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Dermatopathology: Practical & Conceptual July - September 1995
Searching for Diogenes: Bulge-Activation Hypothesis Part III—A Mouse is Not a Man
A. Bernard Ackerman, M.D.
Cosimo Misciali, M.D.
Michael Radonich, M.D.
The follicular cycle in a human portrayed through photomicrographs
"The bulge" as portrayed through photomicrographs
A synopsis of two contrary views of "the bulge"
In order for a reader to appreciate fully the contrasting views of "the bulge" by Lavker, Sun, Cotsarelis, and coworkers on one hand, and by us on the other, knowledge of the follicular cycle is essential. For that reason, before proceeding to set forth those different views of "the bulge," the cycle of a follicle will be illustrated in a series of photomicrographs. And before proceeding to that Atlas, it should be re-called that the follicular cycle has been divided, conventionally, into growing (anagen), involuting (catagen), and resting (telogen) phases. A follicle at the outset of anagen develops from the lowermost portion of the permanent segment of a follicle, which consists of an upper infundibulum and a lower isthmus. The formation of a new transient segment of a follicle, which consists of an upper stem and a lower bulb, recapitulates the development of a follicle in an embryo and is a consequence of interplay of follicular papilla and follicular germ. The lower segment is regarded as transient because it alone participates in the dynamic of the follicular cycle; the upper segment is considered to be permanent because, except for cells at the base of the isthmus, it is not a participant in the cycle.
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