What is the primary function of the kidneys?

The primary function of the kidneys is to filter blood and produce urine, which is fundamental for maintaining homeostasis in the body. The kidneys are responsible for removing waste products and excess substances from the bloodstream, effectively regulating the body's fluid balance, electrolytes, and waste removal.

Through a complex process of filtration, reabsorption, and secretion, the kidneys regulate the composition of bodily fluids by selectively filtering out waste while retaining necessary substances in the bloodstream. The resulting urine is then excreted, allowing the body to eliminate these wastes efficiently.

While regulating blood pressure and producing hormones are important secondary functions of the kidneys, the essential role revolves around filtering blood and producing urine. Storing waste does not accurately describe the kidneys’ function, as waste is not stored but rather actively filtered and excreted.