La fonction glomérulaire (ll) / Le système rénine-angiotensine-aldostérone / Introduction à la fonction tubulaire

Question 1

Where can you find the glomerular capillaries?

Answer 1

Between the afferent and efferent arteriole

Question 2

Where does filtration glomérulaire happen?

Answer 2

capillaires glomérulaires which is then collected in Bowman’s capsule

Question 3

What is the normal GFR for men and women?

Answer 3

men: 2 mL/sec (120 ± 25 mL/min)

women: 1.6 mL/sec (95 ± 20 mL/min)

Question 4

Why is the daily GFR so high?

Answer 4

to keep the blood clean and decrease waste in the blood —> maintain equilibrium

Question 5

Information for the GFR:

Answer 5

After 20 years old… GFR starts decreasing by around 1 mL/min each year

Question 6

What are the categories and respective GFR for kidney function?

Answer 6

Question 7

What is the “débit de filtration glomérulaire”?

Answer 7

volume of filtrate produced by glomérules for a certain period of time

Question 8

What is renal clearance?

Answer 8

Renal clearance of a substance refers to the how quickly a particular substance is removed from the plasma by the kidney and excreted in urine

Question 9

What can renal clearance be used for?

Answer 9

• to calculate the volume of blood that was filtered of the “traceur” expressed in mL
• it is a sorta direct measure of DFG (GFR)

Question 10

What is a “traceur”?

Answer 10

• Substance X in the blood
• Stable plasmatic concentration
• Filtered 100% in the glomerulus —> identical concentration in the filtrate and plasma
• Substance isn’t reabsorbed or secreted in the tubule —> excretion = amount actually filtered out in the glomerulus

Question 11

What is the ideal “traceur”?

Answer 11

Inuline: polysaccharide exogène mais très $$$ —> used mostly in research

Radio-isotopes: once again, mostly used in research

Question 12

What is typically used as the “traceur” in clinical context?

Answer 12

Créatinine —> produced by muscular metabolism

Question 13

Clearance measured using creatinine is overestimated by around 10-20%… why?

Answer 13

it its secreted by the tubule

Question 14

How is creatinine used to determine renal function?

Answer 14

Créatininémie increases with decreasing renal function BUT BE CAREFUL… it is dependent on 2 factors:

1. Renal function (elimination)
2. Muscle mass (production)

Question 15

What can cause elevated creatinine levels?

Answer 15

high muscle mass —> clearance is normal but high creatinine

renal insufficiency —> high levels due to decreased clearance

Question 16

How can you determine the GFR? CRÉATININÉMIE MUST BE STABLE

Answer 16

Measuring —> blood test with 24hr urine collection (creatinine)

Estimating —> two different formulas availableFormule de Cockcroft et Gault (1976) —> measures the creatinine clearance

Question 17

How can GFR be estimated?

Answer 17

Formule de Cockcroft et Gault (1976) —> measures the creatinine clearance

• done on 225 white men… not very accurate
• multiply answer by 85% for women

Formule MDRD puis CKD-EPI —> measures the DFGe based on 4 parameters? what are they?

• age, sex, race and creatinine levels
• Why is this one better?
  
  • Larger and more diverse sample population
  • Calculated on computers in the lab
  • Answer is normalized according to standard body surface
  • Directly estimates DFG not creatinine clearance

Question 18

What do you do if the patient does not have an “approximately normal body shape”? (determining GFR)

Answer 18

Measure it directly

Question 19

What are the four stages of chronic kidney failure (maladie rénale chronique)?

Answer 19

Stage 1: renal lesions with normal GF or elevated GF (normalized filtration rate: > 90)

Stage 2: mild kidney failure, slightly decreased GF (normalized filtration rate: 60-89)

Stage 3: moderate kidney failure, moderately decreased GF (30-59)

Stage 4: severe kidney failure, severely decreased GF (15-29)

Stage 5: terminal kidney failure, terminal GF (< 15 or patient on dialysis)

Question 20

Where is renin stored and produced?

Answer 20

In the afferent arteriole… if the pressure here decreases enough, renin will be released into blood from epithelial cells

Question 21

What is the purpose of the SRAA?

Answer 21

Maintain TA and volume

Question 22

How does the SRAA work?

Answer 22

Question 23

When does renin secretion increase?

Answer 23

When there is a noticeable decrease in effective circulating volume, blood pressure, or overall volume

Question 24

Why are the glomerular capillaries the only capillaries in the body situated between two arterioles?

Answer 24

In systemic capillaries, filtration will happen on the arteriolar side due to a high hydrostatic pressure and reabsorption will happen on the venular side due to low hydrostatic pressure…

In glomerular capillaries you want filtration the entire time —> ULTRAFILTRATION therefore… you need arterioles on both sides

Question 25

So where does the reabsorption happen?

Answer 25

Peritubular capillaries

Question 26

Why were filtration and absorption separated in the kidneys?

Answer 26

to have one time of capillary in ultrafiltration and the other in reabsorption mode

Question 27

Overview of pressure levels in the vascularization of the kidneys:

Answer 27

Question 28

What are the 8 "principes de la fonction tubaire"?

Answer 28

1. Reabsorption and secretion 2. Membrane transport 1. Passive diffusion 2. Facilitated diffusion 3. Transporteur 4. Canal ion-spécificque 5. Active transport 3. Typical tubular cell * Energized by basolateral Na+K+ ATPase * What does it do? * Sodium in, which decreases cytoplasmic sodium levels this then draws intraluminal sodium into the cell which is done through cotransporters 4. **Polarity of epithelial cells (vectorial transport)** 5. **Tight junctions** 6. Proximal tubules vs distal tubules * What does the distal nephron include? 1. Tubule distale et le tubule collecteur 7. Transcellular and paracellular reabsorption * Certain substances can pass by trans or paracellular route and be reabsorbed back into the blood depending on the Starling forces at the moment 8. Tm (maximum tubulaire)

Question 29

How does the schéma d'hydratation work?

Answer 29

**Horizontal axis**: volume on each side **Vertical axis**: osmolality —\> should be consistent between LEC and LIC

Question 30

Why is there double the amount of liquid in your cells compared to outside of them?

Answer 30

the osmoles are distributed 1/3 —\> LEC and 2/3 —\> LIC

Question 31

What happens to the schéma d'hydratation if you either: 1. diminish extracellular volume, 2. lower the osmolality or 3. increase the intracellular volume

Answer 31

Question 32

What happens if you drink a lot of water... lets say 3 glasses?

Answer 32

Water will evenly distribute between LEC and LIC depending on the osmoles ∴ 1/3 to LEC and 2/3 to LIC