Flashcards in Histology Week 2 Deck (99):
What are the two cells involved in the exocrine function of the pancreas?
pancreatic acinar and centroacinar cells
Describe the function of pancreatic acinar cells
produce, store, and release digestive enzymes
Pancreatic acinar cells also produce what type of inhibitor? What is its function?
Protects cell from intracellular activation of trypsin
What drives the release of enzymes from pancreatic acinar cells?
hormones and pancreatic nervous system
Describe the function of centroacinar cells
Centroacinar cells are modified intercalated duct cells located within the acinus that produce bicarbonate.
The bicarbonate functions to adjust the acidic chyme to an optimal pH for pancreatic enzymes.
True/False: In the exocrine pancreas, only mucous acini are present
FALSE ONLY SEROUS
What type of epithelium are centroacinar cells?
They are squamous-to-cuboidal epithelium
Centroacinar cells are in contact with the acinar ______. In addition, due to their continuity with this structure, centroacinar cells are regarded as the intraacinar segment of the ________
lumen, intercalated duct
True/False: Pancreatic acinar cells will have a lot of smooth endoplasmic reticulum
FALSE RER BC OF NZs
In pancreatic acinar cells, enzymes are stored in ________ and are released into the ______
zymogen granules, duodenum
What are the three major cells of the endocrine pancreas and what do they secrete?
Alpha cells - glucagon
Beta cells - insulin
Delta cells - somatostatin
Which major pancreatic endocrine cell is the largest? Most common?
Alpha cells are the largest
Beta cells are the most common (70% of cells)
True/False: The islet of Langerhans are found scattered among the exocrine secretory acini
In humans, where are the islets of langerhans primarily found in the pancreas?
body and tail
What is the function of somatostatin released by delta cells?
inhibits hormone release by neighboring cells
Where are the major endocrine cells located in the islets of langerhans?
alpha are located around the periphery of the islets
beta are concentrated in central region but present throughout
D cells are scattered throughout
What is the difference in appearance between the three types of major endocrine cells of the pancreas?
alpha have a small halo and an electron dense core.
beta have a small but obvious halo and an irregular dense core.
delta are large and electron lucent.
What is the function of glucagon secreted by alpha cells?
increase blood glucose levels
What are three minor cell types in the pancreatic islets?
PP cell (F cell), D-1 cell, EC cell
What does minor pancreatic endocrine cell PP cell (F cell) secrete? describe its function
stimulates gastric chief cells, inhibits bile secretion and intestinal motility, inhibits pancreatic NZs and HCO3- secretion
What does minor pancreatic endocrine cell D-1 cell secrete? Describe its function
vasoactive intestinal peptide
similar action to glucagon - hyperglycemic and glycogenolytic. stimulates pancreatic exocrine secretion and affects secretory activity/motility in the gut.
What does minor pancreatic endocrine cell EC cell secrete? Describe its function
secretin, motillin, substance P
secretin stimulates HCO3- locally, secreted into pancreatic juice
Motillin increases gastric and intestinal motility
Substance P has neurotransmitter properties
D-1 cells and EC cells, two minor pancreatic islet cells, are also found in _______ and ________
exocrine acini, duct epithelium
The pancreas has a dual blood supply, like the liver. What are the two sources of blood supply to the pancreas?
insuloacinar portal system
acinar vascular system
Pancreatic secretions are under control of _________ and _________
duodenal ECL's (enterchromaffin-like cells AKA enteroendocrine cells)
endocrine pancreas [peptide hormones synthesized in islets of langerhans]
Describe how and where zymogen granules are formed
Inactive proenzymes are synthesized in the RER of pancreatic acinar cells then transferred to the Golgi where they are concentrated in vesicles to form zymogen granules.
Each zymogen granule contains several pancreatic enzymes whose relative concentration depends on _________
changes in the diet
Describe the insuloacinar portal system in the pancreas.
Each islet of Langerhans is supplied by afferent arterioles forming a network of capillaries lined by fenestrated endothelial cells.
Capillaries leaving the islet supply blood to the pancreatic acini surrounding the islet.
This network is the insuloacinar portal system.
How does the set up of the insuloacinar portal system enable a local action?
It enables a local action of hormones produced in the islet on the exocrine pancreas
Describe the 2nd blood supply to the pancreas
The 2nd blood supply is the acinar vascular system which is an independent arterial system. It supplies the pancreatic acini as well.
Both components of the dual blood supply to the pancreas supply the ________ but only the _______ supplies the islets of Langerhans
In the pancreatic acinus, _______ located on ______ surface prevent the leakage of pancreatic enzymes into the intercellular space
tight junctions, apical
What do the liver and pancreas have in come in terms of functions?
