GFR Flashcards
Renal failure leads to?
Edema, increase in workload of heart, heart failure, death
Functional unit of the kidney
Nephron (1million in each kidney)
What is the most unique thing about the glomerular capillary system?
Pressure drop occures in two steps so as to keep high hydrostatic pressure within the glomerular capillary.
Where are the two pressure drops?
Afferent areteriole, Efferent arteriole
Concentration of glomerular filtrate?
Similar to plasma but without large proteins
GFR in ml/min?
130
GFR in L/day
180
Three barriers to glomerular filtration. What the hell are they
- ) Capillary enothelium- very leaky comparede to the capillary system of other organs.
- ) Basement Membrane- Collagen and proteoglycan
- ) Epithelium or podocyte monolayer- foot processes forming slit pores
GFR=
Kf x net filtration pressure
WHat is Kf
Filtration coefficeint, relates to the hydraulic conductivity x the surface area of the glomerular capillary
What is net filtration pressure?
(Glomerular hydrostatic pressure (high) + bowmans space oncotic pressure (low)) - (glomerular oncotic + bowmans hydrostatic)
How would Bowmans space hydrostatic pressure go up?
Aome sort of blockage of the lower urinary tract would cause a back up of fluid and therefore an increase in pressure in the bowmans space. This makes filtration harder and lowers GFR
How is net filtration pressure reduced?
Increase capillary oncotic pressure
What is Oncotic pressure
The pressure created by large proteins which draws fluid in.
What is auto-regulation of GFR
The kidneys ability to maintain constant GFR in the face of changes in blood pressure, vascular pressure, obstructions.
How does the body change glomerular filtration rate?
By changing the resistance in the afferent arterioles
How is the afferent arteriole resistance changed?
1.) Myogenic mechanism- contraction of arteriolar smooth muscles.
2.) Tubuloglomerular feedback mechanism- involves the juxtaglomerular complex (macula densa, juxta cells) The theory is that when there is higher NaCl at the MD, afferent resistance goes up and GFR down.
The opposite is true as well.
Important to realize that it is an increase or decrease in GFR that starts this. It somehow causes the NaCl to change conc. Not vice versa
When and how is Renin Angiotensin system activated>
When there is a decrease in arterial pressure or EC volume. The decrease in BP causes a decrease in GFR which leads to a decrease in chloride at teh Macula densa. Signals are sent to Juxta cells to release renin. THis activates angiotensin which activates aldosterone and you get sodium and water retention
Adrenaline does what to GFR?
decreases it
Endothelin 1 does what to GFR
decreases it
NO and Prostaglandin does what to GFR?
decreses it
