Final answer:
About 20 to 25 percent of the cardiac output, which is 1 to 1.25 liters per minute, is received by the kidneys. The renal plasma flow can be calculated as 55 percent of the blood flow to the kidneys when hematocrit is 45. The GFR is calculated based on the amount of plasma entering Bowman's capsule per minute, which is a fraction of the renal plasma flow.
Step-by-step explanation:
The question relates to the proportion of cardiac output received by the kidneys each minute. The heart pumps approximately 5 liters of blood per minute (5 L/min) under resting conditions. Of this, about 20 percent, which equates to 1 liter, is directed towards the kidneys for filtration.
The actual blood flow to the kidneys can be more precisely calculated if the cardiac output is known. With the provided cardiac output of 5,000 mL/min (or 5 L/min) and the known fact that the kidneys receive about 20 to 25 percent of the cardiac output, we can calculate that between 1,000 mL/min (20 percent) and 1,250 mL/min (25 percent) flows through the kidneys. When considering the renal plasma flow, we take into account the hematocrit level, which is the percentage of blood volume that is composed of red blood cells. For an individual with a hematocrit of 45, the renal plasma flow would be 55 percent of the total blood flow to the kidneys.
Further calculation to refine the proportion relating to plasma specifically would involve multiplying the renal blood flow by this percentage. For example, if the renal blood flow is 1,050 mL/min, we calculate 1,050 mL/min multiplied by 0.55 (55 percent) to get 578 mL plasma/min. Additionally, with a 19 percent fraction of the plasma entering Bowman's capsule per minute, the glomerular filtration rate (GFR) can be calculated.