Your hair is a fascinating structure, made up of different layers, chemical bonds and amino acids (proteins).Hair scalp anatomy

Hair grows out of follicles located in the junction between the deep layers of the dermis and the hypodermis. These follicles are also known as hair bulbs.

Blood flow is supplied by a small vessel that passes through the inside of the hair shaft, thus providing the hair with all the vital elements it needs to remain healthy such as amino acids, mineral salts or vitamins.

The hair shaft is surrounded by glands, the most important being the sebaceous gland, which produces sebum that acts as a natural lubricant for the hair.

On the surface of the scalp, pores evacuate the sweat produced by the sweat glands.

HAIR STRUCTURE

The hair is made up of 95% keratin, a fibrous, helicoidal protein (shaped like a helix) that forms part of the skin and all its appendages (body hair, nails, etc.).

Keratin is synthesized by keratinocytes and is insoluble in water, thus ensuring impermeability and protection for the hair.

Some 18 amino acids can be found in the hair, such as proline, threonine, leucine and arginine. Keratin is particularly rich in cysteine (a type of sulfurated amino acid), which forms disulfide bonds between molecules, adding rigidity and resistance to the entire structure.

THE HAIR BULB

The hair bulb is a structure of actively growing cells which eventually produce hair. Cells continually divide in the lower part of the bulb and push upwards, gradually hardening. When they reach the upper part of the bulb they arrange themselves into six cylindrical layers.

 

The three inner layers become the hair, made up of the cuticle, the cortex and the medulla – although the medulla isn’t always present, especially in hairs with a thinner diameter. The outer three layers become the lining of the follicle and form the inner root sheath and basement membrane, around which lie undifferentiated cells. Specific cells in the hair bulb, called melanocytes, make the pigment called melanin that gives your hair its colour.

HAIR SHAFT

Your hair shaft is the part of your hair that can be seen above your scalp. It’s made of a protein called keratin, compacted and cemented together. Keratin is a remarkably strong protein, which is very resistant to wear and tear. It is in fact the same material that feathers, claws, nails and hoofs are composed of! Keratin is a sulphur-rich protein, with strong disulphide bonds holding the protein strands together.  This plays an important role in any chemical processing like perming and relaxing, as these break disulphide bonds and reset them to a different configuration to change the shape of your hair.

 Your hair shaft also consists of hydrogen bonds, which help to give your hair its flexibility. They are weaker and more numerous than disulphide bonds and are easily broken with the application of water. This is what allows you to temporarily change the natural configuration of your hair with heated styling aids after washing.

Your hair shaft consists of three layers:

The Cuticle, Cortex and Medulla

(More to come next week!)