Both are endocrine AND exocrine organs
Hepatocytes have six major functions.
Firstly, they produce most of the circulating plasma proteins. Name three circulating plasma proteins produced by the liver.
albumin, lipoproteins (VLDLs), glycoproteins
Hepatocytes also store and convert ______ and _______
several vitamins, iron
Hepatocytes are involved in many metabolic pathways and degrade _____ and _____
Describe the endocrine and exocrine functions of the liver
Endocrine - ability to modify structure and function of many hormones
Exocrine - bile production
Human hepatocytes are classic _______-shaped lobules
Describe the (4) structures located in the portal area
hepatic artery, portal vein, interlobular bile duct, and lymphatic vessels
Each lobule of the liver has a ________ which drains blood from every ____ of that lobule
central vein, sinusoid
True/False: The liver is the only visceral organ that can regenerate
Previously, there were three basic concepts of liver lobules. What is the current standard?
The Liver Acinus or Acinus of Rappaport
This classification is based on blood flow
There are three poorly defined areas surrounding a distributing artery in the center
Describe Zones 1-3 of the liver acinus in terms of blood flow.
Zone 1 is the richest in oxygen because it is the closest to the distributing artery in the center.
Zone 2 is an intermediate region.
Zone 3 is the closest to the central vein and is the most oxygen poor of the zones.
In the liver acinus, the direction of arterial flow determines a _________ from the periportal space near the portal triad (zone I) to the zone of drainage (zone 3)
What happens in zone 1 of the liver acinus? What is another name for this zone?
Hepatocytes synthesize actively glycogen and plasma proteins
O2 concentration in sinusoidal blood is high
What happens in zone 3 of the liver acinus?
Role in detoxification
True/False: Hepatocytes in zone 1 are the first to show ischemic changes
FALSE ZONE 3
How are the zones defined in a liver acinus?
by hepatic tissue receiving blood from a branch of hepatic artery conducting blood to opposite central veins
Hepatocytes in _____ are the first to show signs of morphological changes after bile duct occlusion
What happens to cells in zone 1 during ischemia?
They are the last to die and the first to regenerate
In the liver acinus model, where are the central veins (terminal hepatic venules) found? How does this differ from the classic lobule?
They are found at the edges of the acinus instead of the center, as in the classic lobule definition
In the liver acinus model, which cells are the first to see blood? Last?
The perilobular cells in zone 1 are the first to see blood and be affected by it.
The centrolobular cells in zone 3 are the last to see blood and the blood they see has already been altered by cells in previous regions.
What types of enzymes are made in perilobular cells of zone 1 to be used by centrolobular cells in zone 3?
key glucose-liberating enzymes and key fatty-acid oxidation enzymes
Hepatocytes have large amounts of what two organelles?
What other three types of organelles are abundant?
rough endoplasmic reticulum
endosomes, lyososomes, peroxisomes
True/False: Hepatocytes have a lot of rough endoplasmic reticulum, but very little free ribosomes
FALSE lots of free ribosomes
The rough endoplasmic reticulum in hepatocytes is involved in the synthesis of what three types of plasma proteins?
2) coagulation factors
3) binding proteins for hormones and growth factors in blood circulation
What organelle in hepatocytes is associated with clusters of glycogen molecules in "rosette-like inclusions"
smooth endoplasmic reticulum
What is the function of albumin, a major product of the hepatocyte? What happens when there is a decrease in albumin due to liver dz?
It maintains plasma oncotic P
A decrease of albumin in liver dz causes edema and ascites
The hepatocyte produces what four blood coagulation factors? What happens in liver failure?
fibrinogen, prothrombin, complement, factor VIII
Smooth endoplasmic reticulum is highest in which zone of the liver acinus? What causes the SER to increase?
increase in presence of drugs and toxins
What three reactions inactivate sites of detoxification in smooth endoplasmic reticulum?
Other than the smooth endoplasmic reticulum, what other organelle detoxifies in the hepatocyte?
Hepatocytes have two domains. What are they?
lateral and sinusoidal
The lateral aspect of the hepatocyte, or _____ domain, is covered with ______ and separated by elaborate ____ spaces that form the _______.
How is this domain represented?
apical, microvilli, INTERcellular, bile cannliculi
This domain is represented by the bile pole.
The sinusoidal or ______ domain also has ______. These structures project into the ________ which increases the _____ by a factor of 6.
basolateral, space of Disse, surface area
The space of Disse found on the sinusoidal domain of hepatocytes is also known as the _______
True/False: Hepatocyte plates on hepatic lobules are formed by two rows of hepatocytes
FALSE SINGLE ROW
What two blood vessels empty into the hepatic sinusoid?
hepatic portal vein, hepatic artery
Where do hepatic sinusoids lie? What do they empty into?
