The Kidneys/Controlling Water content

• How does water enter the body?

  • Through food and drink
• Name three ways water leaves the body

  • Sweating
  • Exhaling through lungs
  • Through kidneys in urine
• What is the role of the kidney?

  • Filter out waste substances like urea
  • Regulate water and ion levels
  • Excretion of urine
• How does the kidney make urine?

  As blood moves through body it filters out waste products

  It then selectively absorbs useful substances like ions,glucose and water
• How are ions processed by Kidneys?

  • Ions are taken in by food and lost by sweating
  • Kidneys reabsorb certain amounts back into blood after it has been filtered out to ensure concentration is maintained
• How is urea filtered out of the body?

  • Can be lost through the Kidneys or sweat
  • The liver deaminates amino acids from protein digestion to form ammonia
  • Ammonia is toxic so body converts it into urea and the kidneys filter it out
• How does the process of filtration work in the kidneys?

  • blood enters kidneys and small molecules like water, ions and urea are filtered out
  • The kidney now selectively reabsorbs essential molecules like water, glucose and ions into the blood stream
  • Urea, excess water and ions that are left behind eventually form urine which goes to bladder for removal
• How do the Kidneys maintain water balance in the body?

  • Blood enters the kidneys and molecules like water,ions and urea are filtered out
  • The kidneys then absorb the right amount of water needed in the body
  • When the body is dehydrated more water is absorbed into the blood via kidney
  • When the body is over-hydrated less water is absorbed allowing more to leave the body as urine
• What is ADH?

  • Hormone released by pituitary gland into kidneys to control loss of water as urine
• How does ADH work when blood is too concentrated?

  • Receptor in brain detects blood is too concentrated and pituitary gland releases ADH
  • It travels to kidney tubules through blood stream
  • Increased amount of ADH causes kidney tubules to be more permeable so more water moves back into blood stream
  • This results in smaller volume of more concentrated urine and blood becoming less concentrated
• How does ADH work when the blood is too dilute?

  • Receptors in brain detect this and pituitary gland releases ADH
  • ADH goes to kidney tubules and causes them to be less permeable so less water is reabsorbed in to the blood
  • As a result the volume of urine is larger and less concentrated whilst the blood is less dilute
• What is kidney failure + consequences?

  • When kidneys stop working
  • Leads to a build up of harmful substances which can lead to death
• What are the two types of kidney treatments?

  • Dialysis
  • Kidney transplant
• Describe how dialysis works

  • Patients blood is passed in and out of a dialysis machine
  • There is a dialysis fluid in the machine separated from the patients blood via a semi permeable membrane (only lets small molecules through)
  • Dialysis fluid has the same concentration of ions as normal blood
  • There is a concentration gradient between the fluid and the patients blood so if a patient has a higher ion concentration this diffuses out of their blood and to the dialysis fluid
  • Their ion concentration is now back to normal
• What do kidney transplants do and how are they obtained?

  • They provide patients with a healthy kidney
  • Transplanted from people who died suddenly or donors
• What is an advantage of Kidney dialysis?

  • Acts as artificial kidney to keep people alive whilst they wait for transplant
• What is an advantage of Kidney transplants?

  • Cheaper than dialysis and doesn't require regular patient visit to hospital
• What are some cons of Kidney transplants?

  • Can be rejected by patient's immune system
  • Requires use of immunosuppressants which can leave patients vulnerable to other diseases
  • They don't last forever
• What is a disadvantage of dialysis?

  • Possibility of blood clots
  • Expensive and time consuming
  • Requires strict diet
  • Build up of harmful substances between treatments can leave patient feeling ill