The primary function of the renal system in the body is to filter blood, remove waste, and regulate fluid and electrolyte balances. The kidneys play a central role by producing urine to excrete waste products, such as urea and creatinine, while retaining necessary substances like water, sodium, and potassium. This filtration process is vital for maintaining homeostasis and blood pressure. Additionally, the renal system contributes to the regulation of blood pH and the production of hormones, underscoring its importance in overall physiological function.