Hair is a thread-like structure made of a protein called keratin and is one of the most defining characteristics of mammals. It grows from follicles in the skin and is most prominent on the head, but may also grow on the chest, arms, legs and other parts of the body. Hair is generally thick and smooth, but it can be a variety of textures and colours. Hair can be long or short, curly or straight. It can be light in colour or a variety of shades, including black, brown and blonde. Unlike fur, hair is not warm and does not provide insulation from cold temperatures.
Hair has two basic parts: the shaft and the root. The root lies beneath the skin in a pit known as a follicle and stem cells in the follicle are continuously dividing to form new hair cells, which eventually get pushed out of the epidermis and become the part of the hair that sticks up above the surface of the skin. The part of the hair that is coloured is called the cortex and contains much of its pigment (which gives the hair its colour). The core of the hair is a soft spongy tissue called the medulla. Coarse hair usually has a medulla, while fine hair does not. The cuticle is the outer layer of the hair and consists of a complex arrangement of flattened overlapping cells that are glued together by disulphide and hydrogen bonds. The healthy condition of the cuticle is important because it minimises movement of moisture in and out of the underlying cortex, keeping the hair shaft flexible and healthy. The health of the cuticle is affected by environmental factors such as sunlight, humidity and chemicals.
While the hair is growing, it is protected by a layer of natural oils called sebum, which helps to keep the scalp and strands of hair moisturized. These oils are produced in glands in the follicles. Once the hair has grown long enough, the glands stop producing sebum and the follicles enter a resting phase. The follicles can be activated again when the hair becomes tangled or matted, which allows them to start producing more oil.
The shape of a person’s scalp hair follicles determines their appearance, as well as the thickness and length of their hair. Differences in follicle shape are thought to be the reason why hair on different parts of the body appear slightly different. Hair has been used as a sign of biological sex, age and ethnicity for many centuries and can be very significant to people as they develop their style and image.
Using a range of descriptive words when describing a character’s hair can help readers to experience the texture, movement and appearance of that hair, which will in turn, enhance their understanding of that character. The use of these descriptive words can make for a more captivating and detailed story.