Blood is movement through vessels. Main artery: definition, purpose, structure, normal operation and pathological changes, methods of diagnosing and treating them Uzdg mag in children

The amount of blood in a person is 1/12 of a person's body weight. This blood is distributed unequally in the vascular system. Approximately 60-65% is in the venous system, 10% is in the heart, 10% in the aorta and large arteries, 2% in arterioles and 5% in capillaries. At rest, approximately half of the blood is in blood stores.

In general, all vessels perform different tasks; depending on this, all vessels are divided into several types.

1. Main vessels- this is the aorta, pulmonary arteries and their large branches. These are vessels elastic type. Function main vessels is to accumulate, store the energy of heart contraction and ensure continuous blood flow throughout the vascular system.

The importance of the elasticity of large arteries for the continuous movement of blood can be explained by the following experiment. Water is released from the tank in an intermittent stream through two tubes: rubber and glass, which end in capillaries. At the same time, water flows out of the glass tube in spurts, and from the rubber tube - continuously and in large quantities.

So in the body during systole, the kinetic energy of blood movement is spent on stretching the aorta and large arteries, since the arterioles resist blood flow. As a result, less blood passes through the arterioles into the capillaries during systole than it came from the heart. Therefore, large vessels stretch, forming a kind of chamber into which a significant amount of blood enters. Kinetic energy turns into potential energy, and when systole ends, the stretched vessels put pressure on the blood, and thereby maintain the uniform movement of blood through the vessels during diastole.

2.Resistance vessels. These include arterioles and precapillaries. The wall of these vessels has a thick layer of circular smooth muscle. The diameter of these vessels depends on the tone of the smooth muscles. A decrease in arteriolar diameter leads to an increase in resistance. If we take the total resistance of the entire vascular system of the systemic circulation as 100%, then 40-60% falls on the arterioles, while the arteries account for 20%, the venous system - 10% and capillaries - 15%. Blood is retained in the arteries, and the pressure in them increases. That., functions arterioles: 1. Participate in maintaining blood pressure levels; 2. Regulate the amount of local blood flow. In a working organ, the tone of the arterioles decreases, which increases blood flow.

3.Vessels of exchange. These include microcirculation vessels, i.e. capillaries (the wall consists of 1 layer of epithelium). There is no ability to contract. According to the structure of the wall, three types of capillaries are distinguished: somatic (skin, skeletal and smooth muscles, cerebral cortex), visceral (“finestrated” - kidneys, gastrointestinal tract, endocrine glands) and sinusoidal (basal membrane may be absent - bone marrow, liver, spleen). Function- exchange between blood and tissues.

4.Shunt vessels. These vessels connect small arteries and veins. Function- transfer of blood, if necessary, from the arterial system to the venous system, bypassing the network of capillaries (for example, in the cold when it is necessary to preserve heat). They are found only in certain areas of the body - ears, nose, feet and some. etc.

5. Capacitive vessels. These vessels include venules and veins. They contain 60 - 65% blood. The venous system has very thin walls, so they are extremely distensible. Thanks to this, capacitive vessels prevent the heart from “choking.”

Thus, despite the functional unity and consistency in the work of various parts of the cardiovascular system, there are currently three levels at which blood flows through the vessels: 1. Systemic hemodynamics, 2. Microhemodynamics (microcirculation), 3. Regional (organ circulation).

Each of these levels performs its own functions.

1. Systemic hemodynamics ensures circulation processes (blood circulation) throughout the system.

Some of the properties of this section were outlined above.

2. Microhemodynamics (microcirculation) – ensures transcapillary exchange between blood and tissues of food products, decomposition, and carries out gas exchange.

3. Regional (organ circulation) - provides blood supply to organs and tissues depending on their functional needs.

Systemic hemodynamics

The main parameters characterizing systemic hemodynamics are: systemic blood pressure, cardiac output (CO or CO), cardiac function (discussed earlier), venous return, central venous pressure, circulating blood volume (CBV).

Systemic blood pressure

This indicator depends on the magnitude of cardiac output and total peripheral vascular resistance (TPVR). Cardiac output is characterized by systolic volume or SV. OPSS is measured using the direct blood method or calculated using special formulas. In particular, to calculate the OPSS, the Frank formula is used:

R=\(P 1 – P 2):Q\x1332, where P 1 - P 2 is the pressure difference at the beginning and end of the path, Q is the amount of blood flow in this area. OPSS = 1200 – 1600 dyn.s.cm -5. Moreover, in middle age it is 1323, and by the age of 60-69 it increases to 2075 dyn.s.cm -5. Depends on blood pressure level. When it increases, it increases by 2 times.

