How many liters of plasma are there in a person. The amount of blood in the body of an adult: how to calculate and basic functions. How much blood in the human body is in the form of plasma, and how much in the form of formed elements

The latter give it its characteristic red color. The state of health depends not only on the composition of the blood, but also on how much of it is contained in the human body.

Plasma makes up about 60% of the total volume. If we separate the shaped elements from it, then 90% of it will consist of water, the remaining 10% are salts, carbohydrates, proteins, carbon dioxide, oxygen, bioactive substances. Men always have more plasma than the fairer sex.

Functions

Blood fulfills essential functions in the human body. It constantly circulates in a system consisting of large and small blood vessels that permeate all organs and tissues, except for the epithelium of the skin and mucous membranes, articular cartilage, the cornea of the eyes, hair and nails.

Red cells are involved in the delivery of oxygen to tissues due to the ability of hemoglobin to reversibly bind to its molecules. Platelets are directly involved in clotting during bleeding: they rush to the site of damage to the vessel and form a blood clot at this site. Leukocytes are the main defenders of the body against internal and external harmful agents.

Blood transports oxygen from the lungs to tissue cells, and carbon dioxide from tissues to the lungs, transports metabolic products, nutrients, hormones, enzymes, biologically active substances, and is also responsible for the delivery of end metabolic products to organs excretory system... It regulates temperature and maintains water, electrolyte and acid balance in the body.

How much blood does a person have?

Its volume varies from person to person. It depends on gender, age, weight and individual characteristics. The norm is taken as a value - from 5 to 9% of body weight. On average, an adult circulates about 5-6 liters of blood, a child, respectively, less. Its amount is maintained by the body at the same level. With deviations in one direction or another, health problems arise.

If an increased amount circulates in the system, nosebleeds may occur. Cuts and other injuries in this case take longer to heal, which is associated with the high pressure under which blood flows out of the wound. As a rule, when excess blood is formed in the body, its redistribution occurs. It enters muscle tissue, skin, is processed by the kidneys and excreted. naturally.

In the body, men constantly circulate about 5-6 liters, women - about 4-5 liters. In a child's body, its volume is much less than that of an adult, and depends on weight and age. Its amount may change periodically, which is associated with bleeding, significant physical exertion, trauma, menstruation, consumption a large number liquids. Blood loss is much easier for women than for men.

How to determine the volume of blood in a person?

For this purpose, a certain amount of a contrast agent, usually a harmless dye, is injected into the blood. After it is distributed along the entire channel, a fence is made to determine its concentration.

Another way is the introduction of radioactive isotopes and counting the number of red blood cells in which they are contained. The amount of blood is determined by the level of its radioactivity.

Blood transfusion is used to normalize the blood volume in the body.

How to make up for the loss?

Today this problem is being solved with the help of donor blood transfusion. This procedure is necessary for severe injuries, surgical operations, childbirth. Plasma is most often transfused, which makes up about 60% of the total. The donor's blood must be suitable for the patient according to the group and the Rh factor.

According to the existing law, you can donate blood at a time no more than 450 ml (or 600 ml of plasma). In addition, there are restrictions on the frequency of donation and the weight of the donor (4 times a year for women, 5 times for men, the interval between samples is at least 60 days, the donor's weight is at least 50 kg). This order is due to the fact that the loss of 10% of blood can lead to a deterioration in health and the development of anemia.

Conclusion

Human health depends not only on the composition of blood, but also on its volume. A significant decrease in its amount in the body can cause disease and even death.

Concept, composition and properties of blood

Physiology of the blood system

Definition of the concept of the blood system

The blood system (according to G.F. Lang, 1939) is a set of blood itself, hematopoietic organs, blood destruction (red bone marrow, thymus, spleen, lymph nodes) and neurohumoral mechanisms of regulation, due to which the constancy of the composition and function of blood is maintained.

Currently, the blood system is functionally supplemented with organs for the synthesis of plasma proteins (liver), delivery into the bloodstream and excretion of water and electrolytes (intestines, nights). The most important features blood as a functional system are as follows:

it can perform its functions only being in a liquid state of aggregation and in constant motion (along the blood vessels and cavities of the heart);
all its constituent parts are formed outside the vascular bed;
she brings together the work of many physiological systems organism.

The composition and amount of blood in the body

Blood is a liquid connective tissue, which consists of a liquid part - plasma and cells suspended in it - shaped elements: erythrocytes (red blood cells), leukocytes (white blood cells), platelets (platelets). In an adult, blood corpuscles make up about 40-48%, and plasma - 52-60%. This ratio is called the hematocrit number (from the Greek haima - blood, kritos - indicator). The composition of the blood is shown in Fig. 1.

Rice. 1. Composition of blood

The total amount of blood (how much blood) in the body of an adult is normally 6-8% of the body weight, i.e. about 5-6 liters.

Physicochemical properties of blood and plasma

How much blood is in the human body?

The share of blood in an adult is 6-8% of body weight, which corresponds to approximately 4.5-6.0 liters (with an average weight of 70 kg). In children and athletes, the blood volume is 1.5-2.0 times greater. In newborns, it is 15% of the body weight, in children of the 1st year of life - 11%. In humans, under conditions of physiological rest, not all blood actively circulates through cardiovascular system... Part of it is located in blood depots - venules and veins of the liver, spleen, lungs, skin, in which the blood flow rate is significantly reduced. The total amount of blood in the body is kept at a relatively constant level. Quick loss 30-50% of blood can lead the body to death. In these cases, urgent transfusion of blood products or blood substitute solutions is required.

The viscosity of blood is due to the presence of corpuscles in it, primarily erythrocytes, proteins and lipoproteins. If the viscosity of water is taken as 1, then the viscosity of the whole blood of a healthy person will be about 4.5 (3.5-5.4), and that of plasma - about 2.2 (1.9-2.6). The relative density (specific gravity) of the blood depends mainly on the number of red blood cells and the protein content in the plasma. In a healthy adult, the relative density of whole blood is 1.050-1.060 kg / l, erythrocyte mass - 1.080-1.090 kg / l, blood plasma - 1.029-1.034 kg / l. For men, it is slightly higher than for women. The highest relative density of whole blood (1.060-1.080 kg / l) is observed in newborns. These differences are explained by the difference in the number of red blood cells in the blood of people of different sexes and ages.

The hematocrit indicator is the part of the blood volume attributable to the corpuscular elements (first of all, erythrocytes). Normally, the hematocrit of the circulating blood of an adult is on average 40-45% (for a husband - a chip - 40-49%, for women - 36-42%). In newborns, it is about 10% higher, and in young children it is about the same amount lower than in an adult.

Blood plasma: composition and properties

Plasma is the liquid part of the blood that remains after the removal of corpuscles from it. Blood plasma is a rather complex biological environment located in close connection with tissue fluid of the body. The volume of plasma from all blood is on average 55-60% (in men - 51-60%, in women - 58-64%). It contains water and dry residue from organic and inorganic substances.

Plasma proteins are represented by albumin, a-, β-, y-globulins, fibrinogen and minor proteins (lysozyme, interferons, b-lysine, haptoglobin, cerulloplasmin, proteins of the complement system, etc.). The content of proteins in blood plasma is g / l. Blood plasma proteins perform a number of important functions: nutritional (source of amino acids), transport (for lipids, hormones, metals), immune (γ-globulins, which are the main part of humoral link of immunity), hemostatic (participation in stopping bleeding in case of damage to the vessel wall), buffer (maintaining blood pH), regulatory function. Proteins also provide plasma viscosity and oncotic pressure (25-30 mm Hg).

By function, proteins are classified into three large groups. The 1st group includes proteins that ensure the maintenance of the proper value of oncotic pressure (albumins determine its value by 80%) and perform a transport function (a-, β-globulins, albumins). The second group includes protective proteins against foreign substances, micro- and macroorganisms (y-globulins, etc.); The 3rd group consists of proteins that regulate the aggregate state of the blood: blood coagulation inhibitors - antithrombin III; coagulation factors - fibrinogen, prothrombin; fibrinolytic proteins - plasminogen, etc.

