Anatomy & Physiology of Hair Growth Flashcards

During catagen, the follicle shortens primarily because of:

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.

Vellus hairs differ from terminal hairs in that they:

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.

The hair medulla, when present, is composed of:

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.

What is the approximate duration of the telogen phase for scalp hair?

Answer: 2–4 months

Scalp telogen typically lasts about 2–4 months before anagen re-initiates and the old club hair is shed.

The pilosebaceous unit consists of:

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.

Which region of the hair shaft contains the bulk of structural keratin and provides tensile strength?

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.

In androgenetic alopecia, repeated anagen cycles lead to follicular miniaturization, meaning terminal follicles progressively produce:

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.