Keratinization Process of the Cuticle Layer in Growing Hair Follicles

This study investigated the keratinization process of the cuticle layer in hair follicles using electron microscopy. The cuticle layer, consisting of 6 cuticular cells, underwent keratinization starting with the formation of an intercellular membrane complex. Observations included destroyed nuclei, swollen mitochondria, and rough endoplasmic reticulum debris in the cuticle cell cytoplasm. Karyolysis was noted, indicating nuclear destruction. In the A layer and exocuticle zone, keratin proteins formed granular spheres that clustered and formed a high electron density band along the cell membrane. The keratinizing cuticular cells were 1-2 μm thick, significantly thicker than those in a normal hair shaft, due to incomplete cytosol loss.