Osmosis is the movement of water across a membrane towards a higher concentration of substances.

Fresh water

The concentration of substances in the cytoplasm of any cell is higher than in fresh water, so water constantly enters the cells that come into contact with fresh water.

• erythrocyte in hypotonic solution fills up with water and bursts.
• In freshwater protozoa, to remove excess water, there is contractile vacuole.
• The cell wall prevents the plant cell from bursting. The pressure exerted by a water-filled cell on the cell wall is called turgor.

salty water

AT hypertonic solution water leaves the erythrocyte and it shrinks. If a person drinks sea water, then the salt will enter the plasma of his blood, and the water will leave the cells into the blood (all cells will shrink). This salt will need to be excreted in urine, the amount of which will exceed the amount of sea water drunk.

Plants have plasmolysis(departure of the protoplast from the cell wall).

Isotonic solution

Saline is a 0.9% sodium chloride solution. The plasma of our blood has the same concentration, osmosis does not occur. In hospitals, on the basis of saline, a solution for a dropper is made.

100 ml of healthy human plasma contains about 93 g of water. The rest of the plasma consists of organic and inorganic substances. Plasma contains minerals, proteins (including enzymes), carbohydrates, fats, metabolic products, hormones, and vitamins.

Plasma minerals are represented by salts: chlorides, phosphates, carbonates and sulfates of sodium, potassium, calcium, magnesium. They can be both in the form of ions and in a non-ionized state.

Osmotic pressure of blood plasma

Even minor violations of the salt composition of the plasma can be detrimental to many tissues, and above all to the cells of the blood itself. The total concentration of mineral salts, proteins, glucose, urea and other substances dissolved in plasma creates osmotic pressure.

Osmosis phenomena occur wherever there are two solutions of different concentrations, separated by a semi-permeable membrane, through which the solvent (water) easily passes, but the solute molecules do not. Under these conditions, the solvent moves towards the solution with a higher concentration of the solute. Unilateral diffusion of a liquid through a semi-permeable partition is called osmosis(Fig. 4). The force that causes the solvent to move through a semipermeable membrane is osmotic pressure. With the help of special methods, it was possible to establish that the osmotic pressure of human blood plasma is kept at a constant level and is 7.6 atm (1 atm ≈ 10 5 N / m 2).

The osmotic pressure of plasma is mainly created by inorganic salts, since the concentration of sugar, proteins, urea and other organic substances dissolved in plasma is low.

Due to osmotic pressure, fluid penetrates through the cell membranes, which ensures the exchange of water between the blood and tissues.

The constancy of the osmotic pressure of the blood is important for the vital activity of the cells of the body. The membranes of many cells, including blood cells, are also semi-permeable. Therefore, when blood cells are placed in solutions with different salt concentrations, and, consequently, with different osmotic pressures, serious changes occur in blood cells due to osmotic forces.

A saline solution that has the same osmotic pressure as blood plasma is called isotonic saline. For humans, a 0.9% solution of common salt (NaCl) is isotonic, and for a frog, a 0.6% solution of the same salt.

A saline solution whose osmotic pressure is higher than the osmotic pressure of blood plasma is called hypertonic; if the osmotic pressure of the solution is lower than in blood plasma, then such a solution is called hypotonic.

A hypertonic solution (usually a 10% saline solution) is used in the treatment of purulent wounds. If a bandage with a hypertonic solution is applied to the wound, then the liquid from the wound will come out onto the bandage, since the concentration of salts in it is higher than inside the wound. In this case, the liquid will carry along pus, microbes, dead tissue particles, and as a result, the wound will soon clear and heal.

Since the solvent always moves towards a solution with a higher osmotic pressure, when erythrocytes are immersed in a hypotonic solution, water, according to the laws of osmosis, begins to intensively penetrate into the cells. Erythrocytes swell, their membranes break, and the contents enter the solution. There is hemolysis. The blood, the erythrocytes of which have undergone hemolysis, becomes transparent, or, as is sometimes said, lacquered.

In human blood, hemolysis begins when erythrocytes are placed in a 0.44-0.48% NaCl solution, and in 0.28-0.32% NaCl solutions, almost all erythrocytes are destroyed. If red blood cells enter a hypertonic solution, they shrink. Verify this by doing experiments 4 and 5.

Note. Before carrying out laboratory work on the study of blood, it is necessary to master the technique of taking blood from a finger for analysis.

First, both the subject and the researcher thoroughly wash their hands with soap and water. Then the subject is wiped with alcohol on the ring (IV) finger of the left hand. The skin of the pulp of this finger is pierced with a sharp and pre-sterilized special feather needle. When pressing on the finger near the injection site, blood comes out.

