Histo Flashcards
T/F The pancreas is both an exocrine & endocrine organ.
True.
What do pancreatic acinar cells do?
It produces, stores, & releases digestive enzymes. It also produces trypsin inhibitor that protects the pancreas. It is super full of zymogen granules.
What influences the release of enzymes from pancreatic acinar cells?
It is influenced by hormones & parasympathetic innervation…
What is the purpose of releasing bicarb? What produces the bicarb?
It buffers the acidity of the chyme as it enters the small intestine. This helps create the optimal pH for the pancreatic enzymes.
Centroacinar cells in the middle of the acinus produce this.
What are centroacinar cells?
modified intercalated duct cells…
How are acinar cells connected to each other?
thru intercalated ducts
T/F Striated ducts & myoepithelial cells are present in the exocrine pancreas.
False. They are NOT.
Which part of the pancreas is endocrine?
islets of Langerhans
Which cells are found in the islets? What does each secrete?
alpha cells–glucagon
beta cells–insulin
delta cells–somatostatin
What do PP cells secrete in the islets? D cells? EC cells?
PP cells: pancreatic polypeptide
D cells: vasoactive intestinal polypeptide
EC cells: secretin, motilin
Explain the process by which we get zymogen granules.
Inactive proenzymes synthesized in the RER of pancreatic acinar cells.
These are transferred to the Golgi apparatus.
They are concentrated in vesicles to form zymogen granules.
What are the 2 things that control the secretion of zymogens?
Enteroendocrine cells in the duodenum secrete peptides that control it. Endocrine pancreas (islets) synthesize peptide hormones.
What connects acinar cells in the pancreas?
tight jcns–>don’t want that crazy stuff leaking out.
What’s the dual blood supply of the pancreas?
Acinar Vascular System–>acini
insuloacinar portal system–>islets
What is the function of a portal system?
It slows things down & allows you to pick stuff up & dump stuff…
Like the insuloacinar portal system in the islets…
Describe the deal with the insuloacinar portal system.
Afferent arterioles surround the islet and form capillaries of fenestrated endothelium…the capillaries then supply blood to the surrounding pancreatic acini so that they can get a local reaction to the endocrine hormones secreted by the islets…
T/F The liver, like the pancreas, is both an endocrine & exocrine organ.
True.
What is the main fcn of the liver?
to detoxify toxins & drugs…
What is the liver made up of?
Very little CT & a lot of plates of hepatocytes
Describe the dual blood supply of the liver.
25% of the blood flowin’ in is from hepatic arteries
75% of the blood flowin’ in is from the portal vein
What drains the blood from the liver?
hepatic veins
T/F Bile flows in the same direction as blood flows.
FALSE.
Countercurrent flow
Describe the arrangement of the hepatocytes.
They arrange in classic lobules that are shaped as hexagons.
3 of them together have a portal area.
Each of the lobules has a central vein that drains blood from the sinusoids of that region.
What is found in the portal area? Where is the portal area?
Portal area found b/w 3 classic lobules 4 things are found there (misnomer of triad) Hepatic Artery Portal Vein Interlobular Bile Duct Lymphatic Vessels
Where does the central vein from each classic lobule flow to?
Sublobular vein
Hepatic vein
IVC (thru bare area)
What is the purpose of the bare area of the liver?
It allows the vessels from the liver to pass behind the peritoneum and get to the IVC. Thus, it is important to have a spot on the liver where there isn’t any peritoneum.
What are the 3 basic concepts of lobules?
Classic Liver Lobule
Portal Lobule
Liver Acinus
What is another name for the Liver acinus?
Acinus of Rappaport
The idea of the classic liver lobule is based on the ___ liver. Describe this lobule concept.
Pig liver.
This is the normal looking lobule with the hexagon shape.
Blood flows from the periphery of the lobule @ portal triad to the central vein (center of lobule)
Bile goes into bile canaliculi & flows from the center to the outside.
The portal lobule emphasize the ____ function of the liver. Describe this lobule concept.
Exocrine function…bile flow in the middle
The portal triad is at the center.
The whole lobule looks like a triangle w/ central veins as its 3 points.
The liver acinus concept is based off of ___ _____ & consists of 3 _____.
blood flow
3 zones
Zone 1 is closest to the portal triad & is the most oxygenated; it also gets nutrients & toxins first
Zone 2 is in the middle
Zone 3 is closest to the central vein & is the most poorly oxygenated
What is a special function of Zone 1?
The hepatocytes here actively synthesize glycogen & plasma proteins.
What is a special function of Zone 3?
It has a role in detoxification.
Which lobule concept best combines: blood perfusion, metabolic activity & liver pathology…
liver acinus
What is the Zone 1 the first to receive? Last to receive?
