The lifespan of human hair is two to seven years. During that time, hair grows in a different density and texture and undergoes three distinct phases, known as anagen, catagen, and telogen. Hairs are divided into three categories, depending on their density and diameter: fine, medium, and coarse. Thick strands are easily identifiable as shed strands, while thin tresses have an ultra-fine texture.
Several mammals use hair for various purposes. It provides insulation against the cold, protects the skull from sun and dust, and extends the sense of touch. In addition, hair acts as a sensory organ, allowing an animal to warn others about danger. It also provides camouflage and serves as a cue for predators. Polar bears use their fur to hide and protect their cubs in the snow. Hence, hair is an essential part of a living creature’s body, and is also used in religion and culture.
In our bodies, hair grows from follicles deep in the dermis. The hair follicle is a stocking-like structure that contains cells that produce new hair and oil glands. The hair bulb is located at the base of the hair follicle, while blood vessels supply the cells of the follicle. Hair follicles are characterized by three distinct layers: the inner layer (called the medulla) and the middle layer, or the cortex, which is the main part of the hair shaft.
The hair shaft contains DNA. It is a living structure with tiny blood vessels that feed it. After a hair falls off, it no longer contains living cells. The hair on every part of the body has a layer of dead cells. The hair follicles may even be used to test a child’s paternity. And although it’s not completely necessary to wash hair every day, a regular hair washing routine will help ensure that it stays healthy and nourished.
The hairstyles of people have different meanings in different cultures. Some people wear their hair in a specific way to express their identity. For example, many hippies and metalheads wear long, flowing hair. While skinheads have short, cropped heads, many indie kids wear long, stylized bangs. Traditionally, Chinese people tied their hair to represent filial piety. The hairstyles of early modern China are also influenced by different racial admixtures.
The color of hair depends on its location. In the head, hair grows for a few years and can grow to one meter in length if not cut. However, in the ears, eyebrows, and nasal hair, it grows for a shorter time. As the hair ages, it begins to lose the melanin pigment in the hair. And this can lead to an uneven and unsightly appearance. The same goes for darker hair.