CPE Anatomy & Physiology of Hair Growth 5 — Questions and Answers
Question 1: Which enzyme converts testosterone to dihydrotestosterone (DHT) within the hair follicle?
- 5-alpha reductase (Correct answer)
- Aromatase
- 17-beta hydroxysteroid dehydrogenase
- Tyrosinase
Correct answer: 5-alpha reductase
5-alpha reductase, present in follicle dermal papilla cells, converts testosterone to the more potent DHT locally within the follicle.
Question 2: The cuticle of the hair shaft is best described as:
- Overlapping flattened keratinized scales pointing toward the hair tip (Correct answer)
- A single continuous outer membrane with no overlapping cells
- Melanin-rich cells covering the cortex
- Loosely packed cells with air pockets
Correct answer: Overlapping flattened keratinized scales pointing toward the hair tip
The hair cuticle consists of overlapping, scale-like keratinized cells angled toward the distal tip, forming a protective outer layer.
Question 3: Which phase immediately follows catagen in the hair cycle?
- Telogen (Correct answer)
- Anagen
- Exogen
- Kenogen
Correct answer: Telogen
After catagen's regression phase concludes, the follicle enters telogen, a resting period during which the club hair is retained before eventual shedding.
Question 4: Hair follicles first appear in the human fetus at approximately:
- 9–12 weeks gestation on the face (Correct answer)
- 24–28 weeks gestation across the body
- 5–6 weeks gestation on the scalp
- 32 weeks gestation in all areas simultaneously
Correct answer: 9–12 weeks gestation on the face
Hair follicle development begins around 9–12 weeks of gestation, first appearing on the face (lips, eyebrows) before progressing over the rest of the body.
Question 5: What is the function of the companion layer within the hair follicle?
- It separates the outer root sheath from the inner root sheath and allows them to move independently (Correct answer)
- It produces melanin for the hair shaft
- It anchors the dermal papilla to the matrix
- It forms the glassy membrane
Correct answer: It separates the outer root sheath from the inner root sheath and allows them to move independently
The companion layer acts as a sliding plane between the inner and outer root sheaths, allowing the inner sheath and hair shaft to move upward while the outer sheath remains relatively stationary.
Question 6: In the context of electrology, a follicle in telogen is more challenging to treat permanently because:
- The germinal cells in the bulge are quiescent and less accessible to the current's focal point (Correct answer)
- The follicle is wider and deeper during telogen
- Sebum production is highest during telogen, insulating the current
- The arrector pili is fully contracted, distorting the follicle angle
Correct answer: The germinal cells in the bulge are quiescent and less accessible to the current's focal point
During telogen the lower follicle has regressed and the active germinal tissue near the papilla is retracted, making it harder to deliver effective current to the full germinal zone.
Question 7: Hypertrichosis differs from hirsutism in that hypertrichosis:
- Is excessive hair growth in a non-androgen-dependent pattern, affecting any body site (Correct answer)
- Is excessive facial hair growth in women due to elevated androgens
- Only occurs in men with genetic predisposition
- Refers exclusively to lanugo persistence after birth
Correct answer: Is excessive hair growth in a non-androgen-dependent pattern, affecting any body site
Hypertrichosis is a generalized or localized excess of hair growth not related to androgen stimulation, whereas hirsutism specifically refers to androgen-driven terminal hair growth in women in male-pattern distribution areas.
CPE Anatomy & Physiology of Hair Growth 5
Which enzyme converts testosterone to dihydrotestosterone (DHT) within the hair follicle?