Anatomy & Physiology of Hair Growth Flashcards

Which layer immediately surrounds the outer root sheath and consists of a thickened basement membrane?

Answer: Glassy membrane (vitreous layer)

The glassy membrane, also called the vitreous layer, is a hyaline basement membrane that forms the outermost boundary of the follicle separating it from the dermis.

In electrology, the dermal papilla is the primary treatment target because it:

Answer: Contains the blood supply and signals that sustain hair growth

The dermal papilla contains the vasculature and inductive mesenchymal cells that signal the matrix to produce hair; its destruction leads to permanent hair removal.

What percentage of scalp follicles are typically in anagen at any given time?

Answer: 85–90%

At any given time, approximately 85–90% of scalp hair follicles are in the anagen (active growth) phase.

Melanocytes in the hair follicle are concentrated in the:

Answer: Bulb matrix surrounding the papilla

Follicular melanocytes reside in the matrix of the hair bulb and transfer melanin granules to cortical cells during anagen.

The sebaceous gland is a type of:

Answer: Holocrine gland

Sebaceous glands are holocrine glands that release sebum by complete cell disintegration.

Which hormone is most directly responsible for converting vellus hairs to terminal hairs in androgen-sensitive follicles?

Answer: Dihydrotestosterone (DHT)

DHT, converted from testosterone by 5-alpha reductase in follicle cells, is the primary androgen driving vellus-to-terminal conversion in sensitive follicles.

Which structure in the hair follicle serves as the reservoir for epithelial stem cells responsible for follicle regeneration?

Answer: Bulge region of the outer root sheath

The bulge, located at the attachment point of the arrector pili, harbors slow-cycling epithelial stem cells that regenerate the lower follicle during each anagen phase.