The liver and excretion

Question 1

What is excretion

Answer 1

Excretion is the removal of waste products of metabolism from the body

Question 2

what are some examples of excretory organs that remove CO2

Answer 2

In mammals: lungs

In Fish: gills

Question 3

What is the livers role

Answer 3

To break down excess amino acids

Question 4

Why does the liver breakdown excess amino acids

Answer 4

• This is because Nitrogenous substances can’t be stored in the body.
• So excess amino acids damage the body: so they must be used by the body, broken down or excreted

Question 5

What is deamination

Answer 5

When amino groups are removed from excess amino acids- forming ammonia and organic acids

Question 6

Process: how are excess amino acids broken down

Answer 6

1) The excess amino acids first undergo deamination

2) The organic acids produced from deamination, are then respired to give ATP.
OR they are converted to carbohydrates to be stored as glycogen.

3) Ammonia combines with CO2 in the ornithine cycle to create urea
- Urea is then released from the liver into the blood and the kidneys filter the blood and remove the urea as urine.

Question 7

As well as amino acids, what else does the liver break down ?

Answer 7

Alcohol, paracetamol and insulin

• insulin is a hormone that controls blood glucose concentration, excess insulin causes problems with blood sugar levels
• excess paracetamol can lead to liver and kidney failure

Question 8

What is the process of the liver breaking down harmful substances called

Answer 8

Detoxification

Question 9

The liver breaks down ethanol into……………, which then breaks down into………………

Answer 9

1) ethanal

2) acetic acid

Question 10

what is cirrhosis of the liver

Answer 10

This is when liver cells die

and the scar tissue blocks blood flow

Question 11

what is glycogen stored as until it is needed for energy?

Answer 11

Its stored as granules in liver cells, until the glucose is needed for energy

Question 12

What does the hepatic artery do?

Answer 12

Supplies the liver with oxygenated blood from the heart

So the liver has a good supply of oxygen needed for respiration.

Question 13

What does the hepatic vein do?

Answer 13

Takes deoxygenated blood away from the liver

Question 14

What does the hepatic portal vein do?

Answer 14

Brings blood from the duodenum and the ileum, which is rich from products of digestion.

Any harmful ingested substances are filtered out and broken down straight away

Question 15

What does the bile duct?

Answer 15

Takes bile to the gall bladder where it is stored

Question 16

what are hepatocytes?

Answer 16

Cells that MAKE UP liver lobules (cylindrical structures radiating out of the central vein)

Hepatocytes remove harmful substances and oxygen from the blood.

Question 17

What do all the central veins connect to form?

Answer 17

It connects to form the hepatic vein

Question 18

How are is the hepatic portal vein and hepatic artery connected to the central vein?

Answer 18

Connected by capillaries called sinusoids

Question 19

where are Kupffer cells found and what do they do?

Answer 19

Kuppfer cells are attached to the walls of the sinusoids

They remove bacteria and break down old red blood cells

Question 20

What produces bile and where is it secreted into?

Answer 20

Hepatocytes produce bile and secrete it into the bile canaliculus, theses tubes then drain into bile ducts,

Eventually, all the bile ducts from all the lobules connect up and leave the liver.

Question 21

When observing a micrsope diagram of the liver

Answer 21

The large white circle is the central vein

The little white spaces are the sinusoids

The cells that radiate out from the central vein are the hepatocytes

The little black dots are nuclei

• microscopes slides normally stained with eosin or haematoxylin, to see the cells easier.