Why can water & solutes pass out of the glomerulus for circulation?

• A. Because there are active transport pumps in the nephron tubules
• B. Because there is a one-way valve
• C. Because there is more pressure inside than outside
• D. Because red blood cells push filtrate

Answer: (C)

The process is driven by a pressure difference across the filtration barrier. The hydrostatic pressure inside the glomerular capillaries is higher than the hydrostatic pressure in Bowman's space, which pushes water and small solutes from the blood into the nephron. This passive filtration relies on the pressure gradient, not active transport. The filtration barrier (endothelium, basement membrane, and podocyte slits) allows water and small molecules to pass while restricting larger proteins and cells. There’s no valve mechanism at the glomerulus, and red blood cells don’t push filtrate—they stay in the capillaries because they’re too large to pass through.