Name the factors affecting glomerular barrier passage (2)
- size (radius)
2. charge
Name some molecules that can pass through the glomerular filtration barrier
water small ions glucose amino acids small hormones
What is the charge of the glomerular filtration barrier?
negative charge (because of glycoproteins on endothelium, basement membrane, and podocytes)
What is the primary measure of kidney function?
production rate of glomerular filtrate
Formula for renal plasma flow
RPF = RBF x (1-Hct)
Formula for filtration fraction
FF = GFR / RPF
Name 3 factor influencing the rate of filtration
- hydraulic permeability of the barrier
- surface area of the barrier
- net filtration pressure across the barrier
Formula for glomerular filtration rate
GFR = Kf x NFP
Kf = ultrafiltration coefficient NFP = net filtration pressure
What is net filtration pressure?
algebraic sum of pressures across the glomerular barrier (Starling Forces!)
Name the Starling Forces (4)
- glomerular capillary pressure (hydraulic)
- Bowman’s space (hydraulic)
- plasma oncotic pressure
- oncotic pressure of Bowman’s space
What can change the filtration coefficient of the glomerulus?
increased glomerular surface area
results in increased GFR
What can change the hydrostatic pressure in glomerular capillaries?
- increased renal arterial pressure
- decreased afferent-arteriolar resistance (afferent dilation)
- increased efferent-arteriolar resistance (efferent constriction)
What can change the hydrostatic pressure in Bowman’s capsule?
increased intratubular pressure (b/c of obstruction of tubule or extrarenal urinary system)
(results in decreased GFR)
What can change the oncotic pressure in glomerular capillaries?
- increased systemic plasma oncotic pressure
- decreased renal plasma flow
(results in decreased GFR)
Yes or No: Does capillary hydraulic pressure change greatly between the beginning and end of the glomerular capillaries?
no
Yes or No: Does net filtration pressure change much between the beginning and end of the glomerular capillaries?
yes
Glomerular filtration rate (GFR) is the sum of what 3 factors?
- net filtration pressure
- intra-capillary oncotic pressure
- pressure in Bowman’s space
As the blood travels from afferent arteriole to efferent arteriole, does intra-capillary oncotic pressure increase or decrease?
increase
As the blood travels from afferent arteriole to efferent arteriole, does net filtration pressure increase or decrease?
decrease
How does each of the following affect GFR (increase or decrease)?
- Relaxation of glomerular mesangial cells expanding the glomerular filter
- Afferent-arteriolar dilation
- Efferent-arteriolar dilation
- Obstruction to the tubule or extrarenal urinary system
- Increased systemic oncotic pressure
- Decreased renal plasma flow
- increase
- increase
- decrease
- decrease
- decrease
- decrease
How might an increase in intraglomerular pressure influence the quantity of protein found in the final urine?
A. increased proteinuria
B. no effect
C. Reduced proteinuria
A. increased proteinuria
How would you predict increased protein binding would affect renal excretion of a drug excreted largely by glomerular filtration? A. increased excretion B. decreased excretion C. no effect on excretion D. cannot predict effect on excretion
B. decreased excretion
Benazepril selectively dilates the post-glomerular arteriole. In a patient with glomerular proteinuria, how would you predict it would affect proteinuria? A. increased proteinuria B. decreased proteinuria C. no effect on proteinuria D. cannot predict effect on proteinuria
B. decreased proteinuria
What effect would a relative reduction in postglomerular arteriolar resistance have on filtration fraction?
A. increased filtration fraction
B. decreased filtration fraction
C. no effect on filtration fraction
B. decreased filtration fraction
