Which part of the kidney does the work in urine formation?

• A. Glomerulus
• B. Nephron
• C. Renal pelvis
• D. Calyces

Answer: (B)

Urine formation is carried out by the nephron, the kidney’s functional unit. Blood is filtered at the glomerulus to form a filtrate, and this filtrate is then modified as it travels through the nephron’s tubules—the proximal tubule, loop of Henle, distal tubule, and collecting duct—by reabsorption and secretion, producing urine. The renal pelvis and calyces simply collect and funnel urine into the ureter; they don’t perform the filtration or processing steps. So, the work of forming urine happens within the nephron, with filtration at the glomerulus being just the first step inside that unit.