How does the metabolism work inside a person?

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

The first cell could not survive if it were not for the special "climate" of life created by the sea. Likewise, each of the hundreds of trillions of cells that make up the human body would die without blood and lymph. Over the millions of years since life appeared, nature has developed an internal transport system that is immeasurably more original, efficient and more clearly controlled than any of the means of transportation ever created by man.

In fact, blood is made up of a variety of transport systems. Plasma, for example, serves as a vehicle for corpuscles, including erythrocytes, leukocytes, and platelets, which move to different parts of the body as needed. In turn, red blood cells are a means of transporting oxygen to cells and carbon dioxide from cells.

Liquid plasma carries in dissolved form many other substances, as well as its own components, which are extremely important for the vital processes of the body. In addition to nutrients and waste, plasma carries heat, accumulating or releasing it as needed and thus maintaining a normal temperature regime in the body. This environment carries many of the main protective substances that protect the body from disease, as well as hormones, enzymes and other complex chemical and biochemical substances that play a wide variety of roles.

Modern medicine has fairly accurate information about how blood performs the listed transport functions. As for other mechanisms, they still remain the object of theoretical speculation, and some, undoubtedly, have yet to be discovered.

It is common knowledge that any single cell dies without a constant and direct supply of essential materials and no less urgent disposal of toxic waste. This means that the "transport" of blood must be in direct contact with all these many trillions of "clients", satisfying the needs of each of them. The enormity of this task truly defies human imagination!

In practice, loading and unloading in this great transport organization is carried out through microcirculation - capillary systems … These tiny vessels penetrate literally every tissue of the body and approach the cells at a distance of no more than 0, 125 millimeters. Thus, each cell of the body has its own access to the River of Life.

The body's most urgent and constant need is for oxygen. A person, fortunately, does not have to constantly eat, because most of the nutrients necessary for metabolism can accumulate in various tissues. The situation is different with oxygen. This vital substance accumulates in the body in negligible amounts, and the need for it is constant and urgent. Therefore, a person cannot stop breathing for more than a few minutes - otherwise it will cause the most serious consequences and death.

To meet this urgent need for a constant supply of oxygen, blood has developed an extremely efficient and specialized delivery system that uses erythrocytes, or red blood cells … The system is based on an amazing property hemoglobinto absorb in large quantities, and then immediately give up oxygen. In fact, the hemoglobin of the blood carries sixty times more than the amount of oxygen that can be dissolved in the liquid part of the blood. Without this iron-containing pigment, it would take about 350 liters of blood to supply oxygen to our cells!

But this unique property of absorbing and transferring large volumes of oxygen from the lungs to all tissues is only one side of the truly invaluable contribution that hemoglobin makes to the operational work of the blood transport system. Hemoglobin also transports large quantities of carbon dioxide from the tissues to the lungs and thus participates in both the initial and final stages of oxidation.

When exchanging oxygen for carbon dioxide, the body uses the characteristic features of liquids with amazing skill. Any liquid - and gases in this respect behave like liquids - tend to move from a high pressure region to a low pressure region. If the gas is on both sides of the porous membrane and on one side of it the pressure is higher than on the other, then it penetrates through the pores from the high-pressure region to the side where the pressure is lower. And similarly, a gas dissolves in a liquid only if the pressure of this gas in the surrounding atmosphere exceeds the pressure of the gas in the liquid. If the pressure of the gas in the liquid is higher, the gas rushes out of the liquid into the atmosphere, as happens, for example, when a bottle of champagne or sparkling water is uncorked.

The tendency of fluids to move to a lower pressure area deserves special attention, because it is related to other aspects of the blood transport system, and also plays a role in a number of other processes occurring in the human body.

It is interesting to trace the path of oxygen from the moment we inhale. Inhaled air, rich in oxygen and containing a small amount of carbon dioxide, enters the lungs and reaches a system of tiny sacs called alveoli … The walls of these alveoli are extremely thin. They consist of a small number of fibers and the finest capillary network.

