Pancreas and Liver Microanatomy Flashcards by Libby Halligan

How is the pancreas structured

lobules with ducts

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Appearance and structure of exocrine pancreatic cells

Dark staining (due to zymogen granules). Granular appearance
Arranged as pancreatic acini

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Appearance and structure of endocrine pancreatic cells

Light/pale staining cells, arranged in clusters, embedded among exocrine cells.
Form Islets of Langerhans

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Function of Ductule cells

To produce HCO3-

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Function of exocrine pancreatic cells

to produce digestive enzymes, fluids and electrolytes

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Function of the endocrine pancreatic cells

Produce hormones to control blood sugar

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exocrine pancreatic gland?

tubulo-acinar gland with highly branched ducts

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What is the exocrine pancreatic gland similar to?

parotid gland (serous)

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Acini

contain 5-8 pyramid-shaped cells surrounding a tiny lumen.
Large spherical nucleus in the basal position
Mitochondria perpendicular to the basal surface.

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How tiny is the pancreatic acinar lumens?

Too small to see with a light microscope

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where are protein secretory products (enzymes) synthesised in the pancreas

Basal rER, packaged in the golgi, and accumulated as zymogen granules in the apical cytoplasm of exocrine acinar cells.

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Acini produce

A small volume of enzyme rich fluid.

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Duct cells produce

Bicarbonate and a large volume of alkaline fluid ~1L/day

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What is the path of product drainage from the acini to the duodenum?

intercalated ducts > intralobular ducts > interlobular ducts > pancreatic duct > Ampulla of Vater > duodenum

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Intercalated duct cells that penetrate the lumen of acini are called?

Centro-acinar cells’

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Some Liver functions

Exocrine
endocrine
synthesis (albumin, prothrombin, bile)
storage (glycogen)
detoxification

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What runs between the radiating columns of hepatocytes, and what is their function

Sinusoids. (special capillary)
Carry the mixed blood flow from branches of the portal vein/ hepatic artery to drain into the central vein.
As blood flows through sinusoids oxygen and nutrients are diffused into adjacent hepatocytes down their concentration gradient.

What lines the sinusoids?

Kupffer cells.

The central veins position, purpose and journey.

Position: Centre of liver lobule
Purpose: collects blood from the lobule sinusoids
Journey: Central veins collect > hepatic veins > IVC

Why are the sinusoids arranged the way they are?

To ensure maximal exposure of the hepatocytes to a blood supply.
Ensure a good supply of nutrients, keeps them nourished

What encases the liver lobules?

Interlobular Septa
made of CT
-with collagen, BV’s and nerves

What are liver lobules meant to look like?

a hexogonal shape, but this often isn’t the reality

Classical anatomical shape within the liver

hexagonal shape. Formed by the hepatic lobule. Each edge has a portal space

Functional unit of the liver?

Liver acinus.

Diamond that radiates from the branches interlobular septa/portal triad out to the central veins.

Portal lobule looks like?

Triangle (points are the central veins). The bile drains through canaliculi in the hepatocytes to the bile duct.

Portal space contains

CT and a portal triad

Branch of the Hepatic portal vein under the microscope looks?

- thin walled | - large lumen (therefore low pressure)

Branch of the Hepatic artery proper looks like

thicker muscular wall | relatively smaller lumen (therefore higher systemic pressure)

Contribution of blood to the liver?

75% From hepatic portal vein (nutrient rich) | 25% from Hepatic artery Proper (oxygen rich)

path of blood from a branch of the portal vein to the IVC

branch of portal vein > {intermediates} > lobule sinusoid > central vein > (hepatic vein > collecting vein > intercalated vein) > IVC

branching from portal triad

PHA: no branches, straight into sinusoid PV: intermediate vessels, then to sinusoids

How does the richness of the blood change from the centre of the hepatic acinus to the central veins? How is this classified?

Decreases the richness as oxygen and nutrients move into hepatocytes down their diffusion gradient. Creates Zones of differential richness = zones 1, 2 and 3

What do these zones represent?

That different hepatocytes in different regions of the liver will have different enzyme profiles due to different functions. These will react differently to disease.

the two important cells to know about with hepatocytes?

Stellate cells | Kupffer cells

Kupffer cells

In the lumen of the sinusoid, 'hoover' any luminal obstructions. Macrophage-like, stop obstruction, antibacterial cells

Stellate cells

found in the 'Space of Disse' (lymphatic space between endothelium and hepatocyte microvilli) - fat storing - have a role in vitamin A metabolism - have implications in scarring with liver damage

How are sinusoids different to regular capillaries?

- they are wider then capillaries, can fit more then one RBC through (upto ten). Faster flow. - More leaky (More diffusion)

Hepatocyte shape is? What in their structure is commonly changed?

Polygonal 1) Bi-nucleate (2x nuclei) or polyploid (2x DNA in nucleus) cells this is bc they undergo such a high rate of regeneration and cell division. 2) Distribution/abundance of organelles change : dependent on what zone they are in

The endothelium of liver?

Lines sinusoids. | Intercellular openings, as well as being fenestrated (more leaky for increased diffusion)

How does bile drain?

canaculi > bile ductules > bile duct

Canniliculi are?

Channels between adjacent hepatocytes Membranous in-foldings (not made of cells) that create channels for bile to flow through Proteins help to seal canaliculi at occluding junctions