Red platelets are too vast to leave any capillaries. As capillaries are just a single cell thick and have thin porous dividers this implies substances can diffuse out of them effortlessly. Helpful substances, for example, oxygen and sustenance diffuse out of the blood in the vessels into the tissue liquid where it is then taken to the cells.
Cellular respiration that proceeds in the absence of oxygen is anaerobic respiration. Cellular respiration that proceeds in the presence of oxygen is aerobic respiration. Anaerobic respiration evolved prior to aerobic respiration.
