Introduction:
Hair forms the external coating of most mammals. However, it has lost its significance among humans as evolution has taken place. But its value should be considered. People feel bad for hair loss on the scalp but keep removing hair on other body extremities, which removes a protective layer from the body. The study of hair will help in understanding its significance.
What Is the Composition of Hair?
Human hair comprises 65 to 95 percent proteins and 32 percent water, lipids, and other components. About 80 percent of human hair is formed by keratin. Keratin is a laminated complex that gives hair strength, durability, flexibility, and functionality. Moreover, hair shows remarkable structural differences among different ethnic groups and individuals of the same group. This factor influences cosmetic attributes.
What Is the Anatomy and Physiology of Hair Fiber?
Hair fiber consists of three main structural components: cuticle, cortex, and medulla.
Cuticle: The cuticle is the overlapping outermost layer covering the hair from the scalp to the end. This component is important as it is most and least affected by cosmetic treatments. Depending on the type, condition, and length of the hair, the hair consists of eight to ten layers of cuticle over which cosmetic products such as conditioners, hair sprays, and gels are deposited. In addition, each cuticle cell has layers such as an epicuticle, cellular membrane complex, endocuticle, and a layer containing cysteine.
Cortex: The cortex occupies about 75 percent of the hair area. Like a cuticle, it has cells filled with cystine and cell membrane complexes. Each cell of the cortex has a spindle shape and ties crossly to each other.
Medulla: The medulla is the thin cylindrical layer in the center of hair containing a high concentration of lipids and poor cysteine. This layer is only evident in the hair tips and has a minimal effect on treating cosmetically. It has three layers: globular structures, unorganized cortical cells, and a smooth covering layer.
What Are the Physical Properties of Hair?
The physical properties of hair include:
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Resistance to Stretching: The resistance to breakage depends on the geometry of the hair fibers. More the diameter of hair fibers, the more the resistance to stretching. And this property is negatively affected by chemical treatments.
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Elasticity: The hair fiber has elastic properties, and it can undergo stretching,,k,kk/ either wet or dry. Under dry conditions, hair can stretch by 20 to 30 percent of its length, and it may reach up to 50 percent in contact with water. When hair is in contact with ammonia, it becomes more elastic. This property is affected by physical and chemical treatments to the hair.
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Hydrophilic Power: Hair can absorb water in both liquid and steam form. Keratin absorbs about 40 percent of water. Hydration of hair changes its elasticity. Keratin is highly attracted to water and interferes with all hair properties, such as resistance to stretching, diameter, and internal viscosity of the fibers.
What Are the Surface Properties of Hair?
The surface properties of hair fibers differ for each hair type and length. The properties include:
Hair Surface Porosity:
There are some situations influencing hair porosity. They are:
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Alkaline pH above eight can increase permeability.
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The high temperature allows water penetration.
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Chemical treatments such as straightening, dyeing, and permanent waving can affect porosity.
Absorption: The hair surface can retain the natural oils. The absorption of such fatty substances is due to surface tension between the scalp and the transfer from one hair thread to the other. Chemical treatments enhance the anionic nature of the hair threads and make them electronegative, increasing their affinity towards cationic components such as dyeing ingredients.
Friction: The cuticle has high friction coefficient, and the friction depends on the geometry of the cuticle and the physical and chemical properties of the hair.
Static Load: Surface electric load gets generated when the comb slides over the hair. This electric load is due to friction and the high electric resistance of the hair. The static electricity effect is reduced or absent when an oily layer covers the hair strands from the sebum or other cosmetic products.
Shine: Shine is an essential cosmetic attribute of hair. The cuticle is responsible for the shine as it is a surface property related to how the hair reflects light. Thus, any damage to the cuticle and scalp secretions can reduce the shine.
Why Is Hair Necessary?
We would always experience a situation when we need hair; it is either too short or not there. When we do not want it, it is all over the place. We would have waxed, pulled, curled, straightened, tied, and stretched our hair in various circumstances. But we have never taken a look at its functions.
They are:
Regulates Body Temperature: The individuals with more hair feel warmer than those with little or no hair. This is because, during a hot climate, the sweat glands secrete sweat that evaporates and cools us, relaxing the muscles and making the hair lie flat to release heat.
Extends the Sense of Touch: Hair is a mechanosensory organ that can sense the feel of touch before an object touches our skin.
Protects the Body: Hair covers almost every part of the body except the palm and soles of the feet and lips. Not only hair covering the body, but a few hair growths in the form of eyebrows, eyelashes, and hair inside the nostrils also protect from dust particles and foreign matter.
Identifies You: Hair stands as a unique identifying feature of an individual. And so, its role in forensic sciences is significant.
Conclusion:
We would not have thought there was a hill of things we should know about hair. However, hair's physical and chemical properties explain how the different hair types would be and how they should be maintained. So before touching your hair for any chemical treatments, think of its characteristics and proceed.
