Hair science is amazing. Our bodies are covered in hair, and yet we still do not know everything about hair. What we know so far about is fascinating. Hair has been important both on an individual and social level throughout history.
Let us look at some facts about hair. Understanding the science behind hair, can help us maintain our hair.
Hair: An Overview
Hair is a complex and interesting structure. The colors and textures of hair vary. When the hair falls out, new hairs grow. Hair science – what we know about hair improves every year. More research is done on understanding the structure and functions of hair, and its growth. Hair is quite resistant to external factors.
What is Hair?
When we say hair, we refer to either the hair follicle, which is under the skin, or the hair shaft, the part of hair which extends above the skin. In our everyday lives, we often refer the hair shaft when we say hair. Hair is, in fact, a type of fiber.
Hair completes our appearance. Physiologically, it does not have much remaining function – it protects the scalp from the sun. And yet psychologically it is very important. Hair has emotional and social importance.
The total number of hair follicles in an adult human body is around 5 million. This number does not change significantly in different sexes or races.
Our genetic code depends most features of our hair. And yet, nutrition, where we live, some other external factors, and psychological factors play an important role in the health of our hair. The hair of people who live in warmer places grows faster. Warmth stimulates hair growth.
How Does Hair Originate?
The hair follicles on our bodies develop when we are still in the womb. By 22 weeks in the womb, the new hair follicle formation is complete for the fetus. No hair follicles normally form after birth. When we are a child, we have the densest hair we can ever have. The density is lower as we age because our scalps grow.
If we look at the anatomy of hair, we can see that it is simple. It is made up of keratin which is layer of protein. Our scalps have around 100.000 hair follicles.
Hair Growth Cycles
Our hair has a growth cycle. The three phases of hair growth are anagen, catagen, and telogen. The length of our hair depends on the length of the anagen phase. Many people know anagen as the growth phase of hair which takes about 1000 days. This is when the active hair growth happens.
The second phase of hair growth is catagen. We can also call it the resting phase. It is a short phase, which takes about two weeks. In the telogen phase, which is the last phase of hair life cycle, the hair is resting. It can last approximately a hundred days.
Hair grows a bit faster in women than in men. Your eyebrows and eyelashes have shorter growth phases than scalp hair. Our scalp hair often grows at one cm per month. The hair on our face grows faster compared to the other hair on our bodies.
The hair sticking out from the skin is technically not living. It is natural to lose around 100 strands of hair each day, and in a healthy scalp there is a balance between hair in different phases.
The Composition of Hair
Hair has protein complexes – keratin. Keratin is water insoluble. Our hair shafts have several layers. We can look at the hair in two parts: the hair shaft and the hair root. These are the parts of hair lengthwise.
The hair root is in the skin – epidermis of the scalp. At the base of the hair root, is a bulb shaped structure. The blood vessels enter the bulb, and provide nutrients to the hair.
The Hair ShaftThere are three layers of the hair shaft. The cuticle is an outer layer which protects the hair. The cortex is the middle layer, and the medulla is the innermost layer of the shaft. Cortex gives the hair its color, and it takes up most of the hair’s mass. Hair follicle gives the hair its shape but specifically it is the cortex that defines the elasticity, and the shape of the hair. The medulla has air spaces. Not all hair strands have a medulla. It is often the thick hair strands and types that have a medulla.