New Aspects of the Structure of Human Hair Based on Optical Microscopic Observations of Disassembled Hair Parts

The study by Asao Yamauchi et al. in 2015 focused on the microscopic structure of human hair by disassembling infant and adult scalp hair fibers using chemical, enzymatic treatments, and mechanical fracturing. The optical microscopic observations revealed previously unknown structures within the hair shaft, particularly a cuticular cell (Cu) with a trowel-like shape, consisting of a blade-like part (CuB) and a handle-like part (CuH). These components formed a honeycomb-like structure on a large cuticular thin plate (CuP). The CuH was similar to cortical cells in dimensions and macrofibril richness. The study concluded that the structural and physicochemical stability of human hair is significantly influenced by the honeycomb-like structure, CuP, and macrofibrils.