Each hair is formed and grows in it's individual follicle.
The hair follicle begins as a soft protein of specialized cells which become the cuticle, cortex, medulla and matrix of the hair. As the assembled hair moves toward the surface it becomes hardened and keratinized.
Hair outside the follicle is a dead protein keratin structure.
The growth period of the hair is called the Anagen phase.
When the hair stops growing it's in the Telogen phase.
During the Telogen phase the follicle withers and a bushy mass forms at the base of the hair shaft.
The hair is anchored in the scalp until after about 3 months when the growth cycle begins again.
When the cycle begins again a new follicle forms and as the new hair grows out it pushes the old hair out.