Exam 4- Pancreas, Liver, Gallbladder Flashcards
Is the pancreas more of an exocrine or endocrine organ?
Exocrine (90%)
How is the exocrine pancreas organized?
Organized like salivary ducts, secretions from acinar and duct cells
What are the 2 major functions of pancreatic juice?
Neutralize acids from stomach (via bicarb) and provide enzymes for digestion of food
What 3 enzymes are secreted from the pancreas?
Amylase, lipase, protease
What is the optimal pH for most intestinal enzymes?
7
What type of cells secrete the enzymatic component of pancreatic juice?
Acinar cells
What 2 types of cells secret the aqeous fraction of pancreative juice via ATP?
Ductal cells and centriacinar cells
What cells remove Cl and add HCO3 to pancreatic juice?
Ductal cells
What is the relationship between the composition of pancreatic juice and the pancreatic flow rate?
As flow rate increases, concentration of HCO3- increases at the expense of Cl- (Na+ and K+ similar to plasma)
Does the cephalic or gastric phase have a greater effect on enzyme secretion?
Gastric (only 20% of enzymes secreted during cephalic phase)
What stimulates the pancrease during the cephalic phase?
PNS → ACh → ductal cells
What mediates pancreatic stimulation in the gastric phase?
Gastric distention and gastrin
The cephalic phase contributes what percentage of aqueous secretion during pancreatic stimulation?
10-15% of max
What is the most important phase of pancreatic stimulation as it controls 80% of the pancreatic secretion?
Intestinal phase
During the gastric phase, is pancreatic stimulation under nueronal or hormonal control?
Hormonal (CCK, secretin)
H+ in the duodenum stimulates what in the intestinal phase of pancreatic stimulation?
S cells- Secretin
Fat and peptides in the duodenal chyme stimulate what in the intestinal phase of pancreatic stimulation?
I cells- CCK
CCK travel to the pancrease via cirulatory system to stimulate what?
Acinar cells → increased enzyme secretion (smaller effect on aqueous secretion)
Stimulation of the ductal cells by H+ results in increased production of what?
Aqeuous component of pancreatic juice
What is “nature’s antacid”?
Secretin (only mildly stimulates enzyme secretion)
What enhances (“potentiates”) the secretion of CCK leading to increased enzyme production/ secretion?
Vagus nerve stimulation/ ACh
What enhances (“potentiates”) the secretion of Secretin leading to increased production/ secretion of aqueous secretion?
ACh and CCK
What organ is responsible for regulation of vascular volume, digestion/absorption of fats/ cholesterol, detoxification, synthesis of plasma proteins?
Liver
Once bile is secreted into the small intestine from the gallbladder, it aids in what? (3)
Fat emulsification/ digestion, transport/ elimination of cholesterol, fat absorption
Liver receives blood from what 2 sources?
Hepatic portal system and hepatic artery
What drains blood from the stomach, spleen, intestines and pancreas and carries absorbed food molecules to the liver for processing?
Heaptic portal system: portal vein (70% of liver’s blood) → hepatic vein → IVC
What supplies liver with oxygenated blood?
Hepatic artery (30% liver’s blood supply)
What is the fundamental unit of the liver and what are its 2 components?
Lobules; CV (central vein) and PS (portal space)
What part of the lobule contains the hepatic portal vein, hepatic artery and bile duct?
Portal space (PS)
How does blood travel from the hepatic portal vein (PS) to the central vein in a lobule?
Via sinusoids
What structure in the lobule is separate from the sinusoids (via tight junctions) and allows for passage of bile into the central vein?
Bile canaliculi
Which cells in the lobule are phagocytic?
Kupffer cells
The sinusoidal endothelium in the lobule has what making it permeable to proteins?
Large fenestrations
GI → portal vein → sinusoids → central vein → vena cava is hight or low reistance?
Low resistance
Materials entering the canaliculi must pass through what structure first?