Table. Indicators of the blood system of an adult

Other organic substances of the blood plasma are represented by nutrients (glucose, amino acids, lipids), products of intermediate metabolism (lactic and pyruvic acid and nogric acids), biologically active substances(vitamins, hormones, cytokines), end products of protein metabolism and nucleic acids(urea, uric acid, creatinine, bilirubin, ammonia).

Inorganic substances of blood plasma account for about 1% and are represented by mineral salts (cations Na +, K +, Ca 2+, Mg 2+, anions СI-, HPO 2 4 - HC0 3 -), as well as microelements (Fe 2+, Cu 2+, Co 2+, J -, F 4-), associated by 90% or more with organic substances of the plasma. Mineral salts create osmotic blood pressure, pH, participate in the process of blood coagulation, and affect all the most important functions. In this sense mineral salts along with proteins can be considered functional elements of plasma. The latter can also include the molecules of gases O 2 and C0 2 soluble in plasma.

Osmotic blood pressure

If two solutions of different concentrations are separated by a semi-permeable partition that allows only the solvent (for example, water) to pass through, then the water passes into a more concentrated solution. The force that determines the movement of a solvent through a semipermeable membrane is called osmotic pressure.

The osmotic pressure of blood, lymph and tissue fluid determines the exchange of water between blood and tissues. A change in the osmotic pressure of the fluid surrounding the cells leads to a violation of their water exchange. This can be seen in the example of erythrocytes, which in a hypertonic solution of NaCl (a lot of salt) lose water and shrink. In a hypotonic solution of NaCl (little salt), erythrocytes, on the contrary, swell, increase in volume and may burst.

The osmotic pressure of the blood depends on the salts dissolved in it. About 60% of this pressure is generated by NaCl. The osmotic pressure of blood, lymph and interstitial fluid is approximately the same (approximately mosm / l, or 7.6 atm) and is constant. Even in cases where a significant amount of water or salt enters the blood, the osmotic pressure does not undergo significant changes. With an excessive intake of water into the blood, water is rapidly excreted by the kidneys and passes into the tissues, which restores the original value of osmotic pressure. If the concentration of salts in the blood increases, then water from the tissue fluid passes into the vascular bed, and the kidneys begin to intensively remove salt. The digestion products of proteins, fats and carbohydrates absorbed into the blood and lymph, as well as low molecular weight products of cellular metabolism, can change the osmotic pressure within small limits.

Maintaining a constant osmotic pressure plays a very important role in the vital activity of cells.

Concentration of hydrogen ions and regulation of blood pH

The blood has a slightly alkaline medium: the arterial blood pH is 7.4; NS venous blood due to great content its carbon dioxide is 7.35. Inside the cells, the pH is slightly lower (7.0-7.2), which is due to the formation of acidic products in them during metabolism. The extreme limits of pH changes, compatible with life, are values from 7.2 to 7.6. A shift in pH beyond these limits causes severe disturbances and can lead to death. In healthy people, blood pH ranges from 7.35 to 7.40. A long-term shift in pH in humans, even by 0.1 -0.2, can be fatal.

So, at pH 6.95, loss of consciousness occurs, and if these shifts are not eliminated in the shortest possible time, then a lethal outcome is inevitable. If the pH becomes 7.7, then severe convulsions (tetany) occur, which can also lead to death.

In the process of metabolism, tissues are released into the tissue fluid, and therefore into the blood, "acidic" metabolic products, which should lead to a shift in pH towards the acidic side. So, as a result of intense muscular activity, up to 90 g of lactic acid can enter the human blood within a few minutes. If this amount of lactic acid is added to the volume of distilled water equal to the volume of circulating blood, then the concentration of ions in it will increase dramatically. The reaction of the blood under these conditions practically does not change, which is explained by the presence of blood buffer systems. In addition, the pH in the body is maintained due to the work of the kidneys and lungs, which remove carbon dioxide, excess salts, acids and alkalis from the blood.

The constancy of blood pH is maintained by buffer systems: hemoglobin, carbonate, phosphate and plasma proteins.

The hemoglobin buffer system is the most powerful. It accounts for 75% of the buffer capacity of the blood. This system consists of reduced hemoglobin (HHb) and its potassium salt(KHb). Its buffering properties are due to the fact that with an excess of H +, KHb gives up K + ions, and itself attaches H + and becomes a very weakly dissociating acid. In tissues, the blood hemoglobin system performs the function of an alkali, preventing blood acidification due to the entry of carbon dioxide and H + ions into it. In the lungs, hemoglobin behaves like an acid, preventing the blood from alkalizing after the release of carbon dioxide from it.

Carbonate buffer system(H 2 CO 3 and NaHCO 3) in terms of its power takes the second place after the hemoglobin system. It functions as follows: NaHCO 3 dissociates into Na + and HCO 3 - ions. When a stronger acid than carbonic acid enters the blood, a reaction of Na + ion exchange occurs with the formation of weakly dissociating and easily soluble H 2 CO 3 Thus, an increase in the concentration of H + ions in the blood is prevented. An increase in the content of carbonic acid in the blood leads to its decay (under the influence of a special enzyme found in erythrocytes - carbonic anhydrase) into water and carbon dioxide. The latter enters the lungs and is released into the environment. As a result of these processes, the flow of acid into the blood leads to only a slight temporary increase in the content of neutral salt without a shift in pH. In the case of alkali entering the blood, it reacts with carbonic acid, forming bicarbonate (NaHCO 3) and water. The resulting deficiency of carbonic acid is immediately compensated for by a decrease in the release of carbon dioxide from the lungs.

The phosphate buffer system is formed by sodium dihydrogen phosphate (NaH 2 P0 4) and sodium hydrogen phosphate (Na 2 HP0 4). The first compound weakly dissociates and behaves like a weak acid. The second compound is alkaline. When a stronger acid is introduced into the blood, it reacts with Na, HP0 4, forming a neutral salt and increasing the amount of little dissociating sodium dihydrogen phosphate. If a strong alkali is introduced into the blood, it interacts with sodium dihydrogenphosphate, forming a weakly alkaline sodium hydrogenphosphate; In this case, the pH of the blood changes insignificantly. In both cases, excess dihydrogen phosphate and sodium hydrogen phosphate are excreted in the urine.

Plasma proteins play the role of a buffer system due to their amphoteric properties. V acidic environment they behave like alkalis, binding acids. In an alkaline environment, proteins react like acids that bind alkalis.

An important role in maintaining blood pH is played by nervous regulation... In this case, the chemoreceptors of the vascular reflexogenic zones are mainly irritated, the impulses from which enter the medulla and other parts of the central nervous system, which reflexively includes peripheral organs in the reaction - kidneys, lungs, sweat glands, gastrointestinal tract, whose activity is aimed at restoring the original pH values. So, when the pH is shifted to the acidic side, the kidneys intensively excrete the anion Н 2 Р0 4 - with urine. When reducing the pH to alkaline side the excretion of the anions НР0 4 -2 and НС0 3 - by the kidneys increases. The human sweat glands are able to excrete excess lactic acid, and the lungs - CO2.

With different pathological conditions there can be a shift in pH to both acidic and alkaline media. The first of them is called acidosis, the second is alkalosis.

Find out how many liters of blood there are in a person

Blood is an essential component of the internal environment of the human body. Due to its constant movement through the vessels, metabolism is carried out in organs and tissues.

Composition

Blood is a liquid connective tissue, which includes cells or shaped elements (leukocytes, erythrocytes, platelets) and intercellular substance (plasma).

On average, corpuscles account for about 40-45% of blood, and plasma - 55-60%. Laboratory analysis shows all deviations from the norm and indicates the presence of a particular disease. Depending on how many liters of blood there are in a person, the number of its constituent elements may be different. Also, its composition can be influenced by health status and geographic location. For example, when climbing to a height, the number of red blood cells increases significantly. Residents of the Caucasus or Switzerland have 50 percent more red blood cells than England or other highlands. The movement of blood through the vessels is carried out at a speed of 40 kilometers per hour.

Functions

The main functions of blood are determined by its composition.

