In 1901, the Russian physiologist and student of Sechenov Nikolai Evgenievich Vvedensky introduced a new term - parabiosis. So he designated a state bordering between life and death of a cell. The scientist discovered that physiological reactions of cells change under the influence of various stimuli in the tissues of the body.
He studied the phenomenon of parabiosis on nerves, muscles, glands, spinal cord and came to the conclusion that this is a general, universal response of excitable tissues to strong or prolonged exposure to stimuli. However, the cells do not die, they can still be brought back to life.
If we analyze how cells in different parts of the body react to one of the stimuli - a sharp decrease in the supply of oxygen to the tissues - we can study in all details the mysterious process of death, which is a picture of uneven failure of various structures of the body.
The life span of cells is determined by the threshold of sensitivity of certain tissues to hypoxia, that is, to a reduced oxygen content. For example, skin cells, having a special mechanism for receiving nutrition, continue to divide for another 12 hours. The fact is that young skin cells are formed in the germ layer of the epidermis.
Skin cells / Depositphotos / Edustock
Within 28 days, they move to the surface of the skin, while losing the cell nucleus. The layer of skin that we observe from the outside is the flat keratin particles that form the so-called stratum corneum. Within three to four weeks, the entire upper skin is completely renewed, and this process is not so dependent on the supply of large amounts of oxygen.
But the growth of nails and hair on a deceased person is, of course, an illusion. The process of formation of new nail cells is impossible without glucose, which is not produced in the deceased body. The same can be said for hair growth. Each hair grows from a hair follicle, at the base of which there is a hair matrix - a group of cells from which new ones are obtained by division. But this requires energy, which occurs when glucose is burned. Nevertheless, nails and hair do seem to have grown back on a person who died, say, two days ago. This is because many of the structures of the body strongly collapse and dry out - these processes are well known and described in detail.
Patient in the intensive care unit / Depositphotos / SimpleFoto
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Heart cells also do not die immediately after they have stopped. Although you should not think that the main "pump" fails instantly and completely. Until the heart stops completely, peculiar phenomena occur in it. The left ventricle stops first, followed by the right, then the left and right atria. But the auricle of the right atrium can beat for several more hours even with the seeming complete rest of the heart. Therefore, a defibrillator is used - a device that is effective for fibrillation - chaotic electrical activity of the atria. And with a complete cardiac arrest, it is already useless.
Defibrillation of the heart / Depositphotos / Plepraisaeng
As for the neurons in the brain, which are believed to die five to six minutes after the cessation of oxygen supply, their functioning depends on many different reasons. Therefore, the diagnosis of brain death is so difficult to make even with all modern equipment.
Severely ill / Fotolia / Sudok1
Indeed, in the deep stages of dying of the entire human body against the background of bioelectric "silence" of the cortex and subcortical formations, an increase in the electrical activity of the caudal part of the brain stem, especially its reticular formation, is often observed.
But even when there is no longer any activity, according to American anesthesiologist Sam Parnia, the brain can return to its activity. “Human consciousness is not immediately switched off when the heartbeat stops,” he explains. - People in the "first phase of death" may still retain the ability to perceive. Cases when survivors of cardiac arrest were able to describe in detail what happened around them after clinical death are significant evidence of this.
Anna Urmantseva