Blood pressure

Blood pressure is the pressure under which blood flows through the vessels and which it exerts on the walls of the vessels. The pressure under which blood flows is called central. The pressure it exerts on the walls of blood vessels is called lateral.

The blood pressure in the arteries is called blood pressure, and it depends on the phases of the cardiac cycle. During systole ( systolic pressure) it is maximum and in an adult it is 120 - 130 mm Hg. If this figure increases to 130-140 mm Hg. and higher - they talk about hypertension if it decreases to 100 mm Hg. and below - about hypotension.

During diastole ( diastolic pressure) the pressure decreases and is normally 60 - 80 mm Hg.

The value of systolic pressure (SP) depends on the amount of blood ejected by the heart during one systole (SO). The more CO, the higher the SD. May increase with physical activity. Moreover, diabetes is an indicator of the functioning of the left ventricle.

The value of diastolic pressure (DP) is determined by the nature of the outflow of blood from the arterial part to the venous part. If the lumen of the arterioles is large, then the outflow is good, then the DD is recorded within normal limits. If the outflow is obstructed, for example, due to narrowing of the arterioles, then the pressure is increased during diastole.

The difference between SD and PP is called pulse pressure (PP). PP is normally 40 - 50 mm Hg.

In addition to DM, DD, and PP, when considering hemodynamic laws, mean dynamic pressure (MDP) is distinguished. SBP is blood pressure, cat. it would have an effect on the walls of blood vessels if it flowed continuously. SDD = 80 - 90 mm Hg. that is, it is less than SD and closer to DD.

Methods for determining blood pressure.

There are two ways to determine blood pressure:

1. bloody, or straight (1733 - Hals)

2. bloodless, or indirect.

In direct measurement, a cannula connected to a mercury manometer is inserted directly into the vessel through a rubber tube. The space between the blood and mercury is filled with an anticoagulant. Most often used in experiments. In humans, this method can be used in cardiac surgery.

Typically, a person’s blood pressure is determined by a bloodless (indirect) method. In this case, lateral pressure (pressure on the walls of blood vessels) is determined.

The Riva-Rocci sphygmomanometer is used for determination. Almost always, the pressure is determined on the brachial artery.

A cuff connected to a pressure gauge is placed on the shoulder. Then air is pumped into the cuff until the pulse disappears in the radial artery. Next, the air is gradually released from the cuff and when the pressure in the cuff is equal to systolic or slightly lower, the blood breaks through the compressed area and the first pulse wave appears. The moment the pulse appears corresponds to systolic pressure, which is determined by the reading of the pressure gauge. Diastolic pressure is difficult to determine using this method.

In 1906, N.S. Korotkov discovered that after releasing a compressed artery, noises (Korotkoff sounds) arise below the place of compression, which are clearly audible with a phonendoscope. Currently, in clinical practice, blood pressure is more often determined by the Korotkoff method, because it allows you to determine both systolic and diastolic pressure.

The essence of the method is as follows: a cuff from the Riva-Rocci apparatus is placed on the shoulder and air is pumped into it. The phonendoscope is placed in the area of ​​the ulnar fossa and air is released from the cuff. As soon as the pressure in the cuff becomes equal to systolic, or slightly lower, the blood breaks through the compressed area and hits the walls of the vessel. Blood flow is turbulent. Therefore, at the moment we hear clear ringing sounds (Korotkoff sounds). As the pressure in the cuff decreases, the tones become dull, change their character (blood movement becomes laminar), and when the pressure in the cuff is equal to DD, the sounds stop, i.e. the cessation of tones corresponds to DD.

The value of blood pressure depends on many factors and changes under various conditions of the body: physical work, when emotions arise, pain, etc.

The main factors influencing blood pressure are vascular tone, heart function and circulating blood volume.

Arterial pulse

The arterial pulse is a rhythmic, jerky oscillation of the vessel wall that occurs as a result of the ejection of blood from the heart into the arterial system. Pulse from lat. рulsus - push.

Ancient doctors paid great attention to studying the properties of the pulse. The scientific basis for the doctrine of the pulse received after Harvey's discovery of the circulatory system. The invention of the sphygmograph and especially the introduction of modern methods of pulse recording (arteriopiesography, high-speed electrosphygmography, etc.) significantly deepened knowledge in this area.

