Renal Filtration And Blood Flow Flashcards
Is glomerular filtration active or passive
Passive
What does glomerular cap bp do to net filtration pressure
Favours filtration
As blood flows along cap remais constant all way
What does bowmas capsule hydrostatic pressure do
Result filtration have fluid which press against glomerular mem acting in opposite direction so opposing filtration
What is capillary oncotic pressure
Plasma protein associated
Pressure opposes filtration in cap have lots of plasma proteins these shouldn’t be filtered into capsule
Proteins in blood as cannot pass mem
What is bowmans capsule oncotic pressure
No plasma proteins in lumen so should be zero
What are starling forces
Balance of hydrostatic pressures and osmotic pressures
What is GFR
Rate at which protein free plasma is filtered form the glomeruli into the bowmans capsule per unit time
GFR -= kf (Filtration coeffiencient -how hokey glomerular mem is) x net filtration pressure
What is the normal GFR
125ml/min
What is the ,a jot determinat of GFR
Glomerular capillary fluid blood pressure
What is the extrinsic regulation of GFR
Symp control via baroreceptors reflex
What so the intrinsic auto regulation of GFR
Myogenic mechanism
Tubuloglomerular feedback mech
What happens to the GFR when the arterial bp increases
Increase arterial bp
Increase glomerular cap pressure
Increase net filtration
Increase GFR
What happens if there is a severe haemorrhage what happens to the GFR
Fall in blood vol Dec arterial bp Detected by artic and carotid sinus baroreceptors Increase symp activity Vasoconstriction Decrease afferent arterioles Decrease GFR Decrease urine vol compensate for loss
What is myogenic auto regulation
If vascular smooth muscle is stretched (arterial blood pressure increases) it contracts thus constricting arteriole
What is the Tubuloglomerular feedback autoregulation
Involves juxtaglomerular apparatus
If GFR rises more Nacl flows through tubule leading to constriction of afferent arterioles
What cells sense the sodium chloride content of tubular fluid
Macula densi of juxtaglomerular apparatus
What would happen if there is a kidney stone
Increase in bowmans capsule fluid pressure
Build up of fluid
Decreases GFR
What happens when an individual has diarrhoea
Increase in capillary oncotic pressure
Become dehydrated as lose fluid and not plamsa proteins
Decreases GFR
What happens if an individual is severely burned
Decrease in capillary oncotic pressure
Lose plasma proteins at site of injury
Increase GFR
What happens if there is a decrease in kf
Change of surface area for filtration
Decreases GFR
What is the plasma clearance a measure of
How effectively the kidneys clean the blood
Volume of plasma completely cleared of a particular substance per minute
Each sub has its specific clearance
How do u work put the clearance
Clearance of sub x = rate of excretion/roads a conc of x
Clearance of x = urine concentration of x (X) Vu / plasma concentration of x
Ml/min
What is a substance used for calculating clearance
Inulin
Why is inulin used for clearance
Freely filtered not abs nor sec
Not metab
Not toxic
Easily eausred in urine and blood
What can be sued for clearance and find GFR
Inulin or creatinine
When clearance=0
Substances completely reabs and not sec such as glucose
When clearance
For substances which are filtered partly reabs and not sec such as urea
When cleanrce > GFR
Subs which filtered sec but not reabs such as hydrogen ions
How to calculate renal plasma flow with para amino hippuric acid
Para amino hippuric acid is an exogenous organic anion not produced naturally by the body
Used clinically to measure renal plasma flow
PAH is freely filtered at glomerulus and sec into tubule completely cleared from plasma
What are the properties needed for a clearance marker
Non toxic
Inert not metab
Easy to measure
What is needed from a GFR marker and what is needed from a RPF marker
GFR - should be filtered freely not sec or abs
RPF - should be filtered and completely sec
What is the filtration fraction
Fraction of plasma flowing through the glomeruli that is filtered into tubules
How do you work out the filtration fraction
Filtration fraction = GFR/ renal plasma flow
What are the filtration barriers of glomerular filtration
Glomerular capillary endothelium
Basement membrane acellular
Slit processes of podocytes Interdigitate with adjacent cells
