Anatomy & Physiology of Hair Growth Flashcards

Which layer of the hair follicle produces the Henle and Huxley layers of the inner root sheath?

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.

What is the term for the club-shaped structure formed at the base of a hair during catagen that anchors it until it sheds?

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.

The arrector pili muscle originates in the dermis and inserts into the:

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.

During which phase of hair growth does mitotic activity in the matrix cells cease?

Answer: Catagen

At the onset of catagen, matrix cell mitosis stops, triggering apoptosis and follicle regression.

Which type of hair is characteristically unpigmented, fine, and covers the fetus in utero?

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.

What primary signaling molecule released by the dermal papilla promotes anagen initiation?

Answer: Wnt ligands

Wnt/β-catenin signaling from dermal papilla cells is a key driver of anagen initiation and follicle regeneration.

The isthmus of the hair follicle is located between which two structures?

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.