The science of hair: Hair Growth & Insights & Facts
It is true that hair makes humans attractive, but the hair performs many other complex functions as well. Besides expressing themselves physically, it also transmits sensory information and creates gender identity for both men and women.
1. Hair’s origin
After 22 weeks of pregnancy, a woman’s hair follicles are fully formed. At this stage in a fetus’ development, there are approximately 5 million hair follicles. In the head region, there are approximately 1 million hair follicles, 100,000 of which are located on the scalp. Since hair follicles do not regenerate throughout our lives, this is the time when we have the most hair follicles.
In mature individuals, the number of hair follicles does not change; however, the area of oily skin increases, decreasing the density of scalp hair. Hair follicles will also gradually shrink with age and certain diseases that cause hair loss.
2. The science of hair structure
In addition to keratin, hair fibers contain water, fats, carbohydrates, vitamins, and minerals in addition to a fibrous structure. An individual hair shaft is located above the scalp, while a follicle lies beneath the skin.
The hair follicle is a section of the epidermis that extends into the dermis. Each layer of the hair follicle serves a different function. Hair follicles contain papillas, which are capillaries that deliver nutrients to the follicles. Usually, the hair bulb at the bottom of the papilla is what grows (the living part).
Cells in the body, including papillae, divide after 23 to 72 hours.
The hair follicle is surrounded by an outer layer and an inner sheath. These structures protect and form upward-growing hairs. Along the hair shaft, the inner sheath runs under the sebaceous glands (oil glands) and sometimes the apocrine glands (scent glands). The outer sheath is located below the line below.
Under the gland, the pili erector muscle has an outer sheath covered in fibrous tissue. A contraction of this muscle releases oil from sebaceous glands, which causes the hair to stand up.Sebum, produced by the sebaceous gland, is essential to hair and skin. The production of sebum by our bodies increases after puberty, but decreases at an older age. Women and men produce significantly different amounts of sebum.
Hair Shaft
The hair shaft is made up of keratin, a tough protein. There are three layers in the shaft. There is a dead layer of protein on the hair, so it is not alive. You can find the marrow in the bone’s inner layer. The skin has two layers, a second layer called the cortex, and an outer layer called the epidermis. Bark makes up the majority of the hair shaft, which is mostly composed of bark. The epidermis is a tight, overlapping structure of scales that make up a skin cell. Those pigments responsible for the color of hair are found in the cortex and marrow.
In the medulla, which is the hair’s innermost layer, there are many keratin cells that produce hair. The layer will not appear in very thin hair unless it is very thin. As long as your hair doesn’t have a pulp layer, the shine of your hair won’t be affected.
Hair’s core layer is the thickest and most important layer, as it contains bundles of small fibers and melanin. Hair color is determined by natural pigments, including melanin. A pigment whose color is black, brown, or red is called Eumelanin, and a pigment whose color is red is called Pheomelanin. Hair can be blonde, tawny, brown, red, or black, depending on the ratio of these two pigment types. White hair lacks melanin.
The percentage of melanin pigment in the hair core changes with age, genetics, and environmental influences. If you have black hair, you can turn it silver, and if you have blonde hair, you can turn it brown. Your hair’s middle layer determines its strength and color.
Stacks of keratin scales constitute the cuticle, the outermost layer of the hair. It is the KIT adhesive that lies between these layers. In addition to the cuticle layer, the hair is covered by an oil layer that serves to waterproof and moisturize it.
When the hair is affected by environmental factors, such as dust, UV rays, or dyes and perms. When hair straighteners, shampoos, conditioners, hairsprays, or chlorine in the pool are used, KIT adhesive will be damaged, breaking the keratin flakes, causing the hair to lose its smooth shine. When using a hair dryer, straightening tools, or combing the hair too hard or too much, the cuticle will be damaged, resulting in dry, frizzy, and dull hair.
3. Growth cycle of hair
The hair on the scalp grows three to four millimeters per day or 18 centimeters per year. Growth and shedding of human hair are random and not seasonal or cyclical like those of other mammals. The growth of hair is divided into three phases, including anagen, catagen, and telogen, at any given time.
In phase three, the hair is in its active phase, Anagen. There is a rapid division of cells in the hair root. In the hair follicle, a new hair is formed and pushes the older hair upward. Anagen phase is the period during which hair is no longer growing and eventually falls out.
About 1cm of hair grows every 28 days during this phase. This active phase of scalp hair growth lasts between two and six years.
A rather short hair growth phase can cause some people to have trouble growing hair below a certain length. In contrast, people with very long hair may have a long active growth phase. It explains why the hair on the arms, legs, eyelashes, and eyebrows is so much shorter than the hair on the scalp since the active growth period is about 30 to 45 days.
In the catagen phase, about 3% of all hairs are in a transitional phase. There is a two- to three-week period during this phase. Sheaths shrink and cling to hairlines as growth stops. As a result, the hair follicle is formed.
There is a resting phase called telogen, which accounts for 6% to 8% of total hair growth. Hair on the scalp stays in this phase for about 100 days, while hair on the eyebrows, eyelashes, arms and legs stays in this phase for longer periods of time.
Hair follicles are completely at rest during this phase, and the hair bulb is fully formed. A single hair will reveal a solid, hard, white structure at the base when pulled out during this stage. Telogen hairs shed physiologically between 25 and 100 times per day.
4. Hair’s function
The hair is an important feature of every individual, expressing beauty, vitality, and creating a personal identity. The pain of smooth, fragrant hair can be excruciating. To make the guys look dashing, their hair is neatly combed and styled. Hairstyles and hair colors allow people to express themselves individually, without overlapping with others. Every person’s fashion statement can be expressed through it.
The human body also benefits from the aesthetic effect of hair. It is important to maintain thick hair in order to prevent foreign objects from falling directly on the scalp. Additionally, scientists believe that hair protects the scalp directly from the sun’s rays. A head’s hair will act as an obstacle to heat and radiation when the sun shines down.
Hair and body hair can also be used to attract women sexually. The length and color of each person’s hair, the position of their hair, and their body hair play a role in their attraction to a mate. Each person’s unique scent is amplified by a certain amount of hair and body hair, which increases the chance of a mate pairing. Besides our services thermoregulation, hair follicles also aid in detoxification and excretion by the sebaceous glands and sweat glands.