The first drop of blood is removed with dry cotton, and the next one is used for research. It is necessary to ensure that the drop does not spread over the skin of the finger. Blood is drawn into a glass capillary by immersing its end into the base of the drop and placing the capillary in a horizontal position.

After taking blood, the finger is again wiped with a cotton swab moistened with alcohol, and then smeared with iodine.

Experience 4

Place a drop of isotonic (0.9 percent) NaCl solution on one end of the slide and a drop of hypotonic (0.3 percent) NaCl solution on the other. Prick the skin of the finger with a needle in the usual way and transfer a drop of blood to each drop of the solution with a glass rod. Mix the liquids, cover with coverslips and examine under a microscope (preferably at high magnification). Swelling of the majority of erythrocytes in a hypotonic solution is seen. Some of the red blood cells are destroyed. (Compare with erythrocytes in isotonic saline.)

Experience 5

Take another glass slide. Place a drop of 0.9% NaCl solution on one end of it, and a drop of hypertonic (10%) NaCl solution on the other. Add a drop of blood to each drop of solutions and, after mixing, examine them under a microscope. In a hypertonic solution, there is a decrease in the size of erythrocytes, their wrinkling, which is easily detected by their characteristic scalloped edge. In an isotonic solution, the edge of the erythrocytes is smooth.

Despite the fact that different amounts of water and mineral salts can enter the blood, the osmotic pressure of the blood is maintained at a constant level. This is achieved through the activity of the kidneys, sweat glands, through which water, salts and other metabolic products are removed from the body.

Saline

For the normal functioning of the body, it is important not only the quantitative content of salts in the blood plasma, which provides a certain osmotic pressure. The qualitative composition of these salts is also extremely important. An isotonic solution of sodium chloride is not able to maintain the work of the organ washed by it for a long time. The heart, for example, will stop if calcium salts are completely excluded from the fluid flowing through it, the same will happen with an excess of potassium salts.

Solutions that, in terms of their qualitative composition and salt concentration, correspond to the composition of plasma are called saline solutions. They are different for different animals. In physiology, Ringer and Tyrode fluids are often used (Table 1).

In liquids for warm-blooded animals, in addition to salts, glucose is often added and the solution is saturated with oxygen. Such fluids are used to maintain the vital functions of organs isolated from the body, as well as blood substitutes for blood loss.

Blood reaction

Blood plasma has not only a constant osmotic pressure and a certain qualitative composition of salts, it maintains a constant reaction. In practice, the reaction of the medium is determined by the concentration of hydrogen ions. To characterize the reaction of the medium, use pH indicator, denoted by pH. (Hydrogen index is the logarithm of the concentration of hydrogen ions with the opposite sign.) For distilled water, the pH value is 7.07, an acidic environment is characterized by a pH of less than 7.07, and an alkaline one is more than 7.07. The pH of human blood at a body temperature of 37°C is 7.36. The active reaction of the blood is slightly alkaline. Even slight shifts in blood pH disrupt the body's activity and threaten its life. At the same time, in the process of vital activity, as a result of metabolism in tissues, significant amounts of acidic products are formed, for example, lactic acid during physical work. With increased breathing, when a significant amount of carbonic acid is removed from the blood, the blood can become alkaline. The body usually quickly copes with such deviations in the pH value. This function is carried out buffer substances that are in the blood. These include hemoglobin, acid salts of carbonic acid (bicarbonates), salts of phosphoric acid (phosphates) and blood proteins.

The constancy of the reaction of the blood is maintained by the activity of the lungs, through which carbon dioxide is removed from the body; excess substances that have an acidic or alkaline reaction are excreted through the kidneys and sweat glands.

Plasma proteins

Of the organic substances in plasma, proteins are of the greatest importance. They ensure the distribution of water between the blood and tissue fluid, maintaining the water-salt balance in the body. Proteins are involved in the formation of protective immune bodies, bind and neutralize toxic substances that have entered the body. The plasma protein fibrinogen is the main factor in blood coagulation. Proteins give the blood the necessary viscosity, which is important for maintaining a constant level of blood pressure.

According to the program of I.N. Ponomareva.

Textbook: Biology Man. A.G. Dragomilov, R.D. Mash.

Lesson type:

1. according to the main didactic goal - the study of new material;

2. according to the method of conducting and the stages of the educational process - combined.

Lesson methods:

1. by the nature of cognitive activity: explanatory-illustrated, problem-search.

2. by type of source of knowledge: verbal-visual.

