/ 14.11.2017

Internal environment human body

B) Superior and inferior vena cava D) Pulmonary arteries

7. Blood enters the aorta from:

A) Left ventricle of the heart B) Left atrium

B) Right ventricle of the heart D) Right atrium

8. Open leaflet heart valves occur at the moment:

A) Ventricular contractions B) Atrial contractions

B) Relaxation of the heart D) Transfer of blood from the left ventricle to the aorta

9. The maximum blood pressure is considered to be:

B) Right ventricle D) Aorta

10. The ability of the heart to self-regulate is evidenced by:

A) Heart rate measured immediately after exercise

B) Pulse measured before exercise

B) The rate at which heart rate returns to normal after exercise

D) Comparison of the physical characteristics of two people

It surrounds all cells of the body, through which metabolic reactions occur in organs and tissues. Blood (except hematopoietic organs) does not come into direct contact with cells. From blood plasma penetrating through the walls of capillaries, tissue fluid is formed that surrounds all cells. There is a constant exchange of substances between cells and tissue fluid. Part of the tissue fluid enters the thin, blindly closed capillaries of the lymphatic system and from that moment turns into lymph.

Since the internal environment of the body maintains the constancy of physical and chemical properties, which persist even under very strong external influences on the body, then all the cells of the body exist in relatively constant conditions. The constancy of the internal environment of the body is called homeostasis. The composition and properties of blood and tissue fluid are maintained at a constant level in the body; bodies; parameters of cardiovascular activity and respiration and more. Homeostasis is maintained by the most complex coordinated work of the nervous and endocrine systems.

Functions and composition of blood: plasma and formed elements

In humans, the circulatory system is closed, and blood circulates through the blood vessels. Blood performs the following functions:

1) respiratory - carries oxygen from the lungs to all organs and tissues and carries out carbon dioxide from tissues to lungs;

2) nutritional - transfers nutrients absorbed in the intestines to all organs and tissues. In this way, the tissues are supplied with water, amino acids, glucose, fat breakdown products, mineral salts, vitamins;

3) excretory - delivers the end products of metabolism (urea, lactic acid salts, creatinine, etc.) from tissues to places of removal (kidneys, sweat glands) or destruction (liver);

4) thermoregulatory - transfers heat with blood plasma water from the place of its formation (skeletal muscles, liver) to heat-consuming organs (brain, skin, etc.). In the heat, the blood vessels in the skin dilate to release excess heat, and the skin turns red. In cold weather, skin vessels contract so that less blood enters the skin and it does not give off heat. At the same time, the skin turns blue;

5) regulatory - blood can retain or release water to tissues, thereby regulating the water content in them. Blood also regulates the acid-base balance in tissues. In addition, it transports hormones and other physiologically active substances from the places of their formation to the organs that they regulate (target organs);

6) protective - substances contained in the blood protect the body from blood loss due to the destruction of blood vessels, forming a blood clot. This also prevents it from entering the bloodstream. pathogens(bacteria, viruses, protozoa, fungi). White blood cells protect the body from toxins and pathogens through phagocytosis and the production of antibodies.

In an adult, blood mass is approximately 6-8% of body weight and equals 5.0-5.5 liters. Some of the blood circulates through the vessels, and about 40% of it is in the so-called depots: vessels of the skin, spleen and liver. If necessary, for example during high physical exertion or blood loss, blood from the depot is included in the circulation and begins to actively perform its functions. Blood consists of 55-60% plasma and 40-45% plasma shaped elements.

Plasma is the liquid medium of blood containing 90-92% water and 8-10% various substances. Plasma proteins (about 7%) perform a number of functions. Albumin - retains water in the plasma; globulins are the basis of antibodies; fibrinogen - necessary for blood clotting; various amino acids are transported by blood plasma from the intestines to all tissues; a number of proteins perform enzymatic functions, etc. Inorganic salts (about 1%) contained in plasma include NaCl, salts of potassium, calcium, phosphorus, magnesium, etc. A strictly defined concentration of sodium chloride (0.9%) is necessary to create stable osmotic pressure. If you place red blood cells - erythrocytes - in an environment with more low content NaCl, they will begin to absorb water until they burst. In this case, a very beautiful and bright “varnish blood” is formed, which is not capable of performing the functions of normal blood. This is why water should not be introduced into the blood during blood loss. If red blood cells are placed in a solution containing more than 0.9% NaCl, it will be sucked out of the red blood cells and they will shrink. In these cases, the so-called saline, which in terms of salt concentration, especially NaCl, strictly corresponds to blood plasma. Glucose is contained in blood plasma at a concentration of 0.1%. It is an essential nutrient for all body tissues, but especially the brain. If the glucose content in plasma decreases by approximately half (to 0.04%), then the brain is deprived of its source of energy, the person loses consciousness and can quickly die. Fat in blood plasma is about 0.8%. These are mainly nutrients carried by the blood to places of consumption.

The formed elements of blood include red blood cells, leukocytes and platelets.

Erythrocytes are red blood cells that are nuclear cells, having the shape of a biconcave disk with a diameter of 7 microns and a thickness of 2 microns. This shape provides the red blood cells with the largest surface area with the smallest volume and allows them to pass through the smallest blood capillaries, quickly delivering oxygen to the tissues. Young human red blood cells have a nucleus, but as they mature, they lose it. Mature red blood cells of most animals have nuclei. One cubic millimeter of blood contains about 5.5 million red blood cells. The main role of red blood cells is respiratory: they deliver oxygen from the lungs to all tissues and remove it from the tissues significant amount carbon dioxide. Oxygen and CO 2 in red blood cells are bound by the respiratory pigment - hemoglobin. Each red blood cell contains about 270 million hemoglobin molecules. Hemoglobin is a combination of protein - globin - and four non-protein parts - hemes. Each heme contains a molecule of ferrous iron and can add or donate an oxygen molecule. When oxygen is added to hemoglobin, an unstable compound is formed in the capillaries of the lungs - oxyhemoglobin. Having reached the capillaries of the tissues, red blood cells containing oxyhemoglobin give oxygen to the tissues, and the so-called reduced hemoglobin is formed, which is now able to attach CO 2.

The resulting also unstable compound HbCO 2 gets into the lungs with the bloodstream, disintegrates, and the resulting CO 2 is removed through Airways. It should also be taken into account that a significant part of CO 2 is removed from tissues not by hemoglobin of erythrocytes, but in the form of carbonic acid anion (HCO 3 -), formed when CO 2 is dissolved in blood plasma. From this anion, CO 2 is formed in the lungs, which is exhaled out. Unfortunately, hemoglobin is capable of forming a strong compound with carbon monoxide (CO) called carboxyhemoglobin. The presence of only 0.03% CO in the inhaled air leads to the rapid binding of hemoglobin molecules, and red blood cells lose their ability to carry oxygen. In this case, rapid death from suffocation occurs.

Red blood cells are able to circulate through the bloodstream, performing their functions, for about 130 days. Then they are destroyed in the liver and spleen, and the non-protein part of hemoglobin - heme - is repeatedly used in the future in the formation of new red blood cells. New red blood cells are formed in the red bone marrow of the cancellous bone.

Leukocytes are blood cells that have nuclei. The size of leukocytes ranges from 8 to 12 microns. There are 6-8 thousand of them in one cubic millimeter of blood, but this number can fluctuate greatly, increasing, for example, in infectious diseases. This increased level of white blood cells in the blood is called leukocytosis. Some leukocytes are capable of independent amoeboid movements. Leukocytes ensure that the blood performs its protective functions.

There are 5 types of leukocytes: neutrophils, eosinophils, basophils, lymphocytes and monocytes. Most of all there are neutrophils in the blood - up to 70% of all leukocytes. Neutrophils and monocytes, actively moving, recognize foreign proteins and protein molecules, capture them and destroy them. This process was discovered by I.I. Mechnikov and he called it phagocytosis. Neutrophils are not only capable of phagocytosis, but also secrete substances that have a bactericidal effect, promoting tissue regeneration, removing damaged and dead cells from them. Monocytes are called macrophages and their diameter reaches 50 microns. They are involved in the process of inflammation and the formation of an immune response and not only destroy pathogenic bacteria and protozoa, but are also capable of destroying cancer cells, old and damaged cells in our body.