First to receive morphological changes from bile duct occlusion…
First to be able to regenerate
Last to receive ischemia/death.
What is Zone 3 the first to show?
necrosis fat accumulation (cirrhosis)
Are there metabolic differences b/w Zones 1, 2, 3? Morphological differences?
Metabolic–yes
Morphological–no, unless there is pathology
If you bought real estate…where should you buy?
ZONE 1
Location, Location, Location
Even though Zone 1 hogs everything…what does Zone 3 have more of (2 things)?
- Key Glycolysis Enzymes
2. Key Fatty-Acid Synthesizing Enzymes
What is a major site of detoxification in the liver…where is a secondary site? Where are these things found in highest conc’n?
Main site: SER
secondary site: peroxisomes
ZONE 3! Poor guys! They just always push the toxins out to us…
B/c hepatocytes are SO hard working what do they have an abundance of?
Rough ER Ribosomes Golgi Mitochondria SER
A bunch of Golgi are often arranged around what?
Bile canaliculi
What are some of the main things that the RER produces? If they didn’t what would happen?
Albumin–>edema & ascites
Coagulation Proteins–>bleeding
**these things are associated w/ liver failure
What are the 2 domains of hepatocytes?
Apical (Lateral)
Basolateral (Sinusoidal)
Describe the apical domain.
It is covered in microvilli.
It is separated by intercellular spaces that form the bile canaliculi–>this is where bile is found!
Where does the bile from the bile canaliculi drain to?
intralobular ductule: colangiole
This converges to form the canal of Hering
This carries it to the portal triad
Describe the basolateral domain.
The microvilli here open up into the space of Disse…they facilitate exchange with the capillary…they increase the surface area by a factor of 6.
What are the hepatic sinusoids lined with?
discontinuous endothelial cells
Kupffer cells: differentiated phagocytic cell from monocytes
Each hepatocyte has how many domains?
2 basolateral domains
2 apical domains
What are the 6 major functions of hepatocytes?
- produces plasma proteins
- Stores & converts vitamins & iron
- involved in metabolic pathways
- detoxifies
- exocrine–bile production
- endocrine–modifies hormones
What are 3 plasma proteins that the liver produces?
albumin
lipoproteins (VLDLs)
glycoproteins
Which 2 things empty into the sinusoid?
hepatic artery & portal vein
Where do sinusoids flow to? Where are they located? What are they lined with?
Flow to central vein…
located b/w hepatic plates
lined with discontinuous endothelium & Kupffer’s cells
What is the function of the Kupffer’s cells?
They eat up foreign stuff in the blood & old RBCs
What is another name for the space of Disse? Where is it located? What is its fcn?
Perisinusoidal space
located next to the sinusoids
**It is a site of exchange b/w blood & hepatocytes
Explain how the exchange works in the space of Disse.
Plasma enters the space of Disse thru the fenestrations in the endothelium (RBCs can’t pass).
Microvilli on hepatocytes here absorb oxygen, toxins, nutrients & release endocrine stuff.
Aside from blood…what else flows in the space of Disse? What is its destination? What direction does it flow?
Lymph!
flows toward lymphatic vessels in the portal area
*countercurrent to the blood flow & in the same direction as bile flow
Where are cells of Ito found? What else are they called? What do they do?
Hepatic Stellate Cells
- *found in space of Disse
- *store Vitamin A
- *differentiate into myofibroblasts & make collagen–>lead to fibrosis (cirrhosis)
T/F The space of Disse contains collagen.
True
What is the space of Mall?
the end of space of Disse…drains into lymphatic vessel by piercing the limiting plate
What is the canal of Hering?
the end point of the bile canaliculi
Describe the mucosa of the gallbladder.
LOTS OF RIDGES
simple columnar epithelium w/ apical microvilli
sodium pump on lateral surface to get water & Na+ movement to concentrate the bile
Is there an LP in the gallbladder?
YES-a typical one.
Is there a muscularis mucosae in the gallbladder?
NO
Is there a submucosa in the gallbladder?
NO
Describe the muscular layer that is found after the LP of the gallbladder.
It is interwoven smooth muscle that contracts in response to cholecystokinin
How is cholecystokinin released?
It is released by enteroendocrine cells in the small intestine…this is triggered by dietary fat
What type of organ is the gallbladder?
a tubular one–>unlike most tubular ones there is no muscularis mucosae or submucosa
Where does the pancreatic duct empty into?
the second portion of the duodenum
Does adventitia or serosa cover the gallbladder?
Both
Adventitia at the spot where the gallbladder attaches to the liver
Serosa on the side facing the peritoneum
What is cholestasis?
impaired formation & excretion of bile
What might intrahepatic cholestasis be?
some problem at the level of the hepatocyte
What might extra hepatic cholestasis be?
tumor of the pancreas or biliary tract
cholelithiasis