3. according to the form of joint activity of the teacher and students: story, conversation

Purpose: To deepen the meaning of the internal environment of the body and homeostasis; explain the mechanism of blood coagulation; continue developing microscopy skills.

Didactic tasks:

1) The composition of the internal environment of the body

2) Composition of blood and its functions

3) Mechanism of blood coagulation

1) Name the constituent components of the internal environment of the human body

2) Determine under a microscope, drawings of blood cells: erythrocytes, leukocytes, platelets

3) Indicate the functions of blood cells

4) Characterize the constituent components of blood plasma

5) Establish the relationship between the structure and functions of blood cells

6) Explain the importance of a blood test as a means of diagnosing diseases. Justify your opinion.

Development tasks:

1) Ability to perform tasks, guided by methodological instructions.

2) Extract the necessary information from knowledge sources.

3) The ability to draw conclusions after viewing the slides on the topic “Blood”

4) Ability to fill in diagrams

5) Analyze and evaluate information

6) Develop students' creativity

Educational tasks:

1) Patriotism on the life of I.I. Mechnikov

2) Formation of a healthy lifestyle: a person should monitor the composition of his blood, eat food rich in protein and iron, avoid blood loss and dehydration.

3) Create conditions for the formation of self-esteem of the individual.

Requirements for the level of training of students:

Learn:

• blood cells under a microscope, drawings

Describe:

• functions of blood cells;
• blood coagulation mechanism;
• the function of the constituent components of blood plasma;
• signs of anemia, hemophilia

Compare:

• young and mature human erythrocyte;
• human and frog erythrocytes;
• the number of red blood cells in newborns and adults.

Blood plasma, erythrocytes, leukocytes, platelets, homeostasis, phagocytes, fibrinogens, blood coagulation, thromboplastin, neutrophils, eosinophils, basophils, monocytes, lymphocytes, isotonic, hypertonic, hypotonic solutions, saline.

Equipment:

1) Table “Blood”

2) Electronic CD “Cyril and Methodius”, theme “Blood”

3) Whole human blood (centrifuged and simple).

4) Microscopes

5) Micropreparations: human and frog blood.

6) Raw potatoes in distilled water and salt

7) Saline solution

8) 2 red robes, white robe, balloons

9) Portraits of I.I. Mechnikov and A. Levenguk

10) Plasticine red and white

11) Student presentations.

Lesson stages

1. Actualization of basic knowledge.

Claude Bernard: “I was the first to insist on the idea that for animals there are actually 2 environments: one environment is external, in which the organism is placed, and the other environment is internal, in which tissue elements live.

Fill the table.

“Components of the internal environment and their location in the body”. See appendix number 1.

2. Studying new material

Mephistopheles, inviting Faust to sign an alliance with "evil spirits", said: "Blood, you need to know, a very special juice." These words reflect the mystical belief in the blood in something mysterious.

A mighty and exceptional power was recognized behind blood: sacred oaths were sealed by 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. Mobility of blood is the most important condition for the life of the body. Just as it is impossible to imagine a state without transport lines of communication, so it is impossible to understand the existence of a person or an animal without the movement of blood through the vessels, when oxygen, water, proteins and other substances are carried to all organs and tissues. With the development of science, the human mind penetrates deeper and deeper into many secrets of the blood.

So, the total amount of blood in the human body is equal to 7% of its weight, in terms of volume it is about 5-6 liters in an adult and about 3 liters in adolescents.

What are the functions of blood?

Student: Demonstrates a basic summary and explains the functions of blood. See appendix #2

At this time, the teacher makes additions to the electronic disk “Blood”.

Teacher: What is blood made of? Demonstrates centrifuged blood showing 2 clearly distinct layers.

The top layer is a slightly yellowish translucent liquid - blood plasma and the bottom layer is a dark red sediment, which is formed by formed elements - blood cells: leukocytes, platelets and erythrocytes.

The peculiarity of blood lies in the fact that it is a connective tissue, the cells of which are suspended in a liquid intermediate substance - plasma. In addition, cell reproduction does not occur in it. The execution of old, dying blood cells with new ones is carried out thanks to the hematopoiesis that occurs in the red bone marrow, which fills the space between the bone crossbars of the spongy substance of all bones. For example, the destruction of aged and damaged red blood cells occurs in the liver and spleen. Its total volume in an adult is 1500 cm 3.

Blood plasma contains many simple and complex substances. 90% of plasma is water, and only 10% of it is dry matter. But how diverse is its composition! Here are the most complex proteins (albumins, globulins and fibrinogen), fats and carbohydrates, metals and halides - all elements of the periodic table, salts, alkalis and acids, various gases, vitamins, enzymes, hormones, etc.

