Flashcards in Renal Physiology Deck (107)
On average how much glomerular filtrate is produced per day?
If the blood plasma volume is roughly 2.8L how many times per day is it filtered?
180/2.8 = 63
What percentage of the plasma leaves the blood and is filtered in the kidneys?
What are the three layers of the filtration barrier?
Cap endothelium, basement membrane and podocytes
Which layer of the filtration barrier contributes the most filtration of the plasma?
Which layer of the filtration barrier restricts the efflux of large proteins and blood cells?
What is the other name for the epithelial layer of the filtration barrier and what is its main role?
Podocytes - mainteneance of structure of the barrier and the phagocytosis of FBs
What is the name given to the gaps between the cells in the endothelial layer of the filtration barrier that the filtrate moves through?
What are the main constituents of the basement membrane?
Glycoproteins - collagen, laminin and fibronectin
What polarity of molecule is given preferential efflux through the basement membrane?
What are the three determinants of filtration of a substance?
Size shape charge
What is the name of the projections from the cell body of the podocytes?
Explain how the pedicels interact to add an additional layer of filtration in the glomerulus?
Pedicels interdigitate to create slit pores in which filtrate can pass through
What is meant by a substance that is freely filtered in the glomerulus?
It can pass freely between the blood plasma and tubular fluid. Conc of both substances will be the same and two compartments willl have a F/P of 1
What is the relationship between the filtrate/plasma ratio and the amount of filtration?
The lower the F/P - less likley to be filtered
Molecules up to a molecular weight of 70kDa are freely filtered, T or F?
F - moleucles up to 10KDA freely filtered above 70 kDa arent filtered at all
Why can Cl- and HCO3-ions pass freely through the filtration barrier despite being negatively charged?
Because they have a tiny mass
What is meant by the filtration constant, Kf?
The perm of the filtration barrier
GFR is proportional to the forces that favour filtration minus the forces that oppose filtration, T or F?
What is the equation for GFR?
Kf((P cap + Π bc ) - (P bc + Π cap ))
What is the symbol for oncotic pressure?
What is the average value of capillary hydrostatic pressure in the glomerulus?
Why is there a small drop in capillary hydrostatic pressure across the length of the afferent arteriole in the glomerulus?
Due to movement of water out of the capillary into the tubular fluid
What is the approximate value of the hydrostatic pressure of the tubular fluid?
Why doesn’t the pressure of the tubular fluid increase?
Because fluid moving through the nephron so pressure is maintained
What is the value of the oncotic pressure in the capillary and why does it increase over the length of the vessel?
30 mmHg - increases due to the loss of fluid over the vessel but the retention of protein leading to an increase in its concentration and thus an increase in osmolality
What is the rough value for the net filtration pressure in the glomerulus?
There is always a positive driving force for fluid efflux across the length of the capillaries and thus a movement of fluid out of the vessels, T or F?
What is the approximate rate of filtration in a single nephron? Use this value to estimate the number of nephrons in the kidney?
50nl min-1 125x10-3/50x10-9 = 2.5x106 – 2.5 million