Final answer:
90% of sensitive surfaces are found in glabrous skin on the fingertips and eyelids, where specialized Meissner's corpuscles detect fine touch and pressure.
Step-by-step explanation:
Approximately 90% of sensitive surfaces are found in glabrous skin, primarily on the fingertips and eyelids. These sensitive areas contain Meissner's corpuscles and other specialized sensory structures which are responsive to fine touch and pressure, as well as low-frequency vibrations. The presence of these sensory receptors explains the high sensitivity found in these regions, with the corpuscles being situated in the upper dermis while projecting into the epidermis. These surfaces act as important entry points for microbes. They include the eyes, nose, mouth, urethra, and anus, which are contiguous with the external skin.