Lymphocytes play a critical role in the formation and maintenance of the immune response. They are able to recognize foreign bodies (antigens) on their surface and produce specific protein molecules (antibodies) that bind these foreign agents. They are also able to remember the structure of antigens, so that when these agents are reintroduced into the body, an immune response occurs very quickly, more antibodies are formed and the disease may not develop. The first to respond to antigens entering the blood are the so-called B lymphocytes, which immediately begin to produce specific antibodies. Some B lymphocytes turn into memory B cells, which exist in the blood for a very long time and are capable of reproduction. They remember the structure of the antigen and store this information for years. Another type of lymphocyte, T lymphocytes, regulates the functioning of all other cells responsible for immunity. Among them there are also immune memory cells. Leukocytes are produced in red bone marrow and lymph nodes, and are destroyed in the spleen.

Platelets are very small, non-nuclear cells. Their number reaches 200-300 thousand in one cubic millimeter of blood. They are formed in the red bone marrow, circulate in the bloodstream for 5-11 days, and then are destroyed in the liver and spleen. When a vessel is damaged, platelets release substances necessary for blood clotting, promoting the formation of a blood clot and stopping bleeding.

Blood groups

The problem of blood transfusion arose a long time ago. Even the ancient Greeks tried to save bleeding wounded soldiers by giving them warm animal blood to drink. But there could not be much benefit from this. IN early XIX century, the first attempts were made to transfuse blood directly from one person to another, but a very large number of complications were observed: after blood transfusion, red blood cells stuck together and were destroyed, which led to the death of the person. At the beginning of the 20th century, K. Landsteiner and J. Jansky created the doctrine of blood groups, which makes it possible to accurately and safely replace blood loss in one person (recipient) with the blood of another (donor).

It turned out that the membranes of red blood cells contain special substances with antigenic properties - agglutinogens. Specific antibodies dissolved in the plasma that belong to the globulin fraction - agglutinins - can react with them. During the antigen-antibody reaction, bridges are formed between several red blood cells and they stick together.

The most common system for dividing blood into 4 groups. If agglutinin α meets agglutinogen A after transfusion, erythrocytes will stick together. The same thing happens when B and β meet. Currently, it has been shown that only the blood of his group can be transfused into a donor, although more recently it was believed that with small volumes of transfusion, the donor’s plasma agglutinins become highly diluted and lose their ability to glue the recipient’s red blood cells together. People with blood group I (0) can receive any blood transfusion, since their red blood cells do not stick together. That's why such people are called universal donors. People with blood group IV (AB) can be transfused with small amounts of any blood - these are universal recipients. However, it is better not to do this.

More than 40% of Europeans have blood group II (A), 40% - I (0), 10% - III (B) and 6% - IV (AB). But 90% of American Indians have I (0) blood type.

Blood clotting

Blood clotting is the most important protective reaction that protects the body from blood loss. Bleeding occurs most often due to mechanical destruction of blood vessels. For an adult man, a blood loss of approximately 1.5-2.0 liters is considered conventionally fatal, but women can tolerate a loss of even 2.5 liters of blood. In order to avoid blood loss, the blood at the site of vessel damage must quickly clot, forming a blood clot. A thrombus is formed by the polymerization of an insoluble plasma protein, fibrin, which, in turn, is formed from a soluble plasma protein, fibrinogen. The process of blood clotting is very complex, includes many stages, and is catalyzed by many enzymes. It is controlled by both nervous and humoral pathways. In a simplified way, the process of blood clotting can be depicted as follows.

There are known diseases in which the body lacks one or another factor necessary for blood clotting. An example of such a disease is hemophilia. Clotting is also slowed when the diet lacks vitamin K, which is necessary for the liver to synthesize certain protein clotting factors. Since the formation of blood clots in the lumens of intact vessels, leading to strokes and heart attacks, is deadly, the body has a special anticoagulant system that protects the body from vascular thrombosis.

Lymph

Excess tissue fluid enters blindly closed lymphatic capillaries and turns into lymph. In its composition, lymph is similar to blood plasma, but it contains much less proteins. The functions of lymph, like blood, are aimed at maintaining homeostasis. With the help of lymph, proteins are returned from the intercellular fluid to the blood. Lymph contains many lymphocytes and macrophages, and plays a large role in immune responses. In addition, the products of fat digestion in the villi of the small intestine are absorbed into the lymph.

The walls of the lymphatic vessels are very thin, they have folds that form valves, thanks to which the lymph moves through the vessel in only one direction. At the confluence of several lymphatic vessels there are lymph nodes that perform a protective function: they retain and destroy pathogenic bacteria, etc. The largest lymph nodes are located in the neck, groin, and axillary areas.

Immunity

Immunity is the body's ability to protect itself from infectious agents(bacteria, viruses, etc.) and foreign substances (toxins, etc.). If a foreign agent has penetrated the protective barriers of the skin or mucous membranes and entered the blood or lymph, it must be destroyed by binding to antibodies and (or) absorption by phagocytes (macrophages, neutrophils).

Immunity can be divided into several types: 1. Natural - congenital and acquired 2. Artificial - active and passive.

Natural innate immunity is transmitted to the body with genetic material from ancestors. Natural acquired immunity occurs when the body itself has developed antibodies to some antigen, for example, having had measles, smallpox, etc., and has retained the memory of the structure of this antigen. Artificial active immunity occurs when a person is injected with weakened bacteria or other pathogens (vaccine) and this leads to the production of antibodies. Artificial passive immunity appears when a person is injected with serum - ready-made antibodies from a recovered animal or another person. This immunity is the most fragile and lasts only a few weeks.

Blood, tissue fluid, lymph and their functions. Immunity

Blood, lymph and tissue fluid form the internal environment of the body, which surrounds all its cells. The chemical composition and physicochemical properties of the internal environment are relatively constant, therefore the cells of the body exist in relatively stable conditions and are little exposed to factors external environment. Ensuring the constancy of the internal environment is achieved by the continuous and coordinated work of many organs (heart, digestive, respiratory, excretory systems), which supply the body with substances necessary for life and remove decay products from it. Regulatory function to maintain the constancy of the parameters of the internal environment of the body - homeostasis-for- carried out by the nervous and endocrine systems.

There is a close relationship between the three components of the body’s internal environment. So, colorless and translucent tissue fluid is formed from the liquid part of the blood - plasma, penetrating through the walls of the capillaries into the intercellular space, and from waste products coming from the cells (Fig. 4.13). In an adult, its volume reaches 20 liters per day. Blood supplies the tissue fluid with the dissolved nutrients, oxygen, hormones necessary for the cells and absorbs the waste products of the cells - carbon dioxide, urea, etc.

A smaller part of the tissue fluid, without having time to return to the bloodstream, enters the blindly closed capillaries of the lymphatic vessels, forming lymph. In appearance it is a translucent yellowish liquid. The composition of lymph is close to the composition of blood plasma. However, it contains 3-4 times less protein than plasma, but more than tissue fluid. Lymph contains a small number of leukocytes. Small lymphatic vessels merge to form larger ones. They have semilunar valves that ensure lymph flow in one direction - to the thoracic and right lymphatic ducts, which flow into

into the superior vena cava. In the numerous lymph nodes through which lymph flows, it is neutralized due to the activity of leukocytes and enters the blood purified. The movement of lymph is slow, about 0.2-0.3 mm per minute. This occurs mainly due to contractions skeletal muscles, the suction action of the chest during inhalation and, to a lesser extent, due to contractions of the muscles of the own walls of the lymphatic vessels. About 2 liters of lymph return to the blood per day. In pathological phenomena that disrupt the outflow of lymph, tissue swelling is observed.

Blood is the third component of the internal environment of the body. This is a bright red liquid that continuously circulates in a closed system of human blood vessels and makes up about 6-8% of the total body weight. The liquid part of the blood - plasma - makes up about 55%, the rest is formed elements - blood cells.

IN plasma about 90-91% water, 7-8% proteins, 0.5% lipids, 0.12% monosaccharides and 0.9% mineral salts. It is plasma that transports various substances and blood cells.

Plasma proteins fibrinogen And prothrombin take part in blood clotting, globulins play important role in the body's immune reactions, albumins impart viscosity to the blood and bind calcium present in the blood.

Among blood cells most red blood cells- red blood cells. These are small biconcave disks without a nucleus. Their diameter is approximately equal to the diameter of the narrowest capillaries. Red blood cells contain hemoglobin, which easily binds to oxygen in areas where its concentration is high (lungs), and just as easily releases it in areas with low oxygen concentration (tissues).

Leukocytes- white nuclear blood cells are slightly larger in size than red blood cells, but contain much less of them in the blood. They play an important role in protecting the body from disease. Due to their ability of amoeboid movement, they can pass through small pores in the walls of capillaries in places where pathogenic bacteria are present and absorb them by phagocytosis. Other

types of white blood cells are capable of producing protective proteins - antibodies- in response to a foreign protein entering the body.

