Gastrointestinal physiology Flashcards
Where does the lacteal system transport fat to?
thoracic duct
What stimulates gastrin release? (1) What inhibits it? (1)
stomach distension. Stomach acid in the duodenum inhibits gastrin release
What are the macrophage-like cells in the liver called?
kupffer cells
Optimal pH for protein degredation by pepsin is ___?
pH 1.0-3.0
How are amino acids absorbed? (2)
secondary active transport linked to Na and receptor-mediated endocytosis.
What are the substrate and products of pancreatic lipase?
lipase digest tiglycerides to two free fatty acids and one 2-monoglyceride.
Normal life span of red blood cells?
120 days
T/F: Parasympathetic activity stimulates salivary secretion while sympathetic activity does not.
false-both parasympathetic and sympathetic activity stimulate salivary secretion
Pancreatic ducts secrete ___ and ___ when stimulated by ___?
mucus and alkaline fluid when stimulated by secretin
What is the function of the lacteals in the gastrointestinal system?
lymphatic drainage that carries fat away from the GI.
Conjugated or unconjugated version of bilirubin is water soluble?
conjugated version
GI secretory products: What is hypersecreted in Zollinger-Ellison syndrome?
gastrin
T/F- Blood and bile flow in the same direction?
false-blood flows toward the central vein while bile flows in the opposite direction
GI secretory products: What stimulates the release of secretin?
fatty acids and acid in the duodenum
Why is only a small amount of enterokinase required to convert trypsinogen into trypsin?
trypsin is atuocatalytic, meaning that a molecule of trypsin can convert more trypsinogen into trypsin.
What are secondary bile acids? (2) How are they produced, and where?
formed by donjugation of bile salts by enteric bacteria-deoxycholic acid (from cholic acid) and lithocolic acid (from chenodeoxycholic acid). Lithocholic acid is helpatotoxic and is excreted.
What are three functions of H+ in stomach secretions?
kills bacteria, breaks down food and activates pepsinogen
What are the main stimuli for the release of CCK? (2)
fat and amino acids entering duodenum
How do parietal cells move H+ into the lumen of the stomach?
H+ ions are exchanged by the proton pump for K+ ions (active antitransport)
Where are the muccous cells of the stomach? What do they secrete? (2) Which paracrine hormone stimulates them?
located in the superficial part if the gastric glands (gastric pits). secrete mucus and HCO3. Secretion is stimulated by PGE2
How are carbohydrates absorbed, generally? Which monosacharide is independently absorbed?
glucose and galactose via active secondary Na cotransporter. fructose is absorbed independently.
Stomach secretions: Mucus functions to:
- protect the stomach surface form H+
2. lubricant
What does bicarbonate in the salivary solution do?
neutralizes bacterial acids and maintains dental health
Does the apical or basolateral surface o hepatocytes face the bile canliculi?
apical
Proenzyme of trypsin is?
trypsinogen
What are the main effects of GIP? (2)
inhibits stomach motility and secretion
Name four pancreatic enzymes for protein digestion?
trypsin, chymotrypsin, elastase, and carboxypeptidases (secreted as proenzymes)
What product of heme metabolism is taken up by hepatocytes?
bilirubin
Sinusoids drain to the ___ vein?
central vein
What is the main effect of secretin?
stimulates HCO3 secretion by pancreas to neutralize acid entering duodenum
Describe the substrates and enzyme that produce H+ in the parietal cells
CO2 is extracted from the blood and combined wit water into H2CO3 by carbonic anhydrase.
GI secretory products: Name 3 compounds that stimulate gastric acid secretion
histamine, Ach, gastrin
Name three pancreatic enzymes for fat digestion?
lipase, hospholipase A, colipase
Name the two large nerve plexuses in digestive tract. What is their function?
submucosal (Meissners)-controls secretions
Myenteric (auerbachs)-controls motility