Glomerular Filtration Flashcards
what are the 2 different types of nephrons
- cortical
- juxtamedullary
describe cortical nephrons
shorter loop of henle which only just penetrates medulla
covered by peritubular capillaries
describe juxtamedullary nephrons
longer loop of henle penetrating deep into the medulla
has peritubular capillaries and vasa recta
what is the vasa recta
straight blood vessels running parallel to the loop of henle in juxtamedullary nephrons
which type of nephron has sympathetic innervation
cortical
which type of nephron has a high renin concentration
cortical
what makes filtration selective
the filtration barrier
what makes up the filtration barrier in the glomerulus
- capillary endothelium
- basement membrane
- podocytes
how do particles filter through the capillary endothelium in the glomerulus
only small particles can pass through the fenestrations in the capillary walls
how does the basement membrane stop some particles from being filtered in the glomerulus
the basement membrane is made up of glycoproteins, making it negatively charged, therefore it will repel negatively charged substances (including proteins)
how do substances filter through podocytes in the glomerulus
they must be small enough to pass through the filtration slits set up by the projections of the podocytes
true or false: negatively charged ions filter through the glomerulus easier than positively charged ions
false - negatively charged substances are repelled by the basement membrane, whereas positively charged substances are attracted
what % of blood flowing through the afferent arteriole is filtered though the nephron
20%
where abouts in the kidney is the nephron found
in the cortex
what are the 3 pressures affecting filtration in the glomerulus
- hydrostatic pressure of the glomerulus
- hydrostatic pressure of the capsule
- oncotic pressure in the glomerulus
how is the hydrostatic pressure in the glomerulus produced
through cardiovascular output
also as the efferent arteriole is smaller than the afferent arteriole this creates a pressure difference
how is the oncotic pressure in the glomerulus set up
as proteins can’t filter through, they are stuck in the glomerulus and so draw water across and back into the glomerulus
what is the net pressure for fluid movement
10 mm out of the glomerulus
what are the 4 mechanisms for autoregulation
- myogenic
- tubuloglomerular feedback
- tubuloglomerular balence
- sympathetic NS
what detect changes in pressure in myogenic regulation
stretch receptors in the smooth muscle of the blood vessels
what is the myogenic regulation to an increase in pressure/GFR
they cause the constriction of the afferent arteriole, limiting the amount of fluid entering the glomerulus, so less is filtering, lowering the GFR
what is the myogenic regulation to an decrease in pressure/GFR
they cause dilation of the afferent arteriole, increasing the amount of fluid entering the glomerulus, so more is being filtered, increasing the GFR
how would happen if both the afferent and efferent articles dilated
there would be no GFR, as this takes away the pressure difference between the AA and AE, so blood would flow straight through, without being filtered
what cells detect pressure change in tubuloglomerular feedback
macula densa cells in the DCT
how do the macula densa cells detect a change in GFR/pressure
by detecting a change in sodium chloride levels
if sodium chloride levels had increased in the DCT what does that mean happened to the GFR/pressure
it had increased to give an increased in chloride
what transporters allow the macula densa cells to detect an include in sodium chloride levels
NaKCC co-transporters on the apical membrane
what happens in the tubuloglomerular feedback mechanism if a high GFR/pressure is detected
adenosine is released from the juxtaglomerular apparatus
how does adenosine work to combat a high GFR
it bind to A1 receptors on the afferent arteriole to constrict it and binds to A2 receptors on the efferent arteriole to dilate it
what happens in the tubuloglomerular feedback mechanism if a low GFR is detected
prostaglandins are released from the juxtaglomerular apparatus to cause dilation of the afferent arteriole
when is the sympathetic NS involved in auto regulation
during haemorrhage, to constrict blood vessels and reduce blood loss
