veins afferent arteriole glomerulus eferent arteriole peritubular capillaries A

Question

veins afferent arteriole glomerulus eferent arteriole peritubular capillaries A model of renal blood flow containing two capillary beds in series is shown in the figure above. Pa represents arterial pressure, PGc represents pressure in the glomerular capillaries, Ppc represents pressure in the peritubular capillaries, and P, is venous pressure. Hematocrit value in the afferent arteriole is Ha-45% The A drug influences blood pressure and renal vascular resistance as shown in the table below. Pressures before and after use of the drug are also provided in the table. Venous Afferent resistance Efferent resistance Arterial pressure P. prssre P Ra (mmHg/(ml/min) Re (mmHg/(ml/min)) (mmHg) (mmHg) Before drug 155 After drug 125 0.082 0.055 0.055 0.027 Find the following quantities both predrug and postdrug: ) Renal blood flow. 2) Plasma flow in afferent arteriole 3) Glomerular capillary pressure

Explanation / Answer

Renal blood flow is defined by pressure gradient across the renal vasculature divided by total renal vasculature resistance.

Renal blood flow= (renal artery pressure- renal venous pressure)/ total renal vascular resistance.

Predrug:

RBF=(155-5)/0.137=1.094L/min

Postdrug:(125-5)/0.082= 1.463L/min

Plasma flow

Predrug:

55% of RPF

.55×1.094=601.7ml/min

Postdrug:

.55×1.463=804.6ml/min

3)glomerular capillary pressure

Predrug :

Pa-Pc=(RBF×Resistance)

Pa-Pc=(1094×.137)

Pa-Pc=149mm hg

155-149=Pc

Pc=6mmhg

Postdrug:

Pa-Pc=1463×.082

Pa-Pc=119.9

125-119.9=Pc

Pc=5.1mmhg

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