Function & anatomy

Question 1

What is the function of the kidneys?

Answer 1

• Regulation of fluid & electrolytes
• Excretion of waste
• Acid-base balance
• Long-term regulation of blood volume
• Production (Vit D & EPO)

Question 2

What is the gross drainage of the kidney?

Answer 2

• Nephron
• Renal calculi
• Pelvis
• Ureter

Question 3

How much filtrate is produced per hour?

Answer 3

7L - with only 100ml/hr urine

Question 4

What receptors are found on all basement cell membranes of the kidney?

Answer 4

Na/K Pump

Question 5

Where is EPO produced?

Answer 5

Paratubular cells

Question 6

How is EPO produced?

Answer 6

• In response to drop in O2 levels in renal tissues
• Stimulate bone marrow to increase differentiation of precursors and therefore RBC

Question 7

How is Vit D produced?

Answer 7

• Cholecalciferol produced from precursors
• Converted to 25-hydroxycholecalciferol in liver
• Converted to 1,25-dihydroxycholecalciferol in kidneys

Question 8

What is the function of Vit D

Answer 8

• Inc Ca2+ (GI absorption, inc renal reabsorption, stim bone reabsorption)

Question 9

What stimulates and inhibits Vit D production?

Answer 9

Stim: PTH
Inhib: High phosphate

Question 10

How does the kidney allow for large amounts of filtration per day?

Answer 10

• High pressure filtration
• Filtration channels in podocytes
• Negatively charged membrane (cations and uncharged particles pass easily)

Question 11

What does glomerular filtrate contain?

Answer 11

• Water
• Na, HCO3, glucose, amino acids
• In same conc as plasma

Question 12

What should not be found in glomerular filtrate?

Answer 12

• Protein
• Cells

Question 13

How is the filtrate initially produced at the Bowman’s capsule?

Answer 13

• Hydrostatic pressure 40mmHg
• Oncotic pressure 26mmHg
• Net filtration pressure 14mmHg into filtrate

Question 14

What is the filtration fraction?

Answer 14

The proportion of renal plasma flow that is filtered
- Determines how much filtrate can be produced

Question 15

What are the characteristics of a good marker of GFR?

Answer 15

• Readily filtered
• Not metabolised/reabsorbed/ secreted
• Filtration rate = rate of excretion

Question 16

What is the glomerular filtration rate?

Answer 16

120-125ml/min

Question 17

What are examples of GFR markers?

Answer 17

• Creatinine: produced at steady state from muscle breakdown, some overestimation
• Inulin: Freely filtered, more accurate, not naturally occurring
• Cystatin C: Produced by all cells

Question 18

What are the auto regulation mechanisms?

Answer 18

• Myogenic: Stretch response
• Tubulo-glomerular feedback: Adenosine, PGE2, Angiotensin II

Question 19

How does Adenosine act on the kidney?

Answer 19

• Released in normal hydrated state from macula densa
• Constricts afferent arteriole
• Reduces GFR
• Inhibits renin release
• Inhibited itself by fall in filtration flow- allows dilatation of afferent arteriole

Question 20

How does PGE2 work?

Answer 20

• Produced in DCT in response to fall in filtration flow
• Dilates afferent arteriole to maintain blood flow
• Inhibited by NSAIDs

Question 21

How does angiotensin II work on the kidneys?

Answer 21

• Produced by RAAS
• Constricts efferent arteriole to maintain capillary pressure & GFR