Filtration is the process of which nephron function?

• A. Excretion
• B. Filtration
• C. Reabsorption
• D. Secretion

Answer: (B)

Filtration is the movement of plasma from the blood into the nephron at the glomerulus, forming the glomerular filtrate that enters Bowman's capsule. This is the first step in urine formation, driven by blood pressure across the filtration barrier. Large components like blood cells and most proteins stay in the bloodstream, while water and small solutes pass into the filtrate.

Reabsorption then pulls needed substances back into the blood from the filtrate, secretion adds additional substances from blood into the filtrate, and excretion is the final elimination of urine after these adjustments. So, filtering the blood to create filtrate is the process described by filtration.