Hair is a keratinous filament that grows out of the epidermis. It consists of dead, keratinized cells that form rope-like structures. The keratinous proteins in hair give it strength and color. Hair grows out of a follicle (FOL-ih-cle) that is a tiny hole in the skin, on your head and throughout your body. Hair follicles get nutrients from blood vessels that run underneath the scalp and through the hair. New strands of hair grow out of the base of each follicle, which is called the papilla. The papilla gets hardened through a process known as keratinization. The resulting strand of hair is known as a hair shaft.
Hair performs many functions, including protection, sensory input, thermoregulation and communication. For example, the hair on the head protects the skull from sun damage. The hair around the nose and eyes (eyelashes) prevents sweat, dust particles and other debris from dripping into or irritating the eyes. Hair in the chest and abdomen helps regulate temperature by trapping air to warm the core and deflecting cold air away from the skin’s surface. Hair on the armpits and legs can repel insects. And hair on the chest can help to deter predators and scare off would-be attackers.
People have different kinds of hair based on their genetic makeup, their culture and their gender. For instance, some people have curly hair while others have straight hair. The hair strands can also vary in thickness and density. Hair color comes from a pigment called melanin, which is produced by the hair follicles. When a person loses melanin as they age, they might begin to develop gray hair.
When writing, it is helpful to understand how to categorize and describe the different types of hair. To make the task easier, it is useful to understand how the different aspects of hair relate to personality traits. Using descriptive words for hair and personality traits will give readers a better picture of the character.
Each strand of hair is anchored to the scalp by a small plug-like structure called a follicle. The follicle contains glands that produce natural oils, which are called sebum. The oil helps to keep the scalp and hair strands moisturized. Each follicle has three phases of growth: anagen, catagen and telogen.
When the follicle is in its anagen phase, it grows new hair. Each new hair cell is pushed up the follicle through a tiny opening in the skin called the pore or follicle pore. The follicle is surrounded by a thin layer of dermal tissue that contains blood vessels and a nerve. The hair cell moves up the follicle, where it gets hardened through the process of keratinization and finally emerges from the follicle as a hair.
Each strand of hair has an outer layer of skin, called the cuticle. This cuticle is protective of the hair shaft and inner medulla, which is responsible for most of the hair’s texture and strength. The medulla also produces melanin, which gives hair its color.