THE ANATOMY OF HAIR
Human hair consists of two parts the root which is in the dermis (the inner layer of the skin) and the shaft which grows out through the epidermis (the outer skin layer) of the skin, to the outside of the body.
The root of the hair has rich blood supply that delivers nutrients to nourish hair. The shaft is considered the dead part of the hair and is composed of a protein known as keratin. On its way through the skin, hair is in proximity to an oil gland that helps to keep it shiny.
Hairs grow on almost every part of the body except the palms and soles of the feet. It is capable of complete regeneration as long as the follicle is not damaged.
Hair follicles begin to grow from week 11, and at about 22 weeks gestational age, every developing human fetus is expected to have acquired all its hair follicles to last a lifetime. The number of hair follicles (about 100 million) do not increase after birth and decreases as an individual grows older.
Quick Hair Facts
- The scalp has about 100 million follicles.
- Males grow hair faster compared to females.
- Average hair loss everyday is between 50-100 hairs.
- Number of follicles decrease as individual get older.
- Hair texture is determined genetically.
- Individuals with curly hair have oval shaped follicles and individuals with straight hair have rounded follicles.
- Melanin pigment in the hair follicle gives hair its colour.
- Grey hair is as a result of death of melanin pigment cells, a process associated with aging.
Hair Growth Cycle
Rate of hair growth vary among individuals. It is estimated to grow at the rate of about 6 inches a year on the scalp. All hair follicles do not grow at the same time, some will be in the active growth phase while some may be in the resting phase.
3 phases of hair growth
- Anagen: This is the growth phase.
- Catagen: This is the transition phase where the hair follicle shrinks and rate of hair growth is reduced.
- Telogen: This is the resting phase where there is complete cessation of hair growth. The old hair falls off as new hair begins to grow from the follicle.