Platelets (blood platelets)- the smallest of blood cells. Platelets contain substances that play an important role in blood clotting.

One of the most important protective functions of blood - protective - is carried out with the participation of three mechanisms:

A) blood clotting, thanks to which blood loss is prevented due to injuries to blood vessels;

b) phagocytosis, carried out by leukocytes capable of amoeboid movement and phagocytosis;

V) immune protection, carried out by antibodies.

Blood clotting- a complex enzymatic process involving the transfer of soluble protein in blood plasma fibrinogen into insoluble protein fibrin, forming the basis of a blood clot - blood clot The blood clotting process is triggered by the release of an active enzyme from platelets destroyed during injury. thromboplastin, which, in the presence of calcium ions and vitamin K, through a series of intermediate substances, leads to the formation of fibrin filamentous protein molecules. Red blood cells are retained in the network formed by fibrin fibers and, as a result, blood clot. Drying and shrinking, it turns into a crust that prevents blood loss.

Phagocytosis carried out by certain types of leukocytes that are capable of moving with the help of pseudopods to places where cells and tissues of the body are damaged, where microorganisms are found. Having approached and then pressed against the microbe, the leukocyte absorbs it into the cell, where it is digested under the influence of lysosome enzymes.

Immune protection carried out thanks to the ability of protective proteins - antibodies- recognize foreign material that has entered the body and induce the most important immunophysiological mechanisms aimed at its neutralization. Foreign material can be protein molecules on the surface of microbial cells or foreign cells, tissues, surgically transplanted organs, or changed cells of one's own body (for example, cancerous ones).

Based on their origin, they distinguish between innate and acquired immunity.

Congenital (hereditary, or species) immunity is predetermined genetically and is determined by biological, hereditary characteristics. This immunity is inherited and is characterized by the immunity of one species of animals and humans to pathogenic agents, causing diseases in other species.

Acquired immunity can be natural or artificial. Natural immunity is immunity to a particular disease obtained by the child’s body as a result of the penetration of mother’s antibodies into the fetus’ body

through the placenta (placental immunity), or acquired as a result past illness(post-infectious immunity).

Artificial immunity can be active and passive. Active artificial immunity is developed in the body after the introduction of a vaccine - a drug containing weakened or killed pathogens of a particular disease. Such immunity is less durable than post-infectious immunity and, as a rule, to maintain it, repeated vaccination is necessary after several years. In medical practice, passive immunization is widely used, when a sick person is injected with therapeutic serums that already contain ready-made antibodies against this pathogen. Such immunity will persist until the antibodies die (1-2 months).

Blood, woven fluid and lymph - internal Wednesday body For What is more characteristic is the relative constancy of the chemical composition Ava and physical chemical properties, which is achieved by the continuous and coordinated work of many organs. Metabolism between blood and cells occurs through tissue liquid.

Protective: function blood is carried out thanks to coagulation, phagocytosis And immune health look for. There are congenital and acquired y immunity. When acquired immunity can be natural or artificial.

I. What is the relationship between the elements of the internal environment of the human body? 2. What is the role of blood plasma? 3. What is the relationship between the structure of erythro-

cytes with the functions they perform? 4. How it is done protective function

5. Give a rationale for the concepts: hereditary, natural and artificial, active and passive immunity.

The body of any animal is extremely complex. This is necessary to maintain homeostasis, that is, constancy. For some, the condition is conditionally constant, while for others, more developed, actual constancy is observed. This means that no matter how the environmental conditions change, the body maintains a stable state of the internal environment. Despite the fact that organisms have not yet fully adapted to living conditions on the planet, the internal environment of the organism plays a crucial role in their life.

The concept of internal environment

The internal environment is a complex of structurally separate areas of the body, under no circumstances other than mechanical damage, not in contact with the outside world. In the human body, the internal environment is represented by blood, interstitial and synovial fluid, cerebrospinal fluid and lymph. These 5 types of fluids together constitute the internal environment of the body. They are called this for three reasons:

• firstly, they do not come into contact with the external environment;
• secondly, these fluids maintain homeostasis;
• thirdly, the environment is an intermediary between cells and the external parts of the body, protecting against external adverse factors.

The importance of the internal environment for the body

The internal environment of the body consists of 5 types of fluids, main task which is to maintain a constant level of nutrient concentrations near the cells, maintaining the same acidity and temperature. Due to these factors, it is possible to ensure the functioning of cells, the most important of which in the body is nothing, since they make up tissues and organs. Therefore, the internal environment of the body is the widest transport system and the area where extracellular reactions occur.

It transports nutrients and carries metabolic products to the site of destruction or excretion. Also, the internal environment of the body transports hormones and mediators, allowing some cells to regulate the work of others. This is the basis of humoral mechanisms that ensure the occurrence of biochemical processes, the overall result of which is homeostasis.

It turns out that the entire internal environment of the body (IEC) is the place where all nutrients and biologically active substances should go. This is an area of ​​the body that should not accumulate metabolic products. And in the basic understanding, VSO is the so-called road along which “couriers” (tissue and synovial fluid, blood, lymph and cerebrospinal fluid) deliver “food” and “building material” and remove harmful metabolic products.

Early internal environment of organisms

All representatives of the animal kingdom evolved from single-celled organisms. Their only component of the internal environment of the body was the cytoplasm. From the external environment it was limited by the cell wall and the cytoplasmic membrane. Then further development animals followed the principle of multicellularity. In coelenterate organisms there was a cavity separating the cells and the external environment. It was filled with hydrolymph, in which nutrients and products of cellular metabolism were transported. This type of internal environment existed in flatworms and coelenterates.

Development of the internal environment

In animal classes roundworms, arthropods, mollusks (with the exception of cephalopods) and insects, the internal environment of the body consists of other structures. These are vessels and areas of an open channel through which hemolymph flows. Its main feature is the acquisition of the ability to transport oxygen through hemoglobin or hemocyanin. In general, such an internal environment is far from perfect, which is why it developed further.

Perfect indoor environment

A perfect internal environment is a closed system, which excludes the possibility of fluid circulation through isolated areas of the body. This is how the bodies of representatives of the classes of vertebrates, annelids and cephalopods are arranged. Moreover, it is most perfect in mammals and birds, which, to support homeostasis, also have a 4-chambered heart, which provides them with warm-bloodedness.

The components of the internal environment of the body are as follows: blood, lymph, joint and tissue fluid, cerebrospinal fluid. It has its own walls: the endothelium of arteries, veins and capillaries, lymphatic vessels, the joint capsule and ependymocytes. On the other side of the internal environment lie the cytoplasmic membranes of the cells with which it is in contact, also included in the BSO.

Blood

The internal environment of the body is partly formed by blood. This is a liquid that contains formed elements, proteins and some elementary substances. A lot of enzymatic processes take place here. But the main function of blood is transport, especially oxygen to cells and carbon dioxide from them. Therefore, the largest proportion of formed elements in the blood is erythrocytes, platelets, and leukocytes. The former are involved in the transport of oxygen and carbon dioxide, although they can also play an important role in immune reactions due to reactive oxygen species.

Leukocytes in the blood are completely occupied only with immune reactions. They participate in the immune response, regulate its strength and completeness, and also store information about antigens with which they have previously been in contact. Since the internal environment of the body is partly formed by blood, which plays the role of a barrier between parts of the body in contact with the external environment and cells, the immune function of blood is second in importance after transport. At the same time, it requires the use of both formed elements and plasma proteins.

The third important function of blood is hemostasis. This concept combines several processes that are aimed at preserving the liquid consistency of the blood and covering defects in the vascular wall when they appear. The hemostasis system ensures that the blood flowing through the vessels remains liquid until the damaged vessel needs to be closed. Moreover, the internal environment of the human body will not be affected, although this requires energy expenditure and the involvement of platelets, erythrocytes and plasma factors of the coagulation and anticoagulation system.

Blood proteins

The second part of the blood is liquid. It consists of water in which proteins, glucose, carbohydrates, lipoproteins, amino acids, vitamins with their carriers and other substances are evenly distributed. Among the proteins, high molecular weight and low molecular weight are distinguished. The first are represented by albumins and globulins. These proteins are responsible for the functioning of the immune system, maintaining plasma oncotic pressure, and the functioning of the coagulation and anticoagulation systems.

