What is a principal function of the urinary system?

• A. Digest fats
• B. Exchange gases
• C. Maintain the volume and composition of body fluids
• D. Produce hormones that regulate metabolism

Answer: (C)

The urinary system’s main job is to keep the volume and composition of body fluids within narrow, healthy limits. The kidneys filter blood to remove waste products and excess substances, then reabsorb what the body still needs. By adjusting how much water and which electrolytes are lost in urine, the system controls blood volume, osmolality, electrolyte balance, and acid-base status. This balance is essential for normal cell function, nerve signaling, muscle activity, and blood pressure regulation.

Other functions listed belong to different body systems. Digesting fats is a task of the digestive system, exchanging gases is handled by the respiratory system, and while the kidneys do produce hormones, regulating metabolism is primarily an endocrine function rather than the principal role of the urinary system.