Hair grows out of a hair follicle. A follicle is an indentation of the epidermis (outer layer of the skin) into the dermis (dense layer of tissue underneath the epidermis).
Hair growth is divided into three stages:
A. Anagen - the growing stage
B. Catagen - where the lower half of the follicle degenerates and the hair receives less nourishment
C. Telogen - the resting stage of the upper half of the follicle.
The original hair falls out, and often, the new hair already waits in the wings to come through and start the cycle again.
The normal growth rate of scalp hair is 1/4 to 1/2 inch per month.
