What substances are needed for blood clotting. Blood clotting. What prevents blood from clotting

One of the most important processes in our body is blood clotting. Its scheme will be described below (images are also provided for clarity). And since this is a complex process, it is worth considering it in detail.

How is it going?

So, the indicated process is responsible for stopping the bleeding that occurred due to damage to one or another component vascular system organism.

If to speak plain language, three phases can be distinguished. The first is activation. After damage to the vessel, successive reactions begin to occur, which ultimately lead to the formation of the so-called prothrombinase. It is a complex complex consisting of V and X. It is formed on the phospholipid surface of platelet membranes.

The second phase is coagulation. At this stage, fibrin is formed from fibrinogen - a high-molecular protein, which is the basis of blood clots, the occurrence of which implies blood clotting. The diagram below illustrates this phase.

And finally, the third stage. It implies the formation of a fibrin clot, which has a dense structure. By the way, it is by washing and drying it that it is possible to obtain a “material”, which is then used to prepare sterile films and sponges to stop bleeding caused by rupture of small vessels during surgical operations.

About reactions

The scheme was briefly described above, by the way, it was developed back in 1905 by a coagulologist named Paul Oskar Morawitz. And it has not lost its relevance to this day.

But since 1905, much has changed in understanding blood clotting as a complex process. With progress, of course. Scientists have been able to discover dozens of new reactions and proteins that are involved in this process. And now the cascade pattern of blood coagulation is more common. Thanks to her, the perception and understanding of such a complex process becomes a little more understandable.

As you can see in the image below, what is happening is literally “broken into bricks”. It takes into account the internal and external system - blood and tissue. Each is characterized by a certain deformation that occurs as a result of damage. In the blood system, damage is done to the vascular walls, collagen, proteases (splitting enzymes) and catecholamines (mediator molecules). In the tissue, cell damage is observed, as a result of which thromboplastin is released from them. Which is the most important stimulator of the coagulation process (otherwise called coagulation). It goes directly into the blood. This is his "way", but it has a protective character. After all, it is thromboplastin that starts the clotting process. After its release into the blood, the implementation of the above three phases begins.

Time

So, what exactly is blood coagulation, the scheme helped to understand. Now I would like to talk a little about time.

The whole process takes a maximum of 7 minutes. The first phase lasts from five to seven. During this time, prothrombin is formed. This substance is a complex type of protein structure responsible for the course of the coagulation process and the ability of blood to thicken. Which is used by our body in order to form a blood clot. It clogs the damaged area, so that the bleeding stops. All this takes 5-7 minutes. The second and third stages happen much faster. For 2-5 seconds. Because these phases of blood clotting (diagram provided above) affect processes that occur everywhere. And that means at the site of damage directly.

Prothrombin, in turn, is formed in the liver. And it takes time to synthesize it. How quickly a sufficient amount of prothrombin is produced depends on the amount of vitamin K contained in the body. If it is not enough, the bleeding will be difficult to stop. And this is a serious problem. Since the lack of vitamin K indicates a violation of the synthesis of prothrombin. And this is a disease that needs to be treated.

Synthesis stabilization

Well, general scheme blood clotting is clear - now we should pay a little attention to the topic of what needs to be done to restore the required amount of vitamin K in the body.

For starters, eat right. Most a large number of Vitamin K is found in green tea - 959 mcg per 100 g! Three times more, by the way, than in black. That is why it is worth drinking it actively. Do not neglect vegetables - spinach, white cabbage, tomatoes, green peas, onions.

Vitamin K is also found in meat, but not in everything - only in veal, beef liver, lamb. But least of all it is in the composition of garlic, raisins, milk, apples and grapes.

However, if the situation is serious, then it will be difficult to help with just a variety of menus. Usually, doctors strongly recommend combining your diet with the drugs they have prescribed. Treatment should not be delayed. It is necessary to start it as soon as possible in order to normalize the mechanism of blood coagulation. The treatment regimen is prescribed directly by the doctor, and he is also obliged to warn what can happen if the recommendations are neglected. And the consequences can be liver dysfunction, thrombohemorrhagic syndrome, tumor diseases and damage to bone marrow stem cells.

