Renal Basics (Muster) - W1

Question 1

List the 9 functions of the kidney:

Answer 1

1. filtration (urine production)
2. Blood pressure
3. Sodium (Na) homeostasis
4. Potassium (K+) homeostasis
5. Bone and mineral
6. RBC production (via EPO)
7. Gluconeogenesis
8. Acid base status
9. water homeostasis

Question 2

• How much of the cardiac output goes through the kidney on the first pass?
  
  • How much of the cardiac output is plasma? ​

Answer 2

• 20% of cardiac output goes through kidney on first pass
• 60% of this is plasma = renal plasma flow

Question 3

How does the glomerulus restrict filtration based on size?

Answer 3

• capillary endothelium - pores, clefts, fenestrations
  
  • no cells or proteins pass
• basement membrane - anionic heparin sulfate, proteoglycan, type IV collagen network, laminin
  
  • acts like sponge
• Podocytes: exterior, form small negatively charged slits - lay out foot proceses

Question 4

What are the glomerulus size limitations?

Answer 4

• <7,000 Da = FREELY FILTERED
  
  • INCLUDES: sodium, potassium, chloride, and urea from the PLASM
• >70,000 is completely excluded in normal state
  
  • albumin is 66,000

Question 5

Do anions or cations filter better?

Answer 5

• anions filter better because GMB and slit diaphragms are negatively charged

Question 6

what is defined as the movement of fluid and solute across from the capillary lumen into Bowman’s space across ALL glomeruli in both kidneys

Answer 6

Glomerular Filtration rate

Question 7

What are the primary forces in the afferent arterial?

Answer 7

(Pgc + Obs) - (Pbs + Ogc) = net ultrafiltration pressure

• Favors Filtration
  
  • Pgc = 50 mmHG
  • Ogc = 18
  • Pgc = 15
  • Obs = 0

Question 8

What are the primary forces on the efferent arteriole?

Answer 8

• see INCREASE in oncotic glomerular capillary.
• favors EQUILIBRATION
  
  • Pgc=50 + Obs = 0
  • Pbs = 15 + Ocg=33

Question 9

What is a normal GFR - how much is filtered per day and per minute?

Answer 9

• 180 L/day
• 125 mL/min
  
  • although 1000mL delivered to kidney, this much isn’t filtered. 20% of flow is filtered of 60% (plasma portion).

Question 10

What happens to filtration & GFR if you change renal plasma flow?

Answer 10

• Decreased renal plasma flow
  
  • Decreased GFR
• Increased renal plasma flow
  
  • increased GFR - up to 20% (20% is filtered)

Question 11

What happens if you increase the hydrostatic pressure at each capillary end?

Answer 11

• Afferent End
  
  • Increased filtration
• Efferent end
  
  • Increased filtraiton (normally at equilibrium)

Question 12

What happens if you increase the oncotic pressure of glomerular capillary at each end?

Answer 12

• Afferent end
  
  • Increase in oncotic = decrease in GFR
• Efferent end
  
  • Increase in oncotic = decrease in GFR - could end up favoring reabsorption.

Question 13

What happens if you increase the oncotic pressure of bowmans space?

Answer 13

• Increased filtration –> increased GFR

Question 14

What is the filtration fraction?

Answer 14

• the amount we filter per day
  
  • 60% of blood is filterable plasma
  • 20% is actually filtered

Question 15

What is the excretion rate?

Answer 15

• the amout the kidney gets rid of
• must get rid of excess sodium and what we eat
• = urine flow rate x solute in urine
• what keeps us in BALANCE

Question 16

What is the clearance of the kidney?

Answer 16

• how much the kidney is clearing per day of solute
• under ideal circumstances creatinine=GFR

Question 17

How can you calcuate GFR from excretion rate and plasma concentration?

Answer 17

• GFR = excretion rate of unique solute/plasma concentration of unique solute

Question 18

List the 3 limitations with using creatinine as a estimator

Answer 18

1. creatinine is secreted
2. creatinine lags
3. can be related to muscle mass
   
   1. less accurate if obese or malnourished

Question 19

Describe what happens when NE acts on afferent and efferent arterioles

Answer 19

• Afferent
  
  • vasoconstriction
  • decreases hydrostatic pressure
  • decreases GFR –> increased creatinine
• Efferent
  
  • vasoconstriction
  • increases hydrostatic P
  • Increases GFR

Question 20

What happens when Ang II is released on afferent and efferent arterioles?

Answer 20

• Afferent
  
  • vasoconstriction
  • decreased pressure, decreased GFR
• Efferent
  
  • vasconstriction
  • increased pressure, increased GFR

Question 21

What happens when prostaglandins are released?

Answer 21

• act on afferent arteriole only.
• dilate arteriole
  
  • ​increases renal flow –> increases pressure –> increases GFR

Question 22

How do ACE inhibitors work and how do they affect the arterioles?

Answer 22

• Prevent constriction of the efferent end.
• Increases RPF –> decreases hydrostatic pressure –> decreases GFR

Question 23

How does advil affect the arterioles?

Answer 23

• acts on afferent end
• blocks prostaglandins
  
  • prevents vasodilation
• decreases renal flow –> decreases hydrostatic pressure –> decreases GFR (increased creatinine)