Renal Blood Flow and Glomerular Filtration - Rao Flashcards
What are the functions of the kidneys?
ridding the body of metabolic by-products
excrete toxins and otehr foreign substances
ability to balance daily intake of salts and water
acid base balance
endocrine function (conversion of vit d to active form and synthesis of epo)
What happens when the kidneys fail? Long pathway…
renal failure edema (due to lack of fluid and salt balance) increase in work load of heart heart failure and pulmonary edema death due to acidemia and hyperkalemia
what percentage of nephrons are superficial? juxtamedullary?
85%
15%
what percentage of body mass is kidney? what percentage of CO?
less than 0.5% but receives more than 20% of cardiac output
Explain the pathway of blood flow in the kidney?
renal artery - interlobular arteries - arcuate arteries - radial arteries - afferent arterioles - glomerular capillaries - efferent arteriole - peritubular capillaries - renal vein
how is the naming of the efferent arteriole an exception?
it’s the only place in the body where blood leaves a capillary bed and remains in something called an arteriole
what is the section of blood taht is surrouding the loop of henle
vasa recta
explain the drops in the arteriovenous pressure in the renal vasculature
the first major drop is within the afferent arteriole. the second major drop is within the efferent arteriole. the third major drop occurs in the peritubular capillaries
explain the blood pressure within the glomerular capillaries
the pressure barely drops, maintaing a high level
what two pressures allow for the unique glomerular filtration
the low oncotic pressure and high capillary pressure, which forces fluid out of the glomerular capillaries and into the urinary space
what are the 3 processes of urine formation?
glomerular filtration
tubular reabsorption
tubular secretion
why is it smart to filter large amount of body fluids and solutes and then reabsorb them later when it is a huge energy use?
- allows the kidney to rapidly remove waste products from the body that depend primarily and glomerular filtration for excretion
- allows all body fluids to be filtered and processed several times each day.
what is the composition of filtrate?
similar to plasma, but without large proteins (less than 1% albumin and globulin, rarely hgb)
explain the gibbs donnan effect
the proteins in the basement membrane of the glomerulus have a negative charge (i.e. heparin sulfate). the negative charge. thus 4-5% more anions and 4-5% less cations
What is the gfr in a normal person?
130 ml/min or 180 l.day
what is the filtration fraction?
GFR/RPF (renal plasma flow)
what percentage of plasma is filtered through glomerulus at a time?
20%
what is a factor that would reduce GFR?
uretral obstruction
what is a factor that would reduce RPF?
renal artery stenosis
what are filtratoin barriers (physical) for glomerular filtration?
- capillary endothelium - leakier than most capillaries
- basement membrane (meshwork of collagen and proteoglycan fibrils)
- epithelium or podocyte monolayer
what are inherent barriers based on size (filterability of solutes) in glomerular filtration?
size selectivity
charge selectivity
what is the filterability of water? albumin?
100%
0.005%
what is the formula for GFR?
Kf x Net filtration pressures
how does diabetes mellitus affect kf?
reduces it and increased thickeness of basement membrane and damaged capillaries
What are factors favoring filtration?
glomerular hydrostatic pressure
bowmans space oncotic pressure
what are factors opposing filtration?
glomerular oncotic pressure
bowmans space hydrostatic pressure
How can i regulate net filtration pressure?
change in glomerular hydrostatic pressure
how can i decrease glomerular pressure?
increase the pressure in the afferent arteriole
what will a decreased glomerular pressure do to the gfr?
it will decrease it
how can i increase glomerular pressure?
increase pressure in the efferent arteriole
what will an increased glomerular pressure do to the gfr?
it will increase it
how will an increase/decreased in afterent pressure effect gfr and rpf?
an increased afferent will decreased both gfr and rpf
a decreased afferent pressure will increase gfr and rpf
how will an increased/decreased efferent pressure effect gfr and rpf?
an increased eff pressure will increased gfr and decrease rpf
a decrease in eff pressure will decrease gfr and increase rpf
What are other regulated factors that can control net filtration pressure?
bowmans hydrostatic pressure
capillary oncotic pressure
what are two major theories on changing vascular tone in autoregulation of net filtration pressure?
myogenic mechanism
tubuloglomerular feedback mechanism
what is myogenic mechanism?
direct stimulation of arteriolar smooth muscle
what is tubuloglomerular feedback mechanism
rapid change in gfr by changes nacl concentration in tubular fluid changes the resistance of afferent arteriole
how does a high/low nacl cocentration at the md affect gfr?
a high leads to decreased gfr
a low leads to increased gfr
explain the renin-angiotensin-aldosterone system
renin is secreted from jg cells when there is low chlorine at the md. this leads to increased angiotensin 1 from a2 globulin. then angiotensin ii, then aldosterone, then sodium retention and water retention
are renal blood vessels regulated by sympathetic or parasymp?
symp
what causes proteinuria?
barrier failure (large pore or loss of charge selectivity) abnormal circulating pretin (mid size due to breakdown of tissue or prodx of abnormal protein by tumor cells)
