Most people asked about the structure of hair will tell you about the part visible to the eye, but not everyone knows how interesting the hair structure is. Only a few people realize, that a large part of the hair is under the skin. Hair is a callous formation of the epidermis, that covers almost the entire human body. Originally, hair had a thermoregulatory function, and today it has assumed an aesthetic role and is protecting our body against mechanical injuries. There are callous cells in the hair composition. However, remeber that only the part of the hair that grows above the skin is dead.

Hair structure

Looking at the cross-section of a hair from the inside, it consists of the core, cortex and sheath. However, not every person has a core in their hair. This part of the hair is only found on very thick hair. The basic structure is therefore the cortex, which takes up to 80% of the hair mass and is made of keratinized cells. The shell is made of scales, i.e. flat and colourless cells. The cuticles protect the hair from damage and weather conditions.

The thickness and shine of the hair depends on the condition. The hair consists of a stem that protrudes to the surface and a root in the skin. The hair root is located in the center of the hair follicle and ends with a bulb connected to the hair papilla. A hair grows out of the hair bulb. The nipple that transports nutrients to the bulb is very important in the structure of the hair.

Hair structure

Hair structure

What does hair consist of?

Before a hair is visible, it has to travel a long way that we cannot see with the naked eye. Hair grows from special channels called a hair follicle or sheath. The main function of the bellows is to protect the root. Human hair is clearly thickened at first. We call this the thickening of the bulb that connects to the wart. The bulb matrix is ​​composed of cells that multiply and differentiate quickly. Later, they form the basis of the hair’s core and cortex.

Where is the hair formed?

The hair is born in the hair bulb. Hair follicles are located all over the human body except for the hands and soles of the feet. There are about 100-150 thousand follicles on a person’s head. This amount does not change until the end of human life. The follicles are made up of a hair root, sheath and sebaceous gland.

cross-section of the hair

Hair cross section

The hair growth cycle

A fully developed hair consists of dead cells that follow the hair cycle. These cells are no longer affected by physiological processes. In humans, hair undergoes cyclical replacement. There are 3 phases of hair growth: anagen, telogen and the transition phase. During anagen, the hair grows and telogen is the resting phase. The hair on the human head is in different stages.

The growth phase lasts the longest and ranges from 2 to 5 years. Young people have up to 90% of their hair in this phase. Telogen should only last a few weeks. The hair grows on average 0.3-0.4 mm per day. The fastest growth is observed in summer, during sleep and after adolescence. The condition of the hair and its growth are influenced by various factors, which include: hormone levels, diet, lifestyle and medications.

Chemical composition and color of the hair

When analyzing the chemical structure of the hair, we notice that it consists of proteins, water, pigments, minerals and lipids. Depending on the individual proportions, the hair takes on different characteristic features. Depending on the amount of cysteine, hair can be straight, wavy or curly. The hair colour depends on the amount of pigment, i.e. melanin. Melanin is formed in the hair matrix thanks to melanocytes. There are two types of melanin, each responsible for a different hair color. Eumelanin is responsible for the dark colour of the hair and phaeomelanin for red.

Last update: 19 October 2020

Dr Piotr Turkowski

About Dr Piotr Turkowski

Aesthetic medicine doctor, specialist and enthusiastic surgery, completing the specialization in plastic surgery. The only officially registered member of the international hair restoration surgery (ISHRS) in Warsaw, which brings together the world's best specialists in this field.

Leave a Reply