In the capillaries that make up the walls of the alveoli, venous blood flows, entering the lungs from the right half of the heart. This blood is dark in color, its hemoglobin, almost deprived of oxygen, is saturated with carbon dioxide, which came as a waste from the tissues of the body.

A remarkable double exchange occurs at the moment when air, rich in oxygen and almost free of carbon dioxide, in the alveoli comes into contact with air rich in carbon dioxide and almost devoid of oxygen. Since the pressure of carbon dioxide in the blood is higher than in the alveoli, this gas enters the alveoli of the lungs through the walls of the capillaries, which, when exhaled, remove it into the atmosphere. The oxygen pressure in the alveoli is higher than in the blood, so the gas of life instantly penetrates through the walls of the capillaries and comes into contact with the blood, the hemoglobin of which quickly absorbs it.

The blood, which has a bright red color due to oxygen, which now saturates the hemoglobin of red cells, returns to the left half of the heart and from there is pumped into the systemic circulation. As soon as it enters the capillaries, red blood cells literally "in the back of the head" squeeze through their narrow lumen. They move along cells and tissue fluids, which in the course of normal life have already used up their supply of oxygen and now contain a relatively high concentration of carbon dioxide. Oxygen is exchanged for carbon dioxide again, but now in the reverse order.

Since the oxygen pressure in these cells is lower than in the blood, hemoglobin quickly gives up its oxygen, which penetrates through the walls of the capillaries into tissue fluids and then into cells. At the same time, high pressure carbon dioxide moves from the cells into the blood. The exchange takes place as if oxygen and carbon dioxide were moving in different directions through revolving doors.

During this process of transport and exchange, blood never releases all of its oxygen or all of its carbon dioxide. Even in venous blood, a small amount of oxygen is retained, and carbon dioxide is always present in oxygenated arterial blood, albeit in an insignificant amount.

Although carbon dioxide is a byproduct of cellular metabolism, it itself is also necessary to sustain life. A small amount of this gas is dissolved in plasma, part of it is associated with hemoglobin, and a certain part in combination with sodium forms sodium bicarbonate.

Sodium bicarbonate, which neutralizes acids, is produced by the "chemical industry" of the organism itself and circulates in the blood to maintain the vital acid-base balance. If, during an illness or under the influence of some irritant, the acidity in the human body rises, then the blood automatically increases the amount of circulating sodium bicarbonate to restore the desired balance.

The blood oxygen transport system is almost never idle. However, one violation should be mentioned, which can be extremely dangerous: hemoglobin easily combines with oxygen, but even faster it absorbs carbon monoxide, which has absolutely no value for vital processes in cells.

If there is an equal volume of oxygen and carbon monoxide in the air, hemoglobin for one part of the oxygen much needed by the body will assimilate 250 parts of completely useless carbon monoxide. Therefore, even with a relatively low content of carbon monoxide in the atmosphere, vehicles of hemoglobin are quickly saturated with this useless gas, thereby depriving the body of oxygen. When the supply of oxygen falls below the level necessary for cells to survive, death occurs from the so-called burnout.

Apart from this external danger, from which even an absolutely healthy person is not insured, the oxygen transfer system with the help of hemoglobin from the point of view of its effectiveness seems to be the pinnacle of perfection. Of course, this does not exclude the possibility of its improvement in the future, either through ongoing natural selection, or through conscious and purposeful human efforts. In the end, nature took probably at least a billion years of error and failure before it created hemoglobin. And chemistry as a science has existed for only a few centuries!

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The transport of nutrients - the chemical products of digestion - by the blood is just as important as the transport of oxygen. Without it, the metabolic processes that feed life would stop. Every cell in our body is a kind of chemical plant that needs constant replenishment of raw materials. Breathing supplies oxygen to the cells. Food supplies them with basic chemical products - amino acids, sugars, fats and fatty acids, mineral salts and vitamins.