Due to plasma, which is water solution proteins, fats, carbohydrates, amino acids, vitamins, hormones, as well as inorganic (mineral) substances, the function of transporting water and nutrients to tissues and organs and excreting metabolic products is carried out. Due to the viscosity that proteins impart to plasma, blood pressure is maintained at the right level... A certain composition of plasma ensures the constancy of its internal environment in the body. Each blood cell also performs a specific function:

Red blood cells (red blood cells) carry oxygen throughout the body. They are responsible for the red color of the blood.

Leukocytes (colorless cells) perform the function of protecting the body by fighting foreign bodies (including viruses, bacteria, cell fragments, particulate matter, allergens and toxins). There are several types of white blood cells. Each of them is responsible for the destruction a certain kind foreign bodies. According to their ratio, leukocyte formulas, which indicate the presence in the body of one or another harmful agent. White blood cells produce certain antibodies that make the body immune to infectious diseases... This property of theirs is the basis of the doctrine of human immunity, as well as the creation of vaccinations and sera to fight severe infections.

Platelets are blood cells that provide blood clotting. This ability allows you to avoid large blood loss as a result of various kinds of injuries. Disruption of the activity of these cells is often associated with genetic changes and leads to dire consequences, when even the most harmless cut or scratch can become fatal.

Blood types

Human blood is divided into 4 groups: the first is O, the second is A, the third is B, and the fourth is AB. This classification was introduced in 1900 by K. Landsteiner, it is called the AVO system. This division of blood is based on the content or absence of erythrocyte antigens A and B, as well as plasma antibodies A and B. Blood transfusion is carried out taking into account the compatibility of the groups with each other. Each group, in turn, can be of two types: Rh-positive and Rh-negative. This feature is very important for couples planning to have a baby, as in some cases Rh-conflict may occur. As a result, pregnancy and carrying a fetus become problematic.

How many liters of blood does a person have? Factors affecting the indicator

The question of how many liters of blood is in a person cannot be answered unequivocally. It is believed that this indicator depends on the individual characteristics of the organism, body weight, age, sex and physical condition of the organism. In general, the norm for an adult is approximately 4-6 liters (6-8% of the total body weight). Thus, if a person has a mass of 65 kg, then he will have about 3.9-5.2 liters. Most of the blood constantly circulates through the vessels, and some of it (up to 40%) is in the so-called "blood depots" of the body. These are the liver, spleen, lungs, skin, etc. With strong muscular loads, large blood loss, lowering atmospheric pressure, it leaves a kind of depot.

The amount of blood in a person

In women, the volume of circulating blood is 4-4.5 liters, in men - 5-5.5 liters. Its amount may vary depending on the volume of fluid drunk, during menstruation and pregnancy, with blood loss due to injuries and operations, with severe physical activity... The amount of blood in children of different age groups significantly different. In relation to body weight, the following indicators are considered the norm:

Safe minimum

How many liters of blood should a person have in order to avoid a threat to life? It is believed that when 2-3 liters are lost, a person dies. This can happen for many reasons. Among them is a sharp and profuse bleeding, operations and postoperative period, treatment of various diseases, hemodialysis.

In order to save lives, in medicine quite often they resort to the donor transfusion procedure. A person who donates blood to help others is called a donor. It is believed that the one-time safe volume, which is taken from him, is equal to 450 ml of blood, and plasma - 600 ml. You can donate plasma no more than 2 times a month, and blood - no more than 1 time a month. During this time, the quantitative and qualitative blood composition is completely restored. Each institution that collects blood donations compiles its own database. There are a number of diseases in which it is contraindicated to be a donor. To identify such facts, everyone's blood is taken for a special analysis.

Dangerous situations

Loss of blood in a volume equal to 20-40% of the total is considered life-threatening. Most people experience heart problems, low blood pressure, breathing problems, dizziness, or fainting. The following are considered external manifestations: pallor of the skin and coldness of the upper and lower extremities. With 50 to 70 percent blood loss, seizures and agony begin, and the chances of survival are close to zero. An important factor with blood loss, its speed is also. So, for example, a sharp loss of blood in the amount of 2-3 liters in a short period of time is fatal, but an extended one will not be so. However, the second case can be latent (internal bleeding), which is sometimes difficult to diagnose and entails a huge threat to the bleeding organ and the body as a whole. The symptoms in this case are similar to those described earlier in this article.

Recovery

Self-healing of blood is allowed with a loss of no more than 30 percent.

Otherwise, a donor blood transfusion is required. For a quick recovery, you need to eat foods rich in iron, including beef and red fish, liver, and also drink a lot. Raisins, dried apricots and nuts are very useful in this regard. Among drinks, pomegranate juice and a small amount of red wine, tea with sugar and milk. Complete self-healing of blood occurs in two weeks. As a result, it turns out that how many liters of blood a person had before blood loss is about the same after the recovery period.

The volume and function of blood in the human body

Blood is the most important part of the human body, it connects all organs and systems with each other. To maintain health, all its characteristics are important: how much blood is in a person, its viscosity, cellular composition, saturation with oxygen, nutrients, hormones, and other biologically active components.

Blood composition

It consists of plasma (liquid part) and cells. Normally, plasma, consisting of 90% water and 10% proteins, carbohydrates and fats, mineral substances, is about 60% of its volume. The rest are blood cells that perform specific functions:

Erythrocytes - provide the tissues with gas exchange - bring oxygen, and take carbon dioxide. Red bone marrow is the site of production of these cells.
Leukocytes protect the body from the introduction of foreign and infectious microorganisms. Synthesized in the lymph nodes, bone marrow, spleen.
Platelets - determine the ability to clot. Also born in the bone marrow. Due to the presence of iron and copper in these cells, they take part in the transfer of oxygen.

Hematocrit

Cell and fluid percentages may change due to exposure external factors or changes in the internal state of the body. The hematocrit number is an indicator of a blood test, which makes it possible to judge its density.

An increase in hematocrit occurs when the body loses fluid during

Also, the blood thickens with an increased formation of red blood cells.

A decrease in hematocrit - blood thinning - is noted when

intake of a large amount of fluid into the body,
violation of the formation of blood cells,
their pathological destruction,
pregnancy,
accumulation of fluid by the body with pathology of the excretory system.

Normal values of the indicator are different for women, men and children:

Blood functions

The main one is transport: flowing through vessels of various diameters, it carries substances necessary for the normal functioning of organs, metabolic products that need to be removed from the body enter it. Due to its composition, it provides tissues

Breath. Oxygen dissolved in plasma and bound to blood elements is transported by blood from the lungs to the cells that need it, and carbon dioxide is transferred from the cells to the lungs.
Nutrition. Useful material- glucose, fats, vitamins, amino acids are transported from the digestive system to the tissue. Also, with a lack of nutrition, blood delivers necessary substances from the places of their deposit.
Allocation of harmful elements. End products of cellular metabolism - uric acid, urea and others with blood are transferred to the excretory organs - intestines, kidneys, sweat glands, lungs.
Exchange of biologically active components. Circulation of hormones signaling molecules, others active connections provides a quick response of the body to various external and internal changes.
Heat transfer: transfers and redistributes heat and energy.
Homeostasis. The water-salt and acid-base balance of the whole organism remains constant.
Protection. Blood cells carry out immune reactions, prevent the penetration and multiplication of infectious agents and their own defective cells. The coagulation system, in case of damage to the vessels, stops bleeding, and the anticoagulant system promotes the dissolution of thrombotic masses and the restoration of the patency of arteries and veins.

How much blood is in a person

If a person is healthy, the amount of blood in his body is relatively constant. It depends on gender, age and personality traits. In women, other things being equal, blood is slightly less. In newborns, there is very little of it - about 300 ml.

So, if the patient is a 70 kg man, then the blood in him is about 5.5 liters. Fat woman 90 kg - the owner is already about 7.5 liters.

The amount of blood in the body of each person largely depends on the work of his hematopoietic system, which includes

It is interesting that in a day, the hematopoietic system of an individual weighing 60 kg provides synthesis

2100 billion red blood cells,
2 billion monocytes,
4600 billion neutrophils,
183 billion platelets.

