1. General feature. 1)contain more cells and less extracellular ground substance 2)Polarisation: --free outer surface: face air or other things basal surface: face underlying CT, have basement membrane 3) Avascularity, but innervation: -m-no blood vessels --rich in nerve terminals 4) Having functions of protection, secretion, absorption excretion and sensory reception1.General feature: 1) contain more cells and less extracellular ground substance 2) Polarisaton: ---free outer surface: face air or other things ---basal surface: face underlying CT, havebasement membrane 3) Avascularity,but innervation: ---no blood vessels ---rich in nerve terminals 4) Having functions of protection, secretion, absorption excretion and sensory reception