What hair is made of

What and how is hair? It seems like a simple, easy-to-answer question, but let us better understand technically their structure, hair anatomy, composition and characteristics.

The structure of the hair: hair anatomy

Hair, technically hair, is located inside the hair follicle, a kind of sac in the skin, which is inclined at about 75° to the skin surface. The hair is therefore a keratinous structure (i.e. formed of keratin) that emerges from the epidermis.

The longitudinal section of the hair

If we observe the structure of the hair along its length, i.e. vertically, we distinguish three parts:

• the shaft: this is the part of the hair that can be seen
• the root: is the continuation of the stem inside the skin
• the bulb: this is the final part, positioned in the deepest portion of the follicle

The cross-section of the hair

If we look at the structure by cutting the hair horizontally, we can distinguish three parts:

• the cuticle: this is the outer layer of the hair
• the cortex: this is the middle layer and is the most abundant; its thickness depends on the type of hair: it is greater in thick hairs and less in thin ones. It contains melanin and is the layer on which most chemical treatments act
• the medulla: is the central part of the hair

The composition of hair: hair chemistry

What is our hair made of?

Apart from water, the other elements that make up the chemistry of hair are: keratin, lipids, minerals and pigments.

Mainly they are made up of keratin, as we have said the hair is a keratin structure (keratin is a protein). The remainder consists of water, lipids, minerals and pigments. By pigments we mean melanin, present within the cortex, which gives hair its colour.

The characteristics of hair

The surface area of an adult’s scalp varies between 550 and 650 cm². The number of follicles per cm² varies with age: there are around 600 around the age of thirty. The number of hairs also varies according to colour. The diameter of the hair is about 70 micrometres and also varies with age. Traditionally, three types of hair are distinguished:

• oval section: wavy and curly hair, typical of Caucasians
• Elliptical section: typical of the Negroid ethnic group, it is woolly and frizzy hair.
• round section: straight hair, typical of the Mongolian ethnic group

The structure, composition of hair; many technical terms (hair cuticle, cortex, etc.) and hair ingredients (keratin, melanin, etc.) we have tried to clarify and simplify. We will certainly go into more detail later!