Topic Set 14: Hair Classes, Cycle, Color & Texture

What are the 3 classes of hair?

Lanugo, vellus hairs, and terminal hairs

What is lanugo?

Fine, nonpigmented fetal hair

When does lanugo develop?

5th or 6th month of gestation

What are the functions of lanugo?

Protects fetus from amniotic fluid and insulates

When is lanugo shed?

Usually by birth

What are vellus hairs?

Short, fine, pale hairs replacing lanugo

What happens to many vellus hairs at puberty?

Replaced by terminal hairs

What are terminal hairs?

Long, coarse, pigmented hairs

What are examples of locations with terminal hairs?

Head, eyebrows, and eyelashes

What are the 3 phases of the hair growth cycle?

Anagen, catagen, and telogen

What occurs during the anagen phase?

Active hair growth at 1–1.5 cm per month

What occurs during the catagen phase?

Lower follicle/bulb breaks down for 2–3 weeks while papilla remains

What occurs during the telogen phase?

Resting phase lasting months with a club hair

What happens in the follicle during the next cycle after telogen?

Follicle reforms and new hair pushes out old hair

What is alopecia areata?

Autoimmune hair loss

What pigment determines hair color?

Melanin

What melanin produces black or brown hair?

Eumelanin

What melanin produces red hair?

Pheomelanin

What melanin composition produces blonde hair?

Small amounts of both eumelanin and pheomelanin

What determines hair texture?

Shape of the follicle