Histopathology Flashcards
What are the hepatocytes supported by?
Not much! A thin capsule (Glisson’s capsule) surrounds the liver and blood vessels and ducts.
A delicate scaffold of reticular fibres (collagen type III)
How are the hepatocytes arranged?
Into polygons called (classic) lobules, which contain single layer stacks of hepatocytes in ‘plates’ (see pic)
How is the blood flow in a lobule arranged?
Blood comes in from portal triads at some of the at the corners, with sinusoids..central vein in the middle, which then drains into the hepatic vein.
What structures make up a portal triad?
A bile duct and 2 vessels, hepatic a and portal v
Sinusoid arrangement?
Mixture of deoxygenated portal blood (80%) and oxygenated hepatic a blood (20%). They run in from portal triads to the centre, and some run along the edge of the lobule, contacting hepatocytes above and below +/- on sides.
Describe the exchange surface
The hepatocyte is bathed in plasma, because the sinusoids are leaky. So essentially the extracellular Space of Disse is continuous (in terms of plasma) with the sinusoid lumen.
Hepatocytes have microvilli to increase the exchange surface area.
How is the HEPATIC lobule arranged what is the pathological significance?
Triangular blood flow, outside in direction, with triads supplying the section of the lobule it is the vertices of (1 triad has flow into 3 adjacent lobules, and 6 triangles).
Each double triangle is diamond, with 3 zones.
Zone 1 is the most peripheral, the base of the triangle. 2 is middle, 3 is the tip.
Zone 1 is high in oxygen, toxins and nutrients.
Zone 3 is the opposite. Has implications for damage in terms of toxins and hypoxia.
What is bile made up of and where do the components come from?
Produced by liver cells, consists of bile salts (surfactants) that emulsify fat and facilitate lipid and fat soluble vitamin digestion.
They are synthesised from cholesterol, and are resorbed in the terminal ileum? and recycled. Also contains bile pigments which make it green due to bilirubin- the break down products of Hb when RBC are broken down in the spleen and liver.
Describe the bile flow
The ducts collect from the centre and flow out.
Begin BETWEEN hepatocytes (bile cannaliculi) and collect in the triads.
The ducts from lobules come together to form the R and L hepatic ducts, then join to become the common hepatic duct. Joins the cystic duct to become the common bile duct, which joins the pancreatic duct to drain into the duodenum.
How does the gall bladder fill?
When the sphincter of Oddi is closed, bile travels back up to be stored in the gall bladder.
What is the structure and function of the gall bladder?
(pic) Smooth muscle sac with simple columnar epithelium and tough serosa.
It concentrates bile by the removal of fluid, and contracts to release bile.
What can go wrong with bile?
Gall stones are spontaneous precipitates of cholesterol and or bile salts. If large they may just sit there. If small enough to pass into the common bile duct can cause problems.
How is gall bladder activity controlled?
Fat in the duodenum stimulates cholecystokinin release. This stimulates GB contraction and relaxation of sphincter of Oddi, thus bile squirts into the duodenum.
What does pancreatic juice contain? Function?
Bulk of the digestive enzymes come from here (some on the epithelial brush border of SI) - proteases, lipases, amylases, nucleases and bicarbonate ions. Thus it has a digestive function BUT also acts to neutralise stomach acid.
What are the two functions of the pancreas?
(pic) Endocrine- islets of Langerhans and exocrine (ducts and lobules)