With each systole of the heart, a certain amount of blood is ejected into the aorta. This blood stretches the initial part of the elastic aorta and increases its pressure. This change in pressure spreads through the aorta and its branches to the arterioles. In the arterioles, the pulse wave stops, because there is high muscle resistance here. The pulse wave propagates much faster than the blood flows. The pulse wave travels at a speed of 5-15 m/s, i.e. it runs 15 times faster than blood. That. the occurrence of a pulse is due to the fact that when the heart works, blood is not pumped into the vessels constantly, but in portions. Pulse examination allows us to judge the functioning of the left ventricle. The greater the systolic volume, the more elastic the artery, the greater the wall oscillations.

Vibrations of arterial walls can be recorded using a sphygmograph. The recorded curve is called a sphygmogram. On the pulse recording curve - sphygmogram - you can always see an ascending knee - anacrotic, plateau, descending knee - catacrotic, dicrotic rise and incisura (tenderloin).

Anacrosis occurs as a result of increased pressure in the arteries and coincides in time with the phase of rapid expulsion of blood into ventricular systole. At this time, there is more blood inflow than outflow.

Plateau - coincides with the phase of slow expulsion of blood into ventricular systole. At this time, the blood inflow into the aorta equals the outflow. After systole, the semilunar valves close at the beginning of diastole. The blood flow stops, but the outflow continues. The outflow predominates, so the pressure gradually decreases. This causes catacrota.

In the proto-diastolic interval (end of systole, beginning of diastole), when the pressure in the ventricles decreases, blood rushes back to the heart. Outflow decreases. An incisura arises. During ventricular diastole, blood closes the semilunar valves and, as a result of the impact on them, a new wave of blood outflow begins. A short-term wave of increased pressure appears in the aorta (dicrotic rise). After this, the catacrota continues. The pressure in the aorta reaches its original level. The outflow is increasing.

Properties of the pulse.

Most often, the pulse is examined on the radial artery (a.radialis). In this case, pay attention to the following properties of the pulse:

1. Pulse rate (HR). The emergency rate characterizes the heart rate. Normal HR = 60 – 80 beats/min. When the heart rate increases above 90 beats/min, they speak of tachycardia. If there is a decrease (less than 60 beats/min), this indicates bradycardia.

Sometimes the left ventricle contracts so weakly that the pulse wave reaches the periphery, then the number of pulse beats becomes less than the heart rate. This phenomenon is called bradysphygmia. And the difference between heart rate and emergency rate is called pulse deficit.

Based on the state of emergency, one can judge what kind of T a person has. An increase in T by 1 0 C leads to an increase in heart rate by 8 beats/min. The exception is the change in T during typhoid fever and peritonitis. With typhoid fever there is a relative slowing of the pulse, with peritonitis - a relative increase.

2. Pulse rhythm. The pulse may be rhythmic or arrhythmic. If the pulse beats follow one after another at equal intervals, then they speak of a regular, rhythmic pulse. If this period of time changes, then they speak of an irregular pulse - the pulse is arrhythmic.

3. Heart rate. The speed of the pulse is determined by the rate of increase and decrease in pressure during the pulse wave. Depending on this indicator, a fast or slow pulse is distinguished.

A fast pulse is characterized by a rapid rise and rapid decrease in pressure in the arteries. A fast pulse is observed with aortic valve insufficiency. A slow pulse is characterized by a slow rise and fall in pressure, i.e. when the arterial system slowly fills with blood. This happens with stenosis (narrowing) of the aortic valve, with weakness of the ventricular myocardium, fainting, collapse, etc.

4. Pulse tension. It is determined by the force that must be applied to completely stop the propagation of the pulse wave. Depending on this, a tense, hard pulse is distinguished, which is observed in hypertension, and a relaxed (soft) pulse, which occurs in hypotension.

5. Filling or pulse amplitude is the change in the diameter of the vessel during the pulse impulse. Depending on this indicator, pulses with large and small amplitude are distinguished, i.e. good and bad filling. The filling of the pulse depends on the amount of blood emitted by the heart and on the elasticity of the vascular wall.

There are many more properties of the pulse that you will become familiar with in therapeutic departments.

Venous return.

