CPE Anatomy & Physiology of Hair Growth 4 — Questions and Answers
Question 1: During catagen, the follicle shortens primarily because of:
- Programmed apoptosis of matrix and lower follicle cells (Correct answer)
- Mechanical compression by the dermis
- Cessation of sebum production
- Loss of melanocyte activity only
Correct answer: Programmed apoptosis of matrix and lower follicle cells
Catagen regression is driven by apoptosis of the epithelial cells in the lower follicle, causing the follicle to shrink upward toward the bulge.
Question 2: Vellus hairs differ from terminal hairs in that they:
- Have little or no medulla and lack significant pigmentation (Correct answer)
- Are always found on the scalp
- Are thicker and darker
- Grow continuously without a rest phase
Correct answer: Have little or no medulla and lack significant pigmentation
Vellus hairs are fine, short, and lightly pigmented with a thin or absent medulla, unlike the thicker, pigmented terminal hairs.
Question 3: The hair medulla, when present, is composed of:
- Loosely packed keratinized cells with air spaces (Correct answer)
- Densely packed cortical cells
- Melanocytes and Langerhans cells
- Living matrix cells
Correct answer: Loosely packed keratinized cells with air spaces
The medulla is the innermost hair layer consisting of loosely arranged, partially keratinized cells with intercellular air spaces, which give coarse hairs their opacity.
Question 4: What is the approximate duration of the telogen phase for scalp hair?
- 2–4 months (Correct answer)
- 2–6 years
- 2–3 weeks
- 6–12 months
Correct answer: 2–4 months
Scalp telogen typically lasts about 2–4 months before anagen re-initiates and the old club hair is shed.
Question 5: The pilosebaceous unit consists of:
- Hair follicle, sebaceous gland, and arrector pili muscle (Correct answer)
- Hair follicle and eccrine sweat gland
- Dermal papilla, matrix, and inner root sheath only
- Hair follicle, apocrine gland, and eccrine gland
Correct answer: Hair follicle, sebaceous gland, and arrector pili muscle
The pilosebaceous unit is made up of the hair follicle, the associated sebaceous gland, and the arrector pili smooth muscle.
Question 6: Which region of the hair shaft contains the bulk of structural keratin and provides tensile strength?
- Cortex (Correct answer)
- Medulla
- Cuticle
- Inner root sheath
Correct answer: Cortex
The cortex, the middle layer of the hair shaft, is densely packed with hard keratin fibers and melanin granules and provides the hair's strength and elasticity.
Question 7: In androgenetic alopecia, repeated anagen cycles lead to follicular miniaturization, meaning terminal follicles progressively produce:
- Shorter, finer, less pigmented hairs (Correct answer)
- Longer, thicker, more pigmented hairs
- Hairs that skip telogen entirely
- Hairs with increased medullary diameter
Correct answer: Shorter, finer, less pigmented hairs
In androgenetic alopecia, DHT shortens successive anagen phases, causing follicles to miniaturize and produce progressively thinner, shorter, paler hairs resembling vellus hairs.
CPE Anatomy & Physiology of Hair Growth 4
During catagen, the follicle shortens primarily because of: