Heterophagic intracellular digestion is the breaking into minute substances of external substances engulfed in the cell by pinocytosis or phagocytosis. Phagosomes or pinosomes fuse with lysosomes making the digestive vacuoles. Within the digestive vacuoles the molecules to be digested are hydrolyzed and the products of the digestion cross by the membrane and reach the cytoplasm or they are kept inside the vacuoles. The vacuole with residues from digestion is known as residual body and by exocytosis it fuses with the plasma membrane and liberates its "waste" in the exterior space.