Kidneys

• What do the kidneys do?

  Filter blood and remove waste products.
• What is selective reabsorption?

  Process in the kidneys where certain substances are reabsorbed from the filtrate back into the bloodstream.
• What is selectively reabsorbed by the kidneys?

  All of the glucose, some ions and water, no urea
• How is urea produced?

  Deamination: Process in the liver where excess proteins are converted to fats and carbohydrates. Ammonia is produced as a waste product and is toxic so it is converted into urea and then filtered out of the blood through the kidneys.
• How is water lost?

  • Through exhalation
  • Sweat
  • Urine
• Which hormone controls the concentration of urine?

  Antidiuretic hormone (ADH)
• Which gland releases ADH?

  Pituitary gland
• What happens if water content is too high?

  • Receptor detects the content is too high
  • Coordination centre receives this information and coordinates a response
  • Pituitary gland releases less ADH so less water is reabsorbed from the kidney tubules
• What happens if water content is too low?

  • Receptor detects the content is too low
  • Coordination centre receives this information and coordinates a response
  • Pituitary gland releases more ADH so more water is reabsorbed from the kidney tubules
• What happens if the kidneys do not work properly?

  Water substances build up in the blood and you lose the ability to control level of ions and water content resulting in death
• How can kidneys be treated?

  • Dialysis
  • Kidney Transplant
• How does a dialysis machine work?

  • Blood flows between partially permeable membranes, surrounded by dialysis fluid
  • Permeable to ions and waste substances but not big molecules like proteins
  • Blood goes back into person
• What does the dialysis fluid contain?

  Same concentration of dissolved ions and glucose as normal blood.

  This is important as it means that useful dissolved ions and glucose won't be lost from the blood during dialysis
• What are the disadvantages of dialysis?

  • Patients have a dialysis session 3 times a week (3-4 hours each)
  • Blood clots or infection
  • Expensive
• What is the risk of kidney transplants?

  Kidney may be rejected from the body