Glossary of FA: GI Physiology

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how is salivary secretion stimulated?
by sympathetics (T1-T3 superior cervical ganglion) and parasympathetics (facial and glossopharyngeal)
what are the 3 functions of salivary secretions from the parotid, submandibular, and sublingual glands?
1. alpha amylase for starch digestion
2. bicarb to neutralize oral bacterial acids and dental health
3. mucins (glycoproteins) to lubricate food
source and action of gastrin?
G cells of stomach antrum

increase HCl production and proliferation of gastic mucosa
how is gastrin secretion regulated? what 2 aa's are very potent stimulators of gastrin?
1. increase: stomach distention, amino acids, peptides, vagal stimulation
2. decrease: acid secretion, pH < 1.5

phenylalanine and tryptophan are potent stimulators
source and action of CCK (cholecystokinin)?
source: I cells of duodenum and jejunum

axn: increase pancreatic secretions, stimulate gallbladder contraction, inhibit gastric emptying
why does pain worsen in cholelithiasis after fatty food ingestion?
CCK secretion promotes gall bladder contraction
regulation of CCK?
decrease: secretin and stomach pH < 1.5

increase: fatty acids and amino acids
source and axn of secretin?
source: S cells of duodenum

axn: increase pancreatic HCO3- secretion and inhibits gastrin secretion
stimulation of secretin secretion? purpose of secretin?
stimulated by acid, fatty acids in lumen of duodenum

bicarb neutralizes acid in duodenum to let pancreatic enzymes to work
source and axn of somatostatin?
source: D cells in pancreatic islet cells, GI mucosa

axn: inhibition of...
1. gastric acid and pepsinogen secretion
2. pancreatic and small bowel fluid secretion
3. gallbladder contraction
4. release of both insulin and glucagon
regulation of somatostatin?
increased by acid and decreased by vagus
general purpose of somatostatin in GI?
inhibitory hormone: anti-growth hormone effects (digestion and absorption of substances needed for growth)
source and axn of gastric inhibitory peptide (GIP)?
source: K cells of duodenum and jejunum

axn: exocrine (lower gastric HCl secretion); endocrine (increase insulin release)
source and axn of intrinsic factor?
source: parietal cells of stomach

axn: vitamin B12 binding
what happens in the autoimmune destruction of parietal cells?
less intrinsic factor -> chronic gastritis and pernicious anemia
source and axn of gastric acid?
source: parietal cells of stomach

axn: lower stomach pH
regulation of gastric acid secretion?
increase: histamine, ACh, gastrin

decrease: somatostatin, GIP, prostaglandin
source and axn of pepsin?
source: chief cells of stomach

axn: protein digestion, optimal axn at pH 1-3
regulation of pepsin?
increased by vagal input and acid

acid converts pepsinogen -> pepsin
bicarb source and function?
source: mucosal cells, stomach and duodenum

axn: neutralize acid and prevent autodigestion
what stimulates bicarb secretion?
what parts of the GI system are retroperitoneal? what is partially peritonealized?
duodenum, body and head of pancreas, esophagus

partial: ascending and descending colons, tail of pancreas
source and axn of VIP (vasoactive intestinal peptide)?
source: smooth muscle and nerves of intestines

axn: relaxes intestinal smooth muscle, causes pancreatic bicarb secretion and block gastric acid secretion
what parts of GI are completely peritonealized?
liver, stomach, transverse and terminal colons, and cecum
what enzyme converts pancreatic trypsinogen to active form? what does trypsin do?
enterokinase, a duodenal brushborder enzyme

activates other proenzymes and activates trypsinogen (positive feedback loop)
what are 4 pancreatic proteases?
what types of carbohydrates are absorbed?
monosaccharides only: glucose, galactose and fructose
what does bacterial colon do to direct bilirubin?
converts to urobilinogen and then stercobilin is excreted in feces
what side of the hepatocytes face the bile canaliculi?

Apical surface faces

basolateral faces liver sinusoids

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