Below the surface of the skin is the hair root, which is enclosed within a hair follicle. Hair root is located under the epidermal layer, it is directed downward towards the place where the growing hair gets nutrients for the development and growth. The inner root sheath consists of several layers. These layers are closely interrelated to feed the hair in its development stage. Nerve cells and the blood capillary network is closely related to the hair follicle. The hair gets all the power supply from the blood. Blood composition depends on many factors, including quality of food and certain food items. If nutrient supply is insufficient or lacks food elements necessary for hair, hair gets weak and may fall out. Negative emotions provoke decreases in blood circulation terioration and hair brittleness. Endocrine gland activity affect the whole body state and any changes in it immediately affects the state of the hair. For example, medicine, particularly hormonal, may have a direct negative effect on hair condition and its loss.

 

Hair root structure: the hair follicle (1), the hair bulb (2) and the hair dermal papilla (3).

 

The hair follicle (1) (folliculus pili) - the follicle is a stocking-like structure that contains several layers with different jobs. At the base of the follicle is a projection formed like sticking a finger in the bottom of a stocking and pushing it in a small amount. This projection is called a dermal papilla (3) and it contains capillaries, or tiny blood vessels, that feed the cells. The living part of the hair is bottom part of this stocking surrounding the papilla called the hair bulb (2). This bottom part is the only part fed by the capillaries. The cells in the bulb divide every 23 to 72 hours, faster than any other cells in the body. The follicle is surrounded by two sheaths - an inner and outer sheath. These sheaths protect and mold the growing hair shaft, the protective coating covers follicle from the root through the entire length of the hair except the lower portion of hair bulb. The inner sheath follows the hair shaft and ends below the opening of a sebaceous (oil) gland, and sometimes an apocrine (scent) gland. The outer sheath continues all the way up to the gland. A muscle called an erector pili muscle attaches below the gland to a fibrous layer around the outer sheath. When this muscle is contracting it causes the hair to stand up. The sebaceous gland is important because it produces sebum which is a natural conditioner. The basic hair follicle structure remains essentially the same throughout the range of mammalian species with modifications for specialized functions. The hair follicle can be recognized as a separate entity within the skin with formation and maintenance based on interaction between dermal and epidermal components.

The hair follicle bulb (2) - the bulb is the deep, bulbous portion of the follicle that surrounds the dermal papilla. The bulb contains the matrix cells, the living, actively proliferating group of cells, which differentiate and become keratinized to form the hair cortex. This rate of proliferation is one of the highest of any tissue in the body. As they grow and develop, these cells steadily push the previously formed cells upwards. When the cells reach the upper part of the bulb they begin to change and arrange themselves into six cylindrical layers, one inside the other. The inner three layers of cells become the actual hair. The outer three layers become the lining of the hair follicle - the inner root sheath. The cells of the future hair shaft are positioned at the apex of the dermal papilla and will form the medulla (in terminal hairs), cortex and hair shaft cuticle.
The dermal papilla (3) - it is the dermal papilla, which directs and dictates the embryonic generation of a hair follicle. The Dermal papilla presents as a healthy "pear" shape in normal hair follicles, and consists of a highly active group of cells shown to be capable of inducing follicle development from the epidermis. It is comprised of spindle-shaped cells with cytoplasmic processes called fibroblasts, collagen bundles, stroma, nerve fibers and a single capillary loop. It is continuous with the perifollicular sheath (dermal sheath) of connective tissue, which envelops the lower follicle.