Carbohydrates dissolved in the blood act as transported energy-intensive substances. This is a nutrient substrate that must enter the intercellular space, from where it will be captured by the cell and processed (oxidized) in its mitochondria. The cell will receive the energy necessary for the operation of systems responsible for the synthesis of proteins and the performance of functions for the benefit of the entire organism. At the same time, amino acids, also dissolved in the blood plasma, also penetrate the cell and serve as a substrate for protein synthesis. The latter is a tool for the cell to realize its hereditary information.

The role of blood plasma lipoproteins

Another important source of energy, in addition to glucose, is triglyceride. This is fat that must be broken down and become an energy carrier for muscle tissue. It is she who, for the most part, is able to process fats. By the way, they contain much more energy than glucose, and therefore are able to provide muscle contraction for a much longer period than glucose.

Fats are transported into cells using membrane receptors. Fat molecules absorbed in the intestine are first combined into chylomicrons and then enter the intestinal veins. From there, chylomicrons pass to the liver and travel to the lungs, where they form low-density lipoproteins. The latter are transport forms in which fats are delivered through the blood into the intercellular fluid to muscle sarcomeres or smooth muscle cells.

Also, blood and intercellular fluid, together with lymph, which make up the internal environment of the human body, transport metabolic products of fats, carbohydrates, and proteins. They are partially contained in the blood, which carries them to the site of filtration (kidney) or disposal (liver). It is obvious that these biological fluids, which are the media and compartments of the body, play a vital role in the life of the body. But much more important is the presence of a solvent, that is, water. Only thanks to it can substances be transported and cells exist.

Intercellular fluid

It is believed that the composition of the internal environment of the body is approximately constant. Any fluctuations in the concentration of nutrients or metabolic products, changes in temperature or acidity lead to dysfunction. Sometimes they can lead to death. By the way, it is acidity disorders and acidification of the internal environment of the body that is the fundamental and most difficult to correct dysfunction.

This is observed in cases of polyarganic insufficiency, when acute hepatic and renal failure. These organs are designed to utilize acidic metabolic products, and when this does not happen, there is an immediate threat to the patient’s life. Therefore, in reality, all components of the internal environment of the body are very important. But much more important is the performance of organs, which also depend on the VSO.

It is the intercellular fluid that reacts first to changes in concentrations nutrients or metabolic products. Only then does this information enter the blood through mediators secreted by the cells. The latter supposedly transmit a signal to cells in other areas of the body, urging them to take action to correct the problems that have arisen. So far, this system is the most effective of all those presented in the biosphere.

Lymph

Lymph is also the internal environment of the body, the functions of which are limited to the distribution of leukocytes throughout the body and the removal of excess fluid from the interstitial space. Lymph is a fluid containing low and high molecular weight proteins, as well as some nutrients.

It is drained from the interstitial space through tiny vessels that collect and form lymph nodes. Lymphocytes actively multiply in them, playing an important role in the implementation of immune reactions. From the lymphatic vessels it is collected in thoracic duct and flows into the left venous angle. Here the fluid returns to the bloodstream.

Synovial fluid and cerebrospinal fluid

Synovial fluid is a variant of the intercellular fluid fraction. Since cells cannot penetrate into the joint capsule, the only way The nutrition of articular cartilage is precisely the synovium. All articular cavities are the internal environment of the body, because they are in no way connected to the structures in contact with the external environment.

Also included in the VSO are all the ventricles of the brain along with the cerebrospinal fluid and the subarachnoid space. CSF is already a variant of lymph, since the nervous system does not have its own lymphatic system. Through cerebrospinal fluid, the brain is cleared of metabolic products, but is not nourished by it. The brain is nourished by blood, products dissolved in it and bound oxygen.

Through the blood-brain barrier they penetrate neurons and glial cells, delivering the necessary substances to them. Metabolic products are removed through cerebrospinal fluid and venous system. And probably the most important function cerebrospinal fluid is protective of the brain and nervous system from temperature fluctuations and mechanical damage. Since the liquid actively dampens mechanical impacts and shocks, this property is really necessary for the body.

Conclusion

The external and internal environments of the body, despite their structural isolation from each other, are inextricably linked by a functional connection. Namely, the external environment is responsible for the flow of substances into the internal environment, from where it removes metabolic products. And the internal environment transfers nutrients to the cells, removing them from them harmful products. In this way homeostasis is maintained, main characteristic life activity. This also means that it is virtually impossible to separate the external environment of otragism from the internal one.

The internal environment of the body is blood, lymph and fluid that fills the spaces between cells and tissues. The blood and lymphatic vessels that penetrate all human organs have tiny pores in their walls through which even some blood cells can penetrate. Water, which forms the basis of all fluids in the body, together with organic and inorganic substances dissolved in it, easily passes through the walls of blood vessels. Consequently chemical composition blood plasma (that is, the liquid part of the blood that does not contain cells), lymph and tissue liquids is largely the same. With age, there are no significant changes in the chemical composition of these liquids. At the same time, differences in the composition of these fluids may be associated with the activity of the organs in which these fluids are located.

Blood

Blood composition. Blood is a red, opaque liquid consisting of two fractions - liquid, or plasma, and solid, or cells - blood cells. It is quite easy to separate blood into these two fractions using a centrifuge: the cells are heavier than plasma and in a centrifuge tube they collect at the bottom in the form of a red clot, and a layer of transparent and almost colorless liquid remains above it. This is plasma.

Plasma. The adult human body contains about 3 liters of plasma. In a healthy adult, plasma makes up more than half (55%) of the blood volume, in children it is slightly less.

More than 90% of plasma composition - water, the rest is inorganic salts dissolved in it, as well as organic matter: carbohydrates, carboxylic, fatty acids and amino acids, glycerin, soluble proteins and polypeptides, urea, etc. Together they determine blood osmotic pressure, which in the body is maintained at a constant level so as not to cause harm to the cells of the blood itself, as well as to all other cells of the body: increased osmotic pressure leads to shrinkage of cells, and with reduced osmotic pressure they swell. In both cases, cells may die. Therefore, for the introduction of various drugs into the body and for transfusion of blood-replacing fluids in case of large blood loss, special solutions are used that have exactly the same osmotic pressure as blood (isotonic). Such solutions are called physiological. The simplest physiological solution in composition is a 0.1% solution of sodium chloride NaCl (1 g of salt per liter of water). Plasma is involved in the transport function of blood (transports substances dissolved in it), as well as the protective function, since some proteins dissolved in plasma have an antimicrobial effect.

Blood cells. There are three main types of cells in the blood: red blood cells, or red blood cells, white blood cells, or leukocytes; blood platelets, or platelets. Cells of each of these types perform specific physiological functions, and together they determine the physiological properties of blood. All blood cells are short-lived (the average lifespan is 2 - 3 weeks), therefore, throughout life, special hematopoietic organs are engaged in the production of more and more new blood cells. Hematopoiesis occurs in the liver, spleen and bone marrow, as well as in the lymph glands.

Red blood cells(Fig. 11) are anucleate disc-shaped cells, devoid of mitochondria and some other organelles and adapted for one main function - to be oxygen carriers. The red color of red blood cells is determined by the fact that they carry the protein hemoglobin (Fig. 12), in which the functional center, the so-called heme, contains an iron atom in the form of a divalent ion. Heme is able to chemically combine with an oxygen molecule (the resulting substance is called oxyhemoglobin) if the partial pressure of oxygen is high. This bond is fragile and is easily destroyed if the partial pressure of oxygen drops. It is on this property that the ability of red blood cells to carry oxygen is based. Once in the lungs, the blood in the pulmonary vesicles finds itself in conditions of increased oxygen tension, and hemoglobin actively captures atoms of this gas, which is poorly soluble in water. But as soon as blood enters working tissues that actively use oxygen, oxyhemoglobin easily gives it away, obeying the “oxygen demand” of the tissues. During active functioning, tissues produce carbon dioxide and other acidic products that exit through cell walls into the blood. This is still to a greater extent stimulates oxyhemoglobin to release oxygen, since the chemical bond between the subject and oxygen is very sensitive to the acidity of the environment. In return, heme attaches a CO 2 molecule to itself, carrying it to the lungs, where this chemical bond is also destroyed, CO 2 is carried out with the current of exhaled air, and hemoglobin is released and is again ready to attach oxygen.

