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40 Cards in this Set
- Front
- Back
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visible circular folds on intestinal mucosa
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folds of Kerckring
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enzymes to digest CHO and where are they?
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* salivary amylase
* pancreatic amylase * disaccharidases** (dis --> mono) |
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how are glucose and galactose absorbed?
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apical: SGLT1 - secondary active trans with Na+
basolateral: GLUT - facilitated diffusion |
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how is fructose absorbed?
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GLUT - facilitated diffusion
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enzymes for protein digestion and where are they?
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*pepsinogen - stomach
*pancreatic proteases - SI *brush boarder peptidases (only peptides**) *cytosolic peptidases |
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remove amino acids from the C-termini of proteins
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exopeptidases
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cleave peptide bonds within proteins
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endopeptidases
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brush border enzyme that cleaves trypsinogen (pancreatic) to form active trypsin
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enterokinase
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cleaves other pancreatic porteases to active forms, including it's precursor
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trypsin
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how are amino acids absorbed?
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apical: with Na+ (secondary active)
bl: facilitated diff |
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how are di and tripeptides absorbed?
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apical: with H+ (secondary active)
bl: facilitated *can be broken down by cytosolic peptidases |
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where and what enzymes digest lipids?
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*lingual lipase
*gastric lipase *pancreatic lipase - SI *colipase* - SI *Cholesterol ester hydrolase - SI *Phospholipase A2 - SI |
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where does emulsification take place?
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*proteins in stomach
*bile salts in SI |
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convert triglycerides to monoglycerides and FA
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lingual, gastric, and pancreatic lipases
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secreted by pancreas
*works in SI to displace bile salts on triglycerides so that pancreatic lipase can get to them |
colipase
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describe a micelle
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* tiny spheres of bile salts around digestible lipids
* hydrophilic on outside * lipiphilic on inside |
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once micelles contact brush border and release digested lipids into cytosol, what happens to the lipids?
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re-esterified with free FA to go back to consumed form
packaged with apoproteins to form chylomicrons |
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what happens to bile salts left behind in the lumen?
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absorbed and recycled in ileum
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most of the outer shell of chylomicrons is composed of?
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phospholipids
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how are chylomicrons picked up?
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by lymphatic capillaries (lacteals) then taken to circulation
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how are fat soluble vitamins absorbed?
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ADEK
incorporated into micelles and chylomicrons |
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how are water soluble vitamins absorbed?
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Na+ cotransport - secondary active
except B12 - IF |
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how is free iron absorbed?
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apoferritin binds in cytosol and transports BL to blood
transferrin binds iron in blood and transports to liver, then bone marrow |
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how is calcium absorbed?
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vitamin D upregulates CALBINDIN that binds to Ca
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what kind of absorption occurs in colon?
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cellular
not para (tight junctions) |
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absorption in the SI is driven by?
jejunum/ileum net absorption |
Na+
jejunum: NaHCO3 ileum: NaCl |
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how does absorption occur in the jejunum
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1. Na+ absorbed with sugar or AA - driven by secondary active (Na+/K+ ATPase pump)
2. Na+ exchanged for H+ (carb anhydrase) 3. HCO3 (carb anhydrase) is absorbed |
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how does absorption occur in the ileum?
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same as jejunum except HCO3 is moved to lumen and Cl is absorbed
1. Na+ with sugar or AA 2. Na+ exchanged with H+ 3. Cl- absorbed and exchanged for HCO3- |
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how does absorption occur in the colon?
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Na+ moves in via channels (gradient due to Na/K ATPase)
aldosterone helps |
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what does aldosterone do?
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increases synthesis of apical Na+ channels
increases Na+/K+ ATPase increased Na+ absorption/increased K+ secretion |
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intestinal secretion is driven by the diffusion of?
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Cl-
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these cells do most of the secretion in SI
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crypt cells - of lieberkuhn
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mechanism of intestinal secretion
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*Cl- secretion by apical channels drives Na+ and H20
*apical Cl- channels are cAMP gated *BL Na+/K+/2Cl- cotransporter and Na+/K+ ATPase |
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stimulates apical Cl- channels to open in intestinal crypt cells
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Ach and VIP
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Diarrhea causes loss of what?
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*ECF - decreased arterial pressure
*HCO3- - hyperchloremic metabolic acidosis * K+ - hypokalemia - mm cramps, arrhythmias, myalgia |
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loss of villi, often caused by infection or inflammation, no absorption
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decreased SA diarrhea
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undigested solutes pull water into lumen
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osmotic diarrhea
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excessive secretion by crypt cells; due to enteropathic bacteria and their toxins
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secretory diarrhea
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how does the toxin cause secretory bacteria?
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*causes ADP ribosylation of G a subunit
* increased cAMP *Cl- channels stay open |
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composition of oral rehyration solution for diarrhea
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*glucose
*sodium and potassium (KCl, NaCl) *citrate |
