9. Histology of the liver, gallbladder, and pancreas Flashcards by Anna Bakeman

What is the largest glandular tissue in the body?

Liver

1200-1500 g

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What are the four lobes of the liver? Which two have the most bulk?

RIght, left, caudate, quadrate

RIght and left

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The liver is unique in that it receives mainly venous blood directly from:

Spleen
Pancreas
Intestine
**first organ to encounter any injested toxic substances as well as nutrients

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The liver is unique in that CT is sparse, and the bulk of the liver is made up of:

Parenchymal cells/ hepatocytes

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6 functions of the liver

Detox of metabolic waste products
Synthesis of plasma lipoproteins
Synthesis of clotting factors
Synthesis, storage, and secretion of carbs and lipids
RBC destruction and recovery of contents
Synthesis and secretion of bile

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What are the endocrine secretions of the hepatocytes that enter the hepatic blood?

ALbumin
Fibronectin
Transferrin
Prothrombin
Lipoproteins 
Alpha 1 antitrypsin
Glucose
Thryoxin

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What is the main exocrine function of the liver?

Production of bile

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What are the four functional groups of liver components?

Connective tissue
Large vessels
Sinusoidal capillaries (sinusoids)
Hepatocytes

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What kind of fibers surround the hepatocytes and sinusoids? Layout?

Reticular fibers–type III collagen
Extend outward from the central vein, only CT in the lobule
Supports the parenchyma and keeps the sinusoids open

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What do the reticular fibers originate from? How can their disruption be identified?

Stellate/ito cells in the Space of Disse

Staining for reticulin

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What are the five main vessel systems in the liver?

Hepatic artery–oxygenated blood to the liver
Hepatic portal vein–venous blood to the liver
Central veins–blood away from the liver toward the hepatic veins, IVC
Bile ducts–bile from the liver
Lymphatic vessels–lymph away from the liver

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Arterial capillaries and inlet venules carry blood from the hepatic artery and portal veins into capillaries called

Sinusoids

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Portal triad

Hepatic artery
Portal vein
Bile duct
**lymphatic vessels also associated

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Sinusoids are made up of two cell types:

Endothelial cells (sinusoidal cells)
Kupffer cells (sinusoidal macrophages)

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Role of Kupffer cells?

Derivatives of monocytes, probably involved in the breakdown of senile RBCs

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Where does exchange of substances between the blood and hepatocytes take place?

Peri-sinusoidal Space of Disse (between the basal surface of the hepatocyte and the sinusoid

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How do hepatocytes increase their SA for absorption?

Extend microvilli from the basal surface

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What calls are found in the perisinusoidal space?

Stellate

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Stellate cells contain ___ and are the major site of ____ stoarage

Lipid droplet

Vitamin A

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What is the functional unit of the liver?

Lobule

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What are the three ways that the functional unit of the liver can be described?

Classic lobule (hexagon)
Portal lobule (triangle between three central veins)
Liver acinus

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The classic lobule has __ at the center and __ at each of its 6 corners

Central vein

Portal triad

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What makes up the short axis and long axis of an acinus?

Short: between two adjacent portal triads
Long: between two adjacent central veins

What zone of the acinus encounters afferent blood first?

Zone 1

Haptocytes are arranged in ___ ___ 1-2 cells thick seperated by sinusoids

Anastomosing plates

Hepatocytes are described as having __ surfaces

6--2 facing the perisinusoidal space and 4 facing other hepatocytes and bile canaliculi

Perisinusoidal surfaces of the hepatocyte represent the ___ aspect of the cell Surfaces facing the bile caniliculi are ____ Transfer of substances between the sinusoids and hepatocytes occurs at the ___ surface

Basal Apical Basal

In the adult, the majority of hepatocytes are __nucelate and ___ploid

Binucleate | Tetraploid (4n DNA)

What orgnanelles are hepatocytes particularly rich in?

rER Mitochondria **glycogen granules are deposited through the cytoplasm and lipid droplets are also prevalent

What are bipotential cells in the biliary epithelium that can differentiate into both biliary epithelium and hepatocytes?

Oval cells

Main role of bile from the liver

Emulsification of fats for absorption by the intestine

Hepatocytes actively secrete bile across their ___ surfaces into the:

Apical surfaces | Bile caniliculi

Bile caniliculi join together to form small terminal ductules called:

Canals of herring

Bililary epithelial cells form a ____ epithelium which forms a ductule

Cuboidal

Human liver secretes ___ of bile a day

1 liter

Dilute bile form the liver is shunted into the gall bladder where it is concentrated ____x

5-10x

The presence of LIPID in the duodenum induces the secretion of ____, which has the role to

Cholecystokinin (CCK) | Stimulates the gall bladder to contract and forces concentrated bile into the duodenum

The gallbladder can store ____ bile a day

100 mililiters

What is the mucosa of the gallbladder made up of?

Simple columnar epithelial cells (resemble the absorbitive cells of the intestine

What is the function of the cells lining the gallbladder (have numerous short apical microvilli and basally located nucleus, junctions to produce barrier)

Concentrate bile by actively absorbing water into a capillary-rich network in the lamina

The main pancreatic duct traverses the length of the organ and joins the

Common bile duct, which enters into the duodenum

What does the exocrine pancrease generally secrete?

Cocktail of enzymes required for digestion

The exocrine pancreas consists of acini that are densely packed and secrete into a system of ducts---(4)

1. Intercalated 2. Intralobular 3. Interlobular 4. Pancreatic

What does the endocrine pancreas consist of?

Islets of Langerhans--randomly distributed through the acini | **secretes hormones that control carbohydrate metabolism

What two hormones produced by the duodenum in the presence of food induce the secretion of pancreatic juice from the exocrine pancreas?

Secretin | Cholecystokinin

Pancreatic juice is a mixture of ___ fluid and enzymes/proenzymes

Alkaline

Digestive enzymes of the pancreas are stored within ___ ___ within the cytoplasm of acinar cells

Zymogen granules

To prevent autodigestion of the pancreas, the proenzymes of the pancreas are only activated by:

Protrolytic cleavage in the intestine | **Acinar cells also secrete proteolytic inhibitors that block any errant activation of the proenzymes in the pancreas

The functional unit of the exocrine pancreas is the:

Acinus

Cholecystokinin induces acinar cells to secrete:

Pancreatic enzymes in the form of zymogen granules into the lumen

What cells respond of secretin?

Centroacinar cells: extend from the end of the duct into the acinus as a discontinuous epithelium--low squamous epithelial cells responsible for the secretion of alkaline fluid

What are the two main roles of the alkaline fluid secreted by centracinar cells in response to secretin?

Solubilization of zymogen granules | Neutralization of acidic chyme as it enters the duodenum

Morphology of acinar cells

Pyramidal cells with basal nucelus--lots of rER for protein synthesis

Newly synthesized proenzymes in acinar cells are modified by ___ to form zymogen granules

Golgi

Zymogen granules are released by exocytosis at the __ surface of the acinar cells

Apical

What is the pathway that pancreatic juice takes after entering the centroacinar lumen?

Intercalated duct Series of intralobular ducts Interlobular ducts Main pancreatic duct