Anatomically, in longitudinal section, the hair is divided into a part external to the skin called stem, having a tubular shape which ends in a thinner part, practically this is the visible part. The cells which form the stem don’t have vital functions, they are actually dead structures.
Immersed in the skin we can find the root, which goes down the dermis and insert itself in the third part of the hair, which is the bulb or hair follicle.
The bulb is an intussusception of epidermis in the dermis and it shows up as a little bag which behaves as an incubator to the hair. The erector muscle of the hair is inserted on the follicle, where the duct of the sebaceous gland blossoms.
Sebum, produced together with sweat, produce a protector film of the skin from chemical and bacterial agents, also it waterproofs the external surface of the hair, as soon as it grows up.
Inside the follicle there is a dermal papilla, highly vascularized, which provides all the necessary elements for birth and growth of hairs. Cells, in contact with the dermal papilla, are called hair matrices. They absorb nutrients and oxygen from capillaries located inside the dermal papilla and form hairs themselves, in essence they are germinative cells which reproduce and push upwards cells previously born.
Inside the bulb we also find melanocytes, responsible for pigmentation and therefore the color of our hair.
In cross section, instead, the hair is composed of the cuticle, which protects its integrity. It is located in the outermost layer and consists of flattened flakes of keratin, overlapped one on the other like roof tiles, with a free margin facing the tip of the hair. Under a microscope they seem like ears of corn. The cuticle is the first part which gets damaged because of external elements
Then we find the bark, intermediate part which gives volume to our hair, containing melanin on which chemical treatments have effect. Indeed melanin, responsible for color, tends to decrease over time and make white hairs appear.
The outermost part is called marrow and is made of spongy keratin, it also have a protection function from cold, but mostly in women.
The substances which form hairs are keratin, fibrous protein, responsible for the hair resistance. Indeed, when hairs go up to the surface, cells synthesize inside them this protein which makes them more rigid and stronger. This is the process of keratinization.
Such process is regulated by hormones, genetic factors and by cholesterol metabolism other than the fatty acid one. So, any dietary deficiencies or defects in the cholesterol synthesis, can cause an abnormal keratinization with structural consequences on the stem, which will appear weaker and less ready to protect the inside of the hair.
Lipids and minerals are also very important. Inside red hair there is more iron, inside black hair magnesium, lead inside brown hair and zinc is essential for the growth process.
When hair is healthy a good hygienic phase is always essential, hair has to be washed using a neutral shampoo which respects as much as possible the natural hydro-lipid balance, with warm water and rinsed with cold water to make protective scales close. During the washing, massage using fingertips and finally stop up with the towel without rubbing hard. After that, proceed to dry your hair using an intermediate speed and temperature.