Human hair is a biological advertisement that represents a person’s health and genetics. Ancient myths and legends discuss the importance of hair, pointing to its role as a sign of power and mystical strength. Hair on the head protects the skull from sunlight, dust, and sand, while eyebrow hair serves a similar function: it prevents sweat and particles from falling into the eye. A man’s hair also has an aesthetic function. The root plexus of hair contains sensory nerves that respond to air movement, making it more sensitive than the skin surface.
In addition to color and texture, hair shape is another important factor. Hair with oval follicles has a curly texture, while round follicles produce straighter hair. Hair shapes are largely determined by genetics, though they can change over the course of a person’s life. In general, however, there are two primary types of hair: thin and medium. Thin hair tends to look translucent when held to light. Medium and coarse hairs are easily distinguishable as shed strands, while curly hair has a distinct appearance.
Hair follicles extend deep into the dermis and may project into the underlying subcutaneous layer. A small peg known as the hair papilla is located at the base of the follicle, surrounded by the epithelium. Hair papillas contain nerves and capillaries. The hair bulb consists of epithelial cells and hard keratin. The hair shaft is then surrounded by a single layer of dead keratinized cells.
In early modern China, a male hairstyle called a queue was common among the Manchus from central Manchuria and Han Chinese during the Qing dynasty. In these cultures, the hair on the front of the head was shaved every ten days, mimicking male-pattern baldness. The hair was braided and worn as a pigtail. This hairstyle became popular among female art students and flappers.
The earliest hairs appear during embryonic development. The lanugo hairs are the lightest and unpigmented hairs, and most are shed before birth. In comparison, the terminal hairs are heavier and deeper pigmented and sometimes curly, and grow from the scalp and arms after puberty. In response to circulating hormones, hair follicles undergo changes in structure and composition, which affect the growth and development of hair.
Many street drugs are absorbed into the hair, so testing a hair sample for drug use can reveal if the person has recently been exposed to drugs. However, hair analysis tests are limited by the difficulty in interpreting the results. The treatment options for hair loss vary widely, including Minoxidil, a medication that is applied to the scalp. Finasteride, also known as Propecia, is a pill that regrows hair. Hair transplant surgery is another option. This involves removing hair and skin from the back of the scalp and transplanting it onto a new location on the head.
The growth of hair depends on melanin. The more melanin the hair has, the darker it is. People with lighter hair have less melanin than those with dark hair. In addition, people with red or brown hair often have less melanin than people with light or dark hair. Melanin production declines as a person ages. Therefore, it is important to understand the process and find the right products for your hair. For best results, follow these steps.