Hair is a symbol of identity, an indication of gender, race or ethnicity, and even a source of pride for some people. It’s also an indicator of health, with certain types of hair being linked to a variety of conditions and illnesses.
For some, a change in hairstyle is an expression of a desire for a new look or to fit into a particular social group. During the English Civil War, followers of Oliver Cromwell cropped their hair close to their head as an act of defiance and were known as Roundheads; similarly, women in the 1920’s adopted the short bobbed style popular among flappers as a sign of independence. Hair can also be an indicator of sociocultural interaction, such as the adornment of beads with Native American tribes or the wearing of a wig in medieval times.
Described by its texture, color, shape and volume, the thickness of hair is determined by the number and size of individual strands that make up the hair shaft. Hair can be fine (feels like an ultra-fine strand of silk), medium (feels more like a cotton thread than a wire and shed strands are difficult to see against a contrasting background) or coarse (feels hard and wiry).
The structure of hair is very complex and has numerous specialized cells that must work together in harmony in order for the hair to grow, maintain its strength and health, and function properly. The most basic cell is the hair follicle, which contains glands that produce natural oils called sebum to moisturize both the scalp and the hair strand. The follicle is also responsible for the growth cycle of each hair.
While it may not be as visible to others as skin or nails, the hair follicles are also an important part of our bodies’ immune system and provide a barrier against bacteria and viruses.
Hair is made up of a fibrous protein known as keratin, which is also found in fingernails and the outer layer of the skin. The protein contributes to the strength and resilience of the hair and is also a pigment that determines its color. The cortex, which is the middle layer of the hair strand, is comprised of tightly packed microfibrils that give it its structure and texture.
The cuticle is the outermost layer that consists of overlapping scale-like cells. It protects the inner layers of the hair and adds sheen and luster to it. In addition to a unique protein composition, hair is extremely sensitive and can respond to environmental stimuli such as air movement and sound, which is why we often feel goose bumps when someone gives us a scare or we get tickled. Hair can also serve other purposes including thermoregulation, camouflage, and communication. For example, some mammals use their fur to signal other animals of danger or other potential mating opportunities. And the guard hairs on a polar bear’s head are designed to warn other predators of its presence.