All these substances, as well as the oxygen with which they combine in the process of intracellular combustion, are the most important components of the metabolic process.

As known, metabolism, or metabolism, consists of two main processes: anabolismand catabolism, creation and destruction of body substances. In the anabolic process, simple digestive products, entering the cells, undergo chemical processing and turn into substances necessary for the body - blood, new cells, bones, muscles and other substances necessary for life, health and growth.

Catabolism is the process of destruction of body tissues. Affected and worn out cells and tissues that have lost their value, useless, are processed into simple chemicals. They are either accumulated and then reused in the same or similar form - just as the iron of hemoglobin is reused to create new red cells - or they are destroyed and excreted from the body as waste.

Energy is released during oxidation and other catabolic processes. It is this energy that makes the heart beat, allows a person to carry out the processes of breathing and chewing food, to run after the outgoing tram and perform countless physical actions.

As can be seen even from this brief description, metabolism is a biochemical manifestation of life itself; the transport of substances involved in this process refers to the function of blood and related fluids.

Before the nutrients from the food we eat can reach the various parts of the body, they must be broken down through the process digestionto the smallest molecules that can pass through the pores of the intestinal membranes. Oddly enough, the digestive tract is not considered part of the internal environment of the body. In fact, it is a huge complex of tubes and associated organs, surrounded by our body. This explains why powerful acids function in the digestive tract, while the internal environment of the body must be alkaline. If these acids were really in the internal environment of a person, they would change it so much that it could lead to death.

During the digestion process, carbohydrates in food are converted into simple sugars, such as glucose, and fats are broken down into glycerin and simple fatty acids. The most complex proteins are converted into amino acid components, of which about 25 species are already known to us. Food processed in this way into these simplest molecules is ready for penetration into the internal environment of the body.

The thinnest tree-like outgrowths, which are part of the mucous membrane lining the inner surface of the small intestine, deliver digested foods to the blood and lymph. These tiny outgrowths, called villi, are composed of a centrally located solitary lymphatic vessel and a capillary loop. Each villi is covered with a single layer of mucus-producing cells that serve as a barrier between the digestive system and the vessels inside the villi. In total, there are about 5 million villi, located so closely to each other that it gives the inner surface of the intestine a velvety appearance. The process of assimilating food is based on the same basic principles as the assimilation of oxygen in the lungs. The concentration and pressure of each nutrient in the intestine is higher than in the blood and lymph flowing through the villi. Therefore, the smallest molecules, into which our food turns, easily penetrate through the pores on the surface of the villi and enter the small vessels located inside them.

Glucose, amino acids and part of fats penetrate into the blood of the capillaries. The rest of the fats enter the lymph. With the help of villi, the blood assimilates vitamins, inorganic salts and microelements, as well as water; part of the water enters the bloodstream and through the colon.

Essential nutrients carried by the bloodstream enter the portal vein and are delivered directly to liver, the greatest gland and the largest "chemical plant" of the human body. Here, the products of digestion are processed into other substances necessary for the body, stored in reserve, or again sent to the blood without changes. Individual amino acids, once in the liver, are converted into blood proteins such as albumin and fibrinogen. Others are processed into protein substances necessary for the growth or repair of tissues, while the rest in their simplest form are sent to the cells and tissues of the body, which pick them up and immediately use them according to their needs.

Part of the glucose entering the liver is directly sent to the circulatory system, which carries it in a state dissolved in the plasma. In this form, sugar can be delivered to any cell and tissue in need of an energy source. Glucose, which the body does not need at the moment, is processed in the liver into a more complex sugar - glycogen, which is stored in the liver in reserve. As soon as the amount of sugar in the blood falls below normal, glycogen is converted back to glucose and enters the circulatory system.

So, thanks to the liver's reaction to signals coming from the blood, the content of transportable sugar in the body is maintained at a relatively constant level.

