Renal Function

Question 1

Name the 2 types of nephrons. Explain the difference

Answer 1

Cortical (in cortex)

Juxtamedullary (long loops into medulla)

Question 2

Juxtaglomerular apparatus (between glomerular and thick ascending limb). Name the functions.

Answer 2

1. autoregulation

2. renin release (salt & water balance)

Question 3

Describe the two capillary beds in series.

Answer 3

1. Glomerulus (high hydrostatic pressure- filtration)

2. Peritubular capillaries (low pressure- reabsorption, secretion)

Question 4

What is the vasa recta?

Answer 4

Thin walled capillary that follows the loop of Henle

Question 5

Describe the formula for urinary excretion.

Answer 5

Urinary excretion = filtered - reabsorbed + secreted

Question 6

Cardiac output of kidneys?
Filtration fraction?
Glomerular filtration rate?

Answer 6

25% cardiac output
20% of plasma is filtered
120 ml/min GFR

Question 7

Which arteriole is smaller? What drives filtration?

Answer 7

Efferent is smaller than afferent. hydrostatic pressure is the driving force.

Question 8

Where is glucose reabsorbed?

Answer 8

Proximal tubule, provided it doesn’t exceed the maximum reabsorptive capacity.

Question 9

Define GFR

Answer 9

Volume of fluid entering Bowman’s capsule per unit time.

Question 10

What cells make up bowman’s capsule?

Answer 10

Epithelial cells
Podocytes
Mesangial cells - structural support

Question 11

What separates podocytes from endothelium?

Answer 11

basement membrane

Question 12

What are mesangial cells and function?

Answer 12

structural support

Question 13

What are the gaps between endothelial cells called?

Answer 13

fenestrations

Question 14

Gaps in between podocytes called?

Answer 14

slit pores

have foot-like processes called pedicels

Question 15

What are on basement membranes that repel negatively charged things? Why is this important?

Answer 15

glycoproteins. repels negatively charged things like proteins
aids filtration

Question 16

Normally, all constituents in plasma filtered except what 2 things?

Answer 16

size and charge

RBCs +cells and plasma proteins

Question 17

3 symptoms of nephrotic syndrome

Answer 17

proteinuria
hypoalbuminaemia
oedema

Question 18

What kind of modules pass through the bowman’s capsule easily?

Answer 18

water

small positively charged molecules passes through easily

Question 19

Forces influencing filtration - name 4. Which one is negligible and why? What is the driving force?

Answer 19

Capillary hydrostatic pressure (driving force)
Colloid osmotic pressure
Bowman’s space pressure
Net filtration pressure

Question 20

Give an example where Kr (filtration coefficient) would change and how it changes.

Answer 20

decrease in kidney diseases, no glomeruli or change in membrane thickness/pore area.

Question 21

What is PGC? If afferent arteriole constricts, how does PGC change? What if the efferent constricts? And dilation of each.

Answer 21

Pressure within glomerular capillaries
arteriole constricts - reduce PGC (GFR drops)
efferent constricts - increase PGC (GFR up)

Question 22

How does GFR change if filtration forces change? Colloid osmotic pressure?
Bowman’s capsule?
Kr?

Answer 22

Colloid osmotic pressure (increases = dec in GFR)
Bowman’s space pressure (dec in GFR)
Kr (increase = inc in GFR)

Question 23

What is the gold standard of measuring GFR?

Answer 23

Measure inulin
freely filtered, not reabsorbed, not secreted, not met by kidney, no effect on renal function
easily measured

Question 24

Easier way of measuring eGFR? Equation?

Answer 24

creatinine clearance as inulin needs to be injected.
gives an estimation
eGFR = [U]CR x V
/[P]CR

U-urine conc
P-plasma conc
V-urine flow rate

Question 25

In what populations should the eGFR equations not be used for?

Answer 25

Other equations: Cockroft-Gault, MDRD, CKD-EPI

Shouldn’t be used in children, malnourished, pregnancy, acute renal failure or oedema.