The thickness of the epidermis is 0.2mm, the length of whole spicules is around 200um can reach the dermis, but broken spicules not long enough to penetrate the epidermal layer, they are useless!
Calculating Formula of Integrity rate(Ir):
* IrAv: Average integrity rate of three different spots
Ira,b,c: Integrity rate in one spot of 100X microscope area