Final answer:
Hair grows from the hair matrix located at the hair bulb base, where basal cells divide and differentiate into the hair shaft's layers. The hair matrix surrounds the hair papilla, which supplies nutrients through blood capillaries and innervation for hair growth.
Step-by-step explanation:
Hair is a keratinous filament growing out of the epidermis. Strands of hair originate in an epidermal penetration of the dermis called the hair follicle. The hair shaft is the visible part of the hair not anchored to the follicle. The rest of the hair, anchored in the follicle, lies below the skin's surface and is referred to as the hair root. At the base of the hair root is the hair bulb, which surrounds the hair papilla, containing blood capillaries and nerve endings.
The hair matrix, a layer of basal cells, is where the hair strand grows. These cells divide and differentiate to form the hair's layers: the medulla is the central core, surrounded by the cortex, and covered by the cuticle. Hair growth begins with the production of keratinocytes in the hair bulb, which is pushed up, keratinized, and formed in the hair shaft.