B12 Kidneys (homeostasis in action)

Question 1

how do the kidneys remove excess water and mineral ions?

Answer 1

blood enters the kidney through an artery and the kidneys remove the waste products.
the waste products leave the kidneys as urine. the urine is stored in the bladder.
the blood then leaves the kidney in a vein

Question 2

how do the kidneys control the levels of waste molecules in the blood?

Answer 2

blood passes through capillaries where small molecules are filtered out of the blood into a tube
then, some of the molecules are reabsorbed back into the blood
the waste products are then removed from the kidneys as urine

Question 3

how does the body deal with excess amino acids?

Answer 3

the liver breaks down the excess amino acids and produces ammonia
this is called deamination
the ammonia is then converted to urea and excreted by the kidneys

Question 4

what hormone is released when the level of water in the blood falls?

Answer 4

the hormone ADH is released by the pituitary gland

Question 5

what does ADH do?

Answer 5

it travels to the kidneys and causes the tubules in the kidneys to become more permeable to water (allow more water out)
this means the kidneys reabsorb more water and the levels of water return to normal

Question 6

what happens when the blood becomes too dilute?

Answer 6

the pituitary gland stops producing ADH
this causes the kidneys to reabsorb less water and produce more urine
this means the concentration of water returns back to normal

Question 7

how does kidney dialysis work?

Answer 7

the patient’s blood passes over a semi-permeable membrane
this allows urea, ions and water to pass through but not larger molecules such as proteins or blood cells to go through
on the other side of the membrane there is dialysis fluid
this creates a concentration gradient of urea so the urea passes into the dialysis fluid

Question 8

what does dialysis fluid contain?

Answer 8

the normal concentrations of water and mineral ions but no urea

Question 9

what are the disadvantages of kidney dialysis?

Answer 9

patients have to visit the hospital several times a week
they have to eat a controlled diet so they do not produce too much urea
expensive long term

Question 10

what are some disadvantages of kidney transplants?

Answer 10

the kidney may be rejected by the patient’s immune system - they have to take anti-rejection drugs
shortage of donors

Question 11

what are the ways that the body loses water?

Answer 11

via the lungs when we exhale
when we sweat
via kidneys in urine