Ultrastructural Characteristics of Neonate Scalp Hair

Background/Objectives: There are many differences between the hair from neonate and those from children and adults. Methods/ Statistical Analysis: The microstructural characteristics and external shape of neonate hairs were investigated using scanning electron microscopy and transmission electron microscopy. Findings: The thickness of the terminal end of neonate hairs was ~2.5 μm, with a slightly round shape, and one cuticle cell surrounded the cortex. Different from normal adult hair, a cuticle layer and cortex are present in neonate hair, but there is no medulla. Cuticle cells in neonate hair showed a typical structure. However, the exocuticle, endocuticle, A layer, and cell membrane complex exhibited markedly different electron densities. The cortex is composed of polygonal cortical cells and was clearly observed by the boundary of these cells. The cytoplasm of keratinized cortical cells is filled with macrofibrils and melanin granules around the cuticle layer and cortex regions. Applications/Improvements: Neonate hair follicles were ~0.5 mm in size, fivefold smaller than adult hair follicles. Neonate hair follicles had a structure identical to that of anagen phase adult hair follicles but differed in size.