What Is Hair and How Does It Grow?


Hair is a filamentous biomaterial composed mostly of proteins, particularly keratin. Keratin is a tough protein that’s also found in our skin and fingernails. Hair also contains fatty acids, which gives it its shine and luster.

Each strand of hair grows from an epidermal penetration in the skin called a follicle. Tiny blood vessels at the base of each follicle supply it with nutrients for growth. As the hair cell at the base of a strand of hair matures, it begins to die. The dead cells move upward through the skin where they are eventually shed and replaced by new cells. As the strand of hair becomes longer, it pushes up through the follicle until it reaches the surface of the skin. Once the strand of hair is exposed to the air, it’s no longer alive, and it’s now made of hardened keratin. The keratin molecules in the strand of hair are bonded together with a complex arrangement of structural lipids, and they’re surrounded by the cuticle, which is a layer of dead overlapping cells that protects the keratin molecules.

Human hair has a strong tensile strength, and a strand of hair can stretch about three feet before breaking. The tensile strength of hair is higher than that of most other biological materials, such as muscle or bones.

Hair serves a number of important functions, such as protection and sensory input. For example, the hair that covers our head helps to protect it from sun damage. The hair around our noses, ears, and eyes prevents sweat and other particles from dripping into and bothering them. Hair also provides thermal insulation, and when it stands up straight it traps a layer of air to add warmth. This is a natural body mechanism that we share with mammals and other animal species that have fur.

Unlike skin, which is continuously renewed, a hair’s life cycle is cyclical, with periods of growth, rest, and fallout. The average life of a hair is about four months for downy hairs, and up to five years for long scalp hairs.

A person’s hairstyle often conveys information about his or her worldview, personality and socioeconomic status. A stereotype is a negative image associated with a particular group or individual, and it is often based on physical traits such as hairstyle and color. Many of these stereotypes are unfair, and it’s important to avoid them when possible.

When writing about someone’s hairstyle, choose the right words to convey the appropriate idea. Messy hair can indicate a lack of care, general unruliness or an active lifestyle. On the other hand, neatly combed hair can show that an individual takes great care to maintain his or her appearance. A well-written biography will connect with readers, but it’s equally important to include a call-to-action at the end of the article, such as “Book your next appointment online” or “Read more about my services.” Be sure to follow through on that call to action.