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Ultrastructure of the human toenail II. Keratinization and formation of the marginal band

1971; Academic Press; Volume: 36; Issue: 3-4 Linguagem: Inglês

10.1016/s0022-5320(71)80112-0

1878-2345

Ken Hashimoto,

Dermatologic Treatments and Research

Human tonenail cells keratinized by accretion of cytoplasmic filaments and without the formation of keratohyaline granules. Clumping of cytoplasmic filaments first formed prekeratin fibrils which eventually filled the entire cytoplasm and became keratin fibrils. Within some of the prekeratin, and in the majority of the keratin fibrils, filaments measuring 65–75 Å showing a central core were observed. Numerous free ribosomes and a number of round, rough-surfaced cisterns of endoplasmic reticulum were present in the keratinizing nail cells. A marginal band formed and was responsible for the doubling of the thickness of the cellular envelope. This was not derived from the material of the membrane-coating granules. The marginal band was protease resistant. The original plasma membrane did not increase in thickness and was observed outside the marginal band.