Excretion Flashcards
What is excretion
The removal of waste products from the body
What is metabolism
All the chemical reactions that happen in your cells. It produces waste products such as CO2 and nitrogenous waste.
Why does excretion happen
The waste products of metabolism are often toxic and so if they built up they would cause damage. So it removes the waste products.
What are the functions of the liver
Excess amino acids are broken down
Removal of harmful substances from the blood
Storage of glycogen
How does the liver carry out it’s function of breaking down amino acids
1) The amine groups are removed from any excess amino acids forming ammonia and organic acids (deamination)
2) The organic acids can be respired to give ATP or converted to carbohydrate and stored as glycogen.
3) Ammonia is too toxic to be excreted directly so it is combined with CO2 in the ornithine cycle to create urea
4) Urea is released from the liver into the blood, the kidneys then filter the blood and remove the urea as urine
Why does the liver carry out it’s function of breaking down amino acids
Amino acids contain nitrogen which can’t usually be stored in the body so excess amino acids can be damaging.
Why does the liver carry out it’s function of removing harmful substances from the blood
They are broken down into less harmful compounds to be excreted called detoxification.
What are some of the harmful products broken down in the liver
Alcohol (ethanol)
Paracetamol
Insulin
How does the liver remove alcohol from the blood
It is broken down into ethanal which is broken into a less harmful substance called acetic acid. Excess alcohol can lead to cirrhosis of the liver and it’s cells die and scar tissue blocks blood flow.
What does the live do with excess glucose
Converts it to glycogen and stores it as granules in its cells until needed
What does the hepatic artery do
Supplies the liver with oxygenated blood from the heart, so the liver has a good supply of oxygen for respiration providing plenty of energy
What does the hepatic vein do
Take deoxygenated blood away from the liver
What does the hepatic portal vein do
Brings blood from the duodenum and ileum so it’s rich in the products of digestion. Any ingested harmful substances are filtered out and broken down straight away
What does the bile duct do
Takes bile to the gall bladder to be stored
What is the liver made up of
Liver lobules - cylindrical structures made of cells called hepatocytes that are arranged in rows radiating out from the centre
What does each liver lobule contain
A central vein that connects to the hepatic vein. Many branches of the hepatic artery, hepatic portal vein and bile duct are also found connected to each lobule
What are the hepatic artery and portal vein connected to
The central vein by capillaries called sinusoids
How does blood run through the lobule
Through the sinusoids past the hepatocytes that remove harmful substances and oxygen from the blood. The harmful substances are broken down by the hepatocytes into less harmful substances that then re-enter the blood. The blood then runs to the central vein and the central veins from the lobules to form hepatic vein. Kupffer cells attached to the walls of the sinusoids remove bacteria and break down old red blood cells.
What do hepatocytes produce
Bile and secrete it into tubes called bile canaliculi. These tubes drain into bile ducts from all the lobules eventually connect up and leave the liver.
What does the central vein look like under a light microscope
Large white circular shape
What does the sinusoids look like under a light microscope
White spaces
What does the hepatocytes look like under a light microscope
Cells that radiate from the hepatocytes with red dots as nuclei
What are the functions of the kidney
To excrete waste products
Regulate water potential of the blood
How does the kidney excrete waste products
- Blood enters through the renal artery and passes through capillaries in the cortex
- As blood passes through substances are filtered out of the blood and into long tubules (ultrafiltration)
- Useful substances (glucose) are reabsorbed back into the blood from the tubules in the medulla and cortex (selective reabsorption)
- The remaining unwanted substances such as urea pass along the tubules, along the ureter to the bladder where they’re expelled as urine
- Filtered blood passes out through the renal vein
What are nephrons
Long tubules along with the bundles of capillaries where blood filtered are called nephrons. There are around 1 million in each kidney
