Pancreas, Liver, And Gallbladder 💚 Flashcards
Pancreatic juice is rich in _____ and _____
Digestive enzymes
Bicarbonate
Is pancreas more of an exocrine or endocrine organ?
Exocrine 90%
What cells in the pancreas release exocrine secretions?
Acinar cells
Duct cells
Exocrine pancreas is organized like what organ?
Salivary gland
What are the functions of pancreatic juice?
Neutralize acids from the stomach
Provide enzymes for digestion of food
How does pancreatic juice neutralize acids from he stomach?
Bicarb
Most intestinal enzymes have optima pH near ____
7
What enzymes are in pancreatic juice?
Amylases- break down starch
Lipases- digest TGs, PLs and cholesterols
Proteases- break down proteins to AA’s and smaller peptides
What do acinar cells do?
Secrete enzymatic component
What do ductal cells do?
Modify the juice by removing Cl- and adding HCO3- the creation of this HCO3- helps offset the alkaline tide created by the parietal cells in the stomach, because it also yields an H+ that gets put into the blood
Where does the aqueous portion of pancreatic juice come from?
Centroacinar cells
Ductal cells
As the pancreatic juice gets secreted faster and faster, how does the composition of it change?
The juice gets MORE HCO3- and LESS Cl-
Na+ and K+ are unchanged
What are the 3 phases of pancreatic stimulation?
Cephalic
Gastric
Intestinal **most important
How much can the cephalic and gastric phase increase pancreatic secretion?
Only 10-15%
What is the MOST important phase of pancreatic stimulation
Intestinal phase- controls 80%
Does the intestinal phase affect the pancreas via Hormonal or Nervous mechanisms?
Hormonal!**
CCK and Secretin
What causes the duodenum to release CCK?
fatty acids and amino acids in duodenal chyme
Where does CCK come from?
I cells (of the duodenum)
Where does Secretin come from?
S cells (of duodenum)
What causes the release of Secretin?
H+ in the duodenum
What is “nature’s antacid?’
Secretin
(In response to H+, it causes ductal cells in pancreas to increase the aqueous component of pancreatic juice, which contains bicarb)
How does CCK get to the pancreas?
Via circulatory system
What does CCK do?n
Stimulates the acinar cells to increase enzyme secretion
Little effect on aqueous secretion
How much does secretin stimulate enzyme secretion?
Not much
What are the functions of the liver?
Regulate blood glucose (stores glycogen) 🍭
Regulates vascular volume (albumin, reservoir for blood)
Detoxification and conjugation
Cholesterol metabolism (making bile)
Synthesis of plasma proteins
Digestion and absorption of fats*
What does bile help you do?
Fat emulsification and digestion
Transport and elimination of cholesterol
Fat absorption
(Breaks up big fat droplets into smaller ones)
What are the 2 blood sources for the liver?
Hepatic portal system- nutrient rich but oxygen poor
Hepatic artery- oxygenated blood
The _____ is the fundamental unit of the liver
Lobule
What is in the very middle of a lobule?
Central vein
What is in the portal space?
Hepatic portal vein
Hepatic artery
Bile duct
What cells secrete bile into the bile canaliculi?
Hepatocytes
What is in the sinusoids within lobules?
Blood from the portal vein
Are all of the cells in the sinusoidal endothelium continuous with each other?
No, they have large fenstrations that allow proteins through
Is the pathway of blood within the liver lobules high or low resistance
Low resistance
GI > portal vein > sinusoids > central vein > vena cava
What happens to the blood as it moves from the portal vein toward the central vein?
Hepatocytes reabsorb bile and transfer it to bile canaliculi
Do the bile canaliculi come into contact with the sinusoids?
NO!! NO !!! NO! NO! ON!OONONONO he said this 3746 times!!
NOOOOO direct passage from blood bile!!
MUST be moved through the hepatocyte
What are Kupffer cells?
Phagocytic cells inside the liver lobules
Not sure this is important
Bile canaliculi are separated from sinusoids by _______
Tight junctions
Materials entering bile canaliculi must ____________
Pass through the hepatocyte
******
What are the components of bile?
Bile salts (50%)
Phospholipids (40%)
Cholesterol (4%)
Bile pigments (2%)
What cells make bile acids and bile salts?
Hepatocytes
What determines how much new bile acid is synthesized?
The amount of bile salts returned to liver via enterohepatic circulation
How much bile salt is in the body ? Does it ever change?
2-4g. TIGHTLY regulated
What are the 3 forms of bile?
Primary (hepatic origin)
Secondary (bacterial origin)
Conjugated (can be primary or secondary)
How does primary bile salt get turned into secondary bile salt?
Bacteria change it
What is the purpose of conjugating bile salts?
Makes it more soluble in the duodenum
What groups are added onto bile salts to conjugate them?
Glycine or Taurine
Why does conjugating bile salts make them more soluble in the duodenum?
It lowers the pK from 7 to <4. Allows them to remain hydrophobic bile salts at duodenal pH (3-5)
Do phosophilpids in bile get recirculated?
No
Are phospholipids water soluble?
No, but they are amphipathic
What purpose do phospholipids serve in bile salts?
Increase ability of bile salts to solubilize cholesterol
What is the most important bile pigment?
Bilirubin
Where does bilirubin come from?
Porphyrins from senescent RBCs
What form is bilirubin in when it’s in the bile: conjugated or uinconjugated?
Conjugated ONLY
What group gets added onto bilirubin to conjugate it?
Glucuronic acid
Tags it for removal by the kidney= reason peepee is yellow
What gives bile its yellow color?
Bilirubin glucuronide
Aka conjugated bilirubin
What is this:
visually detectable buildup of bile pigments (bilirubin) in the blood
Jaundice
What are the 3 types of jaundice?
Prehepatic (hemolytic)
Hepatic (liver disease)
Posthepatic (obstructive)
What causes prehepatic jaundice?
Excessive breakdown or RBCs which creates too much bilirubin for the liver to excrete
Ex: pernicious anemia, infants
What causes hepatic jaundice?
Liver is diseased and unable to deal with the normal load of bilirubin
Ex: cirrhosis, Gilbert’s syndrome (deficiency of conjugating enzyme)
What causes posthepatic jaundice?
Obstruction of the bile duct
Ex: gallstone, pancreatic cancer
What are the 2 ways bile salts aid fat digestion?
- Emulsifying large fat droplets (detergent action)
2. Forming small lipid aggregations called micelles
Why do we need to emulsify fats?
Increases surface area of fat droplets that is available for attack by pancreatic lipase
After emulsification, what keeps all the small fat droplets from just reconvening?
They repel each other due to negative charges of bile salts?
What are micelles?
Aggregations of amphipathic bile components that form spontaneously in aqueous environments
Hydrophilic portions face outward and hydrophobic portions face the interior (cholesterol, phospholipids, FFA’s, etc)
What are the functions of micelles?
Act as lipid “shuttles” to deliver to enterocyte
Increase lipid solubility in chyme
What is happening in the gallbladder in the inter digestive period (aka not processing a meal)
Bile flows to gallbladder and concentrated
Sphincter of Oddi Contracts** to prevent bile flow into duodenum
What is happening to the gallbladder during the digestive period?
Gallbladder contracts (CCK)
Sphincter of Oddi relaxes (CCK)
=Continuous bile duct secretion for as long as CCK is present in the bloodstream
What is the primary regulator of release of bile from the gallbladder?
CCK**
