Know yourself; love yourself; be honest with yourself. These old truths have been celebrated for years by artists, musicians and philosophers, from Jean-Paul Sartre to Bob Dylan. But how do you know yourself if you are constantly changing? The human body is in constant motion: it loses and grows skin, renews lungs, grows new hair.
According to scientists, the body replaces itself with a completely new set of cells every seven to ten years, and some of our most important parts of the body are renewed even faster.
Some of you might be thinking, "Well, that explains why my wife / brother / father is acting like little children." Others may think that new cells may be the key to long life. Unfortunately, things are much more complicated.
Body rejuvenation
In the early 1950s, scientists discovered the power of rejuvenating the body by - seriously - introducing radioactive atoms into objects and observing their movements. They found that, on average, 98% of the atoms in the body - the small particles of matter that form the molecules and cells of the body - are replaced every year. Most of the new atoms are accepted along with the air we breathe, the food we eat, and the liquid we drink.
Fifty years later, Swedish molecular biologist Jonas Frisen studied the renewal of body tissues by measuring the level of a radioactive material - carbon-14. This material was thrown into the air before overhead nuclear weapons testing was banned in 1963. Carbon-14 is inhaled by the plants that humans and animals eat day in and day out, and is part of our DNA. But unlike other atoms and molecules that are constantly changing, a person's DNA remains unchanged from the moment a cell is born - which happens when the parent cells divide - until the end of its life. When a cell divides, in other words, the DNA that is introduced into new cells contains a certain level of carbon-14, which corresponds to the level of this substance in the air around us at that time. Thus, this substance can be considered a kind of timestamp,by which scientists can determine when a cell was created.
Friesen found that cells in the body mostly replace themselves every 7-10 years. In other words, old cells die and are replaced with new ones during this period of time. Cell renewal is faster in some parts of the body, but complete rejuvenation from toes to head takes about ten years.
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This explains why our skin's scales fall off, our nails grow and our hair falls out. But if we are constantly filling up with new cells, why does the body age? Shouldn't the new cells act like a Botox shot? When it comes to aging, it turns out that the secret is not in our cells, but in cellular DNA.
Cell lifespan
The body is renewed in different ways. The time the cells work in certain areas of the body depends on what is required of them. Red blood cells, for example, live for four months because they are required to travel a difficult path through the circulatory system and deliver oxygen to tissues throughout the body.
And here is how long other cells live:
- Skin: The epidermis undergoes a fair amount of wear and tear as it acts as the body's outer protective layer. These skin cells are renewed every two to four weeks.
- Hair: natural body hair has a lifespan of about 6 years for women and 3 years for men.
- Liver: The liver cleanses the human body by removing a wide range of pollutants from our systems. It promotes a constant blood supply and remains immune to damage from these pollutants and toxins, renewing its cells every 150-500 days.
- Stomach and intestines: The cells lining the surface of the stomach and intestines live short and complex lives. Constantly exposed to caustic stomach acids, they usually live for only 5 days, no more.
- Bones: cells of the skeletal system regenerate almost constantly, but the whole process takes up to 10 years. The renewal process slows down as we age, so our bones become thinner.
Despite all this constant regeneration, people who want to live forever should not stop looking for the source of youth. The point is that we continue to age and gradually die. Frisen and others believe it may be due to DNA mutations that get worse, moving on to new cells over time.
There are also a number of cells that never leave us and can contribute to the aging process, or at least the decay of the body over time. Although the cornea of the eye can heal in just one day, the lens and other areas of the eye do not change. It's the same with neurons in the cerebral cortex - the outer layer of the brain that is responsible for memory, thinking, language, attention, and consciousness - they stay with us from birth to death. Since they are not replaced, the loss of these cells leads to serious ailments. The good news is that other areas of the brain, the olfactory bulb, which is responsible for smell, and the hippocampus, which is responsible for learning, can and will be renewed.
Take care of yourself. The first person has already been born who will live forever.
Ilya Khel