The human body is a system with many mechanisms of self-regulation, amazing in its complexity and effectiveness. At the top of this system, hemostasis is rightfully located - an excellent example of a finely tuned mechanism for maintaining the liquid state of the blood. Hemostasis has its own laws, rules and exceptions, which must be understood: it is not just about health, the state of hemostasis is a matter of human life and death.
High Flight Logistics
The human body can be compared with a modern industrial site (as the new high-tech factory complexes are now called). Blood vessels are highways, roads, driveways, and dead ends. Well, blood rightfully plays the role of general contractor for logistics.
Delivery of oxygen and all nutrients on time and precisely to the right addresses to all organs of the human body is the most important “logistic” function of the blood. For its implementation, the blood must be stably 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 occurs with the help of an interesting mechanism for the formation of blood clots - protection against blood loss in violation of the integrity of blood vessels. 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 health and medical forecasts for the future.
The unity of opposites: blood coagulation and anticoagulation
The dynamic balance of opposite functions is the most important factor in hemostasis. This is a manifest requirement for vascular and blood systems, the implementation of which must be monitored in any person without fail. Normally, blood needs liquid - in this case, the transportation of elements through tissues occurs without a hitch. If the tissue ruptures, 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 established, complete order. In the future, this “emergency” thrombus is not needed, it dissolves, the blood is again liquid, the logistics are restored, and the body is back in order.
What function of hemostasis is more important for health - responsible for the liquid state (anticoagulant blood system) or forming protective blood clots (coagulation system)? At first glance, it seems that normally the first function prevails over the second: blood flow without interference is needed, there is no need for thrombosis. In fact, blood coagulation is part of a multifaceted process where the anticoagulation system acts as a regulation of blood coagulation. It is 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 needs to be kept in any situations. To protect this volume, there is a system of thrombosis, but not only. It would be a mistake to think that protection against blood loss is only a coagulation system. This should include the dissolution of the thrombus when it fulfills its function and ceases to be necessary. Hemostasis is a system of functions integrated into each other.
Two coagulation mechanisms
- Vascular-platelet mechanism : the formation of a blood clot starts and works on the principle of dominoes - these are sequential processes where the previous one starts the next. The main characters and performers of this process are small blood cells (platelets) and small-caliber vessels (mainly capillaries). Protection is carried out according to all construction rules: the vessel at the site of damage narrows, platelets swell and change their shape to begin to adhere to the vessel wall (adhesion) and adhere to each other (aggregation). A loose primary thrombus or platelet hemostatic tube is formed.
- Coagulation coagulation mechanism occurs in injuries of larger vessels - these are enzymatic biochemical processes. At its core, this is the conversion of fibrinogen (a water-soluble protein) to fibrin (an insoluble protein), from which a secondary blood clot consists of a blood clot. Fibrin plays the role of a thick reinforcing mesh in it for blood cells that have fallen into it.
Hypocoagulation Syndrome: A Royal Story
Everyone heard about a blood clotting disorder in the form of hemophilia - the patients were very famous. Previously, it was perceived as a disease of royal blood with poor prince Alexei, as in a fairy tale. Hemophilia today is pure hereditary disease with a recessive gene, which is located on the female chromosome of X. Women carry hemophilia, and men suffer from it. Thanks to the British Queen Victoria and her descendants, members of the European royal houses (six women and eleven men in total), the world has a sad and reliable illustration of the transmission of hereditary symptoms of the disease.
Now about the specific mechanism. With 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. For violations in factor IX, hemophilia B. The presence of hemophilia C depends on factor XI. All of the above options relate to the pathology of the first phase of blood clotting disorders - active prothrombinase does not form, which leads to a significant increase coagulation time.
Violations in the second phase of blood coagulation - a failure in the formation of thrombin (decreased 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, 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 - support for microvascular resistance.
- Adhesive-aggregation - the ability to stick together and adhere to the vessel wall at the site of damage.
