Red blood cells in a hypertonic solution. State of red blood cells in NaCl solution of various concentrations Red blood cells placed in a physiological solution of table salt

One of the terrible diseases that claimed hundreds of thousands of lives every year was. In its pre-death stage, the human body, due to the continuous loss of water through vomiting, turns into a kind of mummy. A person dies because his tissues cannot live without the required amount of water. It turns out to be impossible to introduce liquid through, because it is instantly thrown back due to uncontrollable 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 gas, being in a particular vessel, presses on its walls, trying to occupy the largest possible volume. The more strongly 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 strive to occupy as much volume as possible, and the more concentrated the solution, the greater the strength of this desire. How does this property of solutions manifest itself? The fact is that they greedily “attract” additional amounts of solvent to themselves. 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 a solution to attract itself is called osmotic pressure.

If we place them in a glass of clean water, they will quickly “swell” 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 greater than pure water, where there are few salts. Therefore, the red blood cell “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” water from the red blood cells. Other cells in the body behave similarly to 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 this is a 0.9% solution. This solution was called physiological.

Injecting 1-2 liters of such a solution intravenously into a dying cholera patient had a literally miraculous effect. The person “came to life” before our eyes, sat up in bed, asked for food, etc. By repeating the administration of the solution 2-3 times a day, they helped the body overcome the most difficult period of the disease. Such solutions, containing a number of other substances, are now used for many diseases. In particular, the importance of blood replacement solutions in wartime is very great. Blood loss is terrible not only because it deprives the body of red blood cells, but primarily because it disrupts the function “tuned” to work with a certain amount of blood. Therefore, in cases where for one reason or another it is impossible, a simple injection of saline solution 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 foods cause: excess salt increases the osmotic pressure of our tissues, i.e. their “greed” for water. Therefore, patients with edema are given less salt so as not to retain water in the body. On the contrary, workers in hot shops who lose a lot of water should be given salted water, because with sweat they also excrete salts and are deprived of them. If in these cases a person drinks clean water, the tissues’ thirst for water will decrease, and this will intensify. The condition of the body will deteriorate sharply.

Article by professional biology tutor T. M. Kulakova

Blood is the intermediate internal environment of the body, this is liquid connective tissue. Blood consists of plasma and formed elements.

Blood composition- this is 60% plasma and 40% formed elements.

Blood plasma consists of water, organic substances (proteins, glucose, leukocytes, vitamins, hormones), mineral salts and breakdown products.

Shaped elements- red blood cells and platelets

Blood plasma- This is the liquid part of the blood. It contains 90% water and 10% dry matter, mainly proteins and salts.

There are metabolic products in the blood (urea, uric acid) that must be removed from the body. The concentration of salts in plasma is equal to the content of salts in blood cells. Blood plasma mainly contains 0.9% NaCl. The constancy of the salt composition ensures the normal structure and function of cells.

Unified State Exam tests often contain questions about solutions: physiological (solution, NaCl salt concentration is 0.9%), hypertonic (NaCl salt concentration above 0.9%) and hypotonic (NaCl salt concentration below 0.9%).

For example, this question:

The administration of large doses of drugs is accompanied by their dilution with physiological solution (0.9% NaCl solution). Explain why.

Recall that if a cell is in contact with a solution whose water potential is lower than that of its contents (i.e. hypertonic solution), then water will leave the cell due to osmosis through the membrane. Such cells (for example, red blood cells) shrink and settle to the bottom of the tube.

And if you place blood cells in a solution whose water potential is higher than the contents of the cell (that is, the salt concentration in the solution is below 0.9% NaCl), the red blood cells begin to swell because water rushes into the cells. In this case, the red blood cells swell and their membrane ruptures.

Let's formulate an answer to the question:

1. The concentration of salts in the blood plasma corresponds to the concentration of a physiological solution of 0.9% NaCl, which does not cause the death of blood cells;
2. The introduction of large doses of drugs without dilution will be accompanied by a change in the salt composition of the blood and cause cell death.

We remember that when writing an answer to a question, other wording of the answer is allowed that does not distort its meaning.

For erudition: when the membrane of red blood cells is destroyed, hemoglobin is released into the blood plasma, which turns red and becomes transparent. This kind of blood is called lac blood.

