What is the function of the kidneys?

The primary function of the kidneys is to filter blood and regulate fluid levels in the body. This involves removing waste products and excess substances from the bloodstream, which are then excreted as urine. The kidneys also play a crucial role in maintaining the body's electrolyte balance, controlling blood pressure, and producing hormones that regulate various bodily functions, such as erythropoiesis through the production of erythropoietin.

While the kidneys do produce hormones, such as erythropoietin and renin, this is part of their broader role in maintaining homeostasis, rather than their main function. The kidneys are not involved in digestion, which is a process that primarily takes place in the gastrointestinal tract. Additionally, waste filtration from the lymphatic system is not a function of the kidneys; instead, this process is handled by the lymphatic system itself, which helps to remove waste and maintain fluid balance in tissues. Therefore, focusing on the role of the kidneys in blood filtration and fluid regulation highlights their significance in maintaining overall health and homeostasis.