Kindey function Flashcards
Define glomerular filtration?
Formation of an ultrafiltration of plasma in the glomerulus-process by which plasma is removed from blood vessels into glomerulus
What is renal failure?
Acute fall in glomerular filtration-
How is the blood filtrated in glomerulus?
It’s a passive process-driven through fenestrated membrane into bowmans capsule by hydrostatis pressure
The fenestrated endotheium are permeable to fluids and small solutes-but impermeable to cells, proteins, drugs (often protein bounds
What is primary urine?
The ultrafiltrate is free from blood and proteins-only electrolytes and small solutes-primary urine
What cannot pass through the renal filtration?
impermeable to cells, proteins, drugs (often protein bounds)
How does the electrolyte concentration change between plasma and ultrafiltrate?
Electrolytes-SAME concentration in plasma and filtrate
What can happen to the ultrafiltrate after the bowman’s capsule?
But further down within nephron (after capsule)-reabsorbed or secreted (reabsorbed in out of nephron-lower concentration in urine). Amount excreted is amount filtere+amout secreted –amount reabsorbed
What are the main driving forces in kidney filtration? (in and out)
Driving forces for filtration is the hydrostatis pressure of the heart (Pgc), but other forces go the other way round-hydrostatic pressure of tubule (Pf), osmotic pressure of plasma proteins in cappilaries (TTgc). Together that makes the net ultrafiltration pressure (Puf)
What is GFR? How do you calculate it? And what can effect it? How?
Definition-amount of fluid filtered from glomeruli into the bowmans capsule per unit of time
Use Glomerular filtration rate-GFR=Puf x Kf
Kf is a ultrafiltration coefficient-
Any changes in filitration affect Kf
Affected by gaps in endothelium, surface area (like loss of nephron-reduce), dilation of glomerular arterioles (increase surface area-increase Kf). Also pressure (Puf)
What is the average GFR?
120 ml/min
How much blood does the kidney get from the heart? How much of it is plasma? How much actually makes it through to the nephron?
Renal blood flow (RBF)-aprox 1/5 of Cardaic output (so around 1L/min)
Renal plasma flow (RPF) is about 60% -so 0,6L/min
Filtration fraction is about 20%-only 120ml goes properly though
GFR=RPFxFF too
What is the myogenic mechanism in glomerular filtration autoregulation
Myogenic mechanism-
When blood pressure rises (like in exercise)-you should pee a lot right?
When BP increases, afferent ateriole stretch, arteriole constrict-result in increased resistance and blood flow-maintain GFR (SMC based)
What is renal clearance? How do you calculate it?
Renal clearance-rate at which substance its removed from the plasma. Number of litre of plasma cleared of a substance by unit of time
Calculated as C= U x V/P
U-conc of substance in urine, P-conc of substance in plasm V-rate of urine production
This is all important because it can be measure by us
Why would a substance have a low renal clearance?
So anything with low clearance is often rebsorbed, opposite true
So it means if the renal clearance is low then its actively rebsorbed (like sodium). Opposite true
What is the main use of Renal clearance? And what substances are used and why?
The main use of clearance is to find out the GFR Use a susbtrate that can freely pass the kidney but ONLY pass by the kidney. And that isn’t rebsorbed or secreted on top Uses Inulin (plant polysaccharide) and creatinine
