Liver anatomy and histology Flashcards
Describe the blood supply to the liver
Double blood supply:
- hepatic artery - 30%, rich in oxygen
- hepatic portal vein - 70%, rich in nutrients, poor in oxygen
What is the clinical relevance of the double blood supply to the liver
Liver has limited oxygen supply as most is supplied via hepatic portal vein
Stress can cause liver to become anoxic
Describe the regeneration of the liver when cell death is ongoing
Liver is very good at regenerating - not good in this case
Mixture of scar tissue and regenerating cells distorts the architecture
Abnormal architecture damages blood flow and therefore function and more cells die
Creates a cycle of death/scarring/regeneration = Cirrhosis
Describe the regeneration of the liver where lobe has been removed
Liver is very good at regenerating so the same original mass will return (will not look the same)
Describe the histology of the liver
Hepatic parenchyma - functional part of liver
Principal cell = hepatocyte
Hepatic stroma = structural tissue of liver
Describe the histology of the hepatic stroma
Thin fibres of connective tissue (reticulin fibres + collagen type III) forms thin layer => ‘floppy’
Label the histology of the liver
Describe the anatomy of a classic liver lobule?
hepatocytes are organised in radial cords with portal triads at each corner and a single central vein
Label the classic liver lobule
Describe the components of the portal tract/triad in classic liver lobules
Branch of hepatic artery
Branch of hepatic portal vein
Bile duct
Surrounded by connective tissue
Large triads also contain lymphatic vessels and autonomic nerves
Limiting plate: discontinuous border of hepatocytes forms outer boundary
What is a hepatic sinusoid
fenestrated blood vessels running along the plates of hepatocytes
Portal vein blood and hepatic artery blood mix here
What is the function of the central vein in a classic liver lobule?
receive blood from sinusoids and return it to circulation via hepatic vein
Label this portal tract/triad
Label this liver lobule
What are the cell types found in the liver?
Hepatocytes
Endothelial cells
Kupffer cells (sinusoidal macrophages)
Hepatic stellate cells/ Ito cells
Label the cells of the liver lobule
Label the cells of the liver lobule
Describe the morphology and function of kupffer cells
macrophage-like
defend against vascular carrer pathogens and remove debris
Describe the morphology and function of hepatocyes
Polyhedral with round nucleus and prominent nucleolus
Metabolise and store materials absorbed from the SI, and secrete bile
Describe the morphology and function of Ito cells in the liver
Contain big intracytoplasmatic vacuoles
Involved in tissue fibrosis and in retinol metabolism (Store vitamin A)
Label the cells of the liver sinusoids
Label the cells of the liver sinusoid
Label the cells of the liver sinusoid
What is the function of the smooth endoplasmic reticulum in the hepatocyte?
contains main enzymes involved in detoxification (cytochrome P450)
Involved in lipid and glycogen metabolism
What is the function of peroxisomes in the hepatocyte?
contains enzymes involved in detoxification e.g., catalase
Describe the function of the rough endoplasmic reticulum in the hepatocyte?
binds ribosomes engaged in translating mRNA to proteins
involved in protein and lipid modifications
What is the function of the golgi apparatus in the hepatocyte?
associated with protein secretion (important for bile secretion)
involved in protein and lipid modification
Label the organelles of the hepatocyte
What is the role of mitochondria in hepatocytes?
aerobic supply of energy - ATP production
What is the role of lysosymes in the hepatocytes
digestion of macromolecules
What is the role of glycogen in the hepatocytes
Short-term storage of glucose
The liver is the main store of glycogen
What is the function of lipid droplets in hepatocytes?
storage of esterified fatty acids
What organelles can be found in hepatocytes?
What is the biliary tree?
Biliary canaliculi (intercellular channels) formed between adjacent hepatocytes form a network => biliary tree
Canals of Hering drain into bile ducts of portal tracts
What is the function of the gall bladder?
storage, concentration and release of bile - empties via the cystic duct into the duodenum
Bile => fat digestion and hepatic excretion
Describe the histology of the gall bladder
fibromuscular sac lined with simple columnar epithelium with numerous folds when non-distended
No muscularis mucosae or submucosa
Label the histology of the gall bladder
Describe blood and bile flow in the liver lobule
Bile and blood flows are in opposite directions
What is the difference between a classic liver lobule, portal lobule and hepatic acinus?
Portal lobule - triangular area centred on portal tract
Classic lobule - area centred on central vein, stresses the exocrine glandular function
Hepatic acinus - emphasises vascular supply to hepatic parenchyma and the direction of blood flow
Label the different divisions of the hepatic parenchyma
Describe the zones of the hepatic acinus
Zone 1 - closest to portal tract receives most oxygenated blood
Zone 3 - receives least oxygenated blood as is furthest away from portal tract
Zone 3 has a higher detoxification activity (e.g., cytochrome P450)
What are the pathological implications within a hepatic acinus
Zone 3 heptatocytes are more susceptible to hypoxic injury and injury by toxic substances that are metabolically activated by cytochrome P450 = centrilobular necrosis
Zone 1 hepatocytes are more susceptible to direct-acting toxicants = perilobular necrosis
