Renal physiology

Question 1

What are the three layers of the filtration barrier in the Glomerulus?

Answer 1

Podocytes (Visceral epithelium)
Glomerular basement membrane
Fenestrated capillary endothelium

Question 2

What do the Podocytes do to the arteriole? What is the part of the podocyte that does this called?

Answer 2

Wrap around them
Pedicle (Foot Process)

Question 3

Where are the Juxtaglomerular cells + macula densa found? Describe the structure

Answer 3

Hilum of every Glomerulus
Modified muscular layer of afferent arteriole

Question 4

What is the rate of flow to the Kidney?

Answer 4

~1L/min

Question 4

What are the Three functions of Juxtaglomerular cells + Macula densa?

Answer 4

Renal blood flow
Glomerular filtration
Renin release

Question 4

What is the Sequence of Blood vessels from the Aorta to the Glomerulus? (6)

Answer 4

1. Renal artery
2. Segmental arteries
3. Interlobar arteries
4. Arcuate arteries
5. Interlobular arteries
6. Afferent arterioles

Question 5

What is the definition of Glomerular filtration?

Answer 5

Passage of fluid from the blood into the Bowman’s space to form the filtrate

Question 6

What are the five factors that determine Glomerular filtration?

Answer 6

1. Pressure
2. Size of molecule
3. Charge
4. Rate of blood flow
5. Protein binding

Question 7

What pressure favours filtration? Which two pressure oppose glomerular filtration?

Answer 7

Glomerular capillary BP (favours)
Fluid pressure in Bowman’s space +
Osmotic forces due to protein (oppose)

Question 8

What can pass through filtration barrier + 4 examples? What weight

Answer 8

Small molecules and ions up to 10kDa
e.g. Glucose, uric acid, potassium and creatine

Question 9

What is the fixed charge of the Glomerular Basement membrane? What does this repel? 4 examples?

Answer 9

Fixed negative charge
Repels negatively charged ions
Albumin, phosphate, sulfate and organic anions

Question 10

Why can Albumin not easily pass into the glomerulus? What does this mean for other subtances?

Answer 10

Negatively charged and weight of 66kDa
Affects substances that bind to proteins

Question 11

How is GFR calculated? What is the equation?

Answer 11

Measuring excretion of marker (M)
GFR= Urine conc of marker x urine flow rate/ Plasma conc of marker

Question 12

What is the normal GFR? What muscle marker is used?

Answer 12

125 ml/min
Creatinine (Muscle metabolite)

Question 13

What are three properties of a good GFR marker?

Answer 13

1. Freely filtered
2. Not secreted/absorbed
3. Not metabolised

Question 14

What else is used as a marker to test GFR? Why is it worse than creatinine?

Answer 14

Cystatin C
Can be metabolised

Question 15

What is the gold standard glomerular filtration marker? Why is it not used alot?

Answer 15

Inulin
Impractical

Question 16

What are 7 ways in which Renal blood flow is regulated?

Answer 16

1. Renal autoregulation
   2.Neural regulation
2. Hormonal regulation (RAAS)
3. Intrarenal baroreceptors
4. Extracellular fluid volume
5. Blood colloid osmotic pressure
6. Inflammatory mediators

Question 17

Which three Hormones decrease GFR?

Answer 17

Norepinephrine
Epinephrine
Endothelin

Question 18

Which 2 hormones decrease GFR?

Answer 18

NO
Prostaglandins

Question 19

Effect of Vasoconstriction of the afferent and efferent arteriole on the RBF and GFR?

Answer 19

Decreased RBF and GFR

Question 20

Effect of Vasodilation on RBF and GFR

Answer 20

Increases RBF and GFR