Final answer:
The main metabolic byproduct eliminated by the urinary system is urea, which results from protein metabolism. The kidneys are the central organ in this system, performing the filtration and excretion processes to maintain bodily homeostasis.
Step-by-step explanation:
The principal function of the urinary system is the elimination of the body's major metabolic byproduct, which is urea. Urea is produced as a result of protein catabolism, and it is a primary waste product that the kidneys work to remove from the bloodstream. The kidneys are integral components of the urinary system, which also includes the ureters, urinary bladder, and urethra. The entire system works together to maintain homeostasis by filtering blood, eliminating waste products such as urea, uric acid, excess water, and regulating mineral ions. Furthermore, the urinary system plays a crucial role in regulating the body's acid-base balance, controlling blood pressure, and aiding in the maintenance of overall fluid balance.