Capítulo 3 de 520% del examen
Hair & Scalp Sciences
Hair Structure
The hair shaft is the part above the skin; the root sits below in the follicle.
The shaft has three layers: the outer cuticle, the middle cortex, and the inner medulla.
The cortex holds melanin (color) and the bonds that give strength and elasticity.
Hair is made chiefly of keratin, a fibrous protein.
Hair Growth
The dermal papilla supplies blood and nourishment to the growing hair bulb.
Anagen is the active growth phase, catagen the transition, and telogen the resting phase.
Trichology is the scientific study of hair and its care and disorders.
Sebaceous glands produce sebum, which lubricates the hair and skin.
Scalp & Hair Disorders
Pityriasis is the technical term for dandruff (scalp flaking).
Tinea (ringworm) is a contagious fungal infection with ring-shaped patches.
Pediculosis capitis is a contagious infestation of head lice.
Canities is loss of pigment (gray hair); alopecia is abnormal hair loss.
Contraindications & Referral
Do not service clients with contagious conditions such as ringworm or lice.
Do not perform services over open sores, inflamed skin, or signs of infection.
Refer clients with suspected infectious or medical scalp conditions to a physician.
Non-contagious conditions like canities or split ends are not a bar to service.
Bones, Muscles & Nerves of the Head
The frontal bone forms the forehead and the occipital bone the back of the skull.
The mandible is the lower jaw and the only movable bone of the skull.
The sternocleidomastoid is a major neck muscle worked around during shaving.
The trigeminal (fifth cranial) nerve is the chief sensory nerve of the face.
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Preguntas de práctica sobre Hair & Scalp Sciences
Last updated: July 2026