In clinical blood tests, their number is always in the focus of special attention. The platelet content norm should remain the strongest constant in the human body in any condition, no more and no less. Because thrombocytopenia (the number is below normal) is a lack of blood clots, the absence of spasm of the vessel and, as a result, the slowing down of blood coagulation. Thrombocytopathy is a qualitative change in the cell itself - structural, biochemical. Such changes also lead to impaired platelet function.
Anticoagulation normal
The process of blood coagulation includes the mandatory functioning of a group of unique inhibitors. These proteins are nothing but the anticoagulant system of the blood. Physiology is the dynamic balance of opposing processes. Physiological anticoagulants are the main fighters with thrombosis. These special-purpose proteins are divided into three groups with names that speak for themselves:
- Antithromboplastins.
- Antithrombin.
- Antifibrins.
The proteins of the first two groups perform an inhibitory function: they inhibit the adhesion and aggregation of platelets, slow down the formation of fibrin from fibrinogen, etc. The proteins of the third group are special, they perform a completely different job - they split the already formed fibrin (the reinforcing mesh of a blood clot) into so-called fibrin degradation products - PDF.
In the future, a blood clot, already without strengthening fibrin filaments, contracts (a process called retraction) and dissolves, that is, ends its short life with a complete lysis. The cleavage of fibrin filaments followed by dissolution of the thrombus is such an important process that in many sources the cleavage of fibrin with the destruction of an already formed thrombus and the inhibition of thrombus formation are described as separate processes: the fibrinolytic and anticoagulant blood systems. Thus, it will be logical to adopt and adopt the three functional components of hemostasis. These include coagulation, anticoagulation and fibrinolytic blood systems.
When blood clots are harmful: pathological thrombosis
No need to confuse thrombosis and blood coagulation. The latter can be an independent process even outside the body. Thrombosis is the phased formation of a blood clot with the formation of fibrin and impaired blood circulation. The causes of thrombosis are many: 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 of:
- hypercoagulation (lack of anticoagulant factors);
- increase blood viscosity;
- damage to the walls of the vessel (immediate adhesion - gluing of platelets);
- slowing blood flow.
Vascular accidents and thrombosis
Thrombosis is an extremely common and serious pathology. It happens of such types:
- Venous or arterial.
- Acute or chronic.
- Atherothrombosis.
Atherothrombosis can be called real vascular catastrophes. These are heart attacks and brain strokes due to clogged arteries with sclerotic plaques. A huge danger is the risk of a blood clot breaking off with a blockage in the arteries of the lungs or heart, which leads to instant death.
In the treatment of such pathologies, the goal is one - to reduce, that is, regulation of blood coagulation to normal. In such cases, anticoagulant drugs are used, a kind of artificial anticoagulant system. One way or another, increased blood coagulation and pathological formation of blood clots is treated using processes that are opposite in their effect.
Anticoagulation in pathologies
The role of the anticoagulant system of blood is difficult to overestimate. First of all, this is the function of fibrinolysis - splitting a fibrin clot to support the liquid state of the blood and the free lumen of the vessels. The main component is fibrinolysin (plasmin), which destroys fibrin filaments and turns them into PDF (products of fibrin degradation), followed by compression and dissolution of the thrombus.
Anticoagulant blood system: briefly
The effectiveness of hemostasis depends on interrelated factors, the effect of which should be considered only together:
- The condition of the walls of blood vessels.
- A sufficient number of platelets and their high-quality.
- The state of plasma enzymes, especially fibrinolytic.
If we talk about the importance and functional criticality for human health and life, then there is an unconditional leader among these factors: biochemistry of the anticoagulant blood system is a model for the treatment of numerous serious diseases involving the formation of pathological blood clots. The effect of modern drugs is based on these principles. The physiology of the anticoagulation system of the blood is such that it lags behind the coagulation system and is depleted faster: anticoagulants are consumed faster than they are produced. Therefore, the main method of treating thrombosis is to fill in the lack of anticoagulants.