118 - Liver and Pancreas Histology Flashcards
Functions of the liver 1 2 3 4 5 6 7 8 9 10 11 12
1) Major glycogen store 2) Gluconeogenesis 3) Cholesterol synthesis 4) Lipoprotein synthesis 5) Ketone body synthesis 6) Production of all blood proteins except antibodies 7) Makes all non-essential amino acids 8) Detoxifies metabolic wastes 9) Iron storage for haemoglobin 10) Destroys hormones 11) Destroys toxins 12) Bile production
Gluconeogenesis
Breakdown of lactic acid, amino acids, glycerol to glucose
Example of a metabolic waste detoxified by the liver
Ammonia. Converted to urea by the liver.
Shape of hepatocytes
Polyhedral (six surfaces). Around 25micrometers across
Internal structure of hepatocytes 1 2 3 4
1) One or two nuclei. Many cells are tetraploid or polyploid 2) Prominent rough ER, Golgi complexes, vesicles for protein synthesis, transport 3) Prominent smooth ER for fat metabolism 4) Many mitochondria
Which cell type are hepatocytes?
Epithelial
Hepatocyte lifespan
~150 days
Replacement of hepatocytes
Replaced by divisions of existing hepatocytes
Percentage of liver weight that is hepatocyte
75%
Organisation of hepatocytes in the liver
Organised around blood vessels
Name for thin capsule around liver, blood vessels and ducts
Glisson’s capsule
Connective tissue in the liver 1 2
1) Glisson’s capsule (around liver, blood vessels and ducts) 2) Hepatocytes are supported by reticular fibres (type III collagen)
Organisational units of hepatocytes
Lobules
Liver lobules
Stacks of hepatocytes in plates. ~0.7x2mm in size Kinda hexagonal crystal shape
Blood vessels associated with a lobule
Central vein runs through middle Portal triads on edges
Portal triads 1 2 3 4
1) Two blood vessels and a duct 2) A branch of the hepatic portal vein (blood from gut) 3) Branch of hepatic artery (to oxygenate blood) 4) Supplies multiple lobules
How do portal triads and central vein interact?
Vein and artery in portal triads give rise to sinusoids, which flow into the middle of the lobule, into the central vein.
Sinusoids
Network of branches from portal triads (on the exterior of lobules) to the central vein of a lobule.
Type of blood carried by sinusoids
Mixed oxygenated (20%) and deoxygenated (80%)
Central vein role
Carry blood from sinusoids to hepatic vein and out of liver
Arrangement of sinusoids in lobule
Each plate of hepatocytes has a sinusoid above and below it
Name for space around hepatocytes that bathes them in plasma
Space of Disse
How are hepatocytes exposed to blood contents?
Sinusoids run above and below each plate of lobules. Sinusoids have incomplete walls. Space of Disse around hepatocytes is full of plasma from sinusoids
*Histological slide of heatocyte in situ
How do hepatocytes increase surface area?
Microvilli
Two arrangements of vessels in lobules
1) Classical lobule 2) Hepatic lobule
Hepatic lobule
Hepatic and portal vein in middle of lobule. Emphasises metabolic organisation
*Hepatic lobule vs classical lobule
Zone 1 of hepatic acinus
High in O2, high in toxins, high in nutrients
Zone 3 of hepatic acinus
Low in O2, low in toxins, low in metabolites
*Schematic of a hepatic acinus
Hepatic acinus 1 2 3
1) The functional unit of the liver 2) Arranged into zones based on proximity to arterial blood supply: zone1 is closest, zone 3 is furthest 3) Arrangement of classical lobules
*Schematic showing difference between portal and hepatic lobules
Portal lobules are in solid lines, hepatic are in dotted lines
What produce bile salts?
Hepatocytes
Which product do hepatocytes synthesise bile salts from?
Cholesterol
Why is bile green?
Bile pigments are green. Bile pigments are breakdown products of haemoglobin, from destruction of RBCs in the spleen and liver
How is bile released from hepatocytes and liver?
Bile produced by hepatocytes is released into channels between hepatocytes (cannaliculi), which flows outwards into bile ducts in the portal triads
Histological appearance of gall bladder 1 2 3
1) Smooth muscle forms muscular sac 2) Simple columnar epithelium 3) Tough serosa
Functions of gall bladder 1 2
1) Concentration of bile salts 2) Storage of bile
How does the gall bladder concentrate bile salts?
About 90% of bile is resorbed by gall bladder, concentrating bile salts and pigments.
Name for sphincter that diverts bile to gall bladder for storage
Sphincter of Oddi
Gall stones
Precipitates of bile salts and/or cholesterol
Hormonal control of gall bladder 1 2 3
1) Fat in duodenum stimulates specialised cells of duodenal mucosa to release cholecystokinin into blood 2) CCK causes relaxation of sphincter of Oddi, contraction of gall bladder. 3) Bile squirts into the duodenum
Duct that sphincter of Oddi controls
Common bile duct
Functions of pancreas 1 2
1) Enzyme release 2) Bicarbonate release
Components of pancreastic juice
Proteases, lipases, amylases, nucleases and bicarbonate ions
Histological appearance of pancreas
Islets of Langerhans. Pancreatic acini
What forms pancreatic glands
Pancreatic acini. Balls of cells with duct in the middle
What type of enzymes does the pancreas release?
Zymogens
