Hair is a filamentous protein-rich biomaterial that grows from follicles in the skin. It serves a number of functions including protection, sensory input, thermoregulation and communication. Hair may vary in length, thickness and color across species. The word hair is also used to refer to a specific kind of fur, the long, dense coats that some mammals wear over their bodies.
Humans have about 100,000 to 150,000 hairs on the body, which extend from a small area of glabrous skin called the scalp. These strands are made of multi-layered, keratinized (dead) flat cells that give the strand its strength and texture. Hair is often compared to fingernails and to the scales on fish, but it has an even stronger tensile strength than nails. It’s also able to trap a layer of air and add insulation, as illustrated by goose bumps or when a cat stands up its whiskers in fear.
In humans, hair is mainly made of a protein called keratin, which also makes up the skin and nails. Other substances such as fatty acids contribute to hair’s luster, sheen and elasticity.
The outermost layer of the hair is called the cuticle. It’s composed of overlapping cells that look a bit like the tiles on a terra cotta roof and are usually facing downward, which protects the underlying cortex. Hair’s hydration balance and flexibility are determined by this cuticle, so when it’s damaged or unhealthy, the hair can become dry and brittle.
Below the cuticle is the cortex, which contains bundles of keratin-containing cells that create hair’s shape and color. The color of a person’s hair is a result of the genes they inherited from their parents and their environment. Hair is also a good source of vitamin E, which helps it retain its shine and elasticity.
At the base of the follicle is a sebaceous gland that produces lipid-rich sebum, an oily substance that keeps the scalp moisturized. Hair grows as blood vessels deliver nutrients to the follicle, which then pushes out older cells to make way for newer ones. When the follicle is fully grown, its top is covered with a thin layer of dead solidified cells that looks like hair.
Hair can be dyed, permed, straightened or curled. A person’s hair can be a clue to their personality or lifestyle, whether they wear it kinked and messy or neatly styled with a bob. It’s important to understand how a character’s hair is shaped and colored so you can describe it effectively in your story.
Using descriptive words that describe how a character’s hair looks and feels can help readers experience it in their minds. Including these details can make the story feel more real and compelling to readers, so be sure to include them. You can also use words that describe a character’s personality traits and habits to give their appearance more depth and meaning. Just be careful not to stoke any stereotypes, as these can be offensive or off-putting.