Kidney Structure and Function

Question 1

What are the functions of the kidneys?

Answer 1

Balance of water, salt and acid-base balance
Maintenance of plasma volume and osmolarity
Excretion of metabolic waste products and foreign compounds
Secretion of renin and erythropoietin
Conversion of vitamin D to calcitriol

Question 2

What are the functions of the substances produced by the kidneys?

Answer 2

Renin = controls arterial blood pressure
Erythropoietin = role in red blood cell production 
Calcitriol = absorbs calcium in the GI tract

Question 3

What is the primary function of the kidneys?

Answer 3

To regulate the volume, composition and osmolarity of body fluids

Question 4

What is the waste product produced by the kidneys?

Answer 4

Urine

Question 5

What is the functional unit of the kidney?

Answer 5

Nephron = carries out filtration, reabsorption and secretion

Question 6

What are the two types of nephron?

Answer 6

Juxtamedullary (20%) and cortical (80%)

Question 7

What is urine?

Answer 7

Modified filtrate of blood

Question 8

What are some features of the kidney that show its specialisation for its function?

Answer 8

Kidney incorporates filtration system, rich blood supply and mechanism for urine production

Question 9

What are the renal processes involved in producing urine?

Answer 9

Glomerular filtration, tubular reabsorption and tubular secretion

Question 10

How much of the plasma that enters the glomerulus is filtered?

Answer 10

20% = remaining 80% leaves through the efferent arteriole

Question 11

How is the renal tubule like a conveyor belt?

Answer 11

Substances are added or removed as the urinary filtrate moves from the proximal to distal end

Question 12

What are filtration and secretion equal to?

Answer 12

Reabsorption and excretion (for any substance, filtration + secretion = reabsorption + excretion)

Question 13

How can the rate of excretion be calculated?

Answer 13

Rate of filtration + rate of secretion - rate of reabsorption

Question 14

How is the movement of substances within the kidneys described?

Answer 14

In terms of concentration x flow

Question 15

What is the rate of filtration?

Answer 15

Mass of a substance filtered into the Bowman’s capsule per unit time

Question 16

How can rate of filtration be calculated?

Answer 16

Plasma concentration of substance x glomerular filtration rate

Question 17

How can the rate of excretion be calculated using urine values?

Answer 17

Urine concentration of substance x urine production rate

Question 18

How can the rate of reabsorption be calculated?

Answer 18

Rate of filtration x rate of excretion

Question 19

What has happened if rate of filtration is greater than rate of excretion?

Answer 19

Net reabsorption of that substance has occurred

Question 20

How can rate of secretion be calculated?

Answer 20

Rate of excretion - rate of filtration

Question 21

What has happened if rate of filtration is less than rate of excretion?

Answer 21

Net secretion of that substance has occurred

Question 22

Are rate of filtration and rate of excretion easy to measure?

Answer 22

Yes

Question 23

What do rate of reabsorption and secretion reflect?

Answer 23

Tubular modification of filtrate = obtained as the difference between filtration and excretion