It is estimated that the body produces, on average, about 482 kilograms of red blood cells over a lifetime.

When finding out the exact amount of blood in the body, it must be borne in mind that not all of its volume circulates through the vessels. The body stores it in special depots - in the liver and spleen. And uses this stock in emergency situations when it is in conditions increased loads- both mental and physical.

Also, a certain amount of blood is constantly in the organs that produce blood cells and in those that utilize them. For erythrocytes, this is the spleen, for lymphocytes, the lungs.

Diseases of organs that deposit blood are normally fraught with a deterioration in adaptation to stress.

How the exact amount of blood is determined

Radioisotope method. A radioactive isotope is injected into the blood, then the number of erythrocytes that have captured it is counted. Based on this, the amount of radioactivity in the blood is calculated and its corresponding amount is determined.
Contrast method. A dye is injected intravenously, after a while a blood sample is taken and the contrast concentration is determined. Then the volume is calculated.

In normal practice, a quick and easy calculation of the theoretical minimum and maximum amount of blood is most often used. With a patient weighing 80 kg, taking into account the range of 5-9%, his body can contain from 4 to 7.2 liters.

Blood loss

The loss of a small amount of blood for a person is harmless, and in a certain aspect and useful - it stimulates the formation of new young cells, eliminates the excess.

Donation is just such a periodic loss that does not reflect badly on the health of the person who donates blood and saves the life of the person to whom it is transfused. According to the law, women can donate a maximum of 4 times a year, men - 5. They take no more than 450 ml at a time. In this case, the donor's weight cannot be lower than 50 kg. You can read more about the blood transfusion procedure in this article.

Blood loss of up to 20% can lead to serious health problems - the heart stops working rhythmically, blood pressure decreases, and the pulse slows down. When bleeding stops at this stage, the body is able to gradually cope with such blood loss and replenish it. Transfusion is vital for a person who has lost more than 20% of their blood volume.

The rate of blood loss is also of great importance. Heavy bleeding causes more harm than something that happens gradually in small portions.

V dangerous situations, which are accompanied by the risk of blood loss - in case of severe injuries, surgical operations, during childbirth, doctors always have in stock donated blood... Their timely use allows you to control this vital parameter for patients - the amount of blood in the body.

The main functions of the blood. Volume and physicochemical properties of blood

The main functions of blood

The blood circulating in the vessels performs the functions listed below.

Transport – transport of various substances: oxygen, carbon dioxide, nutrients, hormones, mediators, electrolytes, enzymes, etc.

Respiratory(a kind of transport function) - the transfer of oxygen from the lungs to the tissues of the body, carbon dioxide - from cells to the lungs.

Trophic(a kind of transport function) - the transfer of essential nutrients from the digestive system to the tissues of the body.

Excretory(a kind of transport function) transport of end products of metabolism (urea, uric acid, etc.), excess water, organic and mineral substances to the organs of their excretion (kidneys, sweat glands, lungs, intestines).

Thermoregulatory - heat transfer from more heated organs to less heated ones.

Protective - implementation of nonspecific and specific immunity; blood clotting protects against blood loss in case of injury.

Regulatory (humoral) - delivery of hormones, peptides, ions and other physiologically active substances from the sites of their synthesis to the cells of the body, which allows the regulation of many physiological functions.

Homeostatic - maintaining the constancy of the internal environment of the body (acid-base balance, water-electrolyte balance, etc.).

Volume and physicochemical properties blood

Blood volume – total amount blood in the body of an adult is on average 6 - 8% of body weight, which corresponds to 5 - 6 liters. An increase in total blood volume is called hypervolemia, decrease - hypovolemia.

Relative blood density – 1,050 - 1,060 depends mainly on the number of red blood cells. The relative density of blood plasma - 1.025 - 1.034, is determined by the concentration of proteins.

Blood viscosity -5 conventional units, plasma - 1.7 - 2.2 conventional units, if the viscosity of water is taken as 1. It is caused by the presence of erythrocytes in the blood and, to a lesser extent, plasma proteins.

Osmotic pressureblood - the force with which a solvent passes through a semi-permeable membrane from a less concentrated solution to a more concentrated solution. Osmotic blood pressure is calculated cryoscopically by determining freezing points of blood (depression), which for her is equal to 0.56 - 0.58 C. Osmotic blood pressure is on average 7.6 atm. It is due to the osmotically active substances dissolved in it, mainly inorganic electrolytes, to a much lesser extent - proteins. About 60% of the osmotic pressure is created by sodium salts (NaCl).

Osmotic pressure determines the distribution of water between tissues and cells. The functions of the body cells can be carried out only when the osmotic pressure is relatively stable. If red blood cells are placed in saline solution having an osmotic pressure equal to that of blood, they do not change their volume. This solution is called isotonic, or physiological. It can be a 0.85% sodium chloride solution. In a solution, the osmotic pressure of which is higher than the osmotic pressure of blood, erythrocytes shrink as water leaves them into solution. In a solution with a lower osmotic pressure than the blood pressure, erythrocytes swell as a result of the passage of water from solution into the cell. Solutions with a higher osmotic pressure than blood pressure are called are hypertensive, and those with lower pressure - hypotonic.

Oncotic blood pressure – part of the osmotic pressure created by plasma proteins. It is equal to 0.03 - 0.04 atm, or 25 - 30 mm Hg. Oncotic pressure is mainly due to albumin. Due to their small size and high hydrophilicity, they have a pronounced ability to attract water to themselves, due to which it is retained in the vascular bed.When oncotic blood pressure decreases, water flows out of the vessels into the interstitial space, which leads to tissue edema.

Acid-base blood state (CBS) . The active reaction of the blood is due to the ratio of hydrogen and hydroxyl ions. To determine the active reaction of the blood, use pH value pH is the concentration of hydrogen ions, which is expressed as the negative decimal logarithm of the molar concentration of hydrogen ions. Normal pH is 7.36 (weakly basic reaction); arterial blood - 7.4; venous - 7.35. Under various physiological conditions, the pH of the blood can vary from 7.3 to 7.5. The active reaction of the blood is a rigid constant that provides enzymatic activity. The extreme limits of blood pH, compatible with life, are 7.0 - 7.8. The shift in the reaction towards the acidic side is called acidosis which is due to an increase in hydrogen ions in the blood. The shift in the reaction of the blood to the alkaline side is called alkalosis. This is due to an increase in the concentration of OH hydroxyl ions and a decrease in the concentration of hydrogen ions.

In the human body, there are always conditions for a shift in the active reaction of the blood towards acidosis or alkalosis, which can lead to a change in the pH of the blood. Acidic foods are constantly formed in tissue cells. The accumulation of acidic compounds is facilitated by the consumption of protein foods. On the contrary, with increased consumption of plant foods, bases enter the bloodstream. Maintaining a constant blood pH is an important physiological task and is provided by blood buffer systems. The buffer systems of the blood include hemoglobin, carbonate, phosphate and protein.

Buffer systems neutralize a significant part of the acids and alkalis entering the blood, thereby preventing a shift in the active reaction of the blood. In the body, in the process of metabolism, acidic products are formed to a greater extent. Therefore, the reserves of alkaline substances in the blood are many times higher than the reserves of acidic substances. They are considered as an alkaline reserve of blood.

Hemoglobin buffer system provides 75% of the buffer capacity of the blood. Oxyhemoglobin is a stronger acid than reduced hemoglobin. Oxyhemoglobin is usually in the form of the potassium salt. In the capillaries of tissues, a large amount of acidic decay products enters the bloodstream. At the same time, oxygen is released in the tissue capillaries during the dissociation of oxyhemoglobin and a large amount of alkaline-reacting hemoglobin salts appear. The latter interact with acidic decomposition products, for example, carbonic acid. As a result, bicarbonates and reduced hemoglobin are formed. In the pulmonary capillaries, hemoglobin, giving off hydrogen ions, attaches oxygen and becomes a strong acid that binds potassium ions. Hydrogen ions are used to form carbonic acid, which is subsequently released from the lungs in the form of H 2 O and CO 2.

