GFR filtration Flashcards
(26 cards)
list a few functions of the kidney
regulation - control substances
excretion
endocrine - secrete renin
metabolic - active form of vit D
what do the kidneys filter the most
extracellular fluid
what are the different body fluid compartments and how are they divided
what component is directly affected by the kidneys
1/3 intracellular
2/3 extracellular (interstitial and intravascular)
divided by semi permeable membrane
only extracellular fluid is affected by kidney not intracellular
what will happen when there is a failure to control electrolytes
disruptance in electrical functions and transport
what is the functional meaning of osmolarity and osmolality
total concentration of substance that cannot move through the membrane freely (due to oncotic pressure)
give examples of substances that cannot move through the membrane freely
ions and organic molecules
how much of the blood passing through the kidney is actually turned into filtrate
80% reabsorbed whilst 20% filtered at one time
what are the two typed of kidney, what is the difference and do they function the same
cortical and juxtaglomerular, function same but jg has a longer loop of henle
what is auto regulation and what does it apply to
what happens when GFR up or down
auto regulation is the kidneys way of maintaining GFR within normal BP
only occur in cortisol nephrons
afferent constrict when high and dilate when low. GFR remains unchanged
what does the filtrate coming out of the glomerulus resemble in terms components
plasma (no RBC, large proteins etc)
describe how the kidney filters blood within the glomerulus
- blood enters
- BM has fenestrations which are permeable to small ions and small proteins
- BM negatively charged so repels other - ions (proteins)
- beneath this is bowman capsule
- bowman capsule has visceral and parietal layer of podocytes with heparin in between to catch remaining proteins
- ultra filtrate passes through funnel into PCT
what is the biggest substance that can go through the selective membranes
inulin
what happens in proteinuria that allows proteins to pass this selective membrane
membrane lost charge allowing negatively charged particles like albumin and other proteins to seep through
describe the charges applied in the glomerulus
PGC (capillary hydrostatic pressure) - pushing in
COP (oncotic) - pushing out
PBC (hydrostatic p in bowman capsule) - pushing out due to funnel overfilling
BCOP (bowman capillary oncotic pressure) - usually zero as should be no proteins in bowman
all of these determine NFP which is proportional to GFR
what happens to the oncotic protein pressure as ultra filtrate is lost
concentration goes up as it reaches efferent arteriole (important for reabsorption)
what are the 2 types of auto regulation
myogenic and tubuloglomerular
what is myogenic auto regulation
arterial smooth muscle responds to incr or decr in vascular tension
consists of arterial mechanisms (resistance vessels)
describe what happens in myogenic auto regulation (high BP)
mechanoreceptors in afferent arteriole detect pressure , the special Na channels in the smooth muscles cells stretch making them leaky which send Na into arteriole, amount reaches threshold potential and stim Ca release from ER and contracts
efferent article dilate so follow path of least resistance and flow out causing drop in PGC
PGC is proportional to how much blood coming in
reminder
what happens in tubuloglomerular AR
main action is linking Na and CL concentration at macula densa to determine whether dilation or constriction need to occur
by controlling distal solute delivery it control tubular reabsorption
what are the 2 components of TG AR
afferent arteriole resistance and efferent arteriole hormones
describe TG feedback if GFR incr
incr NaCl delivery to macula densa and DCT (cl go into blood while na stays in cells)
triggers ATP release which turn to AMP then adenosine
adenosine bind to mesengial cells through A1 which stim ca concentration to incr and inhibits renin in Jg cells via gap junctions
ca move to afferent arteriole via gap junctions and constricts
vasodilation of EA via A2 receptors also found
what happens when decr GFR via TG system
less adenosine means less ca which means vessel dilates
arachidonic acid broken down to prostaglandins and nitro oxide to help with dilation in macula densa
why is assessing what conditions a patient has in regards to kidneys (and meds) important to know before administering medicines such as ACE inhibitors and NSAIDS
NSAIDS block prostaglandins from working which would decr GFR and impair renal function
when GFR low angiotensin II can help maintain it but ACE inhibitors stop this
