tiny spaces between tissue cells - contain a colorless liquid - tissue fluid transports dissolved substances between the tissue cells and the blood capillaries.

dissolved food substances and O2 - diffuse from the blood in the blood capillaries to the tissue fluid. then they diffuse from tissue fluid to the cells.

Metabolic(or excretory) products diffuse from the cells into the tissue fluid. they are then transferred through the blood capillary walls into the blood. the blood then transports these waste products to excretory organs for removal.