Each of these substances has a certain importance.

A student with a crown “Squirrels” is the “Building Material” of our body. They participate in the processes of blood coagulation, maintain the constancy of the blood reaction (weakly alkaline), form immunoglobulins, antibodies involved in the body's defense reactions. High-molecular proteins that do not penetrate the walls of blood capillaries retain a certain amount of water in the plasma, which is important for a balanced distribution of fluid between the blood and tissues. The presence of proteins in the plasma ensures the viscosity of the blood, the constancy of its vascular pressure, and prevents erythrocyte sedimentation.

The student with the crown “fats and carbohydrates” are sources of energy. Salts, alkalis and acids maintain the constancy of the internal environment, changes in which are life-threatening. Enzymes, vitamins and hormones ensure the proper metabolism in the body, its growth, development and mutual influence of organs and systems.

Teacher: The total concentration of mineral salts, proteins, glucose, urea and other substances dissolved in plasma creates osmotic pressure.

The phenomenon of osmosis occurs wherever there are 2 solutions of different concentrations, separated by a semi-impermeable membrane, through which the solvent (water) easily passes, but the solute molecules do not pass. Under these conditions, the solvent moves towards a solution with a high concentration of the solute.

Due to somatic pressure, fluid penetrates through the cell membranes, which ensures the exchange of water between the blood and tissues. The constancy of the osmotic pressure of the blood is important for the vital activity of the cells of the body. The membranes of many cells, including blood cells, are also semi-permeable. Therefore, when erythrocytes are placed in solutions with different salt concentrations, and, consequently, with different osmotic pressures, serious changes occur in them.

A saline solution having the same osmotic pressure as blood plasma is called an isotonic solution. For humans, 0.9% sodium chloride solution is isotonic.

Salt solution, the osmotic pressure of which is higher than the osmotic pressure of blood plasma, is called hypertonic; if the osmotic pressure is lower than in blood plasma, then such a solution is called hypotonic.

Hypertonic solution (10% NaCl) - used in the treatment of purulent wounds. If a bandage with a hypertonic solution is applied to the wound, then the liquid from the wound will come out onto the bandage, since the concentration of salts in it is higher than inside the wound. In this case, the liquid will carry pus, microbes, dead tissue particles with it, and as a result, the wound will be cleansed and healed.

Since the solvent always moves towards a solution with a higher osmotic pressure, when erythrocytes are immersed in a hypotonic solution, water, according to the law of osmosis, begins to intensively penetrate into the cells. Erythrocytes swell, their membranes break, and the contents enter the solution.

For the normal functioning of the body, not only the quantitative content of salts in the blood plasma is important. The qualitative composition of these salts is also extremely important. The heart, for example, will stop if calcium salts are completely excluded from the fluid flowing through it, the same will happen with an excess of potassium salts. Solutions that, in terms of their qualitative composition and salt concentration, correspond to the composition of plasma are called physiological solutions. They are different for different animals. Such fluids are used to maintain the vital functions of organs isolated from the body, as well as blood substitutes for blood loss.

Task: Prove that the violation of the constancy of the salt composition of blood plasma by diluting it with distilled water leads to the death of erythrocytes.

Experience can be put on display. The same amount of blood is poured into 2 test tubes. Distilled water is added to one sample, and physiological saline (0.9% NaCl solution) is added to the other. Students should notice that the test tube in which the saline solution was added to the blood remained opaque. Consequently, the formed elements of the blood were preserved, remained in suspension. In a test tube, where distilled water was added to the blood, the liquid became transparent. The content of the test tube is no longer a suspension, it has become a solution. This means that the formed elements here, primarily erythrocytes, were destroyed, and hemoglobin went into solution.

Recording experience can be arranged in the form of a table. See Appendix #3.

The value of the constancy of the salt composition of blood plasma.

The reasons for the destruction of erythrocytes under the pressure of blood water can be explained as follows. Erythrocytes have a semi-permeable membrane; it allows water molecules to pass through, but poorly passes salt ions and other substances. In erythrocytes and blood plasma, the percentage of water is approximately equal, therefore, in a certain unit of time, approximately the same number of water molecules enter the erythrocyte from the plasma as it leaves the erythrocyte into the plasma. When blood is diluted with water, the water molecules outside the red blood cells become larger than inside. As a result, the number of water molecules penetrating into the erythrocyte also increases. It swells, its membrane stretches, the cell loses hemoglobin. It goes into plasma. The destruction of red blood cells in the human body can occur under the influence of various substances, such as viper venom. Once in the plasma, hemoglobin is quickly lost: it easily passes through the walls of blood vessels, is excreted from the body by the kidneys, and is destroyed by the liver tissues.

