The Henle, Huxley and cuticle layers of the IRS; the IRS cuticle layer adjoins the cuticle of the presumptive hair fibre.The presumptive hair shaft comprises an outer layer of overlapping cuticle cells surrounding a cellular cortex and sometimes a central medulla. (...) An additional feature of the hair cuticle is the presence of a group of long-chain fatty acids that is responsible for the hydrophobicity of the hair surface.