Hair Science and Structure Flashcards

What percentage of scalp hair is typically in the anagen phase at any given time?

Answer: 85-90%

Approximately 85-90% of scalp hair is in the anagen (active growth) phase at any given time, which is why most of the hair on your head is actively growing.

What is the effect of acidic products on the hair cuticle?

Answer: They close and harden the cuticle

Acidic products (pH below 7) cause the cuticle to contract, close, and harden. This is why acidic rinses and conditioners make hair feel smoother and shinier.

What is vellus hair?

Answer: Short, fine, unpigmented body hair

Vellus hair is the short, fine, nearly colourless hair that covers most of the body. It differs from terminal hair, which is thicker, longer, and pigmented.

Salt bonds in hair are broken by changes in what?

Answer: pH

Salt bonds (also called ionic bonds) are broken by changes in pH. They are weak electrostatic bonds between positive and negative amino acid side chains in the cortex.

What is hair density?

Answer: The number of individual hair strands per area of the scalp

Hair density refers to the number of individual hair strands per square centimetre on the scalp. It is classified as thin (low density), medium, or thick (high density).

What is the main function of the hair cuticle?

Answer: To protect the inner cortex from damage

The cuticle's primary function is to protect the inner cortex of the hair from physical and chemical damage. Its overlapping scale structure acts as a barrier.