What are the forces opposing filtration at the glomerulus?

• A. Capsular hydrostatic pressure and glomerular hydrostatic pressure
• B. Blood colloid osmotic pressure and capsular hydrostatic pressure
• C. Glomerular hydrostatic pressure and blood colloid osmotic pressure
• D. Blood colloid osmotic pressure and tubular reabsorption pressure

Answer: (B)

Verified step by step guidance

1. Begin by understanding the process of glomerular filtration, which occurs in the kidneys. Filtration is driven by pressure differences across the glomerular capillaries.
2. Identify the forces that favor filtration: Glomerular hydrostatic pressure is the main force that pushes water and solutes out of the blood and into the glomerular capsule.
3. Next, consider the forces that oppose filtration. These include blood colloid osmotic pressure, which is the pressure exerted by proteins in the blood that draw water back into the capillaries.
4. Another opposing force is capsular hydrostatic pressure, which is the pressure exerted by the fluid already present in the glomerular capsule that resists the influx of additional fluid.
5. Understand that tubular reabsorption pressure is not typically considered a direct opposing force to filtration at the glomerulus, as it occurs later in the nephron during the reabsorption process.