MICROCIRCULATION-DETERMINANTS OF HYDROSTATIC PRESSURE

SUMMARY

TIP: these factors are described by the Poiseuille-Hagen formula. Remember: greater the hydrostatic pressure, the greater the filtration of fluid into the interstitium.

1. Distance along the capillary: going from the arterial to the venule side, the pressure falls from 35 mmHg to 20 mmHg.

2. Resistance at the arterial and venule sides. Remember: Flow = (Pc-Pi)/R, hence, the lower the resistance, the greater the flow and greater the filtration. Important in the glomerulus where control of GFR is through alterations of pre-post capillary resistances.

3. Gravity: arterial & venous pressures are greater below the heart.

Reference(s)

Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education