Feb19 M1-Histo Liver and Pancreas Flashcards
how liver separated in lobules
CT penetrates and splits it
liver fcts
- endocrine (albumin, transferrin, etc,)
- exocrine (bile, etc.)
- conjugation and elimination
- conversion (T4 to T3)
- hemopoiesis (fetal)
- storage (glycogen, lipids)
liver lobule where bile going
in the triad (on outside of lobule), bile going in opposite direction. duct called cholangiole and then bile duct
lobule histology
- cords of hepatocytes. small canaliculi between adjacent hepatocytes lead to cholangiole
- portal venule and hepatic arteriole lead to capillaries (sinusoids) in the lobule that will join
bile duct cells characteristics (in portal space of the lobule)
cuboidal cells. prominent lumen
charact of sinusoids in lobules
- covered by layer of endothelial cells
- some macrophages there: Kuppfer cells (endocytose RBC,s form particles, etc.)
name of space between hepatocytes and the endothelial cells of the sinusoids
space of Disse
where bile canaliculi are and why don’t reach space of Disse
- between hepatocytes and between hepatocytes plates.
- tight junctions and desmosomes between hepatocytes so can’T go to space of Disse.
hepatocytes EM charact
- MICROVILLI
- peroxisomes (membrane with crystals inside)
- endocytosis with lysosomes, golgi, RER, SER
characteristics of sinusoids (why called like that)
don’t rest on BM. rest on reticular fibers
4 components of endocytic system of the liver
- endocytic vesicle
- endosome
- maturating lysosome
- lysosome
how endocytosis works in the liver
receptor mediated (liver has receptors for almost all hormones in the body to remove them from circulation)
where enzymes (or hormones) digested after endocytosis and what happens to the receptor
- in maturating lysosome
- R sent back to surface (recycled)
important receptors on the liver
R for LDL, HDL, chylomicrons (produced by enterocytes)
what happens when hepatocyte internalizes a chylomicron
- lipids stored in SER
- R sent back to surface to internalize more chylomicrons
organelles of secretory system of hepatocytes
RER: synthesis of proteins like apoB
SER: TGs (and also phospholipids, cholesterol, long chain FAs) sent to golgi apparatus.
bile synthesis and conjugation + bilirubin conjugation
Golgi: apoB conjugated to lipids forming a lipoprotein called VLDL + packs TGs in vesicles
exocytic vesicles
VLDL goes where and what does it contain
goes in sinusoid, contains cholesterol
what happens to VLDL in the blood
- lipoprotein lipase on caps converts it to IDL
- hepatic lipase converts IDL into LDL
what happens to LDL in the blood
- some goes to peripheral tissues (LDL contains cholesterol), they need cholesterol for growth, is an important part of plasma membranes
- rest of LDL goes to liver (LDL-R)
charact of LDL-R on hepatocytes
- almost everyone has mutations, some are more severe
- inefficient LDL-R = cholesterol stays in circulation for longer time. oxidized. macrophages eat it, goes in intima, atherosclerosis, endothelium disruption, clot formation
peroxisome function in hepatocytes
- H2O2 made into H2O and O2
- beta-oxidation of long chain FAs
- catabolism of ETOH
- cholesterol synthesis
- purines break down (AMP, GMP)
SER functions
- send lipids to Golgi
- bile acids synthesis: 1. bile cholesterol + taurine = taurocholic acid
2. bile cholesterol + glycine = glycocholic acid - bilirubin conjugation into glucuronic acid
where SER sends its contents (ultimately)
- lipids to Golgi
- bile salts and conjugated bilirubin to cholangioles (bile canaliculus)
why viral hepatitis causes jaundice
disrupts tight junctions. bilirubin (direct) goes from bile canaliculi to sinusoids
big and small dots seen on liver EM
big dots = fat
small dots = glycogen (stored)
venous drainage of the liver
sinusoids go to central vein to sublobular vein to hepatic vein to IVC
bile system drainage of liver
bile canaliculus (between hepatocyte plates) to cholangiole to bile duct to hepatic duct to CBD
liver turnover
turnover of hepatocytes every 150 days. 1 mitosis every 20 000 cells. at surgical excision, liver will reginirate until normal size
consequence of repeated damage to hepatocytes (like drinking all the time)
proliferation of CT: called cirrhosis
Kupffer cell location
