There are roughly 5 million hairs that cover the body and with the exception of the palms, soles, the lips, the sides of the fingers and toes and some parts of the genitals, the whole body is covered in hair.
- Hair originates from a structure called a hair follicle. This tube like structure extends into the dermis layer and is fed by capillaries and nerves which are attached to it.
- Epithelial cells grow and divide inside the base of the follicle, which forms the hair bulb.
- Keratin, a protein which is found in the epithelial cells coats the hair which causes it to stiffen as it grows up through the follicles. Whilst the hair is in the follicle, it is called the root, but once exposed from the scalp it is called the hair shaft.
Structure of the Hair Root
Below the surface of the skin is the hair root, which is enclosed within a hair
follicle. At the base of the hair follicle is the dermal papilla. The dermal papilla is feed by the bloodstream, which carries nourishment to produce new hair. The dermal papilla is a structure very important to hair growth because it contains receptors for male hormones and androgens. Androgens regulate hair growth and in scalp hair, Androgens may cause the hair follicle to get progressively smaller and the hairs to become finer in individuals who are genetically predisposed to this type of hair loss.
Each strand of hair consists of three layers.
- An innermost layer or medulla, which is only present in large thick hairs.
- The middle layer known as the cortex. The cortex provides strength and
- both the colour and the texture of hair
- The outermost layer is known as the cuticle. The cuticle is thin and
colourless and serves as a protector of the cortex.
As the newly formed cells grow and push up from the follicle base, the older epithelial cells die.
The colour of the hair is determined by pigmented cells called melanocytes, which contain melanin. The amount of melanin will determine the colour of hair.