What does the renal system primarily do?

The renal system, also known as the urinary system, is essential for maintaining the body's internal environment. Its primary function is to filter blood to remove waste products and excess substances, which are then excreted as urine. This process helps regulate electrolyte levels, maintain acid-base balance, and control blood pressure through the adjustment of fluid volume in the body.

Additionally, the renal system plays a vital role in filtering metabolic waste and toxins from the bloodstream, thereby preventing their buildup, which could lead to serious health issues. The production of urine is a critical mechanism for the excretion of waste, ensuring that the body maintains a balance of fluids and electrolytes necessary for overall homeostasis.

Other options pertain to different systems in the body; for instance, processing food and absorbing nutrients relates to the digestive system, temperature regulation involves the integumentary and endocrine systems, and hormone circulation primarily pertains to the circulatory system and endocrine system.