Schmidt's scheme

At the end of the 19th century, there lived a famous physiologist and doctor of medical sciences. His name was Alexander Alexandrovich Schmidt. He lived for 63 years, and devoted most of his time to the study of problems of hematology. But especially carefully he studied the topic of blood coagulation. He managed to establish the enzymatic nature of this process, as a result of which the scientist proposed a theoretical explanation for it. Which clearly depicts the scheme of blood coagulation provided below.

First of all, the damaged vessel is reduced. Then, at the site of the defect, a loose, primary platelet plug is formed. Then it gets stronger. As a result, a red blood clot (otherwise referred to as a blood clot) is formed. After which it partially or completely dissolves.

During this process, certain blood clotting factors are manifested. The scheme, in its expanded version, also displays them. They are denoted by Arabic numerals. And there are 13 of them in total. And you need to tell about each.

Factors

A complete blood coagulation scheme is impossible without listing them. Well, it's worth starting from the first.

Factor I is a colorless protein called fibrinogen. Synthesized in the liver, dissolved in plasma. Factor II - prothrombin, which has already been mentioned above. Its unique ability lies in the binding of calcium ions. And it is precisely after the breakdown of this substance that the coagulation enzyme is formed.

Factor III is a lipoprotein, tissue thromboplastin. It is commonly called the transport of phospholipids, cholesterol, and also triacylglycerides.

The next factor, IV, are Ca2+ ions. The ones that bind under the influence of a colorless protein. They are involved in many complex processes, in addition to clotting, in the secretion of neurotransmitters, for example.

Factor V is a globulin. Which is also formed in the liver. It is necessary for the binding of corticosteroids (hormonal substances) and their transport. Factor VI existed for a certain time, but then it was decided to remove it from the classification. Since scientists have found out - it includes factor V.

But the classification did not change. Therefore, V is followed by factor VII. Includes proconvertin, with the participation of which tissue prothrombinase is formed (first phase).

Factor VIII is a protein expressed in a single chain. It is known as antihemophilic globulin A. It is because of its lack that such a rare hereditary disease as hemophilia develops. Factor IX is "related" to the previously mentioned. Since it is antihemophilic globulin B. Factor X is directly a globulin synthesized in the liver.

And finally, the last three points. These are the Rosenthal, Hageman factor and fibrin stabilization. Together, they affect the formation of intermolecular bonds and the normal functioning of such a process as blood coagulation.

Schmidt's scheme includes all these factors. And it is enough to get acquainted with them briefly in order to understand how the described process is complex and ambiguous.

Anti-clotting system

This concept also needs to be noted attention. The blood coagulation system was described above - the diagram also clearly demonstrates the course of this process. But the so-called "anti-coagulation" also has a place to be.

To begin with, I would like to note that in the course of evolution, scientists solved two completely opposite tasks. They tried to find out - how does the body manage to prevent blood from flowing out of damaged vessels, and at the same time keep it in a liquid state in its entirety? Well, the solution to the second problem was the discovery of an anticoagulant system.

It is a specific set of plasma proteins that are able to slow down chemical reactions. That is to inhibit.

And antithrombin III is involved in this process. Its main function is to control the work of some factors that include the scheme of the blood coagulation process. It is important to clarify: it does not regulate the formation of a blood clot, but eliminates unnecessary enzymes that have entered the bloodstream from the place where it is formed. What is it for? To prevent the spread of clotting to areas of the bloodstream that have been damaged.

obstructing element

Talking about what the blood coagulation system is (the scheme of which is presented above), one cannot but note such a substance as heparin. It is a sulfur-containing acidic glycosaminoglycan (one of the types of polysaccharides).

It is a direct anticoagulant. A substance that contributes to the inhibition of the activity of the coagulation system. It is heparin that prevents the formation of blood clots. How does this happen? Heparin simply reduces the activity of thrombin in the blood. However, it is a natural substance. And it is beneficial. If this anticoagulant is introduced into the body, then it is possible to contribute to the activation of antithrombin III and lipoprotein lipase (enzymes that break down triglycerides - the main sources of energy for cells).