Insulin helps cells absorb glucose and convert it into muscle and other energy. This hormone enters the bloodstream from the cells of the pancreas. The detailed mechanism of action of insulin is still unknown. It is only known that its absence in human blood or insufficient activity causes a serious illness - diabetes mellitus, which is characterized by the inability of the body to use carbohydrates as energy sources.

About 60% of the digested fat enters the liver with the blood, the rest goes to the lymphatic system. These fatty substances are stored as energy reserves and are used in some of the most critical processes in the human body. Some fat molecules, for example, are involved in the formation of biologically important substances such as sex hormones.

Fat appears to be the most important vehicle for energy storage. Approximately 30 grams of fat can generate twice as much energy as an equal amount of carbohydrates or proteins. For this reason, excess sugar and protein that is not excreted from the body is converted to fat and stored as a reserve.

Usually fat is deposited in tissues called fat depots. As additional energy is needed, fat from the depot enters the bloodstream and is transferred to the liver, where it is processed into substances that can be converted into energy. In turn, these substances from the liver enter the bloodstream, which carries them to cells and tissues, where they are used.

One of the main differences between animals and plants is the ability of animals to efficiently store energy in the form of dense fat. Since dense fat is much lighter and less bulky than carbohydrates (the main store of energy in plants), animals are better suited for movement - they can walk, run, crawl, swim or fly. Most of the plants bent under the burden of reserves are chained to one place due to their low-activity energy sources and a number of other factors. There are, of course, exceptions, most of which refer to microscopically small marine plants.

Along with nutrients, the blood carries various chemical elements to the cells, as well as the smallest amounts of certain metals. All of these trace elements and inorganic chemicals play a critical role in life. We have already spoken about iron. But even without copper, which plays the role of a catalyst, the production of hemoglobin would be difficult. Without cobalt in the body, the ability of the bone marrow to produce red blood cells could be reduced to dangerous levels. As you know, the thyroid gland needs iodine, bones need calcium, and phosphorus is needed for teeth and muscle work.

The blood also carries hormones. These potent chemical reagents enter the circulatory system directly from the endocrine glands, which manufacture them from raw materials obtained from blood.

Each hormone (this name comes from the Greek verb meaning "to excite, to induce"), apparently, plays a special role in the management of one of the vital functions of the body. Some hormones are associated with growth and normal development, while others affect mental and physical processes, regulate metabolism, sexual activity and a person's ability to reproduce.

The endocrine glands supply the blood with the necessary doses of the hormones they produce, which through the circulatory system get to the tissues that need them. If there is an interruption in the production of hormones, or there is an excess or deficiency of such potent substances in the blood, this causes various kinds of anomalies and often leads to death.

Human life also depends on the ability of the blood to remove decay products from the body. If the blood did not cope with this function, the person would die from self-poisoning.

As we have noted, carbon dioxide, a by-product of the oxidation process, is excreted from the body through the lungs. Other wastes are taken up by the blood in the capillaries and transported to kidneysthat act like huge filter stations. The kidneys have approximately 130 kilometers of tubes that carry blood. Every day, the kidneys filter about 170 liters of fluid, separating urea and other chemical waste from the blood. The latter are concentrated in about 2.5 liters of urine excreted per day and are removed from the body. (Small amounts of lactic acid as well as urea are excreted through the sweat glands.) The remaining filtered fluid, approximately 467 liters per day, is returned to the blood. This process of filtering the liquid part of the blood is repeated many times. In addition, the kidneys act as a regulator of the content of mineral salts in the blood, separating and discarding any excess.

It is also crucial for human health and life maintaining the body's water balance … Even under normal conditions, the body continually excretes water through urine, saliva, sweat, breath and other routes. At usual and normal temperature and humidity, about 1 milligram of water is released every ten minutes per 1 square centimeter of the skin. In the deserts of the Arabian Peninsula or in Iran, for example, a person loses about 10 liters of water every day in the form of sweat. To compensate for this constant loss of water, fluid must constantly flow into the body, which will be carried through the blood and lymph and thereby contribute to the establishment of the necessary equilibrium between tissue fluid and circulating fluid.