Carbonate buffer system in terms of its power it takes the second place. It is represented by carbonic acid (H 2 CO 3) and sodium or potassium bicarbonate (NaHCO 3, KHCO 3) in a ratio of 1/20. If an acid that is stronger than carbonic acid enters the bloodstream, sodium bicarbonate, for example, reacts. A neutral salt and weakly dissociated carbonic acid are formed. Carbonic acid under the action of erythrocyte carbonic anhydrase decomposes into H 2 O and CO 2, the latter is released by the lungs into the environment. If a base enters the blood, then carbonic acid reacts to form sodium bicarbonate and water. Excess sodium bicarbonate is eliminated through the kidneys. Bicarbonate buffer is widely used to correct disorders of the acid-base state of the body.

Phosphate buffer system consists of sodium dihydrogen phosphate (NaH 2 PO 4) and sodium hydrogen phosphate (Na 2 HPO 4). The first compound has the properties of a weak acid and interacts with alkaline products that enter the bloodstream. The second compound has weak alkali properties and reacts with stronger acids.

Protein buffer system plays the role of neutralizing acids and alkalis due to amphoteric properties: in an acidic medium, plasma proteins behave like bases, in the main one - like acids.

There are also buffer systems in tissues, which helps to maintain tissue pH at a relatively constant level. Proteins and phosphates are the main tissue buffers.

The maintenance of pH is also done with the help of the lungs and kidneys. Excess carbon dioxide is removed through the lungs. With acidosis, the kidneys secrete more acidic monobasic sodium phosphate, and with alkalosis, more alkaline salts: dibasic sodium phosphate and sodium bicarbonate.

How much blood is in the human body

Did you know that blood accounts for approximately 7-8% of total body weight? So, a healthy adult weighing 60 kg has about 4.2-4.8 liters of blood. The average standard is 5 liters. Thus, weight is one of the factors that determine the amount of blood in the body. Other factors include age, gender and health status. Women usually have slightly less blood than men. And in adults, as a rule, more than in children.

Blood volume is greater in people living at high altitudes. It has been found that the difference in blood volume between such people and those who live at sea level is approximately 1.8 liters.

Locations located at high altitudes are characterized by a lower oxygen content in the atmosphere. Therefore, people living in such areas need more blood to supply body cells. enough oxygen.

Human blood consists of a yellowish liquid called plasma, in which blood cells are suspended. 45% of the blood volume is red blood cells, 54.3% is plasma, and the remaining 0.7% is white blood cells. Almost 90% of plasma is water, which contains dissolved glucose, proteins, hormones, mineral ions, platelets and blood cells.

Blood cells are red blood cells (red blood cells) and white blood cells (white blood cells).

In addition to these cells, there are also platelets. The most abundant blood cells are erythrocytes (there are approximately five million cells per cubic millimeter of blood). In the same amount of blood, there are some leukocytes and some platelets. Erythrocytes contain hemoglobin, which gives the blood a red color when saturated with oxygen. Deficiency of hemoglobin can lead to anemia.

The human body resembles a perfectly adjusted machine, consisting of amazing mechanisms. Each body system works in conjunction with others, accurately and efficiently. All systems are equally important for the proper functioning of the body.

Blood is one of the vital components of the circulatory system, which also includes the heart and blood vessels. It is well known that the heart pumps blood, which, moving through the blood vessels, reaches all parts of the body.

How is blood volume measured? Blood volume is measured to determine the total amount of blood circulating in the body, as well as the volume of red blood cells (erythrocytes) and plasma. Exists different methods measuring blood volume. Most of the methods are based on the principle of dilution of indicator substances, such as contrast agents, or radioactive chromium. These substances are injected into the blood, and the volume of blood is determined by the degree of their dilution observed.

Why measure blood volume? Exists various diseases, the development of which causes anomalies associated with the volume of circulating blood. Blood loss can also occur for reasons such as surgery. In such situations, a blood volume measurement is required to determine the total amount of circulating blood, plasma and red blood cells in the body. It helps in assessing the condition of people with hypertension, congestive heart failure, syncope, septic shock, renal failure, etc. Blood volume measurements are also done to detect conditions such as hypercythemia (increased red blood cell count), anemia (decreased red blood cell count), hypovolemia (decreased blood volume), and hypervolemia (increased blood volume). In rare cases, taking a blood volume measurement can cause severe allergic reactions.

How much blood does it take to survive?

In general, the human body contains about five liters of blood, and this volume can decrease due to certain diseases, conditions, surgeries, injuries, etc. It is believed that a healthy adult is able to tolerate the loss of up to 15% of the total blood volume without any problems. However, if the loss rate exceeds this figure, in the absence of medical care, severe symptoms and complications. The maximum allowable loss that still allows the average person to survive, provided immediate assistance is provided, is 30% -40% of the total circulating blood volume.

Blood performs many important functions in the body, such as transporting nutrients and oxygen to the cells of the body. She also takes with her the waste products of cells. The blood is also responsible for the delivery of hormones and other chemicals to various parts of the body. It also plays a critical role in maintaining constant temperature body, transferring excess heat to the skin, through which it is dissipated into the environment. Blood is important component immune system, since it contains white blood cells (leukocytes), which attack foreign substances and pathogens that enter the body. Platelets in the blood clot and stop bleeding from wounds and injuries. Blood clotting is considered a self-healing mechanism in the body that prevents further blood loss, which can be fatal. The kidneys play a key role in maintaining blood volume.

How many liters of blood are in a person and how much can you lose without consequences

How many liters of blood in a person you are unlikely to be interested unnecessarily. However, this indicator is very important in conditions of blood loss for any reason. It seems that we understand that blood plays an important role, that there is no life without it. And to what extent is its loss permissible?

The amount of blood in the body of an adult is, on average, four to six liters. The volume of circulating blood depends on age, gender, body weight, height and volume muscle mass(The blood volume of a person who is actively involved in sports is greater than that of someone who leads an inactive lifestyle).

The amount of blood in the body in women is slightly less than in men and usually ranges from 3.5 to 4.5 liters. However, during pregnancy, the volume of circulating blood in women increases significantly.

How many liters of blood is in a person and what is it for?

Blood in the human body performs the most important functions. It provides:

transport of gases (O2, CO2), nutrients, hormones, neurotransmitters, vitamins, enzymes, electrolytes, etc .;

Blood volume differs slightly from person to person. However, it is possible to roughly calculate how many liters of blood a person has, knowing his weight.

How many liters of blood does an adult have

The volume of blood in the human body ranges from 6 to 8 percent of body weight. Newborns have a slightly larger blood volume than an adult, about fifteen percent of their body weight.

By the first year of life, the amount of blood in a person is approximately 1% of the total body weight.

70 * 0.06 (six percent of 70 kg) = 4.2 liters;
70 * 0.08 (eight percent of 70 kg) = 5.6 liters.

Consequently, a person weighing 70 kg has an average blood volume of 4.2 to 5.6 liters.

However, such a calculation allows only an approximate calculation of how many liters of blood there are in a person. For more accurate calculations, you should be guided by the formulas used in intensive care.

How much blood is in a person in liters - an exact calculation according to the formula

The volume of circulating blood in women is calculated by the formula:

60 milliliters * per body weight in kilograms.

How many liters of blood in male patients is determined by the formula:

70 milliliters * per body weight in kilograms.

In order to accurately determine how many liters of blood a person weighing 50 kilograms has, it is necessary:

50 * 60 = 3000 milliliters or 3 liters (for women);
50 * 70 = 3500 milliliters or 3.5 liters (for men).

How to calculate how much blood a woman has during pregnancy

In the first trimester of pregnancy, the volume of blood changes little, however, by the end of the second and the beginning of the third trimester, the volume of circulating blood in a woman increases significantly. This is due to the growth of the fetus and an increase in its demand for oxygen and nutrients.

The amount of blood in the body of a pregnant woman is calculated by the formula:

75 milliliters per kilogram of mass (75 * by weight, in kg).

How much blood in the human body is in the form of plasma, and how much in the form of formed elements

Normally, part of the blood is located in the blood depots: in the liver, spleen, lungs, vessels of the skin, etc., however, most of the blood continuously circulates in the peripheral vascular bed. The peripheral part of the blood is divided into plasma (liquid part of blood) and uniform components (a suspension of leukocyte, erythrocyte, platelet cells in the plasma).

