tissues fluid

Tissue fluid surrounds cells and substances (e.g. glucose and oxygen) get from the blood to the cell via tissue fluid.

At the arterial part of the capillaries (the bit coming from the heart) there's high hydrostatic pressure (as the blood is being pumped at high pressure through small capillaries)) so plasma from the blood diffuses out of the capillary as they are semi permeable. Only small molecules come out of the capillary walls (ultrafiltration), some molecules, e.g. red blood cells and proteins are too large so they remain in the blood.

The lymph system carries excess tissue fluid towards the heart where it's drained into the blood. Lymph is moved along by contraction of muscles (doesn't use heart/pump) and has semi-lunar valves.

That help at all? lol