Now, heparin is often used to treat thrombotic conditions. Only one of its molecules can activate a large amount of antithrombin III. Accordingly, heparin can be considered a catalyst - since the action in this case is really similar to the effect caused by them.

There are other substances with the same effect contained in Take, for example, α2-macroglobulin. It contributes to the splitting of the thrombus, affects the process of fibrinolysis, performs the function of transport for 2-valent ions and some proteins. It also inhibits substances involved in the clotting process.

Observed changes

There is one more nuance that the traditional blood coagulation scheme does not demonstrate. The physiology of our body is such that many processes involve not only chemical changes. But also physical. If we could observe clotting with the naked eye, we would see that the shape of the platelets changes in the process. They turn into rounded cells with characteristic spiny processes, which are necessary for the intensive implementation of aggregation - the combination of elements into a single whole.

But that is not all. During the clotting process, various substances are released from platelets - catecholamines, serotonin, etc. Because of this, the lumen of the vessels that have been damaged narrows. What causes functional ischemia. The blood supply to the injured area is reduced. And, accordingly, the outpouring is also gradually reduced to a minimum. This gives the platelets the opportunity to cover the damaged areas. They, due to their spiny processes, seem to be “attached” to the edges of the collagen fibers that are located at the edges of the wound. This ends the first, longest activation phase. It ends with the formation of thrombin. This is followed by a few more seconds of the phase of coagulation and retraction. And the last stage is the restoration of normal blood circulation. And it has great importance. Since the full healing of the wound is impossible without a good blood supply.

Good to know

Well, something like this in words and looks like a simplified scheme of blood coagulation. However, there are a few more nuances that I would like to note with attention.

Hemophilia. It has already been mentioned above. This is very dangerous disease. Any hemorrhage by a person suffering from it is experienced hard. The disease is hereditary, develops due to defects in the proteins involved in the coagulation process. It can be detected quite simply - with the slightest cut, a person will lose a lot of blood. And it will take a lot of time to stop it. And with special severe forms hemorrhage can begin for no reason. People with hemophilia can become disabled early. Since frequent hemorrhages in muscle tissue (usual hematomas) and in joints are not uncommon. Is it curable? With difficulties. A person should literally treat his body as a fragile vessel, and always be careful. If bleeding occurs, donated fresh blood containing factor XVIII should be urgently administered.

Men usually suffer from this disease. And women act as carriers of the hemophilia gene. It's interesting that british queen Victoria was. One of her sons contracted the disease. The other two are unknown. Since then, hemophilia, by the way, is often called the royal disease.

But there are also reverse cases. Meaning If it is observed, then a person also needs to be no less careful. Increased clotting indicates high risk formation of intravascular thrombi. Which clog entire vessels. Often the consequence can be thrombophlebitis, accompanied by inflammation of the venous walls. But this defect is easier to treat. Often, by the way, it is acquired.

It's amazing how much happens in the human body when he cuts himself with a piece of paper. You can talk for a long time about the features of blood, its coagulation and the processes that accompany it. But all the most interesting information, as well as diagrams that clearly demonstrate it, are provided above. The rest, if desired, can be viewed individually.

As long as blood flows through intact blood vessels, it remains liquid. But as soon as the vessel is injured, a clot forms quite quickly. A blood clot (thrombus), like a cork, clogs the wound, the bleeding stops, and the wound gradually heals. If the blood did not clot, then a person could die from the smallest scratch.

Human blood released from blood vessel, coagulates within 3-4 minutes.

Blood coagulation is an important protective reaction of the body, preventing blood loss and thus maintaining a constant volume of circulating blood.

Blood coagulation is based on a change in the physicochemical state of the protein dissolved in blood plasma fibrinogen. Fibrinogen becomes insoluble during blood clotting fibrin. Fibrin falls out in the form of thin threads. Fibrin threads form a dense fine-mesh network in which formed elements are retained. A clot or thrombus forms. Gradually, the blood clot thickens. Condensing, it pulls together the edges of the wound and this contributes to its healing. When the clot is compacted, a transparent yellowish liquid is squeezed out of it - serum. Serum is blood plasma from which the protein fibrinogen has been removed. In the compaction of the clot, an important role belongs to platelets, which contain a substance that contributes to the compression of the clot.

