What is the functional unit of the kidney?

• A. Glomerulus
• B. Ureter
• C. Nephron
• D. Renal Pelvis

Answer: (C)

The nephron is the functional unit of the kidney. Each kidney contains about a million nephrons, and it’s within these tiny units that urine is formed. A nephron begins with the renal corpuscle, where plasma is filtered through the glomerulus into Bowman's capsule. But filtration alone isn’t enough—inside the tubular system (proximal tubule, loop of Henle, distal tubule, and collecting duct) the filtrate is selectively reabsorbed and secreted to reclaim water, electrolytes, and nutrients while eliminating wastes. This combination of filtration plus precise reabsorption and secretion is what the nephron does to produce urine. Structures such as the ureter and renal pelvis are part of the drainage pathway, not the processing unit of urine formation.