How do hair and nails grow?

Posted on Feb 18, 2021      137

How much hair do we have?

The human body has between 200,000 and 1 million hairs. Only on the head there are from 80 to 200 thousand hairs. The density of hair on the head is directly related to its color: redheads have about 80 thousand hairs, blackheads have 100 thousand hairs, and blondes have the thickest hairs with an average of 140 thousand hairs. They contain up to 40 chemical elements, including manganese, copper, sodium, bromine, zinc, titanium, and even gold and silver. It is noteworthy that people of intellectual labor are found to have more copper and zinc in their hair than others. But in gray hair, they mostly find nickel and ... a lot of air.

Who has longer hair?

Depending on the location, hair length varies from 1mm to several tens of centimeters. Hair diameter varies from 0,05mm to 0,5mm. They grow at a rate of 0,3-0,4 mm per day, and most rapidly in the evening hours, and at night they rest, and the entire body. In spring and summer, our “vegetation”, like all of nature, also speeds up its growth. Over the course of a year, each head hair can increase by 12.8 cm, and theoretically over a human life, its length could reach 9-10 m. But this does not happen, because hair is constantly falling out, and new hairs grow in its place. Every day a child loses 50-80 hairs, an adult - up to 100, and old people - 120 hairs. Each hair grows for 3 years for men and 10 years for women, so even if we stop cutting hair altogether, women’s hair will still be longer. The record hair length belongs to the Indian ascetic Swami Panarasannadhi, whose hair reached 789 cm.

How does hair grow?

Hair does not grow perpendicularly but at an angle to the surface of the skin from follicles that are like tiny bulbs. Each hair follicle, embedded in the skin's epidermis, has a tiny muscle that makes the hair “grow”. The follicles open the ducts of sebaceous glands that secrete an oily secret to protect the hair. The outer cuticle of the hair is formed by tiny scales that overlap each other like shingles. These keratin scales can fit tightly together, making hair look smooth. If they are frizzy, the hair looks dull and untidy, as they do in shampoo commercials. Underneath the cuticle is the cortex, which comprises elongated cells that support the hair structure. It is these cells that contain the melanin pigments that give hair its unique, individual coloring. In the center of the hair there are loose soft cells and voids between them. It should be noted that fine, feathery hair, which covers our entire body inconspicuously, has virtually no central layer.

How do nails grow? 

The convex plate of the nail lies on the nail bed, and the nail grows forward from the cells of its posterior part. At the base of the nail is the growth zone, where living cells are actively dividing. They produce the waterproof protein keratin, which fills the interior of the living cells, causing the cells to die off. As they divide, the new cells push the dead cells forward and the nail grows as a wide and thick nail plate. Each nail grows an average of 0.83 mm per week. And this process is more active in women than in men, and in children faster than in adults. Also, the nails on the right hand grow faster than on the left hand (vice versa for left-handers), and in summer they grow faster than in winter.

Dead or alive?

20 human nails weigh only about 3 g. There are no nerves in the nails, but they are sensitive because they are in contact with the nerve endings of the skin. Between the layers of keratin are layers of fat and water. If the nail is disturbed, it can delaminate. The nail is a shield that covers the delicate fingertips. Without them, it would be impossible to hold objects in the hand and perform delicate manipulations. Right-handed people have about 2.2 mm wider nails on the right hand and have a flatter surface than on the left (vice versa for left-handed people), but newborns do not yet show such a difference. It is noteworthy that people who work with their hands (mechanics, surgeons, dentists, peasants) have wider and flatter nails than other professions.

There are good reasons to treat nails and hair with special care. After all, they are not only an important component of human beauty but also serve as an indicator of the body’s health!