Classes

Exercise 1. The task includes 60 questions, each of them has 4 possible answers. For each question, select only one answer that you consider the most complete and correct. Place a “+” sign next to the index of the selected answer. In case of correction, the “+” sign must be duplicated.

Muscle tissue is formed:
a) only mononuclear cells;
b) only multinuclear muscle fibers;
c) binuclear fibers tightly adjacent to each other;
d) mononuclear cells or multinuclear muscle fibers. +
Muscle tissue is formed by striated cells that make up the fibers and interact with each other at the points of contact:
a) smooth;
b) cardiac; +
c) skeletal;
d) smooth and skeletal.
Tendons, through which muscles are connected to bones, are formed by connective tissue:
a) bone;
b) cartilaginous;
c) loose fibrous;
d) dense fibrous. +
The anterior horns of the gray matter of the spinal cord (“butterfly wings”) are formed by:
a) interneurons;
b) bodies of sensory neurons;
c) axons of sensory neurons;
d) bodies of motor neurons. +
The anterior roots of the spinal cord are formed by the axons of neurons:
a) motor; +
b) sensitive;
c) only intercalary ones;
d) intercalary and sensitive.
The centers of protective reflexes - coughing, sneezing, vomiting are located in:
a) cerebellum;
c) spinal cord;
c) intermediate part of the brain;
d) medulla oblongata of the brain. +
Red blood cells placed in a physiological solution of table salt:
a) wrinkle;
b) swell and burst;
c) stick to each other;
d) remain without external changes. +
Blood flows faster in vessels whose total lumen is:
a) the largest;
b) the smallest; +
c) average;
d) slightly above average.
The significance of the pleural cavity is that it:
a) protects the lungs from mechanical damage;
b) prevents overheating of the lungs;
c) participates in the removal of a number of metabolic products from the lungs;
d) reduces the friction of the lungs against the walls of the chest cavity, participates in the mechanism of stretching of the lungs. +
The significance of bile produced by the liver and entering the duodenum is that it:
a) breaks down difficult-to-digest proteins;
b) breaks down hard-to-digest carbohydrates;
c) breaks down proteins, carbohydrates and fats;
d) increases the activity of enzymes secreted by the pancreas and intestinal glands, facilitating the breakdown of fats. +
Photosensitivity of rods:
a) not developed;
b) the same as for cones;
c) higher than that of cones; +
d) lower than that of cones.
Jellyfish reproduce:
a) only through sexual intercourse;
b) only asexually;
c) sexually and asexually;
d) some species are only sexual, others are sexual and asexual. +
Why do children develop new signs that are not characteristic of their parents:
a) since all the gametes of the parents are of different types;
b) since during fertilization the gametes fuse randomly;
c) in children, parental genes are combined in new combinations; +
d) since the child receives one half of the genes from the father, and the other from the mother.
The flowering of some plants only in daylight conditions is an example:
a) apical dominance;
b) positive phototropism; +
c) negative phototropism;
d) photoperiodism.
Filtration of blood in the kidneys occurs in:
a) pyramids;
b) pelvis;
c) capsules; +
d) medulla.
When secondary urine is formed, the following are returned to the bloodstream:
a) water and glucose; +
b) water and salts;
c) water and proteins;
d) all of the above products.
For the first time among vertebrates, amphibians have glands:
a) salivary; +
b) sweat;
c) ovaries;
d) greasy.
The lactose molecule consists of residues:
a) glucose;
b) galactose;
c) fructose and galactose;
d) galactose and glucose.

The following statement is incorrect:
a) felines - a family of the carnivorous order;
b) hedgehogs - a family of insectivores;
c) hare - a genus of rodent order; +
d) tiger - a species of the panther genus.

45. Protein synthesis does NOT require:
a) ribosomes;
b) t-RNA;
c) endoplasmic reticulum; +
d) amino acids.

46. The following statement is true for enzymes:
a) enzymes lose some or all of their normal activity if their tertiary structure is destroyed; +
b) enzymes provide the energy necessary to stimulate the reaction;
c) enzyme activity does not depend on temperature and pH;
d) enzymes act only once and then are destroyed.

47. The greatest release of energy occurs in the process:
a) photolysis;
b) glycolysis;
c) Krebs cycle; +
d) fermentation.

