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Renal Blood Flow and Glomerular Filtration

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Blood enters the renal medulla immediately after passing through which vessels?

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a. Arcuate arteries

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b. Peritubular capillaries

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c. Afferent arterioles

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d. Efferent arterioles

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(d) Most efferent arterioles feed peritubular capillaries, but those associated with juxtamedullary glomeruli feed vascular bundles that descend into the medulla.

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Which cell type is the main determinant of the filterability of plasma solutes?

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a. Mesangial cell

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b. Podocyte

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c. Endothelial cell

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d. Vascular smooth muscle

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(b) While mesangial cells and vascular smooth muscle affect how much plasma is filtered, the pedicels bridging the foot processes of podocytes are the key determinants of what is filtered.

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Which one of the following is NOT subject to physiological control on a moment-to-moment basis?

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a. Hydrostatic pressure in glomerular capillaries

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b. Selectivity of the filtration barrier

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c. Filtration coefficient

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d. Resistance of efferent arterioles

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(b) Rapid control is exerted over the contractile properties of vascular smooth muscle and mesangial cells (that affect the net filtration pressure and effective surface area for filtration), but podocyte properties that determine selectivity of the filtration barrier are not subject to rapid changes.

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A substance is freely filtered and has a certain concentration in peripheral plasma. You would expect the substance to have virtually the same concentration in

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a. the glomerular filtrate.

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b. the afferent arteriole.

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c. the efferent arteriole.

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d. all of these places.

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(d) Other than larger molecules that are only partially or slightly filtered, the plasma concentrations of a small freely filtered substance is not altered by filtration because water and the substance in question are filtered in the same proportions.

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In the face of a 20% decrease in arterial pressure, GFR decreases by only 2%. What could account for this finding?

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a. The resistances of the afferent and efferent arterioles both decrease equally.

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b. Glomerular mesangial cells contract.

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