Q 6: Pancreas, Liver, & Gallbladder Flashcards
Merocrine Glands
most common exocrine
releases products via exocytosis at apical end
ex. salivary glands, pancreas
holocrine glands
secretory cells disintegrate to form the secretion (bud off)
ex. sebaceous glands
apocrine glands
secretion of membrane-enclosed apical cytoplasm containing proteins and lipids
like merocrine (but packets are released in apocrine)
ex. mammary glands
pancreas exocrine fx
acinar cells
releases digestive molecules into duodenum
pancreas endocrine fx
islets of langerhans
releases protein and polypeptide hormones
What is a zymogen
inactive enzyme precursors
(in acini, inactive in cells and become active once released into the duct. this is due to pH drop once it leaves the cell)
What are the active proteases?
trypsin, chymotrypsin, and elastase
(trypsinogen is cleaved by enteropeptidases to become trypsin, trypsin activates chymotrypsinogen into chymotrypsin and also activates elastase)
what induces acinar and centroacinar exocrine activity
cholecystokinin (CCK) and secretin
What is CCK?
cholecystokinin
neuropeptide of the central and enteric nervous system
I cells
what is secretin
S cells
what percentage of islet cells are alpha cells?
30%
what percentage of islet cells are beta cells?
65%
what percentage of islet cells are gamma cells?
what do they secrete?
what is the result of its secretion?
4%
somatostatin
inhibits GI & pancreatic endocrine and exo. secretion
What are PP cells?
What percentage of islet cells are PP cells?
what do they secrete/what does that do?
islet cells
less than 1%
secrete pancreatic polypeptide–inhibits pancreatic exo. secretion, GI motility, gastric acid secretion
What are the fx’s of the liver?
blood resevoir
bile secretion
detoxification
metabolic homeostasis
- CHO metabolism
- lipid metabolism
- protein metabolism
- storage
- serum protein production
clotting factors produced in liver
largest organ in body
highly regenerative
dual blood supply, receives 30% of CO* (70% PV)
*CO = cardiac output PV = portal vein
hepatocyte fx
metabolize CHO, proteins, and lipids
produce bile and cholesterol
detoxifies endogenous and xenobiotic molecules
kupffer cell fx
liver-specific macrophage
removes pathogens and debris from the blood
sinusoidal endothelial cells
large pores between cells (fenestrae)
no basement membrane
major liver cell types
1) hepatocyte
2) kupffer cell
3) sinusoidal endothelial cells
4) hepatic stellate cells
hepatic stellate cells
store lipids and vitamins
involved in repairing liver damage
aside from cell types, what is the liver composed of
lobules
lobules are hexagonal in structure and are composed of bile canaliculi, kupffer cells, hepatic sinusoids, hepatocytes, and portal triads (bile duct, hepatic PV, hepatic artery)
Liver blood filtering
PV allows first pass metabolism: liver breaks down and degrades many drugs
liver plays a big role in maintaining blood pressure homeostasis (can expand up to 1.3 L of blood)
rapid assessment of dietary products
kupffer cells filter the blood
-clears colon and intestinal bacteria
classis hepatic lobule model
focuses on drainage into central vein
endocrine focus
portal triads found at each of six corners
portal lobule model
bile drains from hepatocytes to the bile ducts
exocrine focus
hepatic acinus model
microvascular liver unit divided into circulatory zones
gradient of hepatocyte oxygenation
hepatic fx’s differ across zones
- zone 1: periportal zone, oxygen, and nutrient rich
- zone 2: intermediate zone
- zone 3: peripheral zone; oxygen poor
what hepatic cells are usually damaged first?
those found within zone 3 because it’s nutrient and oxygen poor
phase I of liver detoxification/hepatocyte xenobiotic elimination
drugs/molecules converted to more polar compounds/oxidized
phase II of liver detoxification/hepatocyte xenobiotic elimination
drugs/molecules/phase I metabolites conjugated to hydrophillic molecules
transferases
hydrophobic get dumped into bile
hydrophillic molecules get dumped into vasculature
bile
bile salts/acids are products of cholesterol metabolism
mixed micelle solution
produced by hepatocytes
transported and stored in the gallbladder
released into the duodenum
alkalinizes intestinal contents
fx’s toxic endogenous waste and xenobiotics
recycled
gallbladder stores and secretes bile
CCK stimulates bile release
- contracts gallbladder sm. muscle
- relaxes hepatopancreatic sphincter
secretin stimulates HCO3- secretion into the bile