Normally, plasma makes up 52 to 58 percent of the total blood volume, and corpuscles from 42 to 48 percent.

The ratio of the plasma part to the formed elements is called hematocrit. The hematocrit level in women is normally 42%, and in men - 45%.

The ratio of the liquid part and the shaped elements may fluctuate slightly, but in general it remains constant. In this case, the plasma part of the blood consists of 90% water and ten percent of the dry residue of an organic and inorganic nature.

The organic components of plasma include:

protein elements;
nitrogen-containing elements of non-protein nature;
organic components of a nitrogen-free type (glucose, cholesterol, lipoproteins, triglycerides, etc.);
enzymatic and proenzyme substances (enzymes that break down proteins, carbohydrates, fats, substances involved in the process of hemostasis - prothrombin).

The inorganic components of plasma include cations (K, Ca, Mg), chlorine anions, etc.

Concepts such as the ratio of plasma and formed elements, as well as how many liters of blood in the human body are constant (with minimal fluctuations). Thanks to this, homeostasis is maintained in the body.

The constant composition and volume of blood is extremely important for the full functioning of all organs and systems, therefore the human body is sensitive to the slightest changes in the composition of the blood.

What is the danger of a violation of hematocrit

In the presence of pathological fluid losses (dehydration against the background of diarrhea, vomiting, etc.), due to the violation of vascular permeability, the amount of plasma decreases and the so-called blood thickening occurs. An increase in blood viscosity may also be due to erythrocytosis or hereditary coagulopathies, accompanied by an increased tendency of platelets to adhere and aggregate.

Thickening of the blood leads to:

a significant increase in the load on the CVS (cardiovascular system),
blood clots
kidney damage, etc.

A decrease in the number of all formed elements is noted with damage to the bone marrow and a decrease in its hematopoietic function (leukemia). In this case, blood clotting is impaired, the body's resistance to infectious agents decreases, oxygen exchange in organs and tissues is impaired.

A decrease in the number of red blood cells indicates anemia of various origins. A decrease in the level of erythrocytes and hemoglobin leads to oxygen starvation in organs and tissues, a violation heart rate, decreased immunity, constant weakness, hair loss, brittle nails, etc.

Plasma protein deficiency is accompanied by the development of edema, decreased immunity and impaired renal and liver function.

Imbalance of electrolytes in the blood can manifest as seizures, tremors, muscle spasms, life-threatening arrhythmias, edema, heart block, acute renal failure.

A decrease in the amount of the plasma part of the blood and formed elements is observed in acute and chronic blood loss. Chronic blood loss develops against the background:

heavy and prolonged menstruation,
nosebleeds,
hemorrhoidal bleeding,
peptic ulcer of the stomach and duodenum,
malignant neoplasms,
blood clotting disorders.

Patients develop anemia, they are worried about weakness, dizziness, decreased visual acuity, constant sleepiness, pale yellow complexion, hair loss, dry skin, decreased immunity, etc.

As a result, it develops:

arterial hypotension,
hypovolemic shock,
violation of cardiac activity,
tissue and organ hypoxia against the background of a decrease in cardiac output,
renal failure.

How much blood a person has in liters is lost with mild, moderate and severe blood loss

Compensated blood loss is considered to be a decrease in circulating blood volume by ten to fifteen percent. These patients have normal or moderately low blood pressure, compensatory heart rate, and slight weakness.

Such blood loss is manifested:

a decrease in pressure,
weakness
thirst
heart rhythm disturbances and compensatory tachycardia,
sweating
increased breathing,
dizziness.

With a loss of thirty to thirty-five percent of the circulating blood volume (BCC), moderate blood loss is noted. Patients are restless, there is a sharp pallor, blue under the eyes, a violation of skin turgor, profuse sweating, cyanosis, a sharp decline pressure, renal dysfunction, arrhythmias, significant tachycardia.

Symptoms of severe blood loss (pronounced cyanosis, arterial hypotension, respiratory, cardiac and renal failure, impaired consciousness, etc.) develop with a decrease in the BCC by thirty-five to forty percent;

How many liters of blood can a person lose without health consequences

For an adult who does not have concomitant pathologies, blood loss of up to 15% of the BCC is considered compensated.

The loss of more than 35% of the BCC is accompanied by severe disorders and high risk lethal outcome.

What to do if bleeding starts

If bleeding develops, you must immediately call an ambulance. Before her arrival, the patient is provided with first aid.

When bleeding from the stomach, it is necessary to put cold on the stomach, provide the victim with complete rest, give him cold water to drink in small sips.

For nosebleeds, tilt your head slightly forward and apply cold to the bridge of the nose. You can't throw your head back.

For limb injuries with arterial bleeding (scarlet blood flows out under pressure - "beats with a stream"), a tourniquet should be applied or finger pressure of the artery to the bone should be applied, above the bleeding.

The tourniquet should be applied to fabric, not bare skin. Time of application of a tourniquet in mandatory is fixed! In winter, the tourniquet can be kept for no more than 50 minutes, in summer - 1.5 hours. After this time, the tourniquet should be loosened for 5-10 minutes. If necessary, apply it again, above the previous place of imposition.

Venous bleeding is stopped by applying a tight bandage to the wound.

According to indications, the patient is transfused with solutions of crystalloids, colloids, erythromass, albumin preparations, etc.

Blood is a connective, opaque, scarlet liquid, part of the internal environment of the body. It participates in the process of metabolism, saturating the organs with oxygen, without which human life is impossible, and also transfers nutrients obtained from food in the digestive tract, and carries harmful or wasted elements to organs that will neutralize them or remove them from the body.

The blood contains plasma and corpuscles.

The corpuscles are platelets (involved in blood clotting), erythrocytes (red blood cells that carry oxygen from the lungs to the rest of the organs with hemoglobin), leukocytes (white blood cells that absorb and destroy microbes).

Plasma includes water, minerals, proteins, fats, carbohydrates. Thanks to its composition and volume, you can learn a lot about the health of its wearer.

Every day, more than 6,000 billion blood particles are reproduced in an organism weighing 70 kg: 2,000 billion erythrocytes, 4,500 billion neutrophils, 1 billion monocytes, 175 billion platelets. Throughout its life, the body produces an average of 460 kg of erythrocytes, 5400 kg of granulocytes, 40 kg of platelets, 275 kg of lymphocytes, a total of 6-7 tons. In this article, we will calculate how many liters of blood there are in a person.

Biological part

The blood-forming red bone marrow is located in the elements of the bone and stroma (bedding of cells) that make up its microenvironment. The bone, its beams and trabeculae form the main supporting frame, limiting the zones of hematopoiesis. Blood production in the bone marrow looks like this: bone trabeculae and stromal cells form cavities in the bones in which the hematopoietic cells are located. The cavities are not wetted with blood, the system is closed. The venous sinuses are adjacent to the cavities. As it matures, the cell moves to the sinus wall. Ripe cells must pass these adjacent walls in order to find themselves in the venous sinus, and later in the bloodstream.

The movement of blood in the body is called circulation. Inside the organs, small arteries (arterioles) branch out into thin-walled capillary vessels, through the walls of which metabolism takes place with parts of the body.

There are three main circles of blood circulation: large, small (pulmonary), cerebral. The blood makes a full turn in all circles of blood circulation in 30-60 seconds, if the body is in a calm position, with physical work this time is even shorter.

But the speed in the vessels is not the same: 0.5 m / s in the aorta, 0.25 m / s in the vena cava, 0.5 mm / s in the capillaries. In a minute, the heart ejects 5 liters of blood in a calm state and 25-35 liters during strenuous work. Continuity of blood flow is maintained by the heart and blood vessels. The cause of blood flow is the difference in vascular pressure at the beginning and end of the path. Arteries under high pressure (80-120 mm Hg) carry oxygenated blood from the heart to the periphery, and veins under lower pressure (0-20 mm Hg) pump blood from the organs back to the heart for subsequent oxygenation ...

