Hair types, structure & growth cycle Flashcards
Hair type - lanugo
Hair found on a fetus at 3-5 months gestation. Replaced by vellus / terminal hair by 7 months gestation.
Hair type - vellus
Fine, downy unpigmented hair found all over the body except for the lips, palms and soles of the feet. Has no medulla & follicles are shallow.
Hair type - terminal
Coarse pigmented hair which varies in length dependent on location. Includes scalp hair, lashes & brows, underarm and bikini hair. Hairs vary in shape, diameter, length & colour. Follicles are deeply set in the dermis.
Hair structure - hair shaft
The portion of hair which extends beyond the skins surface.
Hair structure - the root
The part of the hair that is in the follicle.
Hair structure - the bulb
The enlarged base of the root – known as the bulb as the lower part of the follicle is wider than the upper part.
Hair structure - the arrector pili muscle
A small muscle which attaches to the base of the hair follicle and the epidermis. On contraction, the hair stands on end creating a ‘goose bump’.
Hair structure - the sebaceous gland
A gland which is attached to the upper thirds of the hair follicle and secretes sebum (the skin’s natural moisturiser) onto the skin.
Hair structure - the dermal papilla
A connective tissue sheath which is surrounded by the hair bulb. It has a good blood supply and supplies the hair with nutrients from the blood.
Hair structure - the matrix
Located within the lower part of the hair bulb. Contains actively dividing cells. New cells push older ones forwards resulting in hair growth.
Mitosis
The method of cell division for all cells in the body other than sex cells (ova & sperm). One cell divides producing 2 identical copies.
Keratin
The protein which makes up hair, nails and skin.
Keratinisation
The process by which epithelial cells become filled with keratin granules, die and form tough, resistant structures such as hair / nail / skin.
Hair growth cycle - anagen stage
The active growing phase. The hair is fully attached to the blood supply at the base of the follicle and cells in the matrix are actively dividing.
Hair growth cycle - catagen stage
The changing or transitional stage where the follicle moves from growth to rest. The hair separated from the dermal papilla and moves up the follicle.
