Hair follicle is a specialized organ located in the dermal layer of mammalian skin. Contains 20 different cell types with distinct functions. Consists of papilla, hair matrix, root sheath, and bulb. Associated with arrector pili muscles, sebaceous glands, and apocrine sweat glands
Hair grows everywhere except specific body parts. Hair is keratinized epithelium with rope-like filaments. Hair follows three phases: anagen, catagen, and telogen. Average hair grows about 1 cm per month. Thicker hair grows faster than thinner hair
Collagen is a protein found in cells, tissues, bones, and skin. By age 30, body starts losing collagen production. Scalp contains 75% collagen, loss affects hair strength
At-home keratin treatments offer similar benefits at lower prices than salon treatments. Formaldehyde is a major chemical to avoid in keratin products. Keratin-infused products strengthen and repair hair, while salon treatments straighten
Lice eggs (nits) are tiny, oval-shaped, yellowish-white spots on hair shafts. Nits can be confused with dandruff or hair spray droplets. Eggs hatch in 6-9 days, nymphs mature in 7 days. Live lice lay up to 8 eggs daily. Nits near scalp are most likely to be infective
Hair density is measured by visible scalp area per square inch. Texture is determined by comparing hair strand to thread. Porosity is tested by feeling damp hair. Oiliness is checked by pressing scalp tissue. Elasticity is measured by stretching dry hair