Pancreas and Liver Microanatomy Flashcards
How is the pancreas structured
lobules with ducts
Appearance and structure of exocrine pancreatic cells
Dark staining (due to zymogen granules). Granular appearance Arranged as pancreatic acini
Appearance and structure of endocrine pancreatic cells
Light/pale staining cells, arranged in clusters, embedded among exocrine cells.
Form Islets of Langerhans
Function of Ductule cells
To produce HCO3-
Function of exocrine pancreatic cells
to produce digestive enzymes, fluids and electrolytes
Function of the endocrine pancreatic cells
Produce hormones to control blood sugar
exocrine pancreatic gland?
tubulo-acinar gland with highly branched ducts
What is the exocrine pancreatic gland similar to?
parotid gland (serous)
Acini
contain 5-8 pyramid-shaped cells surrounding a tiny lumen.
Large spherical nucleus in the basal position
Mitochondria perpendicular to the basal surface.
How tiny is the pancreatic acinar lumens?
Too small to see with a light microscope
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.
Acini produce
A small volume of enzyme rich fluid.
Duct cells produce
Bicarbonate and a large volume of alkaline fluid ~1L/day
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
Intercalated duct cells that penetrate the lumen of acini are called?
Centro-acinar cells’
Some Liver functions
Exocrine endocrine synthesis (albumin, prothrombin, bile) storage (glycogen) detoxification
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
