CPE Anatomy & Physiology of Hair Growth 2 — Questions and Answers
Question 1: Which layer of the hair follicle produces the Henle and Huxley layers of the inner root sheath?
- Matrix cells surrounding the papilla (Correct answer)
- The outer root sheath
- The companion layer
- The glassy membrane
Correct answer: Matrix cells surrounding the papilla
Matrix cells adjacent to the dermal papilla differentiate upward to form the inner root sheath layers including Henle's and Huxley's layers.
Question 2: What is the term for the club-shaped structure formed at the base of a hair during catagen that anchors it until it sheds?
- Club hair (Correct answer)
- Lanugo hair
- Vellus hair
- Terminal hair
Correct answer: Club hair
During catagen, the lower follicle regresses and the hair forms a club-shaped base called a club hair, which remains anchored until telogen ends.
Question 3: The arrector pili muscle originates in the dermis and inserts into the:
- Outer root sheath of the follicle (Correct answer)
- Inner root sheath
- Hair medulla
- Dermal papilla
Correct answer: Outer root sheath of the follicle
The arrector pili originates in the papillary dermis and inserts into the outer root sheath of the hair follicle, causing the hair to stand erect when contracted.
Question 4: During which phase of hair growth does mitotic activity in the matrix cells cease?
- Catagen (Correct answer)
- Anagen
- Telogen
- Exogen
Correct answer: Catagen
At the onset of catagen, matrix cell mitosis stops, triggering apoptosis and follicle regression.
Question 5: Which type of hair is characteristically unpigmented, fine, and covers the fetus in utero?
- Lanugo (Correct answer)
- Vellus
- Terminal
- Intermediate
Correct answer: Lanugo
Lanugo hair is the first hair produced by fetal follicles; it is fine, soft, and lacks pigment, and is shed before or shortly after birth.
Question 6: What primary signaling molecule released by the dermal papilla promotes anagen initiation?
- Wnt ligands (Correct answer)
- Androgens
- Prostaglandin D2
- Transforming Growth Factor-β2
Correct answer: Wnt ligands
Wnt/β-catenin signaling from dermal papilla cells is a key driver of anagen initiation and follicle regeneration.
Question 7: The isthmus of the hair follicle is located between which two structures?
- The insertion of the arrector pili and the opening of the sebaceous duct (Correct answer)
- The dermal papilla and the matrix
- The bulge and the dermal papilla
- The sebaceous duct and the follicular opening
Correct answer: The insertion of the arrector pili and the opening of the sebaceous duct
The isthmus is the middle segment of the follicle, bounded inferiorly by the arrector pili attachment and superiorly by the sebaceous gland duct.
CPE Anatomy & Physiology of Hair Growth 2
Which layer of the hair follicle produces the Henle and Huxley layers of the inner root sheath?