The Kidney

Question 1

What is the function of the kidneys?

Answer 1

Regulate water content of the blood

Excretion - removal of the waste products of metabolism (e.g. urea from the breakdown of proteins)

Question 2

What is the role of the Bowman’s capsule?

Answer 2

To filter the blood flowing through the capillary knot, only allowing small molecules to pass out into the filtrate

Question 3

Which molecules are able to be filtered out of the blood and into the Bowman’s capsule?

Answer 3

Small molecules
- glucose
- salts
- urea
- water

Question 4

How is the pressure generated to filter the blood in the capillary knot?

Answer 4

The arteriole carrying blood away from the capillary knot is narrower than the arteriole carrying blood in

Question 5

Where does selective reabsorption of glucose, salts and water occur in the kidney?

Answer 5

tubule

Question 6

Where does selective reabsorption of glucose, salts and water occur in the kidney?

Answer 6

Water, urea and excess salts, which were not selectively reabsorbed in the tubules

Question 7

What does urine consist of?

Answer 7

-Water
-urea
-excess salts
which were not selectively reabsorbed in the tubules

Question 8

Where is urine stored?

Answer 8

Urine passes out of the kidney via the ureters and is stored in the bladder

Question 9

What does glucose in the urine indicate?

Answer 9

Diabetes
The level of glucose is too high for all of it to be selectively reabsorbed

Question 10

How do you test for glucose in the urine?

Answer 10

Add Benedict’s reagent and heat strongly
A positive result is a colour change from blue to brick-red

Question 11

What reagent is used to test for protein in the urine?

Answer 11

Biuret reagent
A positive test shows a colour change from blue to violet

Question 12

What does the presence of blood, cells or protein in the urine indicate?

Answer 12

Kidney disease
These molecules are normally too large to be filtered out of the blood in a healthy kidney

Question 13

How do kidneys regulate the water content of the blood?

Answer 13

They reabsorb more water from the filtrate if the blood water content is too low, producing concentrated urine

They reabsorb less water if the water content of the blood is too high, producing dilute urine

Question 14

What is the role of the anti-diuretic hormone (ADH) in water regulation?

Answer 14

When a reduction in the water content of the blood is detected by the brain, ADH is secreted causing the kidney to reabsorb more water, leading to the urine becoming more concentrated

Question 15

What happens in the kidneys if the water content of the blood is too high?

Answer 15

ADH secretion stops, the kidneys reabsorb less water and the urine becomes more dilute

Question 16

Know how a dialysis machine works

Answer 16

A selectively permeable membrane separates the patient’s blood and the dialysis fluid
Substances with levels above the normal diffuse across into the dialysis fluid
All the urea diffuses across

Question 17

When and why is dialysis carried out?

Answer 17

Kidney failure results in substances not being able to be filtered out of the blood

The concentration of substances in the blood is restored to normal levels

Question 18

How do substances pass out of the blood into the dialysis fluid?

Answer 18

Diffusion

Question 19

What is the concentration of glucose and salts within the dialysis fluid?

Answer 19

The same as normal blood levels of glucose and salts

Excess amounts in the blood will diffuse across into the dialysis fluid

Question 20

What is the concentration of urea in the dialysis fluid?

Answer 20

Zero - so that all of the urea in the blood will diffuse into the dialysis fluid

Question 21

What is the significance of the counter-current mechanism in a dialysis machine?

Answer 21

The blood and dialysis fluid flow in opposite directions ensuring that a diffusion gradient for urea is always maintained

Question 22

What must be carried out on a donor prior to a kidney transplant?

Answer 22

Tissue typing to ensure the cells in the donor kidney tissue are similar to those of the patient, reducing the risk of rejection

Question 23

Why are close family members the preferred donors?

Answer 23

They are more likely to have kidneys with tissue similar to the recipient

Question 24

What is given to the recipient of the donor kidney to minimise risk of rejection?

Answer 24

Drugs which suppress the immune system - immunosuppressants

Question 25

What causes rejection of the donor kidney?

Answer 25

The donor kidney cell antigens trigger an immune response
The patient’s lymphocytes produce antibodies, destroying the donor kidney cells

Question 26

What are the disadvantages of kidney transplants?

Answer 26

-Shortage of donors
-Risk of surgery
-Risk of rejection of donor kidney
-Risk to health from immunosuppressants

Question 27

What are the benefits of kidney transplants?

Answer 27

-Freedom to eat a normal diet
-No need to spend lengthy periods in hospital every week
receiving dialysis
-Will live a fuller life for longer than a patient on dialysis

Question 28

What are the disadvantages of dialysis?

Answer 28

-Must follow a carefully controlled diet
-Many hours per week spent attached to a dialysis machine
-Dialysis very expensive
-Dialysis not a long term option

Question 29

What are the advantages of dialysis?

Answer 29

-Patient can be kept alive while waiting for a kidney
transplant
-It does not involve major surgery