48. The most characteristic features of the Golgi complex, as a cell organelle:
a) increasing the concentration and compaction of intracellular secretion products intended for release from the cell; +
b) participation in cellular respiration;
c) carrying out photosynthesis;
d) participation in protein synthesis.

49. Cellular organelles that transform energy:
a) chromoplasts and leucoplasts;
b) mitochondria and leukoplasts;
c) mitochondria and chloroplasts; +
d) mitochondria and chromoplasts.

50. The number of chromosomes in tomato cells is 24. Meiosis occurs in a tomato cell. Three of the resulting cells degenerate. The last cell immediately divides by mitosis three times. As a result, in the resulting cells you can find:
a) 4 nuclei with 12 chromosomes each;
b) 4 nuclei with 24 chromosomes each;
c) 8 nuclei with 12 chromosomes each; +
d) 8 nuclei with 24 chromosomes each.

51. Eyes in arthropods:
a) everyone has complex ones;
b) complex only in insects;
c) complex only in crustaceans and insects; +
d) complex in many crustaceans and arachnids.

52. The male gametophyte in the pine reproduction cycle is formed after:
a) 2 divisions;
b) 4 divisions; +
c) 8 divisions;
d) 16 divisions.

53. The final linden bud on the shoot is:
a) apical;
b) lateral; +
c) can be a subordinate clause;
d) sleeping.

54. The signal sequence of amino acids required for the transport of proteins into chloroplasts is located:
a) at the N-terminus; +
b) at the C-terminus;
c) in the middle of the chain;
d) different for different proteins.

55. Centrioles double into:
a) G 1 phase;
b) S-phase; +
c) G 2 phase;
d) mitosis.

56. Of the following connections, the least rich in energy:
a) the bond of the first phosphate with ribose in ATP; +
b) the connection of an amino acid with tRNA in aminoacyl-tRNA;
c) the connection of phosphate with creatine in creatine phosphate;
d) the bond of acetyl to CoA in acetyl-CoA.

57. The phenomenon of heterosis is usually observed when:
a) inbreeding;
b) distant hybridization; +
c) creating genetically pure lines;
d) self-pollination.

Task 2. The task includes 25 questions, with several answer options (from 0 to 5). Place "+" signs next to the indices of the selected answers. In case of corrections, the “+” sign must be duplicated.

Furrows and convolutions are characteristic of:
a) diencephalon;
b) medulla oblongata;
c) cerebral hemispheres; +
d) cerebellum; +
e) midbrain.
In the human body, proteins can be directly converted into:
a) nucleic acids;
b) starch;
c) fats; +
d) carbohydrates; +
e) carbon dioxide and water.
The middle ear contains:
a) hammer; +
b) auditory (Eustachian) tube; +
c) semicircular canals;
d) external auditory canal;
d) stirrup. +
Conditioned reflexes are:
a) species;
b) individual; +
c) permanent;
d) both permanent and temporary; +
d) hereditary.

5. The centers of origin of certain cultivated plants correspond to specific land regions of the Earth. This is because these places:
a) were most optimal for their growth and development;
b) they were subject to serious natural disasters, which contributed to their preservation;
c) geochemical anomalies with the presence of certain mutagenic factors;
d) were free from specific pests and diseases;
e) were the centers of ancient civilizations, where the primary selection and reproduction of the most productive varieties of plants took place. +

6. One population of animals is characterized by:
a) free crossing of individuals; +
b) the possibility of meeting individuals of different sexes; +
c) similarity in genotype;
d) similar living conditions; +
e) balanced polymorphism. +

7. The evolution of organisms leads to:
a) natural selection;
b) diversity of species; +
c) adaptation to living conditions; +
d) mandatory promotion of the organization;
d) the occurrence of mutations.

8. The cell surface complex includes:
a) plasmalemma; +
b) glycocalyx; +
c) cortical layer of cytoplasm; +
d) matrix;
e) cytosol.

9. Lipids that make up the cell membranes of Escherichia coli:
a) cholesterol;
b) phosphatidylethanolamine; +
c) cardiolipin; +
d) phosphatidylcholine;
e) sphingomyelin.

