Excretory Organs

• Lungs


  Excrete CO2, water vapour and heat
• Kidneys & Bladder


  • Kidneys secrete urine and store it in the bladder
  • Urine consists of water, salts and nitrogenous waste(urea & uric acid)
• Liver & Gut 


  • Liver excretes urea and bile
  • Urea goes in the blood to the kidneys and is excreted in urine.
  • Bile passes into the small intestine and is excreted in faeces.
• Skin

  • Excretes sweat
  • Sweat consists of salts, water and urea.
• Origins of waste products

  • CO2 is a by product of cellular respiration
  • Excess water is from cellular respiration and the intake of fluids.
  • Urea is from the liver when it breaks down amino acids.
  • Uric acid is from the metabolism of nucleic acid.
  • Bile is from the breakdown of haemoglobin.