Violation of the plasma composition, like any other violation of the constancy of the composition of the internal environment, is possible only within relatively small limits. Due to nervous and humoral self-regulation, deviation from the norm causes changes in the body that restore the norm. Significant changes in the constancy of the composition of the internal environment lead to disease, and sometimes even cause death.

A student in a red robe and a red blood cell crown with balloons in his hands:

Everything that is contained in the blood, everything that it carries through the vessels, is intended for the cells of our body. They take everything they need from it and use it for their own needs. Only the oxygen-containing substance should be intact. After all, if it settles in the tissues, breaks down there and is used for the needs of the body, it will become difficult to transport oxygen.

At first, nature went to the creation of very large molecules, the molecular weight of which is two, sometimes ten million times more than a volume of hydrogen, the lightest substance. Such proteins are not able to pass through cell membranes, “getting stuck” even in fairly large pores; that is why they were kept in the blood for a long time and could be used many times. For higher animals, a more original solution was found. Nature provided them with hemoglobin, the molecular weight of which is only 16 thousand times greater than that of a hydrogen atom, but in order to prevent hemoglobin from getting to the surrounding tissues, it placed it, as in containers, inside special cells circulating with blood - erythrocytes.

The erythrocytes of most animals are round, although sometimes their shape changes for some reason, becoming oval. Among mammals, such freaks are camels and llamas. Why it was necessary to introduce such significant changes into the design of the erythrocyte of these animals is still not known exactly.

At first, the erythrocytes were large, bulky. In Proteus, a relic cave amphibian, their diameter is 35-58 microns. In most amphibians, they are much smaller, but their volume reaches 1100 cubic microns. It turned out to be inconvenient. After all, the larger the cell, the relatively smaller its surface, in both directions of which oxygen must pass. There is too much hemoglobin per unit surface, which prevents its full use. Convinced of this, nature took the path of reducing the size of erythrocytes to 150 cubic microns for birds and up to 70 for mammals. In humans, their diameter is 8 microns, and the volume is 8 cubic microns.

The erythrocytes of many mammals are even smaller, in goats they barely reach 4, and in musk deer 2.5 microns. Why goats have such small red blood cells is not difficult to understand. The ancestors of domestic goats were mountain animals and lived in a highly rarefied atmosphere. It is not for nothing that the number of red blood cells they have is huge, 14.5 million in each cubic millimeter of blood, while animals such as amphibians, whose metabolic rate is low, have only 40-170 thousand red blood cells.

In pursuit of shrinking, vertebrate red blood cells have evolved into flat disks. Thus, the path of oxygen molecules diffusing into the depths of the erythrocyte was maximally reduced. In humans, in addition, there are depressions in the center of the disk on both sides, which made it possible to further reduce the volume of the cell, increasing the size of its surface.

It is very convenient to transport hemoglobin in a special container inside an erythrocyte, but there is no good without evil. The erythrocyte is a living cell and consumes a lot of oxygen for its respiration. Nature does not tolerate waste. She had to rack her brains a lot to figure out how to cut unnecessary expenses.

The most important part of any cell is the nucleus. If it is quietly removed, and scientists are able to perform such ultramicroscopic operations, then a nuclear-free cell, although it does not die, still becomes unviable, stops its main functions, and drastically reduces metabolism. This is what nature decided to use, she deprived the adult erythrocytes of mammals of their nuclei. The main function of erythrocytes was to be containers for hemoglobin - a passive function, and it could not suffer, and a reduction in metabolism was only beneficial, since oxygen consumption was greatly reduced.

Teacher: make an erythrocyte from red plasticine.

A student in a white coat and a “leukocyte” crown:

Blood is not only a vehicle. It also performs other important functions. Moving through the vessels of the body, the blood in the lungs and intestines almost directly comes into contact with the external environment. And the lungs, and especially the intestines, are undoubtedly dirty places in the body. Not surprisingly, it is very easy for microbes to enter the blood here. And why shouldn't they get in? Blood is a wonderful nutrient medium, rich in oxygen. If vigilant and inexorable guards were not placed right at the entrance, the life path of the organism would become the path of its death.

The guards were easily found. Even at the dawn of the emergence of life, all cells of the body were able to capture and digest particles of organic substances. Almost at the same time, organisms acquired motile cells, very reminiscent of modern amoeba. They did not sit idly by, waiting for the flow of liquid to bring them something tasty, but spent their lives in constant search for their daily bread. These vagrant hunter cells, which from the very beginning were involved in the fight against microbes that entered the body, were called leukocytes.