Adventitious buds can form during cell division:
a) pericycle; +
b) cambium; +
c) sclerenchyma;
d) parenchyma; +
e) wound meristem. +
Adventitious roots can form during cell division:
a) traffic jams;
b) crusts;
c) phellogen; +
d) phelloderms; +
e) medullary rays. +
Substances synthesized from cholesterol:
a) bile acids; +
b) hyaluronic acid;
c) hydrocortisone; +
d) cholecystokinin;
d) estrone. +
Deoxynucleotide triphosphates are necessary for the process:
a) replication; +
b) transcriptions;
c) broadcasts;
d) dark reparation; +
e) photoreactivation.
The process that results in the transfer of genetic material from one cell to another:
a) transition;
b) transversion;
c) translocation;
d) transduction; +
d) transformation. +
Organelles that absorb oxygen:
a) core;
b) mitochondria; +
c) peroxisomes; +
d) Golgi apparatus;
e) endoplasmic reticulum. +
The inorganic basis of the skeleton of various living organisms can be composed of:
a) CaCO 3; +
b) SrSO 4; +
c) SiO 2; +
d) NaCl;
e) Al 2 O 3.
They are of polysaccharide nature:
a) glucose;
b) cellulose; +
c) hemicellulose; +
d) pectin; +
e) lignin.
Proteins containing heme:
a) myoglobin; +
b) FeS – mitochondrial proteins;
c) cytochromes; +
d) DNA polymerase;
e) myeloperoxidase. +
Which of the factors of evolution were first proposed by Charles Darwin:
a) natural selection; +
b) genetic drift;
c) population waves;
d) isolation;
d) struggle for existence. +
Which of the following characteristics that arose during evolution are examples of idioadaptations:
a) warm-blooded;
b) hair of mammals; +
c) exoskeleton of invertebrates; +
d) external gills of the tadpole;
e) horny beak in birds. +
Which of the following selection methods appeared in the twentieth century:
a) interspecific hybridization;
b) artificial selection;
c) polyploidy; +
d) artificial mutagenesis; +
e) cell hybridization. +

22. Anemophilous plants include:
a) rye, oats; +
b) hazel, dandelion;
c) aspen, linden;
d) nettle, hemp; +
d) birch, alder. +

23. All cartilaginous fish have:
a) conus arteriosus; +
b) swim bladder;
c) spiral valve in the intestine; +
d) five gill slits;
e) internal fertilization. +

24. Representatives of marsupials live:
a) in Australia; +
b) in Africa;
c) in Asia;
d) in North America; +
d) in South America. +

25. The following features are characteristic of amphibians:
a) have only pulmonary breathing;
b) have a bladder;
c) larvae live in water, and adults live on land; +
d) adult individuals are characterized by molting;
d) there is no chest. +

Task 3. A task to determine the correctness of judgments (Place a “+” sign next to the numbers of correct judgments). (25 judgments)

1. Epithelial tissues are divided into two groups: integumentary and glandular. +

2. In the pancreas, some cells produce digestive enzymes, while others produce hormones that affect carbohydrate metabolism in the body.

3. Physiological, called a solution of table salt of 9% concentration. +

4. During prolonged fasting, when the level of glucose in the blood decreases, the glycogen disaccharide present in the liver is broken down.

