What is the primary function of the kidneys?

The primary function of the kidneys is to filter blood and produce urine. This vital role is essential for maintaining the body's homeostasis. The kidneys work by removing waste products and excess substances from the bloodstream, which are then excreted as urine. Through this process, they help regulate important aspects of the body's chemistry, such as electrolyte balance, fluid levels, and acid-base balance.

In addition to filtering blood, the kidneys also play a significant role in controlling blood pressure and stimulating the production of red blood cells through the production of erythropoietin. However, their most fundamental function lies in the filtration and excretion process that ensures toxins and excess substances do not accumulate to harmful levels in the body.