Rice. 10. Red blood cells: a - normal red blood cells in the form of a biconcave disk; b - wrinkled red blood cells in hypertonic saline solution

If carbon monoxide CO is present in the inhaled air, it enters into a chemical interaction with hemoglobin in the blood, resulting in the formation of a strong substance, methoxyhemoglobin, which does not disintegrate in the lungs. Thus, hemoglobin in the blood is removed from the process of oxygen transfer, tissues do not receive the required amount of oxygen, and the person feels suffocated. This is the mechanism of human poisoning in a fire. A similar effect is exerted by some other instant poisons, which also disable hemoglobin molecules, for example, hydrocyanic acid and its salts (cyanides).

Rice. 11. Spatial model of the hemoglobin molecule

Every 100 ml of blood contains about 12 g of hemoglobin. Each hemoglobin molecule is capable of “carrying” 4 oxygen atoms. The blood of an adult contains a huge number of red blood cells - up to 5 million in one milliliter. Newborns have even more of them - up to 7 million, which means more hemoglobin. If a person lives for a long time in conditions of lack of oxygen (for example, high in the mountains), then the number of red blood cells in his blood increases even more. As the body ages, the number of red blood cells changes in waves, but in general, children have slightly more of them than adults. A decrease in the number of red blood cells and hemoglobin in the blood below normal indicates a serious illness - anemia (anemia). One of the causes of anemia may be a lack of iron in food. Foods rich in iron include: beef liver, apples and some others. In cases of prolonged anemia, it is necessary to take medications containing iron salts.

Along with determining the level of hemoglobin in the blood, the most common clinical blood tests include measuring the erythrocyte sedimentation rate (ESR), or erythrocyte sedimentation reaction (ERS), - these are two equal names for the same test. If you prevent blood clotting and leave it in a test tube or capillary for several hours, then without mechanical shaking, heavy red blood cells will begin to precipitate. The speed of this process in adults ranges from 1 to 15 mm/h. If this indicator is significantly higher than normal, this indicates the presence of a disease, most often inflammatory. In newborns, ESR is 1-2 mm/h. By the age of 3, ESR begins to fluctuate - from 2 to 17 mm/h. In the period from 7 to 12 years, ESR usually does not exceed 12 mm/h.

Leukocytes- white blood cells. They do not contain hemoglobin, so they are not red in color. The main function of leukocytes is to protect the body from pathogenic microorganisms and toxic substances that have penetrated inside it. Leukocytes are able to move using pseudopodia, like amoebas. This way they can leave the blood capillaries and lymphatic vessels, in which there are also a lot of them, and move towards the accumulation of pathogenic microbes. There they devour microbes, carrying out the so-called phagocytosis.

There are many types of white blood cells, but the most typical are lymphocytes, monocytes and neutrophils. Neutrophils, which, like erythrocytes, are formed in the red bone marrow, are most active in the processes of phagocytosis. Each neutrophil can absorb 20-30 microbes. If the body is invaded by a large foreign body(for example, a splinter), then many neutrophils stick around it, forming a kind of barrier. Monocytes - cells formed in the spleen and liver, also participate in the processes of phagocytosis. Lymphocytes, which are formed mainly in the lymph nodes, are not capable of phagocytosis, but are actively involved in other immune reactions.

1 ml of blood normally contains from 4 to 9 million leukocytes. The ratio between the number of lymphocytes, monocytes and neutrophils is called the blood formula. If a person gets sick, then total number leukocytes increase sharply, and the blood formula also changes. By its change, doctors can determine what type of microbe the body is fighting.

In a newborn child, the number of white blood cells is significantly (2-5 times) higher than in an adult, but after a few days it decreases to a level of 10-12 million per 1 ml. Starting from the 2nd year of life, this value continues to decrease and reaches typical adult values ​​after puberty. In children, the processes of formation of new blood cells are very active, therefore among the blood leukocytes in children there are significantly more young cells than in adults. Young cells differ in their structure and functional activity from mature ones. After 15-16 years, the blood formula acquires the parameters characteristic of adults.

Platelets- the smallest formed elements of blood, the number of which reaches 200-400 million in 1 ml. Muscular work and other types of stress can increase the number of platelets in the blood several times (this, in particular, is the danger of stress for older people: after all, blood clotting depends on platelets, including the formation of blood clots and blockage of small vessels in the brain and heart muscles). Place of platelet formation - red Bone marrow and spleen. Their main function is to ensure blood clotting. Without this function, the body becomes vulnerable at the slightest injury, and the danger lies not only in the fact that a significant amount of blood is lost, but also in the fact that any open wound- this is a gateway for infection.

If a person is injured, even shallowly, the capillaries are damaged, and platelets along with the blood end up on the surface. Here they are affected by two the most important factors- low temperature (much lower than 37 ° C inside the body) and plenty of oxygen. Both of these factors lead to the destruction of platelets, and from them substances are released into the plasma that are necessary for the formation of a blood clot - a thrombus. In order for a blood clot to form, the blood must be stopped by squeezing a large vessel if there is a lot of blood flowing from it, since even the process of thrombus formation that has begun will not go to completion if new and new portions of blood continue to flow into the wound. high temperature and platelets that have not yet been destroyed.

To prevent blood from clotting inside the vessels, it contains special anti-clotting substances - heparin, etc. As long as the vessels are not damaged, there is a balance between substances that stimulate and inhibit coagulation. Damage to blood vessels leads to disruption of this balance. In old age and with increasing disease, this balance in a person is also disturbed, which increases the risk of blood clotting in small vessels and the formation of a life-threatening blood clot.

Age-related changes in platelet function and blood coagulation were studied in detail by A. A. Markosyan, one of the founders of age-related physiology in Russia. It was found that in children, coagulation occurs more slowly than in adults, and the resulting clot has a looser structure. These studies led to the formation of the concept of biological reliability and its increase in ontogenesis.

The internal environment of the body consists of three components combined into a single system:

1) Blood

2) Tissue fluid

3) Lymph

Blood— circulates through a closed system of blood vessels and does not communicate directly with other tissues of the body.

Blood consists of a liquid part - plasma, which plays the role of intercellular substance, and formed elements: cells - erythrocytes and leukocytes and blood platelets - platelets, which belong to the non-cellular formed elements of blood.

In capillaries - the thinnest blood vessels where exchange occurs between blood and tissue cells, the liquid part of the blood partially leaves the blood vessels. It passes into the intercellular spaces and becomes tissue fluid.

Tissue fluid is the second component of the internal environment in which the cells are directly located. It contains about 95% water, 0.9% mineral salts, 1.5% proteins and other organic substances, as well as oxygen and carbon dioxide.

From tissue fluid, cells receive nutrients and oxygen brought by blood. Cells release breakdown products into the tissue fluid. And only from there they enter the blood and are carried away by it.

Lymph is the third component of the internal environment. It moves through the lymphatic vessels. Lymphatic vessels begin in tissues as small blind sacs consisting of an epithelial layer of cells. These are lymphatic capillaries. They intensively absorb excess tissue fluid.

Lymphatic vessels merge with each other and ultimately form the main lymphatic vessel (duct), through which lymph enters the circulatory system.

On the path of lymph there are lymph nodes; they are filters where foreign particles are retained and microorganisms are destroyed.

RELATIVE CONSTANCE OF THE INTERNAL ENVIRONMENT

The internal environment of the body is in fluid equilibrium, since some substances are consumed, and this consumption is replenished. Thus, used nutrients are replaced by new nutrients from the intestines.

There are receptors in the walls of blood vessels that signal an increase or decrease in the concentration of any substances in the blood. If the concentration of these substances approaches upper limit norms, reflexes operate that reduce their concentration. And if it drops below normal, other receptors are excited, which cause opposite reflexes.

Thanks to the work of the nervous and endocrine systems, fluctuations in the concentration of substances in the blood, tissue fluid and lymph do not go beyond normal limits.

BLOOD COMPOSITION

Plasma blood has a relatively constant salt composition. About 0.9% of plasma is table salt (sodium chloride); it also contains potassium, calcium, and phosphoric acid salts. About 7% of plasma is protein. Among them is the protein fibrinogen, which is involved in blood clotting. Blood plasma contains carbon dioxide, glucose, as well as other nutrients and breakdown products.

Red blood cells- red blood cells that transport oxygen to the tissues and carbon dioxide to the lungs. They have a red color due to a special substance - hemoglobin, which colors these cells red.

Leukocytes- are called white blood cells, although they are actually colorless.

The main function of leukocytes is to recognize and destroy foreign compounds and cells that find themselves in the internal environment of the body. Having discovered a foreign body, they capture it with pseudopods, absorb it and destroy it. This phenomenon was called phagocytosis, and the leukocytes themselves were called phagocytes, which means “cells are eaters.”

