Final answer:
The primary determinant of the net filtration pressure (NFP) is the capillary hydrostatic pressure (CHP), balanced against the capillary plasma colloid osmotic pressure (BCOP), which determines the rate of glomerular filtration in the kidneys.
Step-by-step explanation:
The primary determinant of the net filtration pressure (NFP) in the kidneys is the balance between capillary hydrostatic pressure (CHP) and capillary plasma colloid osmotic pressure (BCOP). The NFP is calculated as the difference between glomerular blood hydrostatic pressure (GBHP) and the sum of the capsular hydrostatic pressure (CHP) plus the blood colloid osmotic pressure (BCOP). It represents the interaction of hydrostatic and osmotic pressures, driving fluid out of the glomerular capillaries and into Bowman's capsule, facilitating the process of filtration in the kidneys.
Hydrostatic pressure tends to push fluid out of the capillaries while osmotic pressure, generated by proteins in the plasma such as albumin, draws water back into the capillaries. The combined influence of these pressures results in an NFP that determines the rate of glomerular filtration. A disruption in the balance of these pressures can lead to conditions such as systemic edema, where water is lost from the circulation to interstitial tissues and cells.