Leukocytes are the largest cells in human blood. Their size ranges from 8 to 20 microns. These white-coated orderlies of our body took part in the digestive processes for a long time. They perform this function even in modern amphibians. Not surprisingly, lower animals have a lot of them. In fish, there are up to 80 thousand of them in 1 cubic millimeter of blood, ten times more than in a healthy person.

To successfully fight pathogenic microbes, you need a lot of white blood cells. The body produces them in huge quantities. Scientists have not yet been able to find out their life expectancy. Yes, it is unlikely that it can be accurately established. After all, leukocytes are soldiers and, apparently, never live to old age, but die in the war, in the battles for our health. This is probably why in different animals and under different conditions of the experiment very varied numbers were obtained - from 23 minutes to 15 days. More precisely, it was possible to establish only the life span for lymphocytes - one of the varieties of tiny orderlies. It is equal to 10-12 hours, that is, the body completely renews the composition of lymphocytes at least twice a day.

Leukocytes are able not only to wander inside the bloodstream, but if necessary, they easily leave it, delving into the tissues, towards the microorganisms that have got there. Devouring microbes dangerous to the body, leukocytes are poisoned by their potent toxins and die, but do not give up. Wave after wave of a solid wall they are on a disease-causing focus, until the enemy's resistance is broken. Each leukocyte can swallow up to 20 microorganisms.

Leukocytes crawl out in masses to the surface of the mucous membranes, where there are always a lot of microorganisms. Only in the human oral cavity - 250 thousand every minute. During the day, 1/80 of all our leukocytes die here.

Leukocytes fight not only with microbes. They are entrusted with another important function: to destroy all damaged, worn out cells. In the tissues of the body, they are constantly dismantling, clearing places for the construction of new body cells, and young leukocytes take part in the construction itself, in any case, in the construction of bones, connective tissue and muscles.

Of course, leukocytes alone would not be able to defend the body from microbes penetrating into it. There are many different substances in the blood of any animal that can glue, kill and dissolve microbes that have entered the circulatory system, turn them into insoluble substances and neutralize the toxin they release. Some of these protective substances we inherit from our parents, others we learn to produce ourselves in the fight against countless enemies around us.

Teacher: Task: make a leukocyte from white plasticine.

A student in a pink robe and a “platelet” crown:

No matter how carefully the control devices - baroreceptors monitor the state of blood pressure, an accident is always possible. More often than not, trouble comes from outside. Any, even the most insignificant, wound will destroy hundreds, thousands of vessels, and through these holes the waters of the inner ocean will immediately rush out.

Creating an individual ocean for each animal, nature had to attend to the organization of an emergency rescue service in case of destruction of its shores. At first, this service was not very reliable. Therefore, for the lower beings, nature provided for the possibility of a significant shallowing of internal reservoirs. The loss of 30 percent of blood for a person is fatal, the Japanese beetle easily tolerates the loss of 50 percent of the hemolymph.

If a ship at sea gets a hole, the team tries to plug the hole formed with any auxiliary material. Nature has supplied the blood in abundance with patches of its own. These are special spindle-shaped cells - platelets. In terms of size, they are negligible, only 2-4 microns. It would be impossible to plug such a tiny plug into any significant hole if platelets did not have the ability to stick together under the influence of thrombokinase. Nature has richly supplied the tissues surrounding the vessels and other places most prone to injury with this enzyme. At the slightest tissue damage, thrombokinase is released to the outside, comes into contact with the blood, and the platelets immediately begin to stick together, forming a lump, and the blood brings him more and more new building material, because in each cubic millimeter of blood they contain 150-400 thousand pieces.

By themselves, platelets cannot form a large plug. The plug is obtained by the loss of threads of a special protein - fibrin, which is constantly present in the blood in the form of fibrinogen. In the formed network of fibrin fibers, lumps of adherent platelets, erythrocytes, and leukocytes freeze. A few minutes pass, and a significant traffic jam forms. If a small vessel is damaged and the blood pressure in it is not high enough to push the plug out, the leak will be eliminated.

It is hardly cost-effective for the emergency service on duty to consume a lot of energy, and hence oxygen. Platelets have only one task - to stick together in a moment of danger. The function is passive, does not require a significant expenditure of energy, which means that there is no need to consume oxygen, while everything in the body is calm, and nature is with them the same way as with red blood cells. She deprived them of their nuclei and thereby, by reducing the level of metabolism, greatly reduced the consumption of oxygen.

