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KMID : 0376219830200040901
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Chonnam Medical Journal
1983 Volume.20 No. 4 p.901 ~ p.908
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Electron microscopy of developing hair Follicle in human fetus
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Abstract
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Light and electron microscopic studies were performed on the developing hair follicles in the scalp of the human fetuses at the gestation ages of fourteenth and sixteenth weeks. And the following results were obtained.
In the scalp skin at fourteenth week of development, hair follicles showed various stages of development. The hair follicle in hair peg stage was composed of outer matrix cells arranged radially to the long axis of the follicle and hair cone cells in the center. Entire hair peg was enveloped by a sheath of two or three layers of the mesenchymal cell, and near the tip of the peg mesenchymal cells accumulated and formed a dense cluster of the cells. At early bulbous peg stage, tip of the follicle showed U-shaped invagination into which mesenchymal cells were clustered. At this stage of development, hair follicle consisted of the central hair cone cells, inner root sheath cells containing trichohyalin granules, and outer root sheath cells with clear cytoplasm. DOPA reaction of the skin was noted to be faint and sporadic only in hair follicles.
In the scalp skin at sixteenth week of development, follicle had well developed bulb enclosing dermal papilla. Around the deepest portion of the follicle, group of the mesenchymal cells crowded and showed lamellar arrangement. At the level of the bulb, hair follicle was composed of matrix cells, presumtive hair cone cells, and outer root sheath cells. Matrix cells were single layered columnar cells and were arranged radially to the papilla. Many cytoplasmic processes of the melanocytes were noted among the matrix cells. Presumtive hair cone cells continuous to the inner root sheath cells had no trichohyalin granules in basal portion of the bulb, but contained in its upper portion. Above the level of the apex of the papilla, hair follicle consisted of hair cone cells, inner root sheath cells, and outer root sheath cells. The inner root sheath cells revealed two layers of cells, inner Huxley´s and outer Henle´s layers along its long axis. Inner Huxley´s layer cells contained many trichohyalin granules of various sizes and abundant tonofilaments, and outer Henle´s layer cells contained mainly tonofilaments without trichohyalin granules. Outer root sheath cells had clear cytoplasm which often appeared to be empty spaces and minimum amounts of cell organelles mainly around the nucleus. DOPA reaction of the skin was strongly positive in bulbar matrix and hair cone, and sporadic in basal portion of the epidermis.
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