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

How many litres of filtrate does the kidney produce per day?

Answer 5

180 litres per day

Question 6

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

Answer 6

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

Question 7

What is the diameter of the fenestrations of the glomerular capillary endothelium?

Answer 7

70 - 100 nanometres

Question 8

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

Answer 8

Cells and platelets

Question 9

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

Answer 9

Glomerular capillary fenestrated endothelium

Question 10

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

Answer 10

Proteins

Question 11

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

Answer 11

Negatively charged

Question 12

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

Answer 12

Type IV collagen
Laminin
Fibronectin
Entactin

Question 13

The foot processes of podocytes are bound to the basement membrane by which protein?

Answer 13

Nephrin

Question 14

Define GFR.

Answer 14

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

Question 15

GFR is determined by which 2 factors?

Answer 15

Glomerular capillary filtration coefficient (Kf)

Net filtration pressure (NFP)

Question 16

Give the equation to calculate GFR.

Answer 16

GFR = Kf x NFP

GFR = glomerular capillary filtration coefficient x net filtration pressure

Question 17

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

Answer 17

Surface area available for filtration

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

Question 18

Starling forces are composed of which 2 kinds of pressures?

Answer 18

Hydrostatic pressures
Osmotic pressures

Question 19

Which 2 starling forces favour filtration?

Answer 19

Glomerular hydrostatic pressure

Bowman’s osmotic pressure

Question 20

Which 2 starling forces oppose filtration?

Answer 20

Bowman’s hydrostatic pressure

Glomerular osmotic pressure

Question 21

What is the typical value of NFP in mmHg?

Answer 21

16 mmHg

Question 22

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

Answer 22

Glomerular hydrostatic pressure

Question 23

Glomerular hydrostatic pressure is dependent on which 3 factors?

Answer 23

Systemic arterial pressure

Afferent arteriole resistance

Efferent arteriole resistance

Question 24

How does AA dilation and constriction affect GFR?

Answer 24

AA dilation - increases GFR

AA constriction - decreases GFR

Question 25

How does EA dilation and constriction affect GFR?

Answer 25

EA dilation - decreases GFR EA constriction - increases GFR

Question 26

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

Answer 26

Constricts EA - increases GFR

Question 27

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

Answer 27

Dilate AA - increases GFR

Question 28

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

Answer 28

Dilate AA - increases GFR

Question 29

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

Answer 29

Constricts AA - reducing GFR

Question 30

What are the 2 mechanisms of autoregulation of GFR?

Answer 30

Myogenic response Tubuloglomerular feedback

Question 31

Define the myogenic response.

Answer 31

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

Question 32

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

Answer 32

Calcium

Question 33

Macula densa cells in the DCT detect levels of what?

Answer 33

NaCl - sodium chloride

Question 34

Macula densa cells sense NaCl via which transporter?

Answer 34

NKCC - sodium-potassium-chloride co-transporter

Question 35

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

Answer 35

Adenosine

Question 36

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

Answer 36

Estimated GFR (eGFR) Serum creatinine Serum urea

Question 37

What is creatinine?

Answer 37

Breakdown product of creatine - substance found in skeletal muscle

Question 38

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

Answer 38

Blood creatinine levels will increase because less is being filtered

Question 39

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

Answer 39

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

Question 40

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

Answer 40

Increase serum creatinine levels

Question 41

eGFR is calculated using which 3 factors?

Answer 41

Serum creatinine Age Sex

Question 42

Which equation is recommended by NICE to calculate eGFR?

Answer 42

CKD-EPI