Hair Science and Structure Flashcards

How many layers does the hair shaft consist of?

Answer: Three

The hair shaft consists of three layers: the cuticle (outer), cortex (middle), and medulla (inner core, which may be absent in fine hair).

What type of hair has no medulla?

Answer: Very fine or vellus hair

Very fine hair and vellus hair often lack a medulla entirely. The medulla is more commonly present in coarse or thick hair types.

Which gland attached to the hair follicle produces sebum?

Answer: Sebaceous gland

The sebaceous gland is attached to the hair follicle and produces sebum, a natural oil that lubricates the hair and skin, keeping them moisturized.

What is the catagen phase of the hair growth cycle?

Answer: The short transition phase between growth and rest

The catagen phase is a brief transitional phase lasting about 2 to 3 weeks, during which the hair follicle shrinks and detaches from the dermal papilla.

What determines the natural colour of a person's hair?

Answer: The ratio and type of melanin in the cortex

Natural hair colour is determined by the type, amount, and distribution of melanin pigments (eumelanin and pheomelanin) within the cortex of the hair shaft.

What happens to the cuticle layer when hair is exposed to alkaline solutions?

Answer: It swells and opens up

Alkaline solutions (pH above 7) cause the cuticle scales to swell, lift, and open. This allows chemicals to penetrate into the cortex but also makes hair more vulnerable to damage.