5. Ammonia, formed during the oxidation of proteins, is converted in the liver into a less toxic substance, urea. +

6. All ferns need water for fertilization. +

7. Under the influence of bacteria, milk turns into kefir. +

8. During the dormant period, the vital processes of the seeds stop.

9. Bryophytes are a dead-end branch of evolution. +

10. Polysaccharides predominate in the main substance of the plant cytoplasm. +

11. Living organisms contain almost all the elements of the periodic table. +

12. Pea tendrils and cucumber tendrils are similar organs. +

13. The disappearance of the tail in frog tadpoles occurs due to the fact that dying cells are digested by lysosomes. +

14. Each natural population is always homogeneous in terms of the genotypes of individuals.

15. All biocenoses necessarily include autotrophic plants.

16. The first higher terrestrial plants were rhyniophytes. +

17. All flagellates are characterized by the presence of a green pigment - chlorophyll.

18. In protozoa, each cell is an independent organism. +

19. The ciliate slipper belongs to the phylum Protozoa.

20. Scallops move in a reactive manner. +

21. Chromosomes are the leading components of the cell in the regulation of all metabolic processes. +

22. Algae spores can be formed by mitosis. +

23. In all higher plants, the sexual process is oogamous. +

24. Fern spores divide meiotically to form a prothallus, the cells of which have a haploid set of chromosomes.

25. Ribosomes are formed by self-assembly. +

27. 10 – 11 grade

28. Task 1:

29. 1–d, 2–b, 3–d, 4–d, 5–a, 6–d, 7–d, 8–b, 9–d, 10–d, 11–c, 12–d, 13–c, 14–b, 15–c, 16–a, 17–a, 18–d, 19–c, 20–d, 21–a, 22–d, 23–d, 24–b, 25– d, 26–g, 27–b, 28–c, 29–g, 30–g, 31–c, 32–a, 33–b, 34–b, 35–b, 36–a, 37–c, 38–b, 39–c, 40–b, 41–b, 42–d, 43–c, 44–b, 45–c, 46–a, 47–c, 48–a, 49–c, 50– c, 51–c, 52–b, 53–b, 54–a, 55–b, 56–a, 57–b, 58–c, 59–b, 60–b.

30. Task 2:

31. 1 – c, d; 2 – c, d; 3 – a, b, d; 4 – b, d; 5 – d; 6 – a, b, d, e; 7 – b, c; 8 – a, b, c; 9 – b, c; 10 – a, b, d, e; 11 – c, d, e; 12 – a, c, d; 13 – a, d; 14 – d, d; 15 – b, c, d; 16 – a, b, c; 17 – b, c, d; 18 – a, c, d; 19 – a, d; 20 – b, c, d; 21 – c, d, e; 22 – a, d, d; 23 – a, c, d; 24 – a, d, d; 25 – v, d.

32. Task 3:

33. Correct judgments – 1, 3, 5, 6, 7, 9, 10, 11, 12, 13, 16, 18, 20, 21, 22, 23, 25.

constructor Create(ax, aY, aR, aColor, aShape_Type)

method Change_color (aColor)

method Resize(aR)

method Change_location (ax, aY)

method Change_shape_type (aShape_type)

End of description.

Parameter aShape_type will receive a value that specifies the drawing method to be attached to the object.

When using delegation, you must ensure that the method header matches the type of pointer used to store the method address.

Container classes.Containers - These are specially organized objects used to store and manage objects of other classes. To implement containers, special container classes are developed. A container class usually includes a set of methods that allow you to perform some operations on either an individual object or a group of objects.

As a rule, complex data structures (various types of lists, dynamic arrays, etc.) are implemented in the form of containers. The developer inherits from the element class a class to which he adds the information fields he needs, and receives the required structure. If necessary, it can inherit the class from the container class, adding its own methods to it (Fig. 1.30).

Rice. 1.30. Building classes based on
container class and element class

A container class typically includes methods for creating, adding, and removing elements. In addition, it must provide element-by-element processing (e.g., searching, sorting). All methods are programmed for element class objects. Methods for adding and removing elements when performing operations often refer to special fields of the element class used to create the structure (for example, for a singly linked list, a field storing the address of the next element).

Methods that implement element-by-element processing must work with data fields defined in descendant classes of the element class.

Element-by-element processing of the implemented structure can be carried out in two ways. The first method - universal - is to use iterators, the second is in the definition of a special method, which contains the address of the processing procedure in the list of parameters.

Theoretically, the iterator should provide the ability to implement cyclic actions of the following type:

<очередной элемент>:=<первый элемент>

cycle-bye<очередной элемент>defined

<выполнить обработку>

<очередной элемент>:=<следующий элемент>

Therefore, it usually consists of three parts: a method that allows you to organize data processing from the first element (obtaining the address of the first element of the structure); a method that organizes the transition to the next element, and a method that allows you to check the end of the data. Access to the next portion of data is carried out through a special pointer to the current portion of data (pointer to an element class object).

Example 1.12 Container class with iterator (List class). Let's develop a container class List that implements a linear singly linked list of objects of the Element class, described as follows:

Class Element:

field Pointer_to_next

End of description.

The List class must include three methods that make up the iterator: method Define_first, which should return a pointer to the first element, method Define_next, which should return a pointer to the next element, and a method End_of_list, which should return "yes" if the list is exhausted.

Class List

implementation

fields Pointer_to_first, Pointer_to_current

interface

method Add_before_first(aElement)

method Delete_last

method Define_first

method Define_next

method End_of_list

End of description.

