A STUDY OF THE DIFFERENTIATION PRODUCTS OF THE HAIR FOLLICLE CELLS WITH THE ELECTRON MICROSCOPE.

Abstract

Investigations with the light microscope have shown that the base of the hair follicle consists of undifferentiated, pluri-potential, cuboidal matrix-cells which give rise to four different cell types: those of the medulla, the cortex, the cuticle and the inner root sheath (1). In the center of the hair follicle the ascending matrix cells develop small granules in their cytoplasm, and these cells become the medulla of the hair. Around the medulla, spindle shaped cells emerge from the matrix and develop cytoplasmic fibers, and these cells become the cortex of the hair. Next to the cortex appear cells which on ascending flattened and become hyalinized to form the cuticle of the hair. The peripheral part of the hair follicle is called the inner root sheath and consists of three concentric layers: (1) the cuticle, (2) Huxley's layer and (3) Henle's layer. The cells of the inner root sheath all undergo similar changes as they emerge from the matrix and migrate upwards in the follicle. Each gradually flattens and develops trichohyalin granules in the cytoplasm. During advanced stages of differentiation the trichohyalin granules disappear and the terminal cells become filled with a fibrous horny material. The inner root sheath cells are lost by scaling when they reach the level of the orifice of the sebaceous gland and thus do not contribute to the emerging hair fiber.