Introduction to Excretion

Question 1

What is Excretion?

Answer 1

• The removal of waste products of metabolism from the body (from chemical reactions in the cells)

Question 2

What are the main excretory products in mammals?

Answer 2

• Carbon dioxide
• Nitrogenous waste
• Blue Pigments

Question 3

How is carbon dioxide excreted?

Answer 3

• Waste product of cellular respiration, excreted via the lungs

Question 4

How is Nitrogenous waste excreted?

Answer 4

• contains nitrogen
• all mammals produce urea in the liver, which is then passed to the kidneys to be excreted as urine.

Question 5

Nitrogenous waste - what do fishes excrete?

Answer 5

• Ammonia

Question 6

Nitrogenous waste - what do birds and insects excrete?

Answer 6

• uric acid

Question 7

How are Blue pigments excreted?

Answer 7

• produced from the break down of haemoglobin in old RBC in the liver
• These pigments are passed to the gall bladder for temporary storage, before leaving the body as bile via the intestines
  (these pigments give faeces their colours)

Question 8

Why is the release of faeces from the body called egestion and not excretion?

Answer 8

• it has never been involved in metabolic reactions in the cells, it is simply undigested food