All systems, organs and tissues of the body function due to the production of ATP energy, which, in turn, can be formed in sufficient quantities in the presence of oxygen. How does oxygen get into organs and tissues? It is carried with the help of hemoglobin through the blood vessels that form the microcirculation system or microhemodynamics in the organs.
Circulatory system levels
Conventionally, all blood supply to organs and body systems can be divided into three levels:
- Systemic circulation - formed by large vessels that provide the movement of blood throughout the body.
- Organ circulation - formed by vessels of medium diameter, which provide blood supply to individual organs, depending on their oxygen demand. For example, the brain is supplied with blood very abundantly, as it needs a large amount of energy, and therefore, oxygen.
- Microcirculation - includes the smallest vessels that are in direct contact with cells and tissues.
Microcirculation: what is it?
Microcirculation is the movement of blood through the microscopic, that is, the smallest, part of the vascular bed. There are five types of vessels that are part of it:
- arterioles;
- precapillaries;
- capillaries;
- postcapillaries;
- venules.
Interestingly, not all vessels of this channel function simultaneously. While some of them are actively working (open capillaries), others are in "sleep mode" (closed capillaries).
The regulation of blood movement through the smallest blood vessels is carried out by the contraction of the muscle wall of arteries and arterioles, as well as by the work of special sphincters, which are located in postcapillaries.
Structural features
The microvasculature has a different structure, depending on which organ it is in.
For example, in the kidneys, the capillaries are collected in a glomerulus, which is formed from the bringing artery, and from the glomerulus of capillaries, the efferent artery is formed. Moreover, the diameter of the bringing is twice as large as the carrying. This structure is necessary for the filtration of blood and the formation of primary urine.
And in the liver there are wide capillaries called sinusoids. Both arterial oxygenated and poor venous blood enters into these vessels from the portal vein. Special sinusoids are also present in the bone marrow.
Microcirculation functions
Microcirculation is a very important part of the vascular bed, performing the following functions:
- exchange - the exchange of oxygen and carbon dioxide between blood and cells of internal organs;
- heat exchange;
- draining;
- signaling;
- regulatory;
- participation in the formation of color and consistency of urine.
Pathological conditions
The blood flow in the microvasculature depends on the constancy of the internal environment of the body. Including the normal function of blood vessels the greatest influence is the work of the heart and endocrine glands. However, other internal organs are also influential. Therefore, the state of microcirculation reflects the work of the body as a whole.
Conventionally, all pathological conditions of the vessels of the microvasculature can be divided into three groups:
- changes inside the vessel - a violation of the blood flow inside it with an increase in its viscosity and a violation of the stability of blood cells;
- violation of the integrity of the vessel wall - increased permeability of the vascular wall;
- changes outside the vessel - endocrinological diseases, impaired cardiac activity.
Intravascular changes
Slowing blood flow in the vessels, which can occur both with specific diseases, thrombocytopathies (impaired platelet function) and coagulopathies (impaired blood coagulation), and pathologies that can occur with various diseases of the body. These conditions include red blood cell aggregation and sludge syndrome. In fact, these two processes are successive stages of one phenomenon.
First, a temporary attachment of red blood cells occurs using surface contacts in the form of a column (aggregation of red blood cells). This condition is reversible and usually is short-lived. However, its progression can lead to strong gluing (adhesion) of blood cells, which is already irreversible.
This pathology is called the sludge phenomenon. This leads to a slowdown and complete cessation of blood flow in the vessel. Venules and capillaries are usually clogged. The exchange of oxygen and nutrients stops, which subsequently causes ischemia and tissue necrosis.
Destruction of the vascular wall
Violation of the integrity of the vessel wall can occur both in pathological conditions of the whole organism (acidosis, hypoxia), and with direct damage to the vessel wall by biologically active agents. The role of such agents is mediators of inflammation in vasculitis (inflammation of the vascular wall).
If the damage progresses, leakage (diapedesis) of red blood cells from the blood into the surrounding tissue and the formation of hemorrhages are noted.
Extravascular disorders
Pathological processes in the body can affect the microcirculation vessels in two ways:
- The reaction of tissue basophils, which release biologically active agents and enzymes into the environment that directly affect the vessel and thicken the blood in the vessels.
- Violation of the transport of tissue fluid.
Thus, microcirculation is a complex system that is in constant interaction with the whole organism. It is necessary to know not only the main types of its disorders, but also the methods of diagnosis and treatment of these diseases.
Violation of microhemodynamics: diagnosis
Depending on the affected organ, various methods of instrumental diagnostics can be used, which can indirectly indicate the presence of microcirculation disorders through pathology of the internal organ:
- electrocardiogram, echocardiogram, coronary angiography (myocardium);
- Ultrasound of the vessels of the head and neck, dopplerography, angiography (brain);
- Ultrasound, glomerular filtration rate, excretory urography (kidney);
- Ultrasound, angiography, capillaroscopy, phlebography (lower limbs).
Violation of microhemodynamics: treatment
To improve microcirculation, a group of drugs called angioprotectors is used. These are highly effective drugs that improve blood flow through the vessels and restore the vessel itself. Their main properties are as follows:
- decrease in spasm of arteries;
- ensuring patency of the vessel;
- improvement of rheology (viscosity) of blood;
- strengthening the vascular wall;
- decongestant effect;
- improving metabolism, that is, metabolism, in the vascular wall.
The main drugs that improve microcirculation include the following:
- Troxevasin;
- Detralex
- Trental;
- "Emoxipin";
- "L-lysine escinate."
It can be concluded that, despite their small size and diameter, micro hemodynamic vessels perform a very important function in the body. Therefore, microcirculation is a self-sufficient system of the body, the state of which can and should be given special attention.