What percentage of cardiac output is supplied to kidneys?
**Core Concept**
The **renal blood flow** is a significant fraction of the **cardiac output**, essential for maintaining proper kidney function, including filtration and excretion. The kidneys receive a substantial portion of the cardiac output to perform these critical functions. This is due to the high metabolic rate of renal tissues.
**Why the Correct Answer is Right**
The correct answer is based on the fact that kidneys require about 20-25% of the cardiac output to function properly. This high demand is necessary for the **glomerular filtration rate**, which is crucial for waste removal and electrolyte balance. The **renal arteries** branch off from the **aorta** to supply the kidneys with the necessary blood flow.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it significantly underestimates the blood flow required by the kidneys.
**Option B:** This option overestimates the renal blood flow, which would be excessive for kidney function.
**Option D:** This option also underestimates the renal blood flow, not meeting the demands for proper kidney function.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the kidneys receive approximately 20-25% of the cardiac output, highlighting their significant role in overall bodily function. Any reduction in renal blood flow can lead to acute kidney injury.
**Correct Answer:** C. 20-25%