Question

Net filtration pressure in the glomerulus is determined by the following equation: bhp - (cop cp) = nfp. Which of the following must be true for filtration to occur?

1) Blood hydrostatic pressure (BHP) must be greater than colloid osmotic pressure (COP)
2) Colloid osmotic pressure (COP) must be greater than capillary pressure (CP)
3) Net filtration pressure (NFP) must be positive
4) Blood hydrostatic pressure (BHP) must be equal to capillary pressure (CP)

Answer 1

For glomerular filtration to occur, the Net Filtration Pressure (NFP) must be positive, indicating that the Blood Hydrostatic Pressure must outweigh the total of Capsular Hydrostatic Pressure and Blood Colloid Osmotic Pressure.

Step-by-step explanation:

For filtration to occur in the glomerulus, Net Filtration Pressure (NFP) must be positive. This requires that the Glomerular Blood Hydrostatic Pressure (GBHP) be greater than the sum of the Capsular Hydrostatic Pressure (CHP) and the Blood Colloid Osmotic Pressure (BCOP). Therefore, option 3, stating that NFP must be positive, is correct for filtration to take place.

Options 1 and 4 are not necessarily true, while option 2 is incorrect as COP does not need to be greater than CP for filtration to occur. The equation NFP = GBHP - [CHP + BCOP] = 10 mm Hg illustrates the balance of pressures necessary for filtration, bearing in mind that hydrostatic pressure is the force that drives fluid out of the capillary, opposed by osmotic pressure which attracts water into the bloodstream.