Genetics and the Kidney

Question 1

Renal blood flow

Answer 1

1litre / min

Question 2

Urine flow

Answer 2

1ml / min

Question 3

Blood supply to kidneys

Answer 3

Aorta, renal artery, interlobar artery, arcuate artery, interlobular artery, afferent arteriole, glomerular capillary + peritubular capillary

Question 4

Venous drainage

Answer 4

Efferent, peritubular capillaries, vasa recta, interlobular veins, arcuate veins, interlobar veins and renal vein

Question 5

Juxtaglomerular apparuatus

Answer 5

Located in hilum.
Juxtaglomerular cells + macula densa
Modified muscular layer of the afferent arteriole.

Autoregulation to maintain constant GFR and excretion of water and waste.

Via tubuloglomerular feedback and myogenic mechanism.

Question 6

Tubuloglomerular feedback

Answer 6

Constriction of afferent artery in response to increased filtration rate.

RAAS pathway.

Question 7

Myogenic

Answer 7

Increased bp stretches blood vessel wall.
Opens stretch-activated cation channels so membrane depolarises. This opens voltage gated calcium channels so increased intracellular calcium

Question 8

Myogenic

Answer 8

Increased bp stretches blood vessel wall.
Opens stretch-activated cation channels so membrane depolarises. This opens voltage gated calcium channels so increased intracellular calcium

Question 9

The filtration barrier

Answer 9

Podocytes (visceral epithelium)
Glomerular basement membrane
Fenestrated capillary endothelium.

Question 10

Factors determining filtration

Answer 10

Pressure
Size of molecule
Charge
Rate of blood flow
Protein binding

Question 11

Pressure

Answer 11

Glomerular capillary blood pressure favours filtration,

Fluid pressure in Bowman’s space and osmotic forces due to protein in plasma opposes filtration

Question 12

Size of molecule

Answer 12

Small molecules and ions up to 10 Kda can pass freely eg. glucose, uric acid, potassium, creatinine

Larger molecules increasingly restricted eg plasma proteins.

Question 13

Charge

Answer 13

Fixed negative charge in glomerular basement membrane repels in negatively charged anions

Question 14

Protein binding

Answer 14

Albumin is negatively charted so cannot easily pass into tubule.
Filtered fluid is essentially protein-free

Diabetes –> high glucose conc. damages filter membrane so proteins found in urine

Question 15

Glomerular filtration rate =

Answer 15

filtration volume per unit time (minutes)

Question 16

GFR =

Answer 16

KF (Pgc - Pbs_ - (Pi gc - Pi bs)

KF is the filtration coefficient (F is subscript)

Question 17

Sympathetic nervous innervation

Answer 17

Afferent arterioles receive sympathetic innervation

Constrict afferent arterioles, decreased renal blood flow, decreased GFR

Important in bleeding, shock, ischemia

Question 18

Constriction of what can increase GFR?

Answer 18

efferent arteriole

Question 19

Constriction of what can increase GFR?

Answer 19

efferent arteriole

Question 20

Dilation of what can increase GFR?

Answer 20

afferent arteriole

Question 21

How do NSAIDs decrease GFR?

Answer 21

Constrict afferent arterioles which decreases pressure

Question 22

How does ACE inhibitors decrease GFR?

Answer 22

Dilate efferent arteriole

Question 23

What is used to estimate GFR?

Answer 23

Creatinine

Question 24

Filtration fraction =

Answer 24

GFR / renal plasma flow

(GFR = approx. 120ml/min )

Question 25

Renal Clearance

Answer 25

The volume of plasma from which a substance is completely removed by the kidney per unit time (usually a minute)