Renal Physiology Part 5 Flashcards
(44 cards)
In some kidney diseases,
the negative charges on the basement membrane are lost, what will happen?
Loss of negative charges on the glomerular basement membrane reduces its ability to repel proteins like albumin, leading to proteinuria.
What is the main driving force for glomerular filtration?
Glomerular hydrostatic pressure (60 mm Hg), which promotes filtration.
What forces oppose glomerular filtration?
- Bowman’s capsule pressure (18 mm Hg)
- Glomerular oncotic (colloid osmotic) pressure (32 mm Hg)
How is net filtration pressure (NFP) calculated in the glomerulus?
NFP = Glomerular hydrostatic pressure - (Bowman’s capsule pressure + Glomerular oncotic pressure)
NFP = 60 - (18 + 32) = 10 mm Hg
What is the colloid osmotic pressure of Bowman’s capsule under normal conditions?
0 mm Hg (negligible or absent)
What does a positive net filtration pressure indicate?
That filtration is occurring from the glomerular capillaries into Bowman’s capsule.
How is net glomerular filtration pressure (NFP) calculated?
NFP = Glomerular hydrostatic pressure (PGC) - Bowman’s capsule pressure (PBS) - Glomerular oncotic pressure (πG)
Why is the net filtration pressure usually positive?
Because the glomerular hydrostatic pressure is greater than the opposing forces.
What does a positive net filtration pressure result in?
It drives the movement of protein-free plasma from the glomerulus into Bowman’s space, initiating urine formation.
What is glomerular filtration rate (GFR)?
The volume of fluid filtered from glomerular capillaries into Bowman’s capsule per unit time.
Why is the net filtration pressure usually positive?
Because the glomerular hydrostatic pressure is greater than the opposing forces.
What is the average GFR in a 70 kg person?
180 L/day or 125 mL/min
What is the typical distribution of renal plasma flow (RPF) and reabsorption (REAB)?
RPF = 625 mL/min, GFR = 125 mL/min, REAB = 124 mL/min, Urinary excretion = 1 mL/min
What is the average GFR in a 70 kg person?
180 L/day or 125 mL/min
What is one major advantage of a high glomerular filtration rate (GFR)?
It allows the kidneys to rapidly remove waste products that depend mainly on filtration for excretion.
Why do most waste products depend on high GFR for removal?
Because they are poorly reabsorbed by the renal tubules.
What is the second advantage of a high GFR?
It enables the kidneys to filter and process all body fluids multiple times a day.
Why do most waste products depend on high GFR for removal?
Because they are poorly reabsorbed by the renal tubules.
How often is the entire plasma volume filtered by the kidneys each day?
About 60 times per day.
What is the plasma volume and GFR in an average adult?
Plasma volume ≈ 3 liters; GFR ≈ 180 liters/day.
How does a high GFR help maintain homeostasis?
By allowing precise and rapid control of body fluid volume and composition.
What is the equation for glomerular filtration rate (GFR)?
GFR = Kf × Net Filtration Pressure
What are the three main factors affecting glomerular filtration rate (GFR)?
- Net filtration pressure
- Membrane permeability
- Surface area of the filtration barrier
Is glomerular filtration rate (GFR) a fixed value?
No, GFR is subject to physiological regulation.
