What is the main function of the kidneys in the body?

The primary function of the kidneys is to filter blood. This critical process allows them to remove waste products, excess substances, and toxins from the bloodstream, thus helping to maintain a balanced internal environment, known as homeostasis. As blood flows through the kidneys, nephrons – the functional units of the kidneys – work to filter out urea, creatinine, and other waste products, which are then excreted in urine.

While the removal of wastes is a key component of their function, it is important to note that this process is inherently connected to their ability to filter blood. The filtering action of the kidneys ensures that harmful substances are effectively excreted, which is vital for preventing the accumulation of toxins in the body.

Additionally, the kidneys also play roles in regulating blood pressure, electrolyte balance, and acid-base balance, which further underscores their importance in overall health. Therefore, while removing wastes is a significant outcome of the kidneys' filtering function, it is the act of filtering blood that encapsulates the kidneys' main role in the body.