- This is Starling’s Law of Capillaries:
: hydrostatic forces are outward (from the capillary) directing.
- At the arterial end of the capillary, the hydrostatic forces are very high, which will tend to force fluids into surrounding tissues. Note
- Also at this end, the oncotic and osmotic forces are low compared to the hydrostatic forces, so the hydrostatic forces will dominate. Note: oncotic and osmotic forces are inward (to the capillary) directing.
- At the venule end of the capillary, the hydrostatic forces are weak, which will NOT force fluids into surrounding tissues.
- While at this end, the oncotic and osmotic forces are very high compared to the hydrostatic forces, so the oncotic/osmotic forces will dominate.
- About 90% of the fluid forced out beginning at the arterial end will be recovered prior to the venule end.
Titi seemed to differentiate osmotic from oncotic by way of saying that osmotic is a “salt” or Sodium thing whereas oncotic is a “protein” thing.
Wiki says: “Oncotic pressure, or colloid osmotic pressure, is a form of osmotic pressure exerted by proteins in blood plasma that usually tends to pull water into the circulatory system.”
The book states on page 683: “Osmotic pressure generated by blood colloids (such as plasma proteins).”