Tissue fluid is formed as blood flows through capillaries. Some fluid passes through capillary walls into tissues, carrying nutrients to cells. This fluid, called tissue fluid, bathes cells. Not all tissue fluid returns to blood capillaries. Around 10% enters lymph capillaries, which are part of the lymph system. Lymph vessels drain excess tissue fluid through the lymph system back to the bloodstream, preventing fluid accumulation in tissues.

1. Tissue fluid

5. Tissue fluid – exchange with tissues

6. Quick question – If you take out lots of water from a fluid but leave all the large plasma proteins in it, what happens to the water potential?

16. Tissue fluid

19. Explain what causes the decrease in water potential at the arterial end of the capillary. Explain what causes the increase in water potential towards the venous end of the capillary.