A healthy adult has a GFR of 125 mL/min and a renal plasma flow of 625 mL/min. What is her filtration fraction, and what does this value indicate about the plasma reaching the glomeruli?
- A 10%, meaning most filtered fluid is returned to blood
- B 20%, meaning one fifth of renal plasma is filtered ✓
- C 50%, meaning half of renal plasma enters Bowman space
- D 80%, meaning filtration is highly efficient
Correct answer: B. 20%, meaning one fifth of renal plasma is filtered
Explanation
Filtration fraction equals GFR divided by renal plasma flow: 125/625 = 0.20, so 20 percent of the plasma arriving at the glomerulus is filtered into Bowman space while 80 percent continues into the peritubular capillaries. The normal range is roughly 15 to 20 percent. This ratio also explains why protein concentration rises along the glomerular capillary, increasing colloid osmotic pressure and opposing further filtration.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.