Then element-by-element processing of the list will be programmed as follows:

Element:= Define_first

cycle-bye not End_of_list

Process an element, possibly overriding its type

Item: = Define _next

When using the second method of element-by-element processing of the implemented structure, the procedure for processing the element is passed in the list of parameters. Such a procedure can be determined if the type of processing is known, for example, the procedure for displaying the values of the object’s information fields. The procedure must be called from a method for each data element. In strongly typed languages, the type of a procedure must be specified in advance, and it is often impossible to predict what additional parameters should be passed to the procedure. In such cases, the first method may be preferable.

Example 1.13 Container class with a procedure for processing all objects (List class). In this case, the List class will be described as follows:

Class List

implementation

fields Pointer_to_first, Pointer_to_current

interface

method Add_before_first(aElement)

method Delete_last

method Execute_for_all (aProcessing_procedure)

End of description.

Accordingly, the type of processing procedure must be described in advance, taking into account the fact that it must receive the address of the element being processed through parameters, for example:

Process_procedure (aElement)

Using polymorphic objects when creating containers allows you to create fairly universal classes.

Parameterized classes.Parameterized class(or sample) is a class definition in which some of the used types of class components are defined through parameters. So everyone template defines a group of classes, which, despite the difference in types, are characterized by the same behavior. It is impossible to redefine a type during program execution: all type specification operations are performed by the compiler (more precisely, by the preprocessor).

100 ml of blood plasma from a healthy person 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 in the form of ions or in a non-ionized state.

Osmotic pressure of blood plasma

Even minor disturbances in 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 salts, proteins, glucose, urea and other substances dissolved in plasma creates osmotic pressure.

The phenomena of osmosis occur wherever there are two solutions of different concentrations, separated by a semi-permeable membrane through which the solvent (water) easily passes, but the molecules of the dissolved substance do not pass through. Under these conditions, the solvent moves towards the solution with a higher solute concentration. One-way diffusion of liquid through a semi-permeable partition is called by osmosis(Fig. 4). The force that causes solvent to move across a semipermeable membrane is osmotic pressure. Using special methods, it was possible to establish that the osmotic pressure of human blood plasma is kept at a constant level and amounts to 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.

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

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. Therefore, when blood cells are placed in solutions with different salt concentrations, and therefore with different osmotic pressure, serious changes occur in the blood cells due to osmotic forces.

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

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

A hypertonic solution (usually a 10% sodium chloride solution) is used in the treatment of purulent wounds. If a bandage with a hypertonic solution is applied to the wound, 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, and dead tissue particles, and as a result, the wound will quickly cleanse 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, intensively begins to penetrate into the cells. Red blood cells swell, their membranes rupture, and the contents enter the solution. Hemolysis is observed. Blood, the red blood cells of which have undergone hemolysis, becomes transparent, or, as they sometimes say, lacquered.

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

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

First, both the subject and the researcher wash their hands thoroughly with soap. Then the subject’s ring (IV) finger of the left hand is wiped with alcohol. The skin of the flesh of this finger is pierced with a sharp and pre-sterilized special needle-feather. When you press on your finger, blood appears near the injection site.

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

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

Experience 4

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

Experience 5

Take another slide. Place a drop of 0.9% NaCl solution on one edge, 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, the size of red blood cells decreases and shrinks, which is easily detected by their characteristic scalloped edge. In an isotonic solution, the edge of red blood cells is smooth.

Despite the fact that different amounts of water and mineral salts may enter the blood, the osmotic pressure of the blood is maintained at a constant level. This is achieved thanks to the activity of the kidneys and 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 capable of maintaining the functioning of the organ it washes 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 if there is an excess of potassium salts.

Solutions that, in 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's and Tyrode's 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, and also as blood substitutes for blood loss.

Blood reaction

Blood plasma not only has 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 environment, use pH value, denoted pH. (The 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 environment is characterized by a pH of more than 7.07. The hydrogen index of human blood at a body temperature of 37°C is 7.36. The active blood reaction is slightly alkaline. Even minor changes in the pH value of the blood disrupt the functioning of the body and threaten its life. At the same time, in the process of life, 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 pH deviations. This function is carried out buffers, found in the blood. These include hemoglobin, acid salts of carbonic acid (bicarbonates), salts of phosphoric acid (phosphates) and blood proteins.

The constancy of the blood reaction 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.

Blood plasma proteins

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