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Max secretion: 20~25 mmol/hMax secretion: 20~25 mmol/h
Mechanism of HCl secretionMechanism of HCl secretion
Functions: see next pageFunctions: see next page
Relationship between max volume of HCl Relationship between max volume of HCl secretion & the number of parietal cellssecretion & the number of parietal cells
Functions of HCl:Functions of HCl:
TTurn pepsinogen into pepsin & provide a urn pepsinogen into pepsin & provide a
medium of low pH favoring pepsin action; medium of low pH favoring pepsin action;
KKill many swallowed virulent organisms; ill many swallowed virulent organisms;
PPromote the secretion of pacreas & bile;romote the secretion of pacreas & bile;
PPromote the absorption of calcium & ferrumromote the absorption of calcium & ferrum
PepsinogenPepsinogen
Secreted bySecreted by chief cells chief cells & activate by & activate by HClHCl
Function: Function: digest proteins into proteoses, peptones,digest proteins into proteoses, peptones,
polypeptides, with little free amino acidspolypeptides, with little free amino acids
MucusMucus
Secreted by Secreted by neck neck && surface mucous cells, surface mucous cells,
cardiac & pyloric glandscardiac & pyloric glands
Function: form Function: form mucus-bicarbonate barriermucus-bicarbonate barrier
Intrinsic factorIntrinsic factor
Secreted by Secreted by parietal cellsparietal cells
Function:Function: Promote the absorption of Vit BPromote the absorption of Vit B1212
** Regulation of gastric secretionRegulation of gastric secretion
VVagal efferent & with agal efferent & with GGastrin secretionastrin secretion
through through gastrin-releasing peptide (GRgastrin-releasing peptide (GRP)P)
Experiment: Experiment: Sham feeding Sham feeding by Pavlovby Pavlov
Characteristics:Characteristics:
LLarge quantity (30%)arge quantity (30%)
HHigh acidity & digestive powerigh acidity & digestive power
Experiment of Sham feeding by PavlovExperiment of Sham feeding by Pavlov
Gastric phaseGastric phase Mechanisms:Mechanisms: DDistensionistension of gastric fundus & body initiatingof gastric fundus & body initiating vagovagal & local plexus reflexesvagovagal & local plexus reflexes DDistension of pylorus initiating a release of istension of pylorus initiating a release of gastrin through intrinsic plexusgastrin through intrinsic plexus CChemical stimulation of G cells initiaying ahemical stimulation of G cells initiaying a release of gastrinrelease of gastrin Experiment:Experiment: Pavlov pouchPavlov pouch Characteristics:Characteristics: LLarge quantity (60%)arge quantity (60%) HHigh acidity & digestive powerigh acidity & digestive power
Migrating motor complex (MMC)Migrating motor complex (MMC)
§ 4. Digestion in the intestine§ 4. Digestion in the intestine Pancreatic juicePancreatic juice & i& its secretionts secretion ** Nature, Compositions & functionsNature, Compositions & functions pH 7.8~8.4, colorless & odourless, 1~2 L/daypH 7.8~8.4, colorless & odourless, 1~2 L/day Bicarbonate (HCOBicarbonate (HCO33
)) Neutralize HCl & provide a weak basic Neutralize HCl & provide a weak basic medium favoring digestive enzyme actionmedium favoring digestive enzyme action Pancreatic enzymes: Pancreatic enzymes: amylase, lipase, colipase,amylase, lipase, colipase, trypsinogen & chymtrypsinogen, etc.trypsinogen & chymtrypsinogen, etc. Turn trypsinogen into trypsin by entero-Turn trypsinogen into trypsin by entero- kinase, turn chymtrypsinogen into chym-kinase, turn chymtrypsinogen into chym- trypsin by trypsintrypsin by trypsin Trypsin inhibitor: Trypsin inhibitor: a polypeptidea polypeptide
** Regulation of pancreatic secretionRegulation of pancreatic secretion
Promote the absorption of fat-soluble VitsPromote the absorption of fat-soluble Vits
** Control of bile secretion & gallbladder emptyingControl of bile secretion & gallbladder emptying Nervous regulationNervous regulation Vagus nerve: Vagus nerve: ACh, gastrinACh, gastrin Hepatic bile secretionHepatic bile secretion (small amounts) (small amounts) Gallbladder contractionGallbladder contraction (slightly) (slightly) Humoral reulationHumoral reulation Gastrin:Gastrin: direct to hepatic cells & gallbladder;direct to hepatic cells & gallbladder; indirect to stomachindirect to stomachHClHClsecretin secretin Secretin:Secretin: act to bile duct & not to hepatic cells, act to bile duct & not to hepatic cells, so: Hso: H22O & HCOO & HCO33
, bile salt (, bile salt ()) Cholecystokinin (CCK):Cholecystokinin (CCK): gallbladder gallbladder contraction & Oddi’s sphincter dialationcontraction & Oddi’s sphincter dialation Bile salt:Bile salt: enterohepatic circulation of bile salt enterohepatic circulation of bile salt
Enterohepatic Enterohepatic circulation of circulation of bile saltbile salt
SecretionSecretion ofof the small intestinethe small intestine
Feces &Feces & DefecationDefecation ** Feces:Feces: contain inorganic material, undigested contain inorganic material, undigested plant fibers, bacteria, water, etc.plant fibers, bacteria, water, etc. ** Defecation:Defecation: a reflex initiated by distension of a reflex initiated by distension of the rectum with fecesthe rectum with feces RReflex process, eflex process, PPrimary & rimary & hhigher centersigher centers Action of colonic bacteriaAction of colonic bacteria ** Benefit:Benefit: synthesis Vit. Bsynthesis Vit. Bcoco & K & K ** Harm:Harm: produce some poisonous substancesproduce some poisonous substances Action of dietary fibers on the intestinal functionAction of dietary fibers on the intestinal function RReduce absorption of water; educe absorption of water; EEnhance colonicnhance colonic movement; movement; IIncrease the volume of feces; ncrease the volume of feces; LLowow the caloric ratio of the foodthe caloric ratio of the food
§ 6. Absorption in the small intestine§ 6. Absorption in the small intestine
Sites of absorptionSites of absorption
OOral cavity & ral cavity & SStomach: littletomach: little
DDuodenum & uodenum & UUpper jejunum: most nutrientspper jejunum: most nutrients
IIleum: bile salts & Vit. Bleum: bile salts & Vit. B1212
CColon: water & electrolytesolon: water & electrolytes
Proofs as the main absorptive regionProofs as the main absorptive region