Renal Blood Flow and control 3

Question 1

Renal Blood Flow Formula

Renal Vascular Resistance is determined by:

Answer 1

Renal Arterial Pressure (RAP) - Renal Venous Pressure (VAP) / Renal vascular resistance

blood viscosity length of blood vessels

vascular circuitry

radius of blood vessels

(think of the resistance formula)

Question 2

Renal Fraction

Answer 2

the amount of total cardiac output that the kidney receives

Renal fraction = renal blood flow/ cardiac output

resting CO = 5L/min; RBF = 1 L/min

Renal Fraction = 1L/5L = 0.2 or 20%

Question 3

Filtration Fraction

Answer 3

20% of the plasma entering the glomerulus is filtered–filtration fraction

FF = GFR/RPF

Question 4

Glomerular Filtration Rate (GFR)

Answer 4

the rate at which blood plasma passes from the capillary lumen to Bowmans space

in humans, GFR = 125 ml/min or approximately 180 L/day

side note: urinary excretion is 1 to 2 L per day so 99% of the filtered volume is reabsorbed