One of the important indicators of systemic hemodynamics is the venous return of blood to the heart. It reflects the volume of venous blood flowing through the superior and inferior vena cava. Normally, the amount of blood flowing in 1 minute is equal to the IOC. The ratio of venous return and cardiac output is determined using special electromagnetic sensors.

Movement of blood in the veins.

The movement of blood in the veins also obeys the basic laws of hemodynamics. However, unlike the arterial bed, where the pressure decreases in the distal direction, in the venous bed it is the opposite - the pressure drops in the proximal direction. The pressure at the beginning of the venous system - near the capillaries - ranges from 5 to 15 mm Hg. (60 – 200 mm water column). In large veins the pressure is much lower - and ranges from 0 to 5 mm Hg. Due to the fact that blood pressure in the veins is insignificant, water pressure gauges are used to determine it in the veins. In humans, venous pressure is determined in the veins of the elbow by a direct method. In the veins of the elbow, the pressure is 60 - 120 mm water column.

The speed of blood movement in veins is much less than in arteries. What factors determine the movement of blood in the veins?

1. The residual strength of cardiac activity is of great importance. This force is called the pushing force.

2. Suction action of the chest. In the pleural fissure the pressure is negative, i.e. below atmospheric by 5-6 mm Hg. When you inhale, it increases. Therefore, during inhalation, the pressure between the beginning of the venous system and the point where the vena cava enters the heart increases. Blood flow to the heart is facilitated.

3. Activity of the heart as a vacuum pump. During ventricular systole, the heart decreases in the longitudinal direction. The atria are pulled towards the ventricles. Their volume is increasing. The pressure in them drops. This creates a slight vacuum.

4. Siphon forces. Between the arterioles and venules there are capillaries. Blood flows in a continuous stream and, due to siphon forces, through a system of communicating vessels, it flows from one vessel to another.

5. Contraction of skeletal muscles. When they contract, the thin walls of the veins are compressed and the blood passing through them flows faster, because. the pressure in them increases. The reverse flow of blood in the veins is prevented by the valves located there. Acceleration of blood flow through the veins occurs with increased muscle work, i.e. when alternating contraction and relaxation (walking, running). Standing for a long time causes congestion in the veins.

6. Reduction of the diaphragm. When the diaphragm contracts, its dome moves down and puts pressure on the abdominal organs, squeezing blood out of the veins - first into the portal vein, and then into the cava.

7. The smooth muscles of the veins are important in the movement of blood. Although the muscle elements are poorly expressed, an increase in smooth muscle tone still leads to a narrowing of the veins and thereby promotes blood movement.

8. Gravitational forces. This factor is positive for the veins lying above the heart. In these veins, the blood flows under its own weight towards the heart. For veins lying below the heart, this factor is negative. The heaviness of the blood column leads to stagnation of blood in the veins. However, a large accumulation of blood in the veins is prevented by contractions of the muscles of the veins themselves. If a person is on bed rest for a long time, then the regulatory mechanism is disrupted, so standing up suddenly leads to fainting, because blood flow to the heart decreases and blood supply to the brain deteriorates.

The next indicator that affects the processes of systemic hemodynamics is central venous pressure.

Central venous pressure

The level of CVP (pressure in the right atrium) has a significant influence on the amount of venous return to the heart. A drop in central venous pressure leads to increased blood flow to the heart. However, an increase in inflow is observed only when the central venous pressure is reduced to certain limits, because a further drop in pressure will not lead to increased return of venous blood due to collapse of the vena cava. An increase in central venous pressure reduces blood flow. The minimum central venous pressure in adults is 40 mm water column, the maximum central venous pressure is 120 mm water column.

During inhalation, central venous pressure decreases, resulting in an increase in the velocity of venous blood flow. During exhalation, CVP increases and venous return decreases.

Venous pulse

Venous pulse refers to fluctuations in pressure and volume in the veins during one cardiac cycle, associated with the dynamics of blood outflow into the right atrium in different phases of systole and diastole. These vibrations can be detected in large veins located close to the heart - usually in the hollow and jugular veins.

The cause of the venous pulse is the cessation of the outflow of blood from the veins to the heart during systole of the atria and ventricles.

The venous pulse curve is called a venogram.

On this curve, several teeth can be identified that reflect changes in pressure in the veins and have letter designations.

a – occurs during systole of the right atrium, the outflow of blood from the veins to the heart stops and the pressure rises. Then the blood rushes into the atria, the pressure drops.

c – coincides with the vibration of the wall of the adjacent carotid artery. Occurs during ventricular systole.

n - appears after the atria are filled. Reflects an increase in pressure. Occurs at the end of atrial diastole.

