Glomerular filtration

Question 1

What percentage of cardiac output do the kidneys receive?

What is cardiac output in litres / min?

Answer 1

22% of cardiac output

5l / min

Question 2

What is renal blood flow in ml/min?

What is renal plasma flow in ml/min?

Answer 2

Renal blood flow - 1100ml/min (haematocrit 40%)

Renal plasma flow - 660ml/min

Question 3

What percentage of renal plasma flow passes through the filtration barrier to form filtrate?

Answer 3

20%

Question 4

What is normal GFR in ml/min?

Answer 4

132 ml/min

> 90 ml/min

Question 5

What is the normal value of the filtration fraction as a percentage?

Answer 5

20% (20% of renal plasma flow passes through the filtration barrier)

Question 6

The glomerular capillary fenestrated endothelium blocks the filtration of which one component of blood?

Answer 6

Cells and platelets

Question 7

Blood cells and platelets are blocked from renal filtration by which layer of the glomerular filtration barrier?

Answer 7

Glomerular capillary fenestrated endothelium

Question 8

The basement membrane of the filtration barrier blocks which component of blood from being filtered?

Answer 8

Proteins

Question 9

What is the charge of the basement membrane of the glomerular filtration barrier?

Answer 9

Negatively charged

Question 10

List 4 proteins found in the basement membrane of the glomerular filtration barrier.

Answer 10

Type IV collagen
Laminin
Fibronectin
Entactin

Question 11

Define GFR.

Answer 11

The volume of filtrate formed by all the nephrons in both kidneys per unit time

Question 12

GFR is determined by which 2 factors?

Answer 12

Glomerular capillary filtration coefficient (Kf)

Net filtration pressure (NFP)

Question 13

Give the equation to calculate GFR.

Answer 13

GFR = Kf x NFP

GFR = glomerular capillary filtration coefficient x net filtration pressure

Question 14

The glomerular capillary filtration coefficient is dependent on which 2 factors?

Answer 14

Surface area available for filtration

Hydraulic conductivity (permeability) of the filtration barrier per unit area

Question 15

Starling forces are composed of which 2 kinds of pressures?

Answer 15

Hydrostatic pressures
Osmotic pressures

Question 16

Which 2 starling forces favour filtration?

Answer 16

Glomerular hydrostatic pressure

Bowman’s osmotic pressure

Question 17

Which 2 starling forces oppose filtration?

Answer 17

Bowman’s hydrostatic pressure

Glomerular osmotic pressure

Question 18

Most physiological regulation of GFR occurs due to changes in which starling force?

Answer 18

Glomerular hydrostatic pressure

Question 19

Glomerular hydrostatic pressure is dependent on which 3 factors?

Answer 19

Systemic arterial pressure

Afferent arteriole resistance

Efferent arteriole resistance

Question 20

How does AA dilation and constriction affect GFR?

Answer 20

AA dilation - increases GFR

AA constriction - decreases GFR

Question 21

How does EA dilation and constriction affect GFR?

Answer 21

EA dilation - decreases GFR

EA constriction - increases GFR

Question 22

In what way does angiotensin II affect GFR and by what mechanism?

Answer 22

Constricts EA - increases GFR

Question 23

In what way do prostaglandins affect GFR and by what mechanism?

Answer 23

Dilate AA - increases GFR

Question 24

In what way does atrial natriuretic peptide (ANP) affect GFR and by what mechanism?

Answer 24

Dilate AA - increases GFR

Question 25

In what way does noradrenaline affect GFR and by what mechanism?

Answer 25

Constricts AA - reducing GFR

Question 26

What are the 2 mechanisms of autoregulation of GFR?

Answer 26

Myogenic response Tubuloglomerular feedback

Question 27

Define the myogenic response.

Answer 27

The inherent ability of smooth muscle in afferent arterioles to respond to changes in vessel diameter by contracting or relaxing

Question 28

During the myogenic response, when afferent arterioles are stretched, which ion enters the smooth muscle cells to cause constriction?

Answer 28

Calcium

Question 29

Macula densa cells in the DCT detect levels of what?

Answer 29

NaCl - sodium chloride

Question 30

Macula densa cells sense NaCl via which transporter?

Answer 30

NKCC - sodium-potassium-chloride co-transporter

Question 31

Which mediator is secreted by macula densa cells that causes vasoconstriction of the AA?

Answer 31

Adenosine

Question 32

What are the 3 tests which can be used to assess GFR, starting with the most accurate?

Answer 32

Estimated GFR (eGFR) Serum creatinine Serum urea

Question 33

What is creatinine?

Answer 33

Breakdown product of creatine - substance found in skeletal muscle

Question 34

If renal function / filtration is impaired , how will this affect blood creatinine levels?

Answer 34

Blood creatinine levels will increase because less is being filtered

Question 35

How would an amputation affect serum creatinine levels, and what would this imply in terms of GFR?

Answer 35

Decreased serum creatinine levels due to less muscle mass Could imply GFR is too high

Question 36

How does a diet high in meat affect serum creatinine levels?

Answer 36

Increase serum creatinine levels

Question 37

eGFR is calculated using which 3 factors?

Answer 37

Serum creatinine Age Sex

Question 38

Which equation is recommended by NICE to calculate eGFR?

Answer 38

CKD-EPI