestin
Trypsin
Chymotrypsin
what secretes trypsin and Chymotrypsin
Pancreas
what digests the peptide fragments to amino acids
Carboxypeptidases
Aminopeptidases
where do carboxypeptidases come fro
pancreas
where do aminopeptidases come from
Apical membrane of small-intestine epithelial cells
how do free amino acids enter epithelial cells of the small intestine
Secondary active transport with Na
how are short chains of 2-3 amino acids absorbed into the small intestine
Sec active transport using the H gradient
where are proteins broken down
stomach
Small intestine
how does pepsin come into existence
Pepsinogen produced in stomach to be cleaved to become pepsin
how do small intestine enzymes come to be
pancrease release pro-enzymes into small intestine to digest proteins
what are the pro-enzymes for peptide breakdown in the small intestine
Trypsinogen
Cymotrypsinogen
Procarboxypeptidase A and B
Proelastase
what initiates the conversion of proenzyme to enzyme in the small intestine
Enteropeptidase
what turns trypsinogen to trypsin
Enteropeptidase (on the brush border)
what turns proenzymes into active enzymes
Trypsin
two classes of amino acids transport
Na+ dependent
Na+ independent
where are tranpsorters of amino acids found
Brush bormesder
Basolateral membrane
what degrades protein
HCl
Proteases
how are proteases released
Proenzymes
can luminal peptidases alone breakdown protein
No, also need brush border enzy
what are the sources of lipase
Lingual lipase
Gastric lipase
Pancreatic Lipase
how do you make fats soluble in water
breakdown into lipases
does gastric emptying increase or slow due to fats
Slow
how are fats emulsifed
mechanically
Emulsifying agents
where does fatty acid absorption occur
Small intestine (primarily duodenum)
where does fatty acid digestionoccur
Stomach
Duodenum
what is involved in emulsification
Bile salt (glycocholic acid)
what makes up a bile salt
A non-polar side
A polar side (carboxyl and hydroxyl grousp)
how does lipase interact with fat
Colipase
how do Micelles enhanve absorption of fatty acids
Miceles are in equalibtium with free fatty acids
Micelles constantly break down and reform
are triglycerides, free faty acids, or monoglycerides found in systemic circulation
Triglycerides
how do triglycerides exist in water
enclosed by membrane from endoplasmic reticulum to form a laceal
what vitamines are fat soluble
A
D
E
K
how do vitamins get through intestinal epithelial cells
Solubilized in micelles
Passively diffuse
what are vitamins released into the body with
Chylomicrons
what do the absorption patterns of fat soluble vitamines follow the pathway of
Fat absorption and other lipids
how are water-soluble vitamines absorbed
diffusion
mediated transport
(except B12)
what is needed for B12 to be absorbed
bind to intrinsic factor
what does bound vit B12 to intrinsic factor do
binds to specific sites on the epithelial cells in the lower portion of the ileum where Vit B12 is taken in by endocytosis
what is the important solute for creation of the concentration gradient
Na
where all does Na absorption occur
throughout the entire Gi tract
can Na be absorbed against its electrochemical gradient
Yes, if small
where is absoprtion of Na the highest
areas of glucose and galactose or amino acids are being transported
what other ions are absorbed in part due to Na
Cl
HCO3
K
where is Ca absorbed
actively by all segments of the intestine
is Ca absorbed actively or passively
actively
what pH are salts soluble
Low pH
what enhances Ca absorption
Vitamin D
how efficient is Fe absoprtion
Very inefficient (less than 10% absorbed
what organ enhances ion absorbption
stomach
what type of Iron is absorbed
Fe++ (Not Fe+++)