Blood clotting is a complex process. It involves calcium salts in the blood plasma. A prerequisite for blood clotting is the destruction of platelets (platelets).

According to modern concepts, the transformation of fibrinogen protein dissolved in blood plasma into insoluble fibrin protein occurs under the influence of the enzyme thrombin. There is an inactive form of thrombin in the blood - prothrombin which is produced in the liver. Prothrombin is converted to active thrombin under the influence of thromboplastin in the presence of calcium salts. There are calcium salts in the blood plasma, but there is no thromboplastin in the circulating blood. It is formed when platelets are destroyed or when other cells in the body are damaged. Education thromboplastin also a complex process. In addition to platelets, some other plasma proteins also take part in the formation of thromboplastin. The absence of certain proteins in the blood dramatically affects the process of blood coagulation. If one of the globulins (large molecular proteins) is absent in the blood plasma, then hemophilia disease, or bleeding, occurs. In people with hemophilia, blood clotting is sharply reduced. Even a small wound can cause them to bleed dangerously.

Men are more likely to suffer from hemophilia. This disease is inherited.

The process of blood clotting is regulated nervous system and glandular hormones internal secretion. It can speed up and slow down.

If during bleeding it is important that the blood coagulates, then it is equally important that it, circulating in circulatory system, remained liquid, did not coagulate.

The body produces substances that prevent blood clotting. Such properties are heparin found in lung and liver cells. protein found in serum fibrinolysin- an enzyme that dissolves the formed fibrin. In the blood, thus, there are two systems at the same time: coagulation and anticoagulation. With a certain balance of these systems, the blood inside the vessels does not coagulate. With injuries and some diseases, the balance is disturbed, which leads to blood clotting. Inhibit blood clotting salts of citric and oxalic acids, precipitating calcium salts necessary for clotting. in the cervical glands medicinal leeches formed hirudin, which has a powerful anticoagulant effect. Anticoagulants are widely used in medicine.

There are three main stages of hemocoagulation:

1. formation of blood thromboplastin and tissue thromboplastin;

2. formation of thrombin;

3. formation of a fibrin clot.

There are 2 mechanisms of hemocoagulation: internal clotting mechanism(it involves factors that are inside the vascular bed) and extrinsic clotting mechanism(in addition to intravascular factors, external factors also participate in it).

Internal mechanism of blood coagulation (contact)

The internal mechanism of hemocoagulation is triggered when the vascular endothelium is damaged (for example, in atherosclerosis, under the action of high doses catecholamines) in which there is collagen, phospholipids. Factor XII (trigger factor) joins the altered area of the endothelium. Interacting with the altered endothelium, it undergoes conformational structural changes and becomes a very potent active proteolytic enzyme. XIIa factor simultaneously participates in the coagulation system, anti-coagulation system, kinin system:

activates the blood coagulation system;
activates the anticoagulant system;
activates platelet aggregation;
activates the kinin system;

1 stage internal mechanism of blood clotting formation of complete blood thromboplastin.

XII factor, in contact with the damaged endothelium, passes into active XII. XIIa activates prekallikrein (XIY), which activates kininogen (XY). Kinins, in turn, increase the activity of factor XII.

Factor XII activates factor XI, which then activates factor IX (f. Christmas). Factor IXa interacts with factor YIII and calcium ions. As a result, a complex is formed, including the enzyme, coenzyme, calcium ions (f.IXa, f.YIII, Ca 2+). This complex activates factor X with the participation of platelet factor P 3 . As a result, a active blood thromboplastin, including f.Xa, f.Y, Ca 2+ and R 3 .

P 3 - is a fragment of platelet membranes, contains lipoproteins, rich in phospholipids.

Stage 2 - the formation of thrombin.

Active blood thromboplastin triggers the 2nd stage of blood coagulation, activating the transition of prothrombin to thrombin (f. II → f. II a). Thrombin activates the external and internal mechanisms of hemocoagulation, as well as the anticoagulant system, platelet aggregation and the release of platelet factors.

Active thrombin starts the 3rd stage of blood coagulation.

