 Particles larger than 50 micrometers cannot enter the ostia and pinacocytes consume them by phagocytosis (engulfing and internal digestion).Particles from 0.5 μm to 50 μm are trapped in the ostia, which taper from the outer to inner ends.These particles are consumed by pinacocytes or by archaeocytes which partially extrude themselves through the walls of the ostia.