It is quite obvious that a well-organized emergency blood service is necessary, but, unfortunately, it threatens the body with a terrible danger. What if, for one reason or another, the emergency service does not work on time? Such inappropriate actions will lead to a serious accident. The blood in the vessels will clot and clog them. Therefore, the blood has a second emergency service - an anti-clotting system. It ensures that there is no thrombin in the blood, the interaction of which with fibrinogen leads to the loss of fibrin strands. As soon as fibrin appears, the anticoagulant system immediately inactivates it.

The second emergency service is very active. If a significant dose of thrombin is introduced into the frog's blood, nothing bad will happen, it will be immediately rendered harmless. But if we now take blood from this frog, it turns out that it has lost the ability to coagulate.

The first emergency system works automatically, the second commands the brain. Without his instructions, the system will not work. If a frog's command post located in the medulla oblongata is first destroyed, and then thrombin is injected, the blood will instantly clot. Emergency services are at the ready, but there is no one to sound the alarm.

In addition to the emergency services listed above, the blood also has a major overhaul brigade. When the circulatory system is damaged, not only the rapid formation of a blood clot is important, but also its timely removal is necessary. While the torn vessel is plugged with a cork, it interferes with the healing of the wound. The repair team, restoring the integrity of the tissues, gradually dissolves and dissolves the clot.

Numerous guard, control and emergency services reliably protect the waters of our internal ocean from any surprises, ensuring a very high reliability of the movement of its waves and the invariance of their composition.

Teacher: Explanation of the mechanism of blood clotting.

blood clotting

Thromboplastin + Ca 2+ + prothrombin = thrombin

Thrombin + fibrinogen = fibrin

Thromboplastin is an enzyme protein formed during the destruction of platelets.

Ca 2+ - calcium ions present in blood plasma.

Prothrombin is an inactive plasma protein.

Thrombin is an active protein-enzyme.

Fibrinogen is a protein dissolved in blood plasma.

Fibrin - protein fibers that are insoluble in blood plasma (thrombus)

Throughout the lesson, students fill out the "Blood Cells" table, and then compare it with the reference table. They check with each other, give a grade based on the criteria proposed by the teacher. See Appendix 4.

The practical part of the lesson.

Teacher: Task number 1

Examine blood under a microscope. Describe erythrocytes. Determine if this blood can belong to a person.

Students are offered frog blood for analysis.

During the conversation, students answer the following questions:

1. What color do erythrocytes have?

Answer: The cytoplasm is pink, the nucleus is stained blue with nuclear dyes. Staining makes it possible not only to better distinguish cellular structures, but also to learn their chemical properties.

2. What is the size of erythrocytes?

Answer: Quite large, however, there are not many of them in the field of view.

3. Can this blood belong to a person?

Answer: It cannot. Humans are mammals, and mammalian erythrocytes do not have a nucleus.

Teacher: Task number 2

Compare human and frog erythrocytes.

When comparing, note the following. Human erythrocytes are much smaller than frog erythrocytes. In the field of view of a microscope, there are much more human erythrocytes than frog erythrocytes. The absence of a nucleus increases the useful capacity of the erythrocyte. From these comparisons, it is concluded that human blood is able to bind more oxygen than frog blood.

Enter the information in the table. See Appendix 5.

3. Consolidation of the studied material:

1. According to the medical form “Blood test”, see Appendix No. 6, characterize the composition of the blood:

a) The amount of hemoglobin

b) The number of red blood cells

c) The number of leukocytes

d) ROE and ESR

e) Leukocyte formula

f) Diagnose a person's state of health

2. Work on options:

1. Option: test work on 5 questions with a choice of one to several questions.

2. Option: select sentences in which errors are made and correct these errors.

Option 1

1.Where are red blood cells produced?

a) liver

b) red bone marrow

c) spleen

2.Where are erythrocytes destroyed?

a) liver

b) red bone marrow

c) spleen

3.Where are leukocytes formed?

a) liver

b) red bone marrow

c) spleen

d) lymph nodes

4. What blood cells have a nucleus in the cells?

a) erythrocytes

b) leukocytes

c) platelets

5. What formed elements of blood are involved in its coagulation?

a) erythrocytes

b) platelets

c) leukocytes

Option 2

Find sentences that contain errors and correct them:

1. The internal environment of the body is blood, lymph, tissue fluid.

2. Erythrocytes are red blood cells that have a nucleus.

3. Leukocytes are involved in the body's defense reactions, have an amoeboid shape and a nucleus.

4. Platelets have a nucleus.

5. Red blood cells are destroyed in the red bone marrow.

Tasks for logical thinking:

1. The concentration of salts in physiological saline, which sometimes replaces blood in experiments, is different for cold-blooded (0.65%) and warm-blooded (0.95%). How can you explain this difference?

