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
What are the effects of gastrin? (3)
stimulates acid secretion by parietal cells, increases motility and secretions.
G cells are located in which 2 places?
antrum of the stomach and duodenum
Glucose absorption occurs across the membrane through which mechanism?
sodium-glucose cotransporter
Name three types of endocrine secreting cells of the pancreas, and the main endocrines secreted.
islets of langerhan-alpha cells produce glucagon, beta cells–insulin and PP cells produce pancreatic polypeptide
What are the main effects of CCK? (4)
Inhibits gastric emptying, stimulates pancreatic enzyme secretion, stimulates contraction of the gallbladder and relaxation of sphincter of Oddi.
What compound begins starch digestion?
alpha-amylase
Renal excretion of this form of bilirubin
urobilirubin (4mg/day)
Which enzyme cleaves trypsinogen?
enterokinase
Enzyme for starch digestion that is secreted in the active form from the pancreas is?
alpha-amylase
Bilirubin is conjugated in which organ?
liver
What are the three main components of gastric juices secreted by the stomach?
mucus, pepsin and hydrochloric acid
Where in the GI system are the cells that secrete CCK?
cells lining the duodenum
GI secretory products: Name 2 compounds that inhibit gastric acid secretion
somatostatin, GIP, prostaglandin
What are the substrate and products of cholesterol esterase?
hydrolizes cholesterol esters to yield cholesterol and free fatty acids
List three important electrical characteristics of GI smooth muscle.
stretch stimulates contraction, electrical synctium with gap junctions, pacemaker activity
Name the two primary bile acids. where are they produced?
cholic acid and chenodeoxycolic acid. Synthesized in the liver form cholesterol.
Which enzyme, present in saliva, begins the digestion of carbohydrates?
alpha-amylase
Chief cells secrete?
pepsinogen
Bacterial conversion of which form of bilirubin occurs in the colon?
urobilinogen
Secretory acini of the pancreas secrete zymogens when stimulated by ___ and ____?
acetylcholine and CCK
GI secretory products: Autoimmune destruction of ___ leads to chronic gastritis and/or pernicious anemia
parietal cells
Where in the GI tract is GIP made?
duodenum
Name two important factors that stimulate gastric motility.
distension of the stomach and ACh
Name the three glands involved in salivary secretion?
parotid, submandibular and sublingual
Name four important factors that inhibit gastric motility.
acid in the duodenum (via secretin), fat in the duodenum (via CCK), hyperosmolarity in duodenum, distension of duodenum
What is the term that refers to food and any mixture of enzymes in the stomach?
chyme
G cells secrete_____.
gastrin
Which cells produce secretin? Where are these cells located?
S cells of the duodenum
Recommendations and monitoring for pancreatic insufficiency should include?
limit fat intake and monitor for signs of fat-soluble vitamin deficiency
Which compounds in saliva lubricate food?
mucins (glycoproteins)
Free bilirubin is complexed with ____ in circulation?
albumin
Which cells secrete intrinsic factor?
parietal cells
What is added to bile acids to create bile salts? (2)
bile acids (cholic and dexycholic) are conjugated with glycine and taurine which mix with cations to form salts.
Describe the two types of contractions that occur in the intestines.
segmentation contractions (mixing), peristaltic movements (propulsive).
Name the main components of bile. (4)
conjugated bile acids (cholic and chenodeoxycholic), billirubin, lecithin and cholesterol.
Name three substances that stimulate parietal cells to secrete acid.
acetylcholine, histamine and gastrin
Name the cofactor required by pancreatic lipase to displace bile from the surface of micelles.
colipase
What cells secrete exocrine products in the pancreas?
acinar cells
Where are parietal cells located? What do they secrete? (2)
located in the middle part of the gastric glands. Secrete HCl and intrinsic factor.
What is the main stimulus for secretin release?
acid entering the duodenum
Which form of bilirubin occurs in enterohepatic circulation from colon to liver?
urobilinogen
Where are chief cells located? What do they secrete? (1)
located in the deep part of the gastric glands. Secrete pepsinogen which is converted to pepsin by acid medium. Pepsin begins digestion of proteins to peptides.
Which form of bilirubin excreted in feces?
stercobilin
GI secretory products: T/F: gastrin stimulates gastric motility
true
Conjugated bilirubin is also called?
direct bilirubin
What are the main stimuli for GIP release? (3)
fat, carbs and amino acids
How are lipids absorbed?
micelles diffuse to the brush border and digested lipids (2-monoglycerides, fatty acids, cholesterol and ADEK vitamins) diffuse into enterocytes. Triglycerides are resynthesized and packaged as chlomicrons with apo B48. Leave the intestine via lymphatics to thoracic duct.
Intrinsic factor is needed to absorb which vitamin?
B12
Which condition results form elevated bilirubin levels?
jaundice
Bile acids are reabsorbed only in the _____.
distal ileum
What type of bond does pancreatic amylase break? What are the products?
hydrolyzes a-1,4-glucoside bonds forming a-limit dextrins, maltotriose and a maltose
What makes up the portal triad?
bile ductule, branch of portal vein, branch of hepatic artery
Which cells produce gastrin? Where are they located?
G cells of the stomach anthrum, duodenum
