What role do kidneys play in the urinary system?

• A. They metabolize fats
• B. They filter blood and produce urine
• C. They secrete digestive enzymes
• D. They regulate blood sugar

Answer: (B)

The kidneys’ main job in the urinary system is to filter the blood and produce urine. Nephrons at work filter waste and excess substances from the bloodstream, reabsorb what the body needs (like water and essential electrolytes), and secrete additional wastes into the filtrate. This filtrate becomes urine, which flows from the kidneys through the ureters to the bladder for storage before excretion. The kidneys also help regulate fluid balance, electrolyte levels, and acid-base balance, keeping the internal environment stable.

Metabolizing fats isn’t a function of the kidneys; that’s primarily the role of the liver and adipose tissue. Secreting digestive enzymes is associated with the digestive organs such as the pancreas and stomach. Regulating blood sugar is mainly controlled by hormones from the pancreas (and liver), with the kidneys playing only a secondary role in glucose handling, not primary regulation.