2. If pure water is poured into the blood, the blood cells burst; if you put them in a concentrated salt solution, they shrivel. Why doesn't this happen if a person drinks a lot of water and eats a lot of salt?

3. When keeping tissues alive in a non-organism, they are placed not in water, but in a physiological solution containing 0.9% sodium chloride. Explain why it is necessary to do so?

4. Human erythrocytes are 3 times smaller than frog erythrocytes, but they are 1 mm 3 13 times more in humans than in frogs. How can you explain this fact?

5. Pathogenic microbes that have entered any organ can penetrate the lymph. If microbes got from it into the blood, then this would lead to a general infection of the body. However, this does not happen. Why?

6. In 1 mm 3 of goat blood there are 10 million erythrocytes with a size of 0.007; in the blood of a frog 1 mm 3 - 400,000 erythrocytes with a size of 0.02. Whose blood - human, frog or goat - will transfer more oxygen per unit time? Why?

7. When climbing a mountain quickly, healthy tourists develop “mountain sickness” - shortness of breath, palpitations, dizziness, weakness. These signs with frequent training pass over time. Guess what changes occur in this case in the human blood?

4. Homework

p.13,14. Know the entries in the notebook, work No. 50,51 p. 35 - workbook No. 1, authors: R.D. Mash and A.G. Dragomilov

Creative task for students:

"Immune Memory"

“The work of E. Jenner and L. Pasteur in the study of immunity.”

"Viral Human Diseases".

Reflection: Guys, raise your hands, those who were comfortable and cozy today in the lesson.

1. Do you think we achieved the goal of the lesson?
2. What did you like the most about the lesson?
3. What would you like to change during the lesson?

One of the terrible diseases that claimed hundreds of thousands of lives every year was. In its dying stage, the human body, due to the continuous loss of water by vomiting, turns into a kind of mummy. A person dies, because his tissues cannot live without the necessary amount of water. It is impossible to enter the liquid through, because it is instantly thrown back due to indomitable vomiting. Doctors have long had an idea: to inject water directly into the blood, into the vessels. However, this problem was solved when the phenomenon called osmotic pressure was understood and taken into account.

We know that the gas, being in this or that vessel, puts pressure on its walls, trying to occupy the largest possible volume. The stronger the gas is compressed, i.e., the more particles it contains in a given space, the stronger this pressure will be. It turned out that substances dissolved, for example, in water, are in a certain sense similar to gases: they also tend to occupy the largest possible volume, and the more concentrated the solution, the greater the strength of this desire. What is the manifestation of this property of solutions? The fact that they greedily "attract" to themselves an additional amount of solvent. It is enough to add a little water to the salt solution, and the solution quickly becomes uniform; it seems to absorb this water into itself, thereby increasing its volume. The described property of the solution to attract to itself is called osmotic pressure.

If we place them in a glass of clean water, they will quickly “swell up” and burst. This is understandable: the protoplasm of erythrocytes is a solution of salts and proteins of a certain concentration, which has an osmotic pressure much higher than pure water, where there are few salts. Therefore, the erythrocyte "sucks" water to itself. If, on the contrary, we place red blood cells in a very concentrated salt solution, they will shrink - the osmotic pressure of the solution will be higher, it will "suck" the water out of the red blood cells. The rest of the body cells behave like red blood cells.

It is clear that in order to introduce a liquid into the bloodstream, it must have a concentration corresponding to their concentration in the blood. Experiments have established that such is a 0.9% solution. This solution is called physiological.

The introduction of 1-2 liters of such a solution intravenously to a dying cholera patient had a literally miraculous effect. A person “came to life” before our eyes, sat up in bed, asked for food, etc. Repeating the introduction of the solution 2-3 times a day helped the body overcome the most difficult period of the disease. Such solutions, containing a number of other substances, are now used in many diseases. In particular, the importance of blood-substituting solutions in wartime is very great. Blood loss is terrible not only because it deprives the body of erythrocytes, but above all because the function is disrupted, “tuned” to work with a certain amount of blood. Therefore, in cases where for one reason or another it is impossible, a simple introduction of saline can save the life of the wounded.

Knowledge of the laws of osmotic pressure is of great importance, because it generally helps to regulate the body's water metabolism. So, it becomes clear why salty food causes: an excess of salt increases the osmotic pressure of our tissues, that is, their “greed” for water. Therefore, patients with edema are given less salt so as not to retain water in the body. On the other hand, workers in hot shops, who lose a lot of water, should be poured salted water, because with sweat they excrete salt, and lose it. If in these cases a person drinks pure water, the greed of tissues for water will decrease, and this will increase. The state of the body will deteriorate sharply.