The amount of blood in a person and ways to determine it

The amount of circulating blood in people is different. It depends on gender (5-6 liters for adult men, 4-5 liters for adult women), age (for a newborn child, about 250-300 milliliters), body weight, and some natural characteristics of the body. In a newborn, these figures also vary from the degree of maturity of the child, the time of cutting the umbilical cord, and also from body weight. A normal value is considered - from 5 to 9% of the total body weight in an adult and 14-15% in a newborn. In addition, a newborn's hemoglobin is much higher than that of an adult. As a rule, about 5-6 liters of blood circulate in an adult, less in children. Its volume is maintained by the body at the same level. There are several ways to determine how many liters of blood a person has:

Contrasting. A harmless dye called "contrast" is injected into the blood. When it is distributed throughout the circulatory system, blood is taken, the contrast concentration is determined, on the basis of which conclusions are drawn about the volume of circulating blood.
Radioisotope. Radioactive isotopes are injected into the blood and the number of red blood cells in which they are contained is counted. The volume of circulating blood will be known by the amount of its radioactivity.
Theoretical (easiest and fastest). Considering that the normal value of the volume is 5-9% of the body weight, it is possible to calculate the amount of circulating blood in a particular individual. For example, a person weighing 50 kg has a minimum of 50 * 0.05 = 2.5 liters and a maximum of 50 * 0.09 = 4.5 liters of blood, while another person weighing 70 kg carries from 70 * 0.05 = 3, 5 to 70 * 0.09 = 6.3 liters of blood.

The volume of circulating blood, although it is a constant value, but temporarily the figure may differ by 5-10%, which is associated with the loss or excess of fluid, bleeding. It also decreases with some diseases, for example, with various anemias. The loss of 15-30% of blood is considered significant, 40-50% is already a threat to life, and over 50% will definitely lead to death.

Blood composition

It consists of plasma (liquid part) and cells. Normally, plasma, consisting of 90% water and 10% proteins, carbohydrates and fats, minerals, makes up about 60% of its volume. The rest are blood cells that perform specific functions:

Erythrocytes - provide the tissues with gas exchange - bring oxygen, and take carbon dioxide. Red bone marrow is the site of production of these cells.
Leukocytes protect the body from the introduction of foreign and infectious microorganisms. Synthesized in lymph nodes, bone marrow, spleen.
Platelets - determine the ability to clot. Also born in the bone marrow. Due to the presence of iron and copper in these cells, they take part in the transfer of oxygen.

Hematocrit

The percentage of cells and fluid can change due to external factors or changes in the internal state of the body. The hematocrit number is an indicator of a blood test, which makes it possible to judge its density.

An increase in hematocrit occurs when the body loses fluid during

diarrhea,
vomiting
excessive sweating
extensive burns.

Also, the blood thickens with an increased formation of red blood cells.

A decrease in hematocrit - blood thinning - is noted when

intake of a large amount of fluid into the body,
violation of the formation of blood cells,
their pathological destruction,
pregnancy,
accumulation of fluid by the body with pathology of the excretory system.

Normal values of the indicator are different for women, men and children:

40-49 - in men;
36-42 - in women;
44-62 - in newborns;
32-44 - in children under 3 months;
36-44 - up to 10 years old.

Blood functions

Breath. Oxygen dissolved in plasma and bound to blood elements is transported by blood from the lungs to the cells that need it, and carbon dioxide is transferred from the cells to the lungs.
Nutrition. Useful substances - glucose, fats, vitamins, amino acids are transported from the digestive system to the tissue. Also, with a lack of nutrition, blood delivers the necessary substances from the places of their deposition.
Allocation of harmful elements. The end products of cellular metabolism - uric acid, urea and others are transported with blood to the excretory organs - intestines, kidneys, sweat glands, lungs.
Exchange of biologically active components. The circulation of hormones, signaling molecules, and other active compounds provides an immediate response of the body to various external and internal changes.
Heat transfer: transfers and redistributes heat and energy.
Homeostasis. The water-salt and acid-base balance of the whole organism remains constant.
Protection. Blood cells carry out immune reactions, prevent the penetration and multiplication of infectious agents and their own defective cells. The coagulation system, in case of damage to the vessels, stops bleeding, and the anticoagulant system promotes the dissolution of thrombotic masses and the restoration of the patency of arteries and veins.

How much blood is in a person

It is precisely determined how many liters of blood there are in a person using special methods in the presence of medical indications. The average rate is 5-9% of the body weight for an adult.

So, if the patient is a 70 kg man, then the blood in him is about 5.5 liters. A fat woman of 90 kg - the owner is already about 7.5 liters.

The amount of blood in the body of each person largely depends on the work of his hematopoietic system, which includes

spleen,
red bone marrow,
The lymph nodes.

It is interesting that in a day, the hematopoietic system of an individual weighing 60 kg provides synthesis

2100 billion red blood cells,
2 billion monocytes,
4600 billion neutrophils,
183 billion platelets.

It is estimated that the body produces, on average, about 482 kilograms of red blood cells over a lifetime.

When finding out the exact amount of blood in the body, it must be borne in mind that not all of its volume circulates through the vessels. The body stores it in special depots - in the liver and spleen. And he uses this stock in emergency situations, when he is in conditions of increased stress - both mental and physical.

Also, a certain amount of blood is constantly in the organs that produce blood cells and in those that utilize them. For erythrocytes, this is the spleen, for lymphocytes, the lungs.

Diseases of organs that deposit blood are normally fraught with a deterioration in adaptation to stress.

How the exact amount of blood is determined

Radioisotope method. A radioactive isotope is injected into the blood, then the number of erythrocytes that have captured it is counted. Based on this, the amount of radioactivity in the blood is calculated and its corresponding amount is determined.
Contrast method. A dye is injected intravenously, after a while a blood sample is taken and the contrast concentration is determined. Then the volume is calculated.

Blood loss

The loss of a small amount of blood for a person is harmless, and in a certain aspect and useful - it stimulates the formation of new young cells, eliminates the excess.

Medicine indicates the maximum volume of blood, the loss of which can be perceived by the body as a blessing - up to 10%.

The rate of blood loss is also of great importance. Heavy bleeding is more harmful than something that happens gradually in small portions.

In dangerous situations, which are accompanied by the risk of blood loss - in case of severe injuries, surgical operations, during childbirth, doctors always have donor blood in stock. Their timely use allows you to control this vital parameter for patients - the amount of blood in the body.

Blood is the most important fluid in the human body. The life of people depends on this liquid, and its lack can lead to loss of consciousness and even death. Therefore, people often want to know: how many liters of blood are in a person, what is the minimum amount necessary for life?

Before calculating the amount, it is worth finding out what components it consists of and where it is located in the body. After all, this is not just a liquid, but a special kind connective tissue which circulates throughout the body, delivering nutrients to different parts of the body and removing waste from the body. It consists of two main components:

plasma (liquid part);
shaped elements (erythrocytes, platelets and leukocytes).

The volume of plasma in the body of an adult healthy person is 50-60% of the BCC (volume of circulating blood), corpuscular elements - 40-50%. But these figures are approximate - the exact ratio of plasma to the rest is determined on an individual basis.

Shaped elements consist of three types of bodies:

erythrocytes (red);
leukocytes (white);
platelets (plates).

The former perform a transport function - they combine with oxygen and deliver it from the lungs to all organs and tissues. While releasing oxygen, red blood cells simultaneously attach carbon dioxide, transferring it back to the lungs. White blood cells are the body's defense system, they kill bacteria and other foreign bodies... Platelets are a "plaster", platelets that clog wounds and cuts in a person. Lack of platelets can lead to poor blood clotting.

Blood is distributed unevenly throughout the body, is in two different systems... About half circulates through the body from arterial vessels to venous vessels (and so on in a circle). Its second half is contained in one of the storage organs - the blood depot - the spleen, liver or skin.

Important! Blood is also unevenly distributed throughout the vessels. Approximately 73-75% of it is contained in the veins (therefore, damage to these vessels is so dangerous), about 20% is in the arteries, only 5-7% in the capillaries.

