Excretion and kidneys

By the end of this lesson you should be able to:

  • State that urea is formed in the liver from excess amino acids
  • State that carbon dioxide is excreted through the lungs
  • State that the kidneys excrete urea and excess water and salts
  •  Explain that the volume and concentration of urine produced is affected by water intake, temperature and exercise
  •  Identify on drawings, diagrams and images, the ureters, bladder and urethra
  • Explain the need for excretion, limited to toxicity of urea and carbon dioxide
  • Outline the structure of the kidney, limited to the cortex, medulla and ureter
  • Outline the structure and functioning of a kidney tubule, including:                                              -the role of the glomerulus in the filtration from the blood of water, glucose, urea and salts
  •         – the role of the tubule in the reabsorption of all of the glucose, most of the water and some salts back into the blood, leading to the concentration of urea in the urine as well as loss of excess water and salts (details of these processes are not required)


  1. Read pages 1 and 2 from this site. Pay attention to the different structures of the urinary system
  2. Play this animation. Follow instructions to understand how kidneys work
  3. What happens to the different substances along the kidney tubules. Click on them to find out!
  4. Complete the revision exercises given in class.

Enjoy! 🙂



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