The nephron is composed of which parts?

• A. A glomerulus and a tubule system
• B. Two glomeruli
• C. Tubules only
• D. Arterioles and venules

Answer: (A)

The nephron is built from a filtering unit and a tubular processing unit. The glomerulus, a knot of capillaries, performs filtration to produce a filtrate from blood. The tubule system—which includes the proximal tubule, loop of Henle, distal tubule, and collecting duct—reabsorbs water and solutes and secretes wastes, shaping the filtrate into urine. This combination of a glomerulus for filtration plus a tubular system for processing is the essential structure of a nephron. It isn’t two glomeruli, nor tubules alone without a filtration site, nor just vessels like arterioles and venules.