the liver Flashcards
What is excretion? (1)
The removal of the waste products of metabolism from the body
What are the main metabolic waste products in the body? (3)
CO2
Bile pigments
Nitrogenous waste
How is CO2 formed and excreted? (2)
Waste product of respiration
Excreted by the lungs (too much CO₂ in the blood is toxic)
How are bile pigments formed and excreted? (2)
From the breakdown of haemoglobin in the liver
Excreted into the small intestine via the gall bladder and bile duct
How are nitrogenous waste (urea) formed and excreted? (2)
Formed from the breakdown of excess amino acids in the liver
Excreted by the kidneys in urine
What are the main veins, arteries, and ducts associated with the liver? (4)
Hepatic artery: Supplies the liver with oxygenated blood for respiration (producing ATP)
Hepatic vein: Takes deoxygenated blood away from the liver
Hepatic portal vein: Brings blood from the duodenum and ileum, containing the products of digestion
Bile duct: Takes bile to the gall bladder for storage; bile emulsifies fats
What is the structure of the liver? (4)
The liver is made up of cylindrical structures called liver lobules
Composed of rows of hepatocytes arranged in rows radiating from the center
Each lobule has a central vein connected to the hepatic vein
Branches of the hepatic artery, hepatic portal vein, and bile duct connect to each lobule
How do the hepatic artery and hepatic portal vein connect to the central vein? (3)
Through capillaries called sinusoids
Blood flows through the sinusoids past hepatocytes
Which remove harmful substances and oxygen from the blood
What role do hepatocytes play in liver function? (3)
Hepatocytes remove harmful substances from the blood
Breaking them down into less harmful substances
Which then re-enter the blood
What is the function of Kupffer cells in the liver? (2)
Kupffer cells are attached to the sinusoids
Remove bacteria and break down old red blood cells
How is bile transported in the liver? (2)
The bile duct is connected to the central vein by tubes called canaliculi
Which transport bile
How does the liver contribute to carbohydrate metabolism? (3)
When blood glucose levels rise
Insulin stimulates hepatocytes to convert glucose to glycogen for storage
Which can later be converted back when glucose is needed for energy
How is excess protein converted into urea? (5)
- Protein is converted into amino acids
- Excess amino acids undergo deamination
- Ammonia is formed
- Ammonia is converted into urea in the ornithine cycle
- Urea is released into the blood and excreted by the kidneys in urine
What is deamination? (2)
Process where the nitrogen-containing amino groups are removed from excess amino acids
Producing ammonia and organic acids
Why is deamination necessary? (2)
The organic acids can be respired for ATP production
Or stored as glycogen
Why is ammonia converted into urea in the liver? (3)
Ammonia is too toxic for mammals to excrete directly
So it is combined with CO₂ in the ornithine cycle to form urea
Which is less harmful and can be excreted
How does the liver detoxify harmful substances like alcohol? (2)
The liver breaks down alcohol (ethanol) into ethanal
Which is then broken down into acetic acid, a less harmful substance
What can prolonged alcohol consumption lead to? (2)
Cirrhosis
Where liver cells die, and scar tissue blocks blood flow
How does the liver process paracetamol? (2)
Paracetamol is broken down by the liver
Excess amounts can lead to liver and kidney failure
How does the liver regulate insulin? (2)
The liver breaks down excess insulin
Preventing problems with blood glucose concentration
What is the large white circular shape seen in a stained sample of liver tissue under a light microscope? (1)
Central vein
What are the cells that radiate out from the central vein in a liver tissue sample? (2)
Hepatocytes
The red dots inside the cells are the nuclei
What are the white spaces between the cells in a stained liver tissue sample? (1)
Sinusoids
