Lecture 2: Filtration and Clearance (Bolsor) Flashcards Preview

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Flashcards in Lecture 2: Filtration and Clearance (Bolsor) Deck (28)
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0
Q

what is the filtration barrier between glomerular capillary and Bowman’s capsule composed of? (3 components)

A

glomerular capillary endothelium, basement membrane, and epithelial podocytes of Bowman’s capsule

1
Q

3 main characteristics of filtrate

A

1) virtually protein-free
2) solute concentrations are the same as plasma
3) formed as a result of hydrostatic and oncotic pressure differences across the glomerular membrane

2
Q

why does more blood enter the Bowman’s capsule through the afferent arterioles than leaves through the efferent arterioles?

A

some is filtered out through the capillaries inside the capsule

3
Q

Is it normal to have protein in urine?

A

NO

4
Q

increased molecular size –> ability to filtrate that molecule in Bowman’s capsule

A

decreases

5
Q

which molecule filters more easily in the kidney: myoglobin or hemoglobin?

A

myoglobin, because of its smaller size. Charge also has an effect to a lesser extent

6
Q

Effect of charge on filtration in kidney

A

+ charged molecules filter more easily than - charged molecules. However, molecular size has a larger effect on filterability, so after a certain large molecular size, changes in charge will have no effect on filterability.

7
Q

Index of filterability

A

ratio of the concentration of a given molecule in the filtrate (inside Bowman’s capsule) and in the plasma. Ratio of 1 indicates molecule passes through the filtration barrier easily

8
Q

Do albumin and Hb has high or low index of filterability?

A

low, because they do not pass filtration barrier easily and mainly remain in the plasma

9
Q

glomerular filtration rate (GFR)

A

volume of plasma filtered into Bowman’s capsule per unit time

10
Q

formula for GFR

A

GFR = net filtration pressue (NFP) X filtration coefficient (kf)

11
Q

equation for NFP

A

NFP = glomerular capillary hydraulic pressue (PGC) + Bowman’s capsule oncotic pressure (pieBC) - Bowman’s capsule hydraulic pressure (PBC) - glom. capillar oncotic pressure (pieGC)

12
Q

main force moving fluid into Bowman’s capsule

A

hydrostatic pressure in glomerular capillary

13
Q

5 factors that influence hydrostatic pressure of the glomerular capillary (PGC)

A

1) blood pressure
2) efferent and afferent arteriolar resistance
3) sympathetic nervous system
4) hormonal control
5) obstruction

14
Q

higher PGC –> GFR?

A

increases

15
Q

How does sympathetic system regulate GFR?

A

controls blood flow through the glomerular capillary bed and secondarily controls the hydrostatic pressure in glomerular capillaries

16
Q

increased afferent arteriolar resistance –> PGC? GFR?

A

decreases both

17
Q

increased efferent arteriolar resistance –> PGC and GFR?

A

increases both (pressure backs up in the system like a blocked hose)

18
Q

normal GFR for dogs

A

80ml/min

19
Q

what controls the filtration coefficient Kf? (2 main factors)

A

permeability and surface area for filtration

20
Q

What happens to GFR as filtration coefficient Kf continues to increase?

A

GFR will increase rapidly at first, then reach a plateau as additional increases in Kf don’t have any effect on GFR

21
Q

How can surface area for filtration be changed?

A

by controlling the number of glomerular capillaries that are perfused

22
Q

starvation –> oncotic pressure of glom. capillary? GFR?

A

oncotic pressure drops due to decreased plasma protein concentrations. GFR rises

23
Q

cellular debris in renal tubules –> GFR, urine flow?

A

both decrease. GFR decreases because high pressure in bladder raises pressure in ureters up to the kidney, causing resistance to filtration.

24
Q

clearance

A

volume of plasma from which a substance is completely removed per unit time. Used to assess overall renal function

25
Q

equation for renal clearance Cx

A

Cx = (Ux*V)/Px where Ux is conc. in urine, V is urine flow rate, and Px is conc. in plasma

26
Q

inulin and its important properties

A

synthetic substance used as a tool to study renal clearance. clearance of inulin is a marker for GFR

  • freely filtered
  • not reabsorbed, secreted, produced, or metabolized by the kidney
  • doesn’t alter GFR itself

GFR = Cin = (Uin*V)/Pin
GFR

27
Q

clinical relevance of creatinine with respect to kidney

A

used as an indicator of GFR because plasma creatinine is inversely correlated with GFR

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