The human body is an amazingly complex and efficient system with many mechanisms of self-regulation. At the top of this system rightfully sits hemostasis, a magnificent example of a finely tuned mechanism for keeping the blood fluid. Hemostasis has its own laws, rules and exceptions that you need to understand: it is not just about he alth, the state of hemostasis is a matter of life and death of a person.
High flight logistics
The human body can be compared to a modern industrial site (as new high-tech factory complexes are now called). Blood vessels are highways, roadways, driveways and dead ends. Well, blood rightfully plays the role of a general logistics contractor.
Delivery of oxygen and all nutrients on time and exactly as neededaddresses to all organs of the human body - the most important "logistic" function of blood. To perform this, the blood must be stable in a liquid state. This is not the only criterion for a normally functioning blood system. The second, no less important requirement is the preservation of the volume of circulating blood. This happens with the help of an interesting mechanism for the formation of blood clots - protection from blood loss in violation of the integrity of blood vessels. The regulation of blood consistency depending on the state of the body is called hemostasis. It includes many factors and mechanisms that determine both the current state of human he alth and medical forecasts for the future.
Unity of opposites: blood coagulation and anticoagulation systems
Dynamic balance of opposite functions is the most important factor of hemostasis. This is a manifest requirement for the vascular and blood systems, the fulfillment of which must be monitored in any person without fail. Normally, blood is needed liquid - in this case, the transportation of elements through the tissues occurs without a hitch. If, however, there is a rupture in the tissue, and the person begins to bleed, the blood turns into jelly in the form of a blood clot - the wound is “sealed”, the protection is installed, everything is in order. In the future, this "emergency" thrombus is not needed, it dissolves, the blood is again liquid, logistics is restored, and the body is in order again.
Which function of hemostasis is more important for he alth - responsible for the liquid state (blood anticoagulation system) orforming protective thrombi (clotting system)? At first glance, it seems that normally the first function prevails over the second: blood flow is needed without interference, there is no need for thrombosis. In fact, blood clotting is part of a multifaceted process where the anticoagulant system acts as a regulator of blood clotting. It's time to start detailing the processes of hemostasis.
When blood clots are needed: protection against blood loss
The blood volume of an adult is approximately five liters. This volume must be maintained in all situations. To protect this volume, there is a thrombogenesis system, but not only. It would be a mistake to think that protection against blood loss is only a coagulation system. This should also include the dissolution of a thrombus when it fulfills its function and ceases to be needed. Hemostasis is a system of functions integrated into each other.
Two mechanisms of blood clotting
- Vascular-platelet mechanism: the formation of a thrombus starts and works according to the domino principle - these are sequential processes, where the previous one starts the next one. The main characters and executors of this process are small blood cells (platelets) and small vessels (mainly capillaries). Protection is carried out according to all the rules of construction: the vessel narrows at the site of damage, platelets swell and change their shape in order to start sticking to the vessel wall (adhesion) and stick together (aggregation). A loose primary thrombus, or platelet hemostatic plug, forms.
- Coagulation clotting mechanism occurs in traumalarger vessels are enzymatic biochemical processes. At its core, this is the conversion of fibrinogen (a water-soluble protein) into fibrin (an insoluble protein), of which the secondary thrombus consists - a blood clot. Fibrin plays the role of a thick reinforcing mesh for the blood cells that have fallen into it.
Hypocoagulation syndrome: a royal story
Everyone heard about the blood clotting disorder in the form of hemophilia - the patients were already very famous. Previously, it was perceived as a disease of royal blood with poor Tsarevich Alexei, as in a fairy tale. Hemophilia today is a pure hereditary disease with a recessive gene that is located on the female X chromosome. Women suffer from hemophilia, and men suffer from it. Thanks to the British Queen Victoria and her descendants, members of European royal houses (six women and eleven men in total), the world has a sad and reliable illustration of the transmission of hereditary signs of the disease.
Now about the specific mechanism. In hemophilia, the synthesis of platelets and other components of the kallikrein-kinin system is impaired. With a gene mutation of factor VIII, they speak of hemophilia A. With disorders in factor IX, hemophilia B. The presence of hemophilia C depends on factor XI. All of the above options refer to the pathology of the first phase of blood clotting disorders - active prothrombinase is not formed, which leads to a significant clotting time.
Disturbances in the second phase of blood coagulation - failure of thrombin formation(decrease in the synthesis of prothrombin and other related components). The third phase leads to an increase in the main "dissolving" process - fibrinolysis.