How much blood is in the human body

The approximate volume of blood - the figure is rather inaccurate, it may fluctuate depending on different factors... Gender, age, physical fitness, nutrition, pregnancy (in expectant mothers, the volume is higher due to the common circulatory system with the child) strongly affect the average.

The exact total is measured by introducing radioactive isotopes into the body and counting the erythrocyte count. According to research, the average numbers are:

in men - 5-6 liters;
for a woman - 4-4.5 liters;
in children (8-10) years old - 2-2.5 liters;
in the elderly - 4-5.5 liters.

Important! The higher the indicator of physical activity, the greater the volume of circulating blood. People with bed rest in two weeks, the number of red blood cells decreases by 10-15 percent.

How to calculate blood volume yourself

But these numbers are still very approximate. After all, the volume of blood in the body depends mainly on the weight of a person, and these calculations are made on the basis of average data. How to find out your number yourself? To do this, you do not have to go to the clinic - it is enough to know your weight and make simple calculations.

So, let's say the weight is 60 kg. The normal percentage of the ratio of blood volume to body weight is from 6 to 9. First, we calculate at the extreme values. At 6%, this is 3.6 liters, and at 8% - 5.4 liters. We add the resulting values and divide by 2 - we get 4.5 liters. This is the average blood volume and can fluctuate depending on various factors.

You can go the other way. The average blood content per kg of body weight is 70-75 ml / kg for men, 60-65 ml / kg for women. We multiply this figure by our weight, we get the volume in ml, which must be divided by 1000. But the method does not really matter - the numbers will be approximately equal.

Important! In pregnant women, the value of the volume per unit of mass increases greatly - 75 ml / kg. This is due to the common circulatory system in the child and the mother.

Safe volume for life

Ordinary cuts or scratches are not terrible for a person's life. Only small vessels are damaged - capillaries, violations of the integrity of which quickly eliminate platelets. The only threat is blood loss from large vessels - arteries and veins.

Since almost half of the blood is in storage, the loss of up to 30% of the total circulating blood volume is not considered life-threatening. Loss of a third of the BCC can cause sweating, nausea, dizziness, and others unpleasant symptoms- but the person will remain alive. In such a situation, it is recommended to drink a lot to replenish the circulating blood volume - a transfusion from a donor is usually not required.

Need to remember! Donation does not pose a health hazard - about 400 ml of blood is donated. A healthy person can easily make up for such blood loss by releasing blood into the bloodstream from the depot. The maximum that you can feel is a little dizziness.

Massive blood loss

When a person loses from 30 to 50% of the BCC, this is already more serious. A person's skin turns pale, the body becomes cold, and the limbs become bluish from a lack of oxygen. In such a situation, an urgent blood transfusion is necessary - otherwise, loss of consciousness or falling into a coma is possible. The loss of 50% of the volume is already fatal, few people experience this. It is possible to survive under such circumstances only if an emergency health care... Death occurs if more than 4 liters (60%) were lost during bleeding.

Important! Women tolerate blood loss much better than men, they can survive the loss of even 50% of calves. This is due to childbirth, during which they lose up to several hundred milliliters of blood.

Human blood volume is an important indicator that affects health. Heavy bleeding is extremely dangerous, especially if the major arteries or veins are damaged. Therefore, in such a situation, it is necessary to stop blood loss with a tourniquet and call doctors. Be sure to check the instructions on how to help people with severe bleeding... Later, such skills can save someone's life.

Of course, everyone knows what blood is, what it consists of and what its main functions are, as a rule, all these issues are studied at the level of the school curriculum. However, not everyone knows how many liters of blood there are in a person. Without blood, which consists of erythrocytes, leukocytes, plasma and platelets, our body, in principle, is not able to exist and perform its functions, since it is this blood that provides the necessary connection between all organs. If the composition of this liquid undergoes some changes, then the indicators of the state of health begin to change, and this applies to both an adult and a child.

The blood level in an adult and an already formed person remains practically unchanged.... On average, the human body contains about five liters of blood circulating through the vessels and arteries. So, if a person weighs 50 kg, then the volume of his blood should not be lower than three liters, respectively, with a weight of 60 kg - 4 liters, and with 70 kg - five. It is rather difficult to indicate more accurate indicators without appropriate research, since the individual characteristics of the organism are different for all people. In addition, according to most experts, the level of blood in the body can increase and this is influenced by the fluid that a person consumes.

The bulk of the blood constantly circulates throughout our body, ensuring timely delivery of oxygen and nutrients to the cells. A certain percentage of excess blood is redistributed to the skin or simply excreted from the body in a natural way, after it has been processed in the kidneys. It is known that the volume of circulating blood through the veins and arteries in a strong half of humanity is greater than that of women, on average, the indicators differ by one liter.

Do not forget that blood is capable of performing and protective function for example, leukocytes and certain substances contained in plasma rid our body of toxins and microbes that inevitably enter it. By its composition, blood is nothing more than a liquid circulating in the body of adults and children, which provides normal life the whole organism.

Today, anyone with a weight of 50, 60 or 70 kg can find out the exact volume of blood in their body, for this it is necessary to undergo a safe study, which includes the following steps:

In the body of adults and children, a special contrast agent, which is not withdrawn from it immediately, but after a certain amount of time. The dosage of such a substance is monitored by a specialist, who is also involved in determining it based on weight. It should be noted that the concentrate is a colloidal dye, which is absolutely harmless not only for an adult 60 kg person, but also for a child - it does not negatively affect the composition and main function of blood.
After the concentrate is evenly distributed throughout the body, you can begin to draw blood to determine its exact volume. By using the latest technologies in a modernly furnished laboratory, it is not difficult to do this, and after a while you will have the results of a study on your hands, describing in detail the percentage and composition of leukocytes and erythrocytes.

In addition to this method, in medical practice one more is used, at least effective method, but to some it may seem less secure. The method consists in the fact that an artificial radioactive isotope is injected into the blood, after certain manipulations, the doctor can accurately name the number of erythrocytes and calculate the volume. No matter how much you weigh, 50, 60 or 70 kg, finding out the exact volume of blood circulating in the body is easy and simple thanks to modern methods research.

Extreme indicators

Both adults and children have their own specific indicators, at a decrease in which the loss of red fluid can cause death. A minute loss of two or more liters of blood may well be fatal, which is why it is so important to try to stop it by all means. Blood loss can provoke such a dangerous disease as anemia. An interesting fact - the fairer sex is easier to tolerate blood loss than men.

The most dangerous thing is rapid bleeding, when in just a few minutes a person loses a significant amount of red fluid. If the appropriate measures are not taken urgently, the person will die, and the transfusion will no longer help.

Remember that during blood loss, every minute counts, so you always need to act quickly and clearly - you cannot give in to panic, because someone's life may depend on it. Blood transfusions are used successfully for large losses, such as during surgery on internal organs, usually requiring at least eight liters, even if the patient weighs only 60 kg. Each patient has his own blood group and Rh factor, which is naturally taken into account during transfusion, otherwise it will not be able to perform its main functions. Sometimes transfusion is necessary even if adults or children have special diseases.

Donation benefits

Many, for one reason or another, had to act as a donor and donate their blood or plasma, someone had their own reasons for this, but someone just does it for charity for the sake of sick children. Of course, you won't be able to come to a blood transfusion center just like that without an appropriate examination, first you will need to go through such doctors as:

Therapist.
Venereologist.
Dermatologist.

Only after you receive permission from each specialist, you can become a donor, it does not matter if you weigh 50 or 60 kg, the volume of the red liquid taken will not exceed 450 ml - this is the indicator that will not affect the functions of the body. All new arrivals must be checked against the database, and those who have recently had some illnesses may not be admitted at all. Red liquid is donated no more than once a month, while plasma is allowed to donate twice. The blood collection procedure takes no more than ten minutes, there is nothing complicated about it. If you came to the delivery of plasma, then you will have to lie on the couch for at least thirty minutes.

If you have the opportunity to donate blood or plasma for adults and children in need, take advantage of this, because it is donation that can save the lives of most of them. Some people think that donation is a life-threatening procedure, in fact it is not, you can verify this by consulting a doctor.