Hepatocyte
What are the 4 amphipathic constituents of bile?
Bile salts (50%), phospholipids (40%), cholesterol, and bile pigments
Bile acids and bile salts are synthsized by what and from what?
By hepatocytes from cholesterol
Synthesis of new bile acids depends on what?
Amount of bile salts returned to liver via enterohepatic circulation
The body pool of bile salts is tightly regulated at what amount?
2-4 grams
Primary (hepatic origin) and secondary bile (bacterial origin) acids are conjugated with glycine and taurine to form what?
Bile salts
What are deoxycholic acids and lithocholic acids?
Secondary bile acids
At lower pH’s how does the activity of bile salts change?
More bile salts are dissociated at lower pH = more amphipathic activity
What increases the ability of bile salts to solubilze cholesterol?
Phosphlidis
Phospholipids makes up what % of bile?
20-40%
Cholesterol makes up what % of bile?
4%
What bile acid constituent does not undergo recirculation, is amphipathic (but not water-soluble) and is soluble in bile salts?
Phospholipids
What is the most important bile pigment?
Bilirubin
What bile acid constituent is from dietary and hepatic origin and is primary excreted (with the except of reabsorption of bile salts)?
Cholesterol
Bilirubin is the precursor for what 2 things?
Urobilin (gives urine yellow color), stercoblin (gives feces brown color)
Bile pigments are carried in blood bound to albumin and derived from what?
Porphyrins from senescent RBCs
The liver removes bilirubin from blood and conjugates to what?
Glucuronic acid (more soluble)
Jaundice is visually detectable buildup of what in the blood?
Bile pigments (bilirubin)
What are the 3 general types of jaundice?
Prehepatic, hepatic, posthepatic
What type of jaundice is due to excessive breakdown of RBCs (too much liver bilirubin for liver to excrete)?
Prehepatic (hemolytic)
Hepatic jaundice is characterized by a diseased liver/ a liver unable to deal with the normal load of bilirubin. What conditions can lead to this? (2)
Cirrhosis, Gilbert’s syndome (deficiency of conjugating enzyme)
A blockage of bile ducts either due to a gallstone or pancreatic CA will result in what?
Posthepatic jaundice (obstructive)
How do bile salts aid in fat digestion? (2)
Emulsifying large fat droplets (detergent action) and forming small lipid aggregations (micelles)
What process of fat digestion by bile salt results in small drops of fat?
Emulsification
What is the benefit of emulsifying fat droplets?
Increases SA (↑ area available for attack by pancreatic lipase)
What act as lipid shuttles and increased lipid solubility in chyme?
Micelles
What does contraction of the sphincter of oddi prevent?
Bile flow into the duodenum
What impact does CCK have one the gallbladder and sphincter of oddi during the digestive period? What does this result in?
Contracts galbladder, relaxes sphincter of oddi. Bile released from gallbladder and enters into duodenum
Bile acid flowing to gallbladder, concentrated, and prevented from flowing into duodenum is part of what period of gallbladder emptying?
Interdigestive period
Continuous bile duct secretion will occur so long as what hormone as present?
CCK
Bile salts go through how many cycles of reuptake and re-secretion per day?
6-10
How are bile salts reabsorbed in the ileum?
Via Na+ co-transporter
What is the relationship between bile salt synthesis and bile salt reabsoprtion?
Inverse (bile salts inhibit cholesterol 7alpha-hydroxylase, which converts cholesterol into primary bile acids)
85% of gallstones are made of what?
Cholesterol
What 3 factors favor gallstone formation?
Bile stasis, suprsaturation of bile w/ cholesterol, nucleating factors
What is the role of bacteria in gallstone formation?
Can initiate or perpetuate stone formation
What imaging can ID gallstones?
US, CT w/ iodine contrast dyes
How does the production of beta-glucuronidase by E.coli favor gallstone formation?
Deconjugates conjugated bile pigments
