Scanning electron microscopy of human cerebral meningeal stomata.

The human dura mater and pia mater were studied by using a scanning electron microscope and a computer image processing system (C.I.P.). The human cerebral meningeal stomata are located between the mesothelial cells of the cerebral meninges. They are round or oval in shape with diameters of 0.33-2.98 microns. The cerebral meningeal stomata are stable structures, scattered or clustered together. Their density in the dura mater is greater than in the pia mater (P < 0.01), and they are regularly distributed. The statistical analysis showed that the stomata diameter and distribution density in the dura mater are 1.34 microns and 381.55/0.1 mm2; while in the pia mater they are 0.88 micron and 195.06/0.1 mm2 respectively. The cerebral meningeal stomata are probably part of the cerebral prelymphatic capillary system, which undertakes the cerebral lymph drainage because there are no lymphatic vessels in the brain although yet there is lymph drainage. Thus, we believe that the cerebral meningeal stomata are involved in maintaining the physiological function of the brain as part of the cerebrospinal fluid (CSF) which absorbs the cerebral interstitial fluid.