Introduction to the Renal System Flashcards
six main functions of the kidney
filtration of blood
detoxification
regulation of blood pressure
regulation of blood pH
regulation of haematopoiesis
making vitamin D
what percentage of cardiac output is used by the kidneys?
20%
which kidney sits more superiorly
left
what size of molecules can pass through the glomerular filter
4nm is cut off
free flow below 1.8nm
how many layers make up the glomerular filter?
three
what is the coarsest layer of the glomerular filter
fenestrae in enthothelial cells
can blood cells pass through the the fenestrae in endothelial cells
no
how is the fenestrae in endothelial cells cleaned
mainly by bulk fluid flow
what is the second layer of the glomerular filter
glomerular basement membrane
what is the glomerular basement membrane made of
mesangial cells
how is the glomerular basement membrane cleaned?
by continuous replacement
what is the finest layer of the glomerular filter?
the slit diaphragm between podocyte processes (e.g. proteins like nephrin)
how is the finest layer of the glomerular filter cleaned
endocytosis of trapped proteins
what is the role of pressure in glomerular filtration
pressure is required to drive filtration against the colloid osmotic gradient back to the filtered plasma
pressure is also required to drive flow
how is pressure controlled through the glomerular filter
by how easily the blood is able to flow in and out which is controlled by afferent and efferent arteriole contraction
does higher pressure lead to more or less flow across the filter
more
what percentage of plasma is removed in the filtrate typically
20%
what type of substance is creatinine
nitrogenous waste
why is creatinine a good substance to use to estimate GFR
it is filtered from the plasma and is not subject to any transport mechanism thereafter/there is not recovery mechanism so everything filtered from plasma is excreted
why can urea not be used to estimate GFR
some can be reuptaken into the blood stream after initial filtration from the plasma
what is GFR
glomerular filtration rate
what is the equation for GFR
GFR = (urine flow rate x concentration of solute in urine)/concentration of solute in plasma
when can the concentration of creatinine rise in the plasma
with muscle use or muscle damage
what would you expect to happen to the plasma creatinine in someone who has just ran a marathon compared to before
it will rise a lot