glomerular filtration Flashcards
what are the functions of the kidney
regulation of ECF volume and blood pressure regulate osmolality maintain ion balance regulate pH excrete waste produce hormones
what are the 5 steps in the nephron
1 filtration by the glomerulus
2 absorption and secretion by the PCT
3 generation of osmotic gradient by the loop of Henle
4 regulated absorption and secretion by the DCT
5 water uptake in the collecting ducts
what are podocytes
cells in the Bowman’s capsule that wrap around the capillaries of the glomerulus
they have long projections which wrap around the capillaries and leave slits between them through which blood is filtered
they have foot processes and secondary processes
describe the triple barrier of the glomerulus
endothelial lining of capillaries
basement membrane of the capillaries
foot processes of the podocytes
what size solutes can form the filtrate
up to 60 kDa
no cells or large proteins
positively charged molecular are filtered more easily
what is renal blood/ plasma flow
total amount of blood/ plasma that traverses the renal artery/vein per unit time
what is approximate RBF
1100 ml/min
what is approximate RPF
1- haematocrit x RBF = 0.55 x 1100 = 600 ml
what pressures ( starling forces) favour movement into the tubule
hydrostatic blood pressue (+55)
oncotic tubule pressure (0)
what forces oppose movement into the tubule
hydrostatic pressure of the tubule (-15)
oncotic pressure of the blood ( -30mmHg)
what is the overall pressure of movement into the tubule
10 mmhg
what is the GFR
rate of filtrate production
125 ml/min
how is myogenic autoregulation mediated
stretch receptors in the arteriole
how is pressure in the glomerulus increased
dilate the afferent arteriole
or constrict the efferent arteriole
change to blood flow and pressure
how much is renal blood flow
20% of CO
1 L/min
renal blood flow is mostly constant over a wide range of BPs so GFR is essentially constant
