Hair Science and Structure Flashcards

What is the typical rate of hair growth per month on the human scalp?

Answer: 1.25 cm

Scalp hair grows at an average rate of approximately 1.25 cm (half an inch) per month, or about 15 cm (6 inches) per year.

Which amino acid is most responsible for the formation of disulfide bonds in hair?

Answer: Cysteine

Cysteine is a sulfur-containing amino acid. The sulfur atoms in two cysteine molecules bond together to form the strong disulfide bonds that give hair its shape and strength.

What is the term for the degree of coarseness or fineness of individual hair strands?

Answer: Texture

Texture refers to the diameter or thickness of individual hair strands. It is classified as fine, medium, or coarse and affects how hair responds to chemical services.

What does hair porosity refer to?

Answer: The ability of hair to absorb and retain moisture

Porosity is the hair's ability to absorb and retain moisture. It is determined by the condition of the cuticle layer — raised cuticles mean high porosity, flat cuticles mean low porosity.

Which layer of the skin contains the hair follicle?

Answer: Dermis

Hair follicles are rooted in the dermis, the second layer of the skin. The dermis contains connective tissue, blood vessels, and the structures that support hair growth.

What is the hair bulb?

Answer: The club-shaped structure at the lower end of the hair root

The hair bulb is the rounded, club-shaped structure at the base of the hair root that surrounds the dermal papilla. It contains matrix cells that produce new hair growth.