Define glomerular filtration rate (GFR).

Define glomerular filtration rate (GFR).

• A. The rate at which blood is filtered by the tubules
• B. The rate at which filtrate is produced by the glomeruli, about 125 mL/min in a typical adult
• C. The rate of urine formation
• D. The rate of reabsorption in the proximal tubule

Answer: (B)

GFR measures the rate at which filtrate is produced by the glomeruli. It reflects how much fluid is filtered from the blood into the Bowman's capsule per minute, not how much blood flows through the kidney or how much urine is ultimately formed. In a healthy adult, this filtrate production rate is about 125 mL per minute, roughly 180 liters per day. This distinguishes filtration from urine formation, which depends on later tubular reabsorption and secretion, and from proximal tubule reabsorption, which is a separate process that modifies the filtrate after it has been formed.

GFR measures the rate at which filtrate is produced by the glomeruli. It reflects how much fluid is filtered from the blood into the Bowman's capsule per minute, not how much blood flows through the kidney or how much urine is ultimately formed. In a healthy adult, this filtrate production rate is about 125 mL per minute, roughly 180 liters per day. This distinguishes filtration from urine formation, which depends on later tubular reabsorption and secretion, and from proximal tubule reabsorption, which is a separate process that modifies the filtrate after it has been formed.