A large group of blood cells is called lymphocytes, since their maturation is completed in the lymph nodes and thymus gland. These cells are able to recognize chemical structure foreign antigen compounds and produce special chemical substances called antibodies that neutralize or destroy these antigens.

Not only blood leukocytes have the ability to phagocytose, but also larger cells located in tissues - macrophages. When microorganisms penetrate through the skin and mucous membranes into the internal environment of the body, macrophages move to them and participate in their destruction.

Platelets, or blood platelets, take part in blood clotting. If an injury occurs and blood leaves the vessel, the platelets clump together and are destroyed. At the same time, they secrete enzymes that cause a whole chain chemical reactions leading to blood clotting. Blood clotting is possible because a network is formed in which blood cells are retained. This blood clot closes the wound and stops the bleeding.

For a clot to form, it is necessary that the blood contains calcium salts, vitamin K and some other substances. If calcium salts are removed or there is no vitamin K in the blood, the blood will not clot.

Blood analysis. The composition of the blood is an important characteristic of the body’s condition, so a blood test is one of the most frequently performed studies. A blood test determines the number of blood cells, hemoglobin content, the concentration of sugar and other substances, as well as the erythrocyte sedimentation rate (ESR). If there is any inflammatory process ESR increases.

Hematopoiesis. Red blood cells, white blood cells and platelets are formed in the red bone marrow. However, the maturation of many lymphocytes occurs in the thymus (thymus gland) and lymph nodes. These lymphocytes enter the blood along with lymph.

Hematopoiesis is a very intensive process, since the lifespan of blood cells is short. Leukocytes live from several hours to 3-5 days, erythrocytes - 120-130 days, platelets - 5-7 days.

OUR INTERNAL ENVIRONMENT LIKES:

1. Complete nutrition. Our internal environment loves good nutrition: proteins, fats and carbohydrates rich in vitamins, macro- and microelements.
2. Adequate fluid intake. As you understand, blood, lymph and intercellular fluid consist of 98% water, so drink enough liquid, or rather plain water.
3. Proper alternation of work and rest. Properly alternate your rest and work. Work moderately and get enough rest to allow your body to recover from physical and mental stress.
4. Active lifestyle. Our body simply needs an active lifestyle, otherwise it will begin to suffer, like lymphatic system, and circulatory.

OUR INTERNAL ENVIRONMENT DOESN'T LIKE:

1. Poor food. A monotonous, poor diet directly affects the state of the lymph and the composition of the blood.
2. Insufficient fluid intake makes blood and lymph thick, and this is a direct path to health problems.
3. Sedentary lifestyle. Flaw motor activity does not have the best effect on the condition of the blood and lymph.
4. Diseases.Diseases such as diabetes, anemia and others affect not only the lymphatic and cardiovascularjudicial systems, but also on the health of the whole organism.

Test on the topic:

Internal environment of the body.

Option I

1. The internal environment of the body is formed by:

A) body cavities; IN) internal organs;

B) blood, lymph, tissue fluid; D) tissues that form internal organs.

2. Blood is a type of tissue:

A) connecting; B) muscular; B) epithelial.

3.Red blood cells are involved:

A) in the process of phagocytosis; B) in the formation of blood clots;

B) in the production of antibodies; D) in gas exchange.

4. With anemia (anemia), the content of:

A) platelets; B) plasma;

B) red blood cells; D) lymphocytes.

5.The body’s immunity to any infection is:

A) anemia; B) hemophilia;

B) phagocytosis; D) immunity.

6. Antigens are:

A) foreign substances that can cause an immune response;

B) formed elements of blood;

C) a special protein called the Rh factor;

D) all of the above.

7. Invented the first vaccine:

B) Louis Pasteur; D) I. Pavlov.

8. During preventive vaccinations, the following are introduced into the body:

A) killed or weakened microorganisms; C) drugs that kill microorganisms;

B) protective substances (antibodies) D) phagocytes.

9.People with I The following blood types can be used for blood transfusion:

A) IIgroups; B) onlyI groups;

B) III And IVgroups; D) any group.

10.Which vessels have valves inside :

11. Metabolism between blood and body cells is possible only

A) in the arteries; B) capillaries; B) veins.

12. The outer layer of the heart (epicardium) is formed by cells:

13. The inner surface of the pericardial sac is filled with:

A) air; B) adipose tissue;

B) liquid; D) connective tissue.

14.The left side of the heart contains blood:

A) rich in oxygen– arterial; B) rich in carbon dioxide;

B) poor in oxygen; D) all of the above.

15.The liquid part of the blood is called:

A) tissue fluid; B) lymph;

B) plasma; D) saline solution.

16. Internal environment of the body:

A) ensures the stability of all body functions; B) has self-regulation;

B) maintains homeostasis; D) all answers are correct.

17.Human red blood cells have:

A) biconcave shape; B) spherical shape;

B) elongated core; D) strictly constant amount in the body.

18. Blood clotting occurs due to:

A) destruction of leukocytes; B) destruction of red blood cells;

B) narrowing of capillaries; D) fibrin formation.

19.Phagocytosis is a process:

A) blood clotting;

B) movement of phagocytes;

C) absorption and digestion of microbes and foreign particles by leukocytes;

D) reproduction of leukocytes.

20.The body’s ability to produce antibodies provides the body with:

A) constancy of the internal environment; C) protection against the formation of blood clots;

B) immunity; D) all of the above.

Test on the topic:

Internal environment of the body.

II option

The internal environment includes:

A) blood; B) lymph;

B) tissue fluid; D) all of the above.

From tissue fluid is formed:

A) lymph; B) blood plasma;

B) blood; D) saliva.

Functions of red blood cells:

A) participation in blood clotting; B) oxygen transfer;

B) neutralization of bacteria; D) production of antibodies.

A lack of red blood cells in the blood is:

A) hemophilia; B) phagocytosis;

B) anemia; D) thrombosis.

If you have AIDS:

A) the body’s ability to produce antibodies decreases;

B) the body’s resistance to infections decreases;

C) rapid weight loss occurs;

Antibodies are:

A) special substances formed in the blood to destroy antigens;

B) substances that participate in blood clotting;

C) substances that cause anemia (anemia);

D) all of the above.

Nonspecific immunity by phagocytosis, discovered:

A) I. Mechnikov; B) E. Jenner;

B) Louis Pasteur; D) I. Pavlov.

When administering the vaccine:

A) the body receives weakened microbes or their poisons;

B) the body receives antigens that cause the patient to produce its own antibodies;

C) the body produces antibodies on its own;

D) all of the above are true.

9.Blood of people I groups (taking into account the Rh factor) can be transfused to people:

A) only with Iblood type; B) only withIV blood type;

B) only with IIblood type; D) with any blood group.

10.Which vessels have the thinnest walls:

A) veins; B) capillaries; B) arteries.

11. Arteries are vessels that carry blood:

12. The inner layer of the heart (endocardium) is formed by cells:

A) muscle tissue; IN) epithelial tissue;

B) connective tissue; D) nervous tissue.

13. Any circle of blood circulation ends:

A) in one of the atria; B) in the lymph nodes;

B) in one of the ventricles; D) in the tissues of internal organs.

14.The thickest walls of the heart:

A) left atrium; B) right atrium;

B) left ventricle; D) right ventricle.

15. preventive vaccinations, as a means of fighting infections, discovered:

A) I. Mechnikov; B) E. Jenner;

B) Louis Pasteur; D) I. Pavlov.

16.Healing serums are:

A) killed pathogens; B) weakened pathogens;

B) ready-made protective substances; D) poisons secreted by pathogens.

17. Blood of people IV groups can be transfused to people who have:

A) I group; IN) III group;

B) II group; G) IV group.

18. In which vessels does blood flow under the greatest pressure:

A) in the veins; B) capillaries; B) arteries.

19. Veins are vessels that carry blood:

A) only arterial; B) from organs to heart;

B) only venous; D) from the heart to the organs.

20. The middle layer of the heart (myocardium) is formed by cells:

A) muscle tissue; B) epithelial tissue;

B) connective tissue; D) nervous tissue.

Option 1

10A

11B

12B

13B

14A

15B

16G

17A

18G

19V

20B

Option-2

Option-2

10B

11G

12V

13A

14B

15B

16B

17G

18V

19V

Any organism - unicellular or multicellular - needs certain conditions of existence. These conditions are provided to organisms by the environment to which they have adapted during evolutionary development.

The first living formations arose in the waters of the World Ocean, and sea water served as their habitat. As living organisms became more complex, some of their cells became isolated from the external environment. So part of the habitat ended up inside the organism, which allowed many organisms to leave aquatic environment and start living on land. The content of salts in the internal environment of the body and in sea ​​water approximately the same.

