Knowra Hair growth Hair growth Hair growth is the cyclic production of hair fibers by follicles, followed by a resting period and eventual shedding. Its timing and pattern vary across body regions and individuals.
Hair follicle : A skin organ that produces a hair fiber and cycles through phases of growth, regression, and rest. The follicle is the structure that generates each hair and controls its cycle.
Hair shaft : The visible portion of a hair fiber extending above the skin, composed chiefly of keratinized cells. It is the product whose formation and eventual release define the cycle.
Androgenetic alopecia : A common patterned form of hair loss caused by genetically influenced follicle sensitivity to androgens. Affected follicles progressively miniaturize and spend less time producing thick hairs.
Vellus hair : Short, fine, lightly pigmented hair that covers much of the body and lacks the thickness of terminal hair. It contrasts with the thicker fibers produced by many actively growing scalp follicles.
Hair follicle neogenesis : The formation of new hair follicles, especially during wound repair or experimental tissue regeneration. It asks whether adult skin can create follicles rather than merely reactivate existing ones.
Anagen : The active growth phase of a hair follicle, during which its cells produce the hair shaft. Its duration largely determines the maximum length of scalp hair.
Keratin : A family of structural proteins that gives hair, nails, and the outer skin layers strength and resilience. Hair-shaft cells become durable fibers through keratin production.
Telogen effluvium : Diffuse hair shedding that occurs when an unusually large share of follicles enters telogen after a trigger. A shift in cycle timing produces visible shedding without destroying follicles.
Terminal hair : Coarse, often pigmented hair found on the scalp and, after puberty, in several other body regions. Its size and duration differ from fine vellus hair, even though both arise from follicles.
Hair follicle organoid : A laboratory-grown three-dimensional cell model designed to reproduce features of a hair follicle. Organoids offer ways to study cycle regulation and test treatments outside the body.
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