Keratin and Hair Structure

What is Keratin?

Keratin is a fibrous structural protein that forms the primary component of hair, skin, and nails. In hair, keratin makes up approximately 90% of its dry weight. It is a complex protein, rich in the amino acid cysteine, which allows for the formation of disulfide bonds. These bonds are crucial for hair's strength, elasticity, and shape.

There are two main types of keratin: alpha-keratin and beta-keratin. Human hair, like other mammalian hair, is composed primarily of alpha-keratin. Beta-keratin is found in the scales, feathers, and claws of reptiles and birds.

The Structure of Hair

Hair is composed of three main layers:

1. Cuticle: The outermost layer of the hair shaft, consisting of overlapping, scale-like cells. These cells, typically 6 to 10 layers deep, protect the inner layers from damage. A healthy cuticle lies flat, reflecting light and giving hair a smooth, shiny appearance. When the cuticle is damaged or raised, hair can appear dull, rough, and prone to tangles.
2. Cortex: The middle and thickest layer of the hair shaft, accounting for 75-90% of the hair's total weight. The cortex contains the keratin proteins, which are arranged in long, twisted chains called macrofibrils. These macrofibrils are further organized into smaller microfibrils. The cortex is also where melanin, the pigment responsible for hair color, is located. The strength, elasticity, and texture of hair are largely determined by the cortex.
3. Medulla: The innermost layer of the hair, often absent in fine or vellus hair. Its exact function is not fully understood, but it is believed to play a role in the hair's resistance to breakage and its thermal insulation properties.

The Role of Keratin in Hair Strength and Elasticity

The unique properties of keratin are what give hair its remarkable strength and flexibility. The primary contributors to this are:

• Disulfide Bonds: These are strong chemical bonds formed between sulfur atoms in the cysteine amino acids within keratin. Disulfide bonds contribute significantly to the hair's structural integrity and determine its permanent shape. Chemical processes like perms and relaxers work by breaking and then reforming these bonds to alter hair texture.
• Hydrogen Bonds: These are weaker, temporary bonds that form between the hydrogen atoms of water molecules and the oxygen and nitrogen atoms in keratin. Hydrogen bonds are easily broken by water (e.g., when hair gets wet) and reformed when hair dries. This is why hair can be temporarily restyled with heat.
• Salt Bonds: Also weaker, temporary bonds, salt bonds are formed between oppositely charged amino acid groups within the keratin structure. Like hydrogen bonds, they are affected by changes in pH and can be temporarily broken by water and reformed when dry.

The interwoven network of these bonds within the keratin structure provides hair with its characteristic tensile strength (resistance to being pulled apart) and elasticity (ability to stretch and return to its original shape).

Keratin and Hair Damage

Hair can become damaged through various factors, including chemical treatments (coloring, perming), heat styling, environmental exposure (UV radiation, pollution), and mechanical stress (brushing, tight hairstyles). This damage often manifests as a breakdown of the keratin structure, leading to:

• Loss of disulfide bonds: Weakens the hair, making it more prone to breakage.
• Damage to the cuticle: Causes the scales to lift, leading to rough texture, frizz, and dullness.
• Porosity: Increased gaps and holes in the cuticle and cortex, making hair more susceptible to moisture loss and further damage.

Keratin Treatments and Products

Many haircare products aim to improve hair health by supporting or replenishing keratin. These can generally be categorized as:

• Hydrolysed Keratin: Keratin proteins that have been broken down into smaller molecules, making them able to penetrate the hair shaft or sit on the cuticle. These can help to temporarily fill in gaps in the hair shaft, smooth the cuticle, and provide a protective layer.
• Amino Acids: The building blocks of proteins. Products rich in specific amino acids, particularly cysteine, can help support the hair's natural keratin production and repair process.
• Keratin Smoothing Treatments: Professional salon treatments that typically involve applying a keratin-based solution to the hair, followed by heat sealing. These treatments temporarily smooth frizz, reduce curl, and add shine by forming a protective layer over the hair and temporarily altering its structure. The effects generally last for several weeks to months, depending on the specific treatment and aftercare.

It's important to note that while external keratin treatments can provide temporary improvements in hair appearance and feel, they do not permanently alter the hair's internal structure. The hair growth process originates from the hair follicle in the scalp, where new keratin proteins are continuously produced. For long-term hair health, nourishing the scalp and supporting healthy hair growth from the root is paramount. Watermans Hair growth shampoos often include ingredients that support the scalp and the hair follicle, aiming to promote optimal conditions for keratin production.", seo_title=