The internal environment for human cells and organs is blood, lymph and tissue fluid.

Relative constancy of the internal environment

In the internal environment of the body, in addition to salts, there are a lot of different substances - proteins, sugar, fat-like substances, hormones, etc. Each organ constantly releases the products of its vital activity into the internal environment and receives from it the substances it needs. And, despite such active exchange, the composition of the internal environment remains practically unchanged.

The fluid leaving the blood becomes part of the tissue fluid. Most of this fluid returns to the capillaries before they connect with the veins that return blood to the heart, but about 10% of the fluid does not enter the vessels. The walls of capillaries consist of a single layer of cells, but there are narrow gaps between adjacent cells. The contraction of the heart muscle creates blood pressure, causing water with dissolved salts and nutrients to pass through these gaps.

All body fluids are connected to each other. The extracellular fluid comes into contact with the blood and the cerebrospinal fluid that bathes the spinal cord and brain. This means that the regulation of the composition of body fluids occurs centrally.

Tissue fluid washes cells and serves as a habitat for them. It is constantly renewed through the system of lymphatic vessels: this fluid is collected in vessels, and then through the largest lymphatic vessel it enters the general bloodstream, where it mixes with the blood.

Blood composition

The well-known red liquid is actually tissue. For a long time blood was recognized as a powerful force: sacred oaths were sealed with blood; the priests made their wooden idols “cry blood”; The ancient Greeks sacrificed blood to their gods.

Some philosophers of Ancient Greece considered blood to be the carrier of the soul. The ancient Greek physician Hippocrates prescribed the blood of healthy people to the mentally ill. He thought that in the blood of healthy people there is a healthy soul. Indeed, blood is the most amazing tissue of our body. Blood mobility - the most important condition life of the organism.

About half of the blood volume is its liquid part - plasma with salts and proteins dissolved in it; the other half consists of various formed elements of blood.

Blood cells are divided into three main groups: white blood cells (leukocytes), red blood cells (erythrocytes) and platelets, or platelets. All of them are formed in the bone marrow ( soft fabric filling the cavity tubular bones), but some leukocytes are able to multiply already when leaving the bone marrow. There are many various types leukocytes - most are involved in protecting the body from diseases.

Blood plasma

In 100 ml of blood plasma healthy person contains about 93 g of water. The rest of the plasma consists of organic and inorganic substances. Plasma contains minerals, proteins, carbohydrates, fats, metabolic products, hormones, vitamins.

Plasma minerals are represented by salts: chlorides, phosphates, carbonates and sulfates of sodium, potassium, calcium and magnesium. They can be in the form of ions or in a non-ionized state. Even minor violation the salt composition of plasma can be detrimental to many tissues, and above all to the cells of the blood itself. The total concentration of mineral soda, proteins, glucose, urea and other substances dissolved in plasma creates osmotic pressure. Due to osmotic pressure, liquid penetrates through cell membranes, which ensures the exchange of water between blood and tissue. The constancy of the osmotic pressure of the blood is important for the life of the body's cells. The membranes of many cells, including blood cells, are also semi-permeable.

Red blood cells

Red blood cells are the most numerous blood cells; their main function is to transport oxygen. Conditions that increase the body's need for oxygen, such as living at high altitudes or constantly exercise stress, stimulate the formation of red blood cells. Red blood cells live in the bloodstream for about four months, after which they are destroyed.

Leukocytes

Leukocytes, or white blood cells of irregular shape. They have a nucleus embedded in a colorless cytoplasm. The main function of leukocytes is protective. Leukocytes are not only carried by the bloodstream, but are also capable of independent movement with the help of pseudopods (pseudopods). Penetrating through the walls of capillaries, leukocytes move towards the accumulation of pathogenic microbes in the tissue and, with the help of pseudopods, capture and digest them. This phenomenon was discovered by I.I. Mechnikov.

Platelets, or blood platelets

Platelets, or blood platelets are very fragile, easily destroyed when blood vessels are damaged or when blood comes into contact with air.

Platelets play an important role in blood clotting. Damaged tissue releases histomine, a substance that increases blood flow to the damaged area and promotes the release of fluid and proteins of the blood coagulation system from the bloodstream into the tissue. As a result of a complex sequence of reactions, blood clots quickly form, stopping the bleeding. Blood clots prevent bacteria and other foreign factors from entering the wound.

The mechanism of blood clotting is very complex. Plasma contains a soluble protein, fibrinogen, which, during blood clotting, turns into insoluble fibrin and precipitates in the form of long threads. From the network of these threads and blood cells that linger in the network, a thrombus.

This process occurs only in the presence of calcium salts. Therefore, if calcium is removed from the blood, the blood loses its ability to clot. This property is used in canning and blood transfusions.

In addition to calcium, other factors also take part in the coagulation process, such as vitamin K, without which the formation of prothrombin is disrupted.

Blood functions

Blood performs various functions in the body: it delivers oxygen and nutrients to cells; carries away carbon dioxide and metabolic end products; participates in the regulation of activities various organs and systems through biological transfer active substances- hormones, etc.; helps maintain the constancy of the internal environment - chemical and gas composition, body temperature; protects the body from foreign bodies and harmful substances, destroying and neutralizing them.

The body's protective barriers

The body's protection from infections is ensured not only by the phagocytic function of leukocytes, but also by the formation of special protective substances - antibodies And antitoxins. They are produced by leukocytes and tissues of various organs in response to the introduction of pathogens into the body.

Antibodies are protein substances that can glue microorganisms together, dissolve or destroy them. Antitoxins neutralize poisons secreted by microbes.

Protective substances are specific and act only on those microorganisms and their poisons under the influence of which they were formed. Antibodies can remain in the blood for a long time. Thanks to this, a person becomes immune to certain infectious diseases.

Immunity to diseases due to the presence of special protective substances in the blood and tissues is called immunity.

The immune system

Immunity, by modern views, - the body’s immunity to various factors (cells, substances) that carry genetically foreign information.

If any cells or complex organic substances appear in the body that differ from the cells and substances of the body, then thanks to immunity they are eliminated and destroyed. The main task of the immune system is to maintain the genetic constancy of the organism during ontogenesis. When cells divide due to mutations in the body, cells with an altered genome are often formed. To prevent these mutant cells from causing disturbances in the development of organs and tissues during further division, they are destroyed immune systems body.

In the body, immunity is ensured due to the phagocytic properties of leukocytes and the ability of some body cells to produce protective substances - antibodies. Therefore, by its nature, immunity can be cellular (phagocytic) and humoral (antibodies).

Immunity to infectious diseases is divided into natural, developed by the body itself without artificial interventions, and artificial, resulting from the introduction of special substances into the body. Natural immunity manifests itself in a person from birth ( congenital) or occurs after illnesses ( acquired). Artificial immunity can be active or passive. Active immunity is developed when weakened or killed pathogens or their weakened toxins are introduced into the body. This immunity does not occur immediately, but persists long time- for several years and even for the rest of your life. Passive immunity occurs when a therapeutic serum with ready-made protective properties is introduced into the body. This immunity is short-lived, but appears immediately after administration of the serum.

Blood clotting also refers to the body's protective reactions. It protects the body from blood loss. The reaction consists of the formation of a blood clot - thrombus, which seals the wound area and stops bleeding.

The internal environment of the body is blood, lymph and fluid that fills the spaces between cells and tissues. The blood and lymphatic vessels that penetrate all human organs have tiny pores in their walls through which even some blood cells can penetrate. Water, which forms the basis of all fluids in the body, together with organic and inorganic substances dissolved in it, easily passes through the walls of blood vessels. As a result, the chemical composition of blood plasma (that is, the liquid part of the blood that does not contain cells), lymph and tissue liquids is largely the same. With age, there are no significant changes in the chemical composition of these liquids. At the same time, differences in the composition of these fluids may be associated with the activity of the organs in which these fluids are located.

Blood

Blood composition. Blood is a red, opaque liquid consisting of two fractions - liquid, or plasma, and solid, or cells - blood cells. It is quite easy to separate blood into these two fractions using a centrifuge: the cells are heavier than plasma and in a centrifuge tube they collect at the bottom in the form of a red clot, and a layer of transparent and almost colorless liquid remains above it. This is plasma.

Plasma. The adult human body contains about 3 liters of plasma. In a healthy adult, plasma makes up more than half (55%) of the blood volume, in children it is slightly less.