Word platelet
Platelets are the most important and interesting blood cells with a very unpresentable appearance: irregularly variable shape, colorless. There is no nucleus, they do not live long - only 10 days. They are responsible for the coagulation and anticoagulation systems of the blood. Platelets have the most important functions:
- Angiotrophic – supporting microvascular resistance.
- Adhesive-aggregation - the ability to stick together with each other and stick to the vessel wall at the site of damage.
In clinical blood tests, their number is always the focus of special attention. The platelet count should remain the strongest constant in the human body in any condition, no more and no less. Because thrombocytopenia (a number below the norm) is a lack of blood clots, the absence of vessel spasm and, as a result, a slowdown in blood clotting. Thrombocytopathy is a qualitative change in the cell itself - structural, biochemical. These changes also lead to impaired platelet function.
Anticoagulation normal
The process of blood coagulation includes the obligatory functioning of a group of unique inhibitors. These proteins are nothing more than an anticoagulant blood system. Physiology lies in the dynamic balance of opposing processes. Physiological anticoagulants are the mainthrombosis fighters. These special purpose proteins are divided into three groups with names that speak for themselves:
- Antithrombotic plates.
- Antithrombins.
- Antifibrins.
Proteins of the first two groups perform an inhibitory function: they inhibit adhesion and aggregation of platelets, slow down the formation of fibrin from fibrinogen, etc. Proteins of the third group are special, they perform a completely different job - they break down the already formed fibrin (reinforcing mesh of the blood clot) to the so-called fibrin degradation products - PDF.
In the future, the thrombus, already without reinforcing fibrin threads, shrinks (the process is called retraction) and dissolves, that is, it ends its short life with complete lysis. The splitting of fibrin filaments with subsequent dissolution of a thrombus is such an important process that in many sources fibrin splitting with the destruction of an already formed thrombus and inhibition of thrombus formation are described as separate processes: fibrinolytic and anticoagulant blood systems. Thus, it would be logical to accept and adopt three functional components of hemostasis. These include the coagulation, anticoagulation, and fibrinolytic systems of the blood.
When blood clots are harmful: pathological thrombosis
Don't confuse thrombosis with blood clotting. The latter can be an independent process even outside the body. Thrombosis - the gradual formation of a blood clot with the formation of fibrin and a violationblood circulation. There are many reasons for the occurrence of thrombosis: tumors, infections, diseases of the cardiovascular system, etc. But for all possible reasons, the main conditions for the birth of pathological blood clots depend on changes in the anticoagulant blood system in the form:
- hypercoagulation (lack of anticoagulant factors);
- increased blood viscosity;
- damage to the walls of the vessel (immediate adhesion - adhesion of platelets);
- slow blood flow.
Vascular accidents and thrombosis
Thrombosis is an extremely common and serious pathology. It comes in the following forms:
- Venous or arterial.
- Acute or chronic.
- Atherothrombosis.
Atherothrombosis can be called real vascular disasters. These are heart attacks of organs and strokes of the brain due to blockage of the artery by sclerotic plaques. A huge danger is the risk of a blood clot breaking off with blockage of the arteries of the lungs or heart, which leads to instant death.
In the treatment of such pathologies, the goal is the same - reduction, that is, regulation of blood coagulation to normal. In such cases, anticoagulant drugs are used, a kind of artificial anticoagulant system. Either way, increased blood clotting and pathological clotting are treated with opposite processes.
Anticoagulation in pathologies
The role of the anticoagulant system of blood is difficultoverestimate. First of all, this is the function of fibrinolysis - the splitting of a fibrin clot to maintain the liquid state of the blood and the free lumen of the vessels. The main component is fibrinolysin (plasmin), which destroys fibrin threads and turns them into FDP (fibrin degradation products) with subsequent compression and dissolution of the thrombus.
Anti-coagulant blood system in brief
The effectiveness of hemostasis depends on interrelated factors, the action of which must be considered only together:
- The condition of the walls of blood vessels.
- Sufficient number of platelets and their quality usefulness.
- The state of plasma enzymes, especially fibrinolytic ones.
If we talk about the importance and functional criticality for human he alth and life, then among these factors there is an undisputed leader: the biochemistry of the anticoagulant blood system is a model for the treatment of numerous serious diseases, consisting in the formation of pathological blood clots. The action of modern medicines is based on these principles. The physiology of the anticoagulant blood system is such that it lags behind the coagulation system and depletes faster: anticoagulants are consumed faster than they are produced. Therefore, the main method of treating thrombosis is to compensate for the lack of anticoagulants.
