An Electron Microscopic Study of Melanin in the Hair and Hair Follicles

The distribution of melanin pigment in all black guinea-pig hairs and anagen hair follicles was studied with the electron microscope. Melanocytes were identified in the upper part of the hair bulb, the outer root sheath and in the dermis adjacent to the follicle. In the immature medullary and cortical cells large numbers of melanosomes were seen among the other cytoplasmic structures. The cuticle cells contained a few melanosomes. As the different cell lines matured and underwent keratinization the melanosomes became embedded in the keratin. In the cortical cells the melanosomes were surrounded by a dense amorphous material which at many sites was attached to the inner surface of the plasma membrane. No melanin was seen in the cells of the inner root sheath. In the upper part of the outer root sheath the distribution of melanin closely resembled that found in the epidermis. In the lower part of the sheath the majority of the cells contained only a small amount of melanin pigment