3 stage lies in formation of insoluble fibrin(I factor). Under the influence of thrombin, soluble fibrinogen sequentially passes into fibrin monomer, and then into insoluble fibrin polymer.

Fibrinogen is a water-soluble protein consisting of 6 polypeptide chains, including 3 domains. Under the action of thrombin, peptides A and B are cleaved from fibrinogen, and aggregation sites are formed in it. Fibrin strands are connected first into linear chains, and then covalent interchain crosslinks are formed. Factor XIIIa (fibrin-stabilizing) is involved in their formation, which is activated by thrombin. Under the action of factor XIIIa, which is a transamidinase enzyme, bonds between glutamine and lysine appear in fibrin during its polymerization.

In the future, under the influence of platelet factors, contraction of fibrin filaments (retraction), resulting in a compaction of the clot and the release of serum.

Consequently, blood serum differs in its composition from plasma by the absence of fibrinogen and some other substances involved in the process of blood coagulation.

Blood from which fibrin has been removed is called defibrinated. It consists of shaped elements and serum.

Hemocoagulation inhibitors interfere with intravascular coagulation or slow down this process. The most potent inhibitor of blood clotting is heparin.

Heparin- natural anticoagulant a wide range action, is formed in labrocytes (mast cells) and basophilic leukocytes. Heparin inhibits all phases of the blood coagulation process.

Blood, leaving the vascular bed, coagulates and thereby limits blood loss. In the vascular bed, the blood is liquid, so it performs all its functions. This is due to three main reasons:

· factors of the blood coagulation system in the vascular bed are in an inactive state;

The presence in the blood, formed elements and tissues of anticoagulants (inhibitors) that prevent the formation of thrombin;

· the presence of intact (intact) vascular endothelium.

The antipode of the hemocoagulation system is the fibrinolytic system, the main function of which is the splitting of fibrin strands into soluble components. It consists of the enzyme plasmin (fibrinolysin), which is in the blood in an inactive state, in the form of plasminogen (profibrinolysin), activators and inhibitors of fibrinolysis. Activators stimulate the conversion of plasminogen to plasmin, inhibitors inhibit this process.

The process of fibrinolysis must be considered in conjunction with the process of blood coagulation. A change in the functional state of one of them is accompanied by compensatory shifts in the activity of the other. Violation of functional relationships between the systems of hemocoagulation and fibrinolysis can lead to severe pathological conditions organism, or to increased bleeding, or to intravascular thrombosis.

Factors that speed up the process of blood clotting include: 1) heat, since blood clotting is an enzymatic process; 2) calcium ions, as they are involved in all phases of hemocoagulation; 3) contact of blood with a rough surface (vascular damage by atherosclerosis, vascular sutures in surgery); 4) mechanical influences (pressure, fragmentation of tissues, shaking of containers with blood, as this leads to the destruction of blood cells and the release of factors involved in blood clotting).

Factors that slow down and prevent hemocoagulation include: 1) lowering the temperature; 2) sodium citrate and oxalate (bind calcium ions); 3) heparin (suppresses all phases of hemocoagulation); 4) smooth surface (smooth seams when suturing vessels in surgery, silicone coating or waxing of cannulas and containers for donated blood).

How is blood coagulation carried out?

Blood clotting is a complex process. It involves 13 factors present in the blood plasma, as well as substances released during the destruction of platelets and tissue damage.

Blood clotting occurs in several stages:

1. In the first stage, thromboplastin precursor is isolated from damaged platelets and tissue cells. This substance, interacting with blood plasma proteins, is converted into active thromboplastin. For the formation of thromboplastin, the presence of Ca 2+ is necessary, as well as plasma proteins, in particular the anti-hemolytic factor. If there is no anti-hemolytic factor in the blood, the blood does not coagulate. This condition is called hemophilia.

2. In the second stage, the blood plasma protein prothrombin, with the participation of thromboplastin, is converted into the active enzyme thrombin.

3. Under the action of thrombin, the plasma-soluble protein fibrinogen is converted into insoluble fibrin. Fibrin forms a clot consisting of plexuses of the finest fibers. Blood cells settle in their network, forming a blood clot.

Blood clotting protects the body from blood loss.

How is blood coagulation carried out?

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