Will all the cells be replaced in 7 years? Is this a "scientific" explanation of the seven-year itch? Let ’s calm down. The replacement of the old and the new cells is not the case, and the reason for the change in emotions will not be so simple ...

[Lengyue Rushuang / text] Rumor: [What is the itch of seven years?] Love will come to an end in seven years. The cells of the human body are metabolized and replaced every three months. As the old cells die, new cells are born. Due to the different time and interval of different cell metabolisms, all cells are replaced. It takes seven years, that is to say, physiologically, we are another person every seven years. You are you, but you are not you anymore.

Truth: In 1955, a movie starring Marilyn Monroe was hit in the United States. In the movie, the actor always uses all circumstances to imagine having an affair with Monroe. This romantic comedy, which was well-received at the time, had a profound impact on future generations: the white dress in the film where Monroe was blown by the wind became a well-known symbol. The seven-year itch in the Chinese translation is directly synonymous with marriage instability.

Why is it seven years? A recently circulated Weibo gave an explanation-"The cells of the human body will be metabolized and replaced every three months. Due to the different time and interval of different cell metabolisms, all the cells in the body It takes seven years to replace it. That is to say, in physiology, we are another person every seven years. "What? I am not me after seven years? This is quite suspected of talking nonsense in a scientific coat. However, there are serious studies on the age of the cells.

How old are the cells?

Cells do n’t speak, how can we know the age of a cell? Professor Jonas Frisén from the Karolinska Institute in Sweden got inspiration from archaeology ― ―Carbon 14 concentration can be used as a marker of cell age.

Carbon 14 is a radioactive isotope of carbon. It comes from the impact of cosmic rays on the atmosphere. It has a half-life of 5730 years and its content in the atmosphere is relatively stable. But from the mid-1950s to the early 1960s, humans conducted many nuclear tests on the ground, and the extra radiation produced caused a significant increase in the concentration of carbon 14 in the atmosphere. After a paper ban in 1963, there was no such source on the ground that could produce a large amount of carbon 14, so with the diffusion and exchange with ocean water, the carbon 14 content in the atmosphere showed a rapid exponential decline. For a single cell, from the day of birth, the DNA has almost no material exchange, and the carbon 14 contained in it is at a relatively stable level (the natural decay of carbon 14 is insignificant on the scale of decades ), Equal to the concentration of atmospheric carbon 14 at that time. Therefore, by measuring the carbon 14 content of the organism's cell DNA first, and then corresponding to the atmospheric carbon 14 concentration change curve, the time when the cell was born can be derived.

The content of C14 in the biosphere. Figure A shows that the content of C14 in nature has been stable for thousands of years, and the content increased sharply in 1955-1963 due to a large number of nuclear tests. Figure B shows the annual rings produced by pine trees over the past few decades (the cellulose in which carbon 14 is deposited). Figure C shows the changes in carbon 14 throughout the northern hemisphere over the past few decades. It can be seen that the carbon 14 content in the annual rings in Figure B can correspond to the actual changes in Figure C, confirming the reliability of this experimental scheme.

With the carbon 14 labeling tool, Professor Friesen began to analyze the age of some cells in the human body. Due to limited samples, his team can only temporarily focus on human cells in some areas. Through analysis, they found that the average age of intestinal cells in adults is about 10.7 ± 3.6 years. However, some previous studies have shown that due to the harsh environment, the intestinal epidermal cells have a life span of only 5 days. When Professor Friesen removed these short-lived epidermal cells, the average age of intestinal cells was about 15.9 years. In addition, they also found that the average age of human skeletal muscle is about 15.1 years old.

As a neurobiologist Professor De Vriesen, the main purpose of this research is to study whether the neurons in the cerebral cortex will regenerate. This study shows that neurons in the occipital cortex are the same age as humans, but because glial cells are still renewed, the average age measured is a few years lower than the human age. The occipital cortex is considered to be the most prone to cell regeneration in the mammalian cerebral cortex, so the researchers believe that this study suggests that almost all neuronal cells in our cerebral cortex should already exist shortly after birth, except in the case of injury Under or in individual areas, no new cells will be born.

The Ship of Theseus

The types of cells in the human body are far more than those studied by Professor Friesen, and there are also a few cells with higher replacement rates. In addition to the intestinal epidermal cells mentioned above, red blood cells can only live for an average of 120 days. Liver cells with a slightly longer lifespan have a lifespan of about 300-500 days, and the seemingly unchanged human skeleton will be replaced every 10 years. If you combine these different types of cells, the average age of cells in the entire human body is about 7-10 years old. At this point, the 7-year statement in the original Weibo is not too ridiculous, but the interpretation of this is quite wrong.

I believe that no one will "itch" because of the metabolism of the partner's intestinal cells or skeletal muscle cells. Within the scope of existing knowledge, except for a few olfactory bulb or hippocampal neurons that can be renewed, other neuronal cells are almost accompanied. Human life includes neuronal cells that are the basis of human emotion. Even if there is really a "seven-year itch" between men and women, and it has to be interpreted with knowledge limited to cell biology, it should be blamed on the changes in the influence of these neurons on human behavior, rather than repelling For the undesirable metabolism of nerve cells. In addition, the problem of feelings between men and women is not just a problem at the cellular level. The education people receive, the environment they live in, and their previous experiences all have a certain impact. To understand the reason for the "seven-year itch", perhaps not only need to continue to explore in neuroscience, but also need to find the reason for the mentality appraisal team.

Take a step back and say, even if the cells of the human body really have a replacement period, do we really have to become a new person in physiology? This actually implies the question of "These Ship". Theseus described a ship traveling a long distance at sea, which was inevitably damaged, so the craftsmen on the ship regularly replaced part of the ship to maintain the normal navigation of the ship. A few years later, the parts of the entire ship were replaced, so is the ship the same ship as it was originally set off? If it is, then if the discarded parts are collected and reassembled into a ship, these two ships What is the relationship between the ship and the original ship at the time of departure? If not, then when did the ship become different from the original one? These ancient questions are left to the readers and friends to think for themselves .

Conclusion: Rumors smashed. To explain that "seven-year itch" with "all cells replaced in seven years" is too far-fetched. The cells of the human body do have new and old replacements. The average age of some short-lived intestinal epithelial cells is only a pitiful 5 days, and the gray matter cells of the cerebellum can almost accompany a person's life. Although the different cells are calculated together, the average cell age is about 7-10 years, but I am afraid that no one will think that he has become another person because of the metabolism of intestinal cells or liver cells. As for the so-called seven-year itch, it has nothing to do with the life of the cells.

Furniture Knobs

Furniture Knobs,Furniture Door Pull Handles,Mini Cabinet Knob,Round Cabinet Knobs

Shenzhen Hongjingyuan Metal&Plastic Products Co., Ltd. , https://www.hjypull.com