More than 90% of plasma composition - water, the rest is inorganic salts dissolved in it, as well as organic matter: carbohydrates, carbon, fatty acid and amino acids, glycerol, soluble proteins and polypeptides, urea, etc. Together they determine blood osmotic pressure, which in the body is maintained at a constant level so as not to cause harm to the cells of the blood itself, as well as to all other cells of the body: increased osmotic pressure leads to shrinkage of cells, and with reduced osmotic pressure they swell. In both cases, cells may die. Therefore, for the introduction of various drugs into the body and for transfusion of blood-replacing fluids in case of large blood loss, special solutions are used that have exactly the same osmotic pressure as blood (isotonic). Such solutions are called physiological. The simplest physiological solution in composition is a 0.1% solution of sodium chloride NaCl (1 g of salt per liter of water). Plasma is involved in the transport function of blood (transports substances dissolved in it), as well as the protective function, since some proteins dissolved in plasma have an antimicrobial effect.

Blood cells. There are three main types of cells in the blood: red blood cells, or red blood cells, white blood cells, or leukocytes; blood platelets, or platelets. Cells of each of these types perform specific physiological functions, and together they determine the physiological properties of blood. All blood cells are short-lived (the average lifespan is 2 - 3 weeks), therefore, throughout life, special hematopoietic organs are engaged in the production of more and more new blood cells. Hematopoiesis occurs in the liver, spleen and bone marrow, as well as in the lymph glands.

Red blood cells(Fig. 11) are anucleate disc-shaped cells, devoid of mitochondria and some other organelles and adapted for one main function - to be oxygen carriers. The red color of red blood cells is determined by the fact that they carry the protein hemoglobin (Fig. 12), in which the functional center, the so-called heme, contains an iron atom in the form of a divalent ion. Heme is able to chemically combine with an oxygen molecule (the resulting substance is called oxyhemoglobin) if the partial pressure of oxygen is high. This bond is fragile and is easily destroyed if the partial pressure of oxygen drops. It is on this property that the ability of red blood cells to carry oxygen is based. Once in the lungs, the blood in the pulmonary vesicles finds itself in conditions of increased oxygen tension, and hemoglobin actively captures atoms of this gas, which is poorly soluble in water. But as soon as blood enters working tissues that actively use oxygen, oxyhemoglobin easily gives it away, obeying the “oxygen demand” of the tissues. During active functioning, tissues produce carbon dioxide and other acidic products that exit through the cell walls into the blood. This further stimulates oxyhemoglobin to release oxygen, since the chemical bond between hemoglobin and oxygen is very sensitive to the acidity of the environment. In return, heme attaches a CO 2 molecule to itself, carrying it to the lungs, where this chemical bond is also destroyed, CO 2 is carried out with the current of exhaled air, and hemoglobin is released and is again ready to attach oxygen.

Rice. 10. Red blood cells: a - normal red blood cells in the shape of a biconcave disc; b - wrinkled red blood cells in hypertonic saline solution

If carbon monoxide CO is present in the inhaled air, it enters into a chemical interaction with hemoglobin in the blood, resulting in the formation of a strong substance, methoxyhemoglobin, which does not disintegrate in the lungs. Thus, hemoglobin in the blood is removed from the process of oxygen transfer, tissues do not receive the required amount of oxygen, and the person feels suffocated. This is the mechanism of human poisoning in a fire. A similar effect is exerted by some other instant poisons, which also disable hemoglobin molecules, for example, hydrocyanic acid and its salts (cyanides).

Rice. 11. Spatial model of the hemoglobin molecule

Every 100 ml of blood contains about 12 g of hemoglobin. Each hemoglobin molecule is capable of “carrying” 4 oxygen atoms. The blood of an adult contains a huge number of red blood cells - up to 5 million in one milliliter. Newborns have even more of them - up to 7 million, which means more hemoglobin. If a person lives for a long time in conditions of lack of oxygen (for example, high in the mountains), then the number of red blood cells in his blood increases even more. As the body ages, the number of red blood cells changes in waves, but in general, children have slightly more of them than adults. A decrease in the number of red blood cells and hemoglobin in the blood below normal indicates a serious illness - anemia (anemia). One of the causes of anemia may be a lack of iron in food. Foods such as beef liver, apples and some others are rich in iron. In cases of prolonged anemia, it is necessary to take medications containing iron salts.

Along with determining the level of hemoglobin in the blood, the most common clinical blood tests include measuring the erythrocyte sedimentation rate (ESR), or erythrocyte sedimentation reaction (ERS), - these are two equal names for the same test. If you prevent blood clotting and leave it in a test tube or capillary for several hours, then without mechanical shaking, heavy red blood cells will begin to precipitate. The speed of this process in adults ranges from 1 to 15 mm/h. If this indicator is significantly higher than normal, this indicates the presence of a disease, most often inflammatory. In newborns, ESR is 1-2 mm/h. By the age of 3, ESR begins to fluctuate - from 2 to 17 mm/h. In the period from 7 to 12 years, ESR usually does not exceed 12 mm/h.

Leukocytes- white blood cells. They do not contain hemoglobin, so they are not red in color. The main function of leukocytes is to protect the body from pathogenic microorganisms and toxic substances that have penetrated inside it. Leukocytes are able to move using pseudopodia, like amoebas. This way they can leave the blood capillaries and lymphatic vessels, in which there are also a lot of them, and move towards the accumulation of pathogenic microbes. There they devour microbes, carrying out the so-called phagocytosis.

There are many types of white blood cells, but the most typical are lymphocytes, monocytes and neutrophils. Neutrophils, which, like erythrocytes, are formed in the red bone marrow, are most active in the processes of phagocytosis. Each neutrophil can absorb 20-30 microbes. If a large foreign body (for example, a splinter) invades the body, then many neutrophils stick around it, forming a kind of barrier. Monocytes - cells formed in the spleen and liver, also participate in the processes of phagocytosis. Lymphocytes, which are formed mainly in the lymph nodes, are not capable of phagocytosis, but are actively involved in other immune reactions.

1 ml of blood normally contains from 4 to 9 million leukocytes. The ratio between the number of lymphocytes, monocytes and neutrophils is called the blood formula. If a person gets sick, the total number of leukocytes increases sharply, and the blood formula also changes. By its change, doctors can determine what type of microbe the body is fighting.

In a newborn child, the number of white blood cells is significantly (2-5 times) higher than in an adult, but after a few days it decreases to a level of 10-12 million per 1 ml. Starting from the 2nd year of life, this value continues to decrease and reaches typical adult values ​​after puberty. In children, the processes of formation of new blood cells are very active, therefore among the blood leukocytes in children there are significantly more young cells than in adults. Young cells differ in their structure and functional activity from mature ones. After 15-16 years, the blood formula acquires the parameters characteristic of adults.

Platelets- the smallest formed elements of blood, the number of which reaches 200-400 million in 1 ml. Muscular work and other types of stress can increase the number of platelets in the blood several times (this, in particular, is the danger of stress for older people: after all, blood clotting depends on platelets, including the formation of blood clots and blockage of small vessels in the brain and heart muscles). The place of platelet formation is the red bone marrow and spleen. Their main function is to ensure blood clotting. Without this function, the body becomes vulnerable at the slightest injury, and the danger lies not only in the fact that a significant amount of blood is lost, but also in the fact that any open wound is a gateway to infection.

If a person is injured, even shallowly, the capillaries are damaged, and platelets along with the blood end up on the surface. Here they are affected by two important factors - low temperature (much lower than 37 ° C inside the body) and an abundance of oxygen. Both of these factors lead to the destruction of platelets, and from them substances are released into the plasma that are necessary for the formation of a blood clot - a thrombus. In order for a blood clot to form, the blood must be stopped by squeezing a large vessel if blood is pouring heavily from it, since even the process of thrombus formation that has begun will not go to completion if new and new portions of blood with a high temperature are constantly entering the wound and not yet destroyed platelets.

To prevent blood from clotting inside the vessels, it contains special anti-clotting substances - heparin, etc. As long as the vessels are not damaged, there is a balance between substances that stimulate and inhibit coagulation. Damage to blood vessels leads to disruption of this balance. In old age and with increasing disease, this balance in a person is also disturbed, which increases the risk of blood clotting in small vessels and the formation of a life-threatening blood clot.

Age-related changes in platelet function and blood coagulation were studied in detail by A. A. Markosyan, one of the founders of age-related physiology in Russia. It was found that in children, coagulation occurs more slowly than in adults, and the resulting clot has a looser structure. These studies led to the formation of the concept of biological reliability and its increase in ontogenesis.