B3.3.1 Removal of waste and water control

Question 1

What is homeostasis?

Answer 1

The regulation of the body’s constant internal environment.

Question 2

What two waste products have to be constantly removed from the body?

Answer 2

Carbon Dioxide

Urea

Question 3

How is carbon dioxide produced in the body?

Answer 3

It is a product of aerobic respiration

Question 4

How is urea produced in the body?

Answer 4

It is produced in the liver when excess amino acids are broken down.

Question 5

How is carbon dioxide removed from the body?

Answer 5

Through the lungs when we breathe out.

Question 6

How is urea removed from the body?

Answer 6

The kidneys remove it from the blood and make urine which is temporarily stored in the bladder.

Question 7

How do our bodies take in water?

Answer 7

When we eat and drink.

Question 8

How do our bodies lose water?

Answer 8

Sweat, faeces, urine and when we breathe out.

Question 9

What would happen if the water or ion content of the body was wrong?

Answer 9

Too much water may move into or out of our cells, causing them to become damaged.

Question 10

What organ maintains the balance between the water we take in and the water we lose?

Answer 10

The kidneys.

Question 11

How does a healthy kidney produce urine?

Answer 11

• First filtering the blood
• Reabsorbing all the sugar
• Reabsorbing the dissolved ions needed by the body
• Reabsorbing as much water as the body needs
• Releasing urea, excess ions and water as urine.

Question 12

What happens when the water level of our blood plasma is low?

Answer 12

More water is reabsorbed back into the blood and the urine becomes more concentrated.

Question 13

What happens when the water level of our blood plasma is high?

Answer 13

Less water is reabsorbed back into the blood and the urine becomes less concentrated.

Question 14

What are the consequences of kidney failure?

Answer 14

The levels of water and ions cannot be regulated and the levels of urea build up in the body.

Question 15

What are the two ways of treating kidney failure?

Answer 15

Kidney dialysis

Transplant

Question 16

What does a kidney dialysis machine do?

Answer 16

A person’s blood flows between partially permeable membranes.

Removes most of the urea from the patients blood.

Maintains the water/ion balance in the blood.

Question 17

Why does dialysis fluid contain the same concentration of useful substances (glucose, ions) as normal blood?

Answer 17

So that if the blood contains the correct amount of useful substances it does not lose or gain any as there is no concentration gradient.

If the patients blood contains a low/high concentration of useful substances there is a concentration gradient and the substances diffuse into/out of the blood.

Question 18

Why does a dialysis fluid not contain urea?

Answer 18

So that there is a concentration gradient between the fluid and the blood and the urea diffuses out of the blood into the fluid.

Question 19

What does a kidney patient have to do between dialysis sessions?

Answer 19

Monitor their diet carefully

Avoid high salt and high protein content as excess amino acids are broken down into urea.

Question 20

What happens in a kidney transplant?

Answer 20

A diseased kidney is replaced with a healthy one from a donor.

Question 21

What is organ rejection?

Answer 21

When the body’s immune system sees the transplanted organ as alien and attacks it.

Question 22

Why does organ rejection happen?

Answer 22

Because the person’s immune system detects that the antigens on the cells of the organ are different to the rest of the body and so it attacks the ‘foreign’ cells.

Question 23

What is tissue typing?

Answer 23

Only giving the kidney to patients who have antigens that are very similar to the antigens of the donor kidney.

Question 24

What is the problem with tissue typing?

Answer 24

It can lead to long waits for a transplant for many kidney patients while compatible donors become available - during which time patients must undergo dialysis.

Question 25

What are immuno-suppressant drugs?

Answer 25

Drugs that suppress the immune system, greatly reducing the immune response against the donor kidney.

Question 26

What is the problem with immuno-suppressant drugs

Answer 26

They also suppresses the immune response against pathogens which enter the body, increasing the risk of getting infections.

Question 27

What is the advantage of kidney dialysis over transplants?

Answer 27

It is available for all patients and the patient does not need to take immuno-suppressant drugs.

Question 28

What is the advantage of transplants over kidney dialysis?

Answer 28

The patient can live a normal life without having to watch what they eat and drink and it is cheaper in the long run for the NHS.