The kidneys: structure and function

Question 1

What are the 10 functions of the kidney?

Answer 1

1) Water balance
2) Salt balance
3) Maintenance of plasma volume
4) Maintenance of plasma osmolarity
5) Acid-base balance
6) Excretion of metabolic waste products
7) Excretion of exogenous foreign compounds
8) Secretion of renin (control of arterial blood pressure)
9) Secretion of erythropoietin (RBC production)
10) Conversion of vitamin D into active form (Calcitriol: Ca2+ absorption in GI tract)

Question 2

what is the main function of the kidney?

Answer 2

Regulates volume, composition and osmolarity of body fluids

Question 3

what is the balance concept of any substance?

Answer 3

Total ingested + Total excreted= Total produced + Total consumed

Question 4

how can kidneys contribute to the balance of these substances?

Answer 4

Kidneys role is the controlled excretion of ions such as Na+ and K+ and fluids such as urine to maintain constant internal environment

Question 5

what does the urinary system consist of?

Answer 5

• the kidneys (produce urine)

- the structures that store and carry the urine from the kidneys to the outside for elimination from the body

Question 6

what veins and arteries go into the kidneys?

Answer 6

Renal artery and renal veins

Question 7

what is the kidney made up of?

Answer 7

• renal cortex
• renal medulla
• renal pyramid
• renal pelvis
• ureter

Question 8

what is the appearance of the renal cortex and renal medulla?

Answer 8

Cortex- granulated

medulla- striated

Question 9

how much cardiac output does the kidneys receive?

Answer 9

25%

Question 10

what makes up the renal medulla?

Answer 10

renal pyramids

Question 11

where does urine travel in the kidneys?

Answer 11

urine comes from the renal pyramids and collects in the renal pelvis before draining into the ureter

Question 12

what is a nephron?

Answer 12

the functional unit of the kidney

Question 13

what are the functional mechanisms of the nephron?

Answer 13

1. Filtration
2. Reabsorption
3. Secretion

Question 14

what are the two parts to the renal artery?

Answer 14

• afferent arteriole

- efferent arteriole

Question 15

what is the tubular loop in a nephron?

Answer 15

loop of Henle

Question 16

what are the 2 types of nephron?

Answer 16

• juxtamedullary (20%)

- cortical (80%)

Question 17

what are the differences between juxtamedullary and cortical nephron?

Answer 17

• the juxtamedullary has a bigger loop of henle so it depends down further into medulla
• it doesn’t have peritubular capillaries but has vasa recta capillaries

Question 18

what is the difference in diameter between afferent and efferent arterioles/

Answer 18

the diameter of the afferent arteriole is larger than that of efferent arterioles

Question 19

what is the outer layer of bowman capsule made of?

Answer 19

Epithelial cells

Question 20

what is the inner layer of bowman capsule made of?

Answer 20

podocytes

Question 21

what is the juxtaglomerular apparatus?

Answer 21

where the distal tubule of the nephron passes between the efferent and afferent arterioles

Question 22

what are macula densa?

Answer 22

a group of specialised tubular cells that are salt sensitive to see its concentration in tubular fluid

Question 23

what is urine?

Answer 23

Modified filtrate of the blood

Question 24

what do the kidneys incorporate?

Answer 24

1. Filtration system
2. Rich blood supply
3. Mechanisms for urine modification
   i) reabsorption and ii) secretion

Question 25

what are the 3 basic renal processes?

Answer 25

1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion

Question 26

what happens to the plasma that enters the glomerulus?

Answer 26

• 20% is filtered

- 80% is not filtered and leaves through the efferent arteriole

Question 27

why is the renal tubule described as a “conveyor belt”?

Answer 27

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

Question 28

what is the equation for rate of excretion?

Answer 28

Rate of excretion = rate of filtration + rate of secretion - rate of reabsorption

Question 29

what is the rate of filtration of a substance?

Answer 29

[X}plasma x GFR ( glomerular filtration rate)

Question 30

what is the rate of excretion of a substance?

Answer 30

Rate of excretion of X = [X]urine x Vu (urine flow rate)

Question 31

what happens if rate of filtration is higher than rate of excretion?

Answer 31

net reabsorption of that substance has occurred

Question 32

what is the equation for rate of reabsorption?

Answer 32

Rate of reabsorption of X = rate of filtration of X – rate of excretion of X

Question 33

what is the equation for rate of secretion?

Answer 33

Rate of secretion of X = rate of excretion of X – rate of filtration of X