CPE Anatomy & Physiology of Hair Growth 3 — Questions and Answers
Question 1: Which layer immediately surrounds the outer root sheath and consists of a thickened basement membrane?
- Glassy membrane (vitreous layer) (Correct answer)
- Henle's layer
- Huxley's layer
- Companion layer
Correct 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.
Question 2: In electrology, the dermal papilla is the primary treatment target because it:
- Contains the blood supply and signals that sustain hair growth (Correct answer)
- Is the hardest structure to destroy in the follicle
- Produces melanin that pigments the hair
- Forms the outer root sheath
Correct 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.
Question 3: What percentage of scalp follicles are typically in anagen at any given time?
- 85–90% (Correct answer)
- 10–15%
- 50–60%
- 30–40%
Correct answer: 85–90%
At any given time, approximately 85–90% of scalp hair follicles are in the anagen (active growth) phase.
Question 4: Melanocytes in the hair follicle are concentrated in the:
- Bulb matrix surrounding the papilla (Correct answer)
- Outer root sheath at the isthmus
- Sebaceous gland
- Arrector pili muscle
Correct 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.
Question 5: The sebaceous gland is a type of:
- Holocrine gland (Correct answer)
- Merocrine gland
- Apocrine gland
- Eccrine gland
Correct answer: Holocrine gland
Sebaceous glands are holocrine glands that release sebum by complete cell disintegration.
Question 6: Which hormone is most directly responsible for converting vellus hairs to terminal hairs in androgen-sensitive follicles?
- Dihydrotestosterone (DHT) (Correct answer)
- Estrogen
- Cortisol
- Prolactin
Correct 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.
Question 7: Which structure in the hair follicle serves as the reservoir for epithelial stem cells responsible for follicle regeneration?
- Bulge region of the outer root sheath (Correct answer)
- Dermal papilla
- Matrix layer
- Companion layer
Correct 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.
CPE Anatomy & Physiology of Hair Growth 3
Which layer immediately surrounds the outer root sheath and consists of a thickened basement membrane?