Tissues that need water replenish their reserves by obtaining water from the blood as a result of the osmosis process. In turn, blood, as we have already said, usually receives water for transportation from the digestive tract and carries a ready-to-use supply that quenches the body's thirst. If, during an illness or accident, a person loses a large amount of blood, the blood tries to replace the loss of tissue at the expense of water.

The function of blood for the delivery and distribution of water is closely related to body heat control system … The average body temperature is 36.6 ° C. At different times of the day it can vary slightly in individuals and even in the same person. For some unknown reason, the body temperature early in the morning can be one to one and a half degrees lower than the evening temperature. However, the normal temperature of any person remains relatively constant, and its abrupt deviations from the norm usually serve as a signal of danger.

Metabolic processes constantly occurring in living cells are accompanied by the release of heat. If it accumulates in the body and is not removed from it, then the internal body temperature may become too high for normal functioning. Fortunately, at the same time as heat builds up, the body also loses some of it. Since the air temperature is usually below 36.6 ° C, i.e., body temperature, heat, penetrating through the skin into the surrounding atmosphere, leaves the body. If the air temperature is higher than body temperature, excess heat is removed from the body through perspiration.

Usually, a person on average excretes about three thousand calories per day. If he transfers more than three thousand calories to the environment, then his body temperature drops. If less than three thousand calories are released into the atmosphere, the body temperature rises. The heat generated in the body must balance the amount of heat given off to the environment. The regulation of heat exchange is entirely entrusted to the blood.

Just as gases move from a high pressure area to a low pressure area, heat energy is directed from a warm area to a cold area. Thus, the body's heat exchange with the environment occurs through such physical processes as radiation and convection.

Blood absorbs and carries away excess heat in much the same way as water in a car's radiator absorbs and carries away excess engine heat. The body performs this heat exchange by changing the volume of blood flowing through the skin vessels. On a hot day, these vessels dilate and a larger volume of blood flows to the skin than usual. This blood carries heat away from the internal organs of a person, and as it passes through the vessels of the skin, the heat is radiated into a cooler atmosphere.

In cold weather, the vessels of the skin contract, thereby reducing the volume of blood supplied to the surface of the body, and the transfer of heat from the internal organs is reduced. This occurs in those parts of the body that are hidden under clothing and protected from the cold. However, the vessels of exposed areas of the skin, such as the face and ears, dilate to protect them from the cold with additional heat.

Two other blood mechanisms are also involved in regulating body temperature. On hot days, the spleen contracts, releasing an additional portion of blood into the circulatory system. As a result, more blood flows to the skin. In the cold season, the spleen expands, increasing the blood reserve and thereby reducing the amount of blood in the circulatory system, so less heat is transferred to the body surface.

Radiation and convection as a means of heat exchange act only in those cases when the body gives off heat to a colder environment. On very hot days, when the air temperature exceeds normal body temperature, these methods only transfer heat from a hot environment to a less heated body. In these conditions, sweating saves us from excessive overheating of the body.

Through the process of sweating and breathing, the body gives off heat to the environment through the evaporation of fluids. In either case, blood plays a key role in delivering fluids for evaporation. The blood heated by the internal organs of the body gives up part of its water to the surface tissues. This is how perspiration occurs, sweat is released through the pores of the skin and evaporates from its surface.

A similar picture is observed in the lungs. On very hot days, the blood, passing through the alveoli, together with carbon dioxide, gives them part of its water. This water is released during exhalation and evaporates, which helps to remove excess heat from the body.

In these and many other ways, which are not yet entirely clear to us, the transport of the River of Life serves a person. Without his energetic and eminently organized services, the many trillions of cells that make up the human body could decay, waste away, and eventually perish.