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Fig. 26-1: Anatomy of the Gastrointestinal Tract

Mouth

Upper esophageal sphincter

Esophagus

Lower esophagealsphincter

Pharynx

Cardiac orifice

Pyloric sphincter (?)

Stomach(fundus, body, antrum, pylorus)

Iliocecal valve

Small intestine(duodenum, jejunum, ileum)

Large intestine(cecum, colon, rectum, anal canal)

Anal sphincter

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Fig. 26-3: Hormones of the Gastrointestinal Tract

Mouth

Upper esophageal sphincter

Esophagus

Lower esophagealsphincter

Pharynx

Cardiac orifice

Pyloric sphincter (?)

Stomach

Iliocecal valve

Small intestine

Large intestine(cecum, colon, rectum, anal canal)

Anal sphincter

Gastrin Somatostatin

Histamine

SecretinCholecystokininGastric inhibitory

peptide MotilinVasoactive

intestinal peptideGastrin-releasing

peptide Enkephalins

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Fig. 26-4: Carbohydrate Digestion and Absorption

Ingested

Passes through stomach

Chyme enters duodenum

Secretin andcholecystokininsecreted by duodenum

Salivary amylase

Pancreas releasespancreatic amylase intoduodenum

Brush border enzymes split

disaccharides intomonosaccharides

Monosaccharides absorbedinto blood

Amylase breakscarbohydrates intodisaccharides

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Fig. 26-5: Protein Digestion and Absorption

Bolus enters stomach

Stomach secretes the following:HCl, pepsinogen

Acid convertspepsinogen to pepsin

Gastrin secreted

Some proteins brokeninto polypeptides

Gastrin-inhibiting

peptide stops gastrinand other stomach secretions

Secretin andcholecystokinin secreted

Chyme enters duodenum

Pancreas secretes the following:Elastase, Trypsinogen BicarbonateChymotrypsin, Carboxypeptidase

Bicarbonateinactivatespepsin

Proteins broken intopolypeptides (two places)

Brush border enzymes turntrypsinogen into trypsin

Brush border enzymesbreak polypeptides into peptides

Peptides absorbed into blood

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Fig. 26-6: Fat Digestion and Absorption

Chyme enters duodenum

Pancreas secreteslipase

Gallbladderreleases bile

Secretin and cholecystokininsecreted

Bile emulsifiesfats

Glycerol and fatty acidsabsorbed into intestinal cells

Glycerol and fatty acidsre-formed into triglyceridesinside intestinal cells

Triglycerides broken into

glycerol and fatty acids

Re-formed triglyceridescoated with protein, released

into blood as chylomicrons

Chylomicrons taken upby liver cells

Liver cells repackagetriglycerides into lipoproteins

Lipoproteins released

into blood