Human hair functions as a means of regulating body temperature and it acts as a sensory organ. Hair also helps to protect the skin from external damage such as sun, wind and foreign particles.
Hair acts as insulation for the body. When a person becomes cold, body hair stands up, creating added insulation and making body temperature rise. It also traps warm air next to the body, reducing a loss of heat.
Hair found in the ears and around the eyes prevents foreign matter from entering the body. Eyebrows reduce the amount of light that enters the eyes.
Hair is made of a strong protein called keratin. It is anchored to the skin by a hair follicle whose base is called the hair bulb. Blood vessels in the skin nourish hair bulbs and follicles, and each strand of hair is infused with hormones that determine the hair structure and growth at different stages of life. New hair grows for years before it stops growing and eventually falls out.
Hair color is determined by the presence of pigment cells called melanin. As a person ages, these pigment cells die and the hair turns gray. In today's society, hair is mainly cosmetic and contributes greatly to the way a person looks.