Final answer:
The movement of fluid through the capillary walls is controlled by both hydrostatic and osmotic pressures, not just blood pressure. High blood pressure can contribute to edema, but it is not the sole factor in fluid exchange and swelling in tissues.
Step-by-step explanation:
The statement that only blood pressure controls the movement of fluid through the capillary wall into the tissue is false. Fluid movement, particularly in the capillaries, is influenced by hydrostatic pressure and osmotic pressure.
Hydrostatic pressure, generated by the heart's pumping action, pushes water out of the capillaries into the tissue spaces.
However, osmotic pressure, predominantly due to plasma proteins like albumin, draws water back into the capillaries. These two pressures are in a dynamic equilibrium, ensuring proper fluid distribution.
People with high blood pressure may have an increased risk of edema or swelling in the tissues due to the higher hydrostatic pressure forcing more fluid out into the tissues than can be reabsorbed.
This is because at the arterial end of the capillary, the hydrostatic pressure is usually greater than the osmotic pressure, favoring fluid exit. Conversely, at the venous end, with lower hydrostatic pressure and higher osmotic pressure, fluid is drawn back into the capillaries.
When these pressures are imbalanced, as in hypertension, or when lymphatic drainage is inadequate, swelling can occur. Furthermore, factors such as valvular insufficiencies, gravity's effect on the lower limbs, and systemic health issues can also contribute towards edema.