Hepatic sinusoids lie between hepatic plates and empty directly into central veins
What are hepatic sinusoids lined with? (2)
discontinous endotheliu and kupffer's cells
What is the action of Kupffer cells and what is special about them in the liver?
Kupffer cells phagocytose blood-borne foreign particulate matter and when needed worn out RBC's
Kupffer cells are differentiated phago cells derived from monocytes.
The liver is the only place in the body where Kupffer cells are found in the bloodstream
True/False: Blood NEVER touches the hepatocyte
True, goes through sinusoidal spaces
What happens in the perisinusoidal space?
Site of exchange of materials between blood and hepatocytes
How does plasma enter the space of Disse?
plasma enters via openings between endothelial cells that are too small for blood cells to pass
Hepatocytes in the space of Disse absorb nutrients, oxygen, and toxins via what structures?
microvillus that are covering the free surface
Besides absorption, what are two other functions of hepatocytes in the space of Disse?
release metabolic products and endocrine secretions
The space of Disse also serves as the_______ for the liver with fluid flowing towards _________ in the portal area, and flowing _____ to blood flow
lymphatic system, lymphatic vessels, opposite
What are the cells of Ito?
Where are they found and what do they store?
The cells of ito AKA hepatic stellate cells store vitamin A.
What happens to cells of Ito AKA hepatic stellate cells in pathological states?
In pathological states, they differentiate into myofibroblasts and synthesize collagen, leading to liver fibrosis
Overall, the space of Disse separates the _______ domain of the hepatocyte from blood circulating in the _______
hepatocyte; hepatic sinusoid
What types of collagen fibers are contained within the space of Disse?
I, III, and IV collagen fibers
The ______ is found at the periphery of the hepatic lobule and is continuous with the space of Disse
Space of Mall
The space of Mall is drained by the lymphatic vessels piercing the _______. These lymphatic vessels surround the blood vessels and bile ductules in the portal space.
The ______ is the terminal point of the network of bile canalicular trenches found on the hepatocyte surfaces.
canal of Hering
Where is the canal of Hering located? What type of epithelium lines it?
The canal of hering is located at the periphery of the hepatic lobule (inside the lobule) and is lined by squamous-to-cuboidal simple epithelium
The canal of Hering connects with the ______ in the portal space after perforating the ________
bile ductules, limiting plate
Name the layers of the gallbladder. What layers typically found in organs are missing?
The gallbladder contains a mucosa, muscularis layer, adventitia, and serosa.
The gallbladder does NOT have muscularis mucosae or submucosa muscularis.
What types of epithelium are found in the mucosa of the gallbladder?
simple columnar epithelium
Describe three characteristics of the single columnar epithelium found in the mucosa of the gallbladder
- apical microvilli
- concentration of bile requires coupled transport of salt and water
- Na pump on lateral surface to facilitate H20 absorption from bile
What is present in the muscularis layer of the gallbladder?
interwoven smooth muscle
What causes the interwoven smooth muscle in the gallbladder to contract?
cholecystikinin release by enteroendocrine cells in the small intestine [duodenum]. release of CCK triggered by dietary fat.
Where are the adventitia and serosa found on the liver?
The adventitia attaches the gallbladder to the liver
The serosa covers its free peritoneal surface
What are the three major functions of the gallbladder?
- Concentration and storage of bile between meals
- Release of bile by contraction of the muscularis in response together with relaxation of the Sphincter of Oddi
- regulation of hydrostatic pressure within the biliary tract
What is the sphincter of Oddi?
a muscular ring surrounding the opening of the bile duct in the wall of the duodenum
What is cholestasis (general)?
The impaired formation and excretion of bile
What is the difference between intrahepatic cholestasis and extrahepatic cholestasis?
Intrahepatic - impaired formation/excretion of bile at level of hepatocyte
Extrahepatic - structural or mechanical perturbation in the excretion of bile
What is an example of a structural perturbation in the excretion of bile? Mechanical?
Structural - tumor of the pancreas or biliary tract (cholangiocarcinoma)
Mechanical - cholelithiasis (produced by gallstones)
Clinically, by what 3 ways is cholestasis detected?
elevated bilirubin, elevated alk phos, gallstones
1) presence in blood of bilirubin and bile acids (secreted into bile under normal conditions)
2) elevation in serum of alkaline phosphatase (an NZ associated with the plasma memb of bile cannaliculis)
3) radiological examination