are the only places where water and materials are exchanged between the blood and tissue fluids
Capillary to Tissue Fluid Exchange. Capillaries are where fluids, gasses, nutrients, and wastes are exchanged between the blood and body tissues by diffusion. Capillary walls contain small pores that allow certain substances to pass into and out of the blood vessel.apillaries measure in size from about 5-10 microns in diameter. Capillary walls are thin and are composed of endothelium (a type of simple squamous epithelial tissue). Oxygen, carbon dioxide, nutrients and wastes are exchanged through the thin walls of the capillaries.