Glomerular Filtration Flashcards
What is the equation for filtration?
K [(Pc (hydrostatic) +Pit (oncotic))-((Pt(hydrostatic) +Pic (oncotic))]
C=glomerulus
t= bowmen’s space
Pit is always zero!!
What factors favor filtation from glomerulus to bowmens space?
What factors oppose it?
Favor=glomerular hydrostatic pressure, oncotic pressure due to proteins in the bowman’s space
Oppose= oncotic pressure in the glomerulus, hydrostatic pressure in the bowman’s space
Describe how a glomerular capillary differs from skeletal capillaries?
As you move along the length of the capillary, you maintain a net filtration and Never have net reabsorption
Why does plasma oncotic pressure increase along the length of the capillary?
What is the significance of this?
- Because you are decreasing the amount of water in the capillary so your proteins are becoming more concentrated
- limits filtration
The k filtration constant is dependent upon what 2 things?
capillary surface area ad permeability of this surface
When you have a urinary tract obstruction what happens?
you increase hydrostatic pressure in the capsule space therefore you reduce net filtration
When you have hypoalbumineria what happens?
you have decrease in oncotic pressure in the capillary therefore you increase the net filtration
When you have diabetic nephropathy what happens?
you have increase in K filtration due to permeability of the glomerulus to albmumin which results in increase in oncotic pressure of capsule space and an increase in net filtration
When you go from the affarent arteriole to the efferent arteriole what happens to your oncotic pressure in them?
increases towards the efferent
What happens to your oncotic pressure as move from the efferent capillary to the peritubular capillary?
What happens to your hydrostatic pressure?
- the oncotic pressure stays the same until the very end of the peritubular capillary where it decreases.
- You have a decrease in hydrostatic pressure
The drop of hydrostatic pressure in the efferent arteriole and in the peritubular capillary favors what?
reabsorption
What happens to reabsorption with a decrease in peritubular hydrostatic pressure?
increased reabsorption
What happens to reabsorption with a decrease in peritubular colloid osmotic pressure?
decreased reabsorption
as particles get larger and their charges become more negative their ability to be (blank) decreases.
filtered
Why do negatively charges particles have a hard time crossing the barrier to become filtered?
the barrier also has a negative charge
What is the volume of plasma per minute from which all of a substance is removed?
clearance
Is clearance a volume or a concentration?
a volume
What are the three reasons why you can you Cleareance of inulin to determine GFR?
1 )freely filtered
2) not reabsorbed
3) not secreted
What is the clearance equation?
Cleareance rate= (concenrtaion of substane in urine times urine flow rate)/ (concentration of substance in the plasma)
Cx=(Ux * V)/ Px
If you dont want to inject inulin then what can you use instead to determine GFR?
Creatinine clearance
What is the filtered load?
gives you information about the rate at which a substance is filtered. So if a substance is freely filtered than u know, that there is an equal concentration in both compartments. If you multiply it with the GFR you get the filtered load.
What is the equation for filtered load?
GFR X concentration in plasam
How much sodium do we excrete per day?
2.4 g Na
What is the equation for fractional excretion?
excretion rate/filtered load
What is the equation for fractional reabsorption?
reabsorption rate/ filtered load
