Maintaining Water and Nitrogen balance in our bodies

Question 1

How is water lost in the body?

Answer 1

• Via lungs during exhalation
• Water, ions and urea are lost from skin whilst sweating
• Excretion via kidneys gets rid of urea, water and ions

There is no control of water loss through sweating or exhalation

Question 2

How are proteins digested?

Answer 2

Digestion of proteins

• Forms excess amino acids
• Which are deaminated to form ammonia
• Ammonia is toxic and so it is immediately turned to urea for safe excretion

Question 3

How do the kidneys maintain water balance in the body?

Answer 3

• Filter the blood and selectively reabsorb useful substances
• Such as glucose, some ions and water

Question 4

What is the effect of ADH on the kidney tubules?

Answer 4

• Pituitary gland releases ADH
• When blood is too concentrated ( ie. too little water)
• So more water is usefully absorbed back into the bloodstream from the kidney tubules
• This is controlled negative feedback

Question 5

What is kidney dialysis?

Answer 5

• Patient attached to artificial machine to act as a kidney

- Can be used until a transplant is ready

Question 6

Disadvantages of Kidney Dialysis?

Answer 6

• Expensive
• Time consuming
• Patients musty follow very strict diet
• Only work for a limited time for a patient

Question 7

Advantages of Kidney Dialysis?

Answer 7

• Greatly reduces levels of urea

- Correct water / ion balance maintained or restored

Question 8

How does kidney dialysis work?

Answer 8

• Blood is removed for cleaning
• Pumped through machine where dialysis fluid is removed
• Clean dialysis fluid in
• Clean blood in

Question 9

Kidney transplants

Answer 9

Adv -

• Patients can live a more normal life
• Cheaper for NHS overall

Disadv -

• Shortage of organ donors
• Only lasts 8-9 years on average
• Operation carries risk