flat bulky cell attached to surface of hepatocytes and endothelial cells
main components of pancreas
endocrine glands: islet of Langerhans
exocrine: compound acinar gland similar to parotid gland
exocrine pancreas produces what
alkaline fluid and proteins (15 or more zymoens) to digest any macromolecule
why pancreas looks like salivary glands
both derived from evaginations of the endodermal lining of the embryonic intestine
2 important pathologies of the pancreas
cancer, pancreatitis
how pancreas forms glands (if cut a portion)
- blind ended tubes lined by undiff simple columnar epithelium undergo sequential branching
- epith organizes in acini and lobules
- islets of Langerhans get formed by some cells of SEROUS acini
what cells of pancreas may be involved in pancreatic cancer
the undifferentiated cells of serous acini that form the islets of Langerhans
divisions of ducts in pancreas (smaller to bigger) (are divided by CT)
- acinus
- intercalated duct
- intralobular duct
- interlobular duct
- interlobar duct
- main pancreatic duct
hilum of the pancreas
major papilla the ducts merge
charact of interlobular duct
- lined by columnar cells
- lot of CT around them
- arterioles and venules in the CT
charact of intercalated ducts
- lined by cuboidal cells
- are connected to exocrine cells
- centroacinar cells are part of the duct system
islets of langerhans charact
- large number of capillaries and secretory cells
- surrounded by thin layer of CT and reticular fibers
charact of serous acinus
- intercalated duct coming in, centroacinal cells (no zymogen granules
- acinar cells nuclei at base, have zymogenic granules
serous acinar cells on EM
- rough ER, many cisternae and RER, many mts, Golgi forms granules with enzymes from RER.
- granules open at level of lumen
pancreatitis pathophgy
tight junctions between acinar cells are disrupted and enzymes reach the CT
what regulates the exocrine pancreas
- secretin stims H2O and bicarb secretions (high water low enzyme)
- CCK (enteroendocrine cells of duodenum) promotes exocytosis of zymogenic granules
proenzymes released by zymogenic granules of pancreas and what activates them
- trypsinogen
- pro-carboxypeptidase
- pro-elastase
- pro-phospholipase-A
- activated by enterokinase in glycocalyx of SI microvilli
active enzymes released by acinar cells of pancreas
- lipase
- amylase
- RNAse
- DNAse
protective mechanisms in pancreas acini
- tight junctions to protect from lipase
- trypsin inhibitor made by centroacinar cells
alpha vs beta cells charact in islets
alpha: acidophilic (make glucagon)
beta: pale and don’t stain well (make insulin)
how to diff pancreas and parotid gland
presence of islets of langerhans = pancreas
glucagon (alpha cells) charact
15% of islet. big cells. on periphery of islet. glucagon promotes glycogen breakdoen and GNG to maintain basal glycemia
how to stain for alph cells
Ab to glucagon
glucagon charact
- single polypeptide chain
- very conserved across species
- some endocrine cells may produce a glucagon-like peptide
beta cells charact
70% of islets. in all islet. are small. insulin for glucose uptake and reduce glycemia
how to see beta cells on histo
stain with Ab to insulin
steps of insulin synthesis
- single polypeptide chain (N term - B chain - C chain - A chain - C term) with S bonds between B and A chain
- cathepsin E removes the C chain to leave 2 chains B and A linked by S bonds
how islet cells do endocrine secretion
- RER, golgi, secretory vesicles
- insulin and glucagon go to fenestrated capillaries
other cell types in islets of Langerhans
- delta cells
- PP cells
delta cells charact
- 5% of islet
- large
- everywhere in islet
- make sts (inhibits glucagon AND insulin secretion + inhibits HCl secretion by parietal cells)
PP cells charact
- 1% of islet
- large
- everywhere in islet
- make pancreatic polypeptide (a hormone that stimulates the secretion of pepsinogen by chief cells
acute pancreatitis pathophgy
chronic ingestion of alcohol causes it (obstruction of duct system, activation of trypsin, release of enzymes in IC space)
type 1 DM pathophgy
before age 15, autoimmune destruction of beta cells of islets
pancreatic cancer pathophgy
cancer of stem cells of the exocrine pancreas
