The filtrate entering the nephron from the blood is called?

• A. Urine
• B. Filtrate (glomerular filtrate)
• C. Blood plasma
• D. Primary urine

Answer: (B)

Filtration at the glomerulus produces the fluid that enters the nephron, and this is called glomerular filtrate. As plasma is pushed through the filtration barrier into Bowman's capsule, the resulting filtrate is a filtered version of blood plasma—containing water, ions, glucose, amino acids, and small waste molecules but lacking cells and large proteins that can’t pass. It’s not yet urine because it will be modified as it moves through the tubules; urine only forms after reabsorption, secretion, and collection. Some texts call this fluid primary urine, but the precise term for the fluid entering the nephron is glomerular filtrate (a filtrate). Blood plasma, meanwhile, remains in the circulatory system and does not enter the nephron.