Your hair is a fascinating structure, made up of different layers, chemical bonds and proteins.
The Hair Bulb
The hair bulb is a collection of actively growing cells that form a structure which will produce hair. Cells divide continuously in the lower part of the bulb and push upwards, gradually becoming hard. Once they reach the upper part of the bulb, they form six cylindrical layers.
The inner three layers become hair which is made up of the cuticle, the cortex and the medulla. The outer three layers become the lining of the hair follicle. Cells within the hair bulb called melanocytes make the pigment called melanin which give your hair its color.
The hair shaft is the part of your hair that is visible above your scalp. It is made up of a protein called keratin. Keratin is a strong protein, strong enough to resist wear and tear. Feathers, claws, nails and hoofs are all composed of keratin. Keratin is rich in Sulphur with strong disulphide bonds which hold the protein strands together. When hair is chemically processed, the configuration of these bonds gets rearranged giving hair a different shape or texture.
Hydrogen bonds also make up your hair’s consistency. They help give hair its flexibility. The hydrogen bonds are weaker and more numerous than the disulphide bonds. They are also more easily broken down with water. This is what allows you to heat style your hair either straightening or curling.
Your hair shaft consists of three layers:
Overlapping cells compose a protective layer around the hair, sort of like fish scales or roof tiles. The outer portion of the cuticle holds your hair in your hair follicle, sort of like Velcro. When healthy, smooth and intact, your outer cuticle gives your hair shine and protects the inner layers from damage. Chemical processes can lift the cuticle and let moisture into the underlying cortex which can disrupt the Velcro like hold of the hair follicle.
The cortex forms your hairs’ main bulk and color. It consists of keratin filaments held together by disulphide and hydrogen bonds. Your hairs’ health depends on the integrity of the cuticle protecting it.
If present, this consists of a thin core of transparent cells and air spaces. When the diameter of the hair shaft is small, sometimes there is no medulla.