And the last indicator characterizing systemic hemodynamics is the volume of circulating blood.

Blood volume.

The total blood volume is divided on the blood circulating through the vessels, And blood that is not currently in circulation. Moreover, the volume of the second part (deposited blood) in a state of relative rest is 2 times greater than the first part (bcc). In an adult, the BCC ranges from 50 to 80 ml per 1 kg of body weight.

Damage to blood vessels is among the most dramatic in terms of intensity and speed of developing consequences. There is perhaps no other injury where emergency care is so necessary and where it does not save life as clearly as with arterial or venous bleeding. There are many reasons that cause damage to blood vessels. These are open and closed injuries, wounds. Among the civilian population, 1/3 of simultaneous damage to blood vessels and the heart is recorded, and in more than 80% of cases these wounds are either of gunshot origin or inflicted with knives. Vascular injuries predominate in wounds of the extremities and in penetrating wounds of the abdomen.

With the development of firearms, the proportion of wounds to blood vessels in relation to the total number of wounds began to gradually increase. Since about 1900, when lighter, smaller-caliber bullets appeared in armies, vascular wounds have become relatively more common.

According to Nguyen Han Zy, with gunshot wounds of blood vessels, isolated wounds of arteries account for 47.42%, isolated wounds of veins - 6.77%, and combined wounds of arteries and veins account for 45.8% of the total.

The localization of wounds, according to the same author, can be presented as follows: neck (carotid arteries, jugular veins) - 8.96%, vessels of the shoulder girdle and upper extremities - 16%, vessels of the abdominal cavity and pelvis - 11.55%, vessels of the lower extremities - 63.40%.

Traumatic injuries to brachycephalic branches are observed relatively rarely and account for about 6-7% of the total number of arterial injuries.

The most severe are fragmentation wounds, in which combined damage to the artery, vein and nerve trunk occurs, accompanied by a clinical picture of traumatic or hemorrhagic shock.

Combined injuries of arteries and nerves account for approximately 7% of all vascular injuries.

Traumatic arterial aneurysms lead to various kinds of complications in approximately 12% of cases, and arterial-venous fistulas - in no less than 28%, and primarily to cardiac disorders.

Apparently, there is reason to divide damage to blood vessels into three groups:

• damage (most often ruptures) of arterial and venous trunks that occur during closed injuries;
• damage from open injuries (wounds, fractures)
• with gunshot wounds.

It is also important to distinguish between damage to blood vessels accompanied by a defect in the vascular wall, which is most often observed with gunshot wounds, and without its defect, which is typical for wounds with cold weapons. When an artery ruptures, for example as a result of a dislocation in the knee or elbow joint, a defect necessarily occurs, since when stretched, all three membranes of the artery tear at different levels due to their different mechanical strength.

When an artery is injured, the wall may dissect over a large distance from the site of injury.

There are many classifications of damage to central and peripheral blood vessels, but for practical purposes a fairly simple classification is needed, from which diagnostic and therapeutic measures would be obvious.

It is known that to damage the walls of the main venous and especially arterial trunk, a fairly large force is required, taking into account their high degree of elasticity. Even when exposed to a factor such as a firearm projectile (bullet or shrapnel), the vascular bundle often moves away from the developing wound channel. If a blood vessel is damaged by any wounding projectile (shrapnel, bullet) or a piece of bone, the following damage is possible.

• Damage to part of the wall of an artery or vein with the formation of a “window” from which arterial or venous bleeding immediately begins into the surrounding tissue and outward with a sufficiently wide lumen of the primary wound channel. A more detailed division of damage to the wall of an artery or vein into 1/3 3/4 of the lumen does not add anything significant to diagnosis and treatment.
• Total damage (complete interruption) of an artery or vein, or both. In this case, there may be two options:
  • massive prolonged bleeding from both ends of the vessel, leading to rapid and severe blood loss;
  • screwing the intima of the artery into the lumen, as a result of which the bleeding stops, for example, in the event of a traumatic separation of a limb at the level of the shoulder joint. In this case, bleeding may be moderate. When a large venous trunk is completely interrupted, the intima does not roll inward, so venous bleeding from wounds of various origins sometimes turns out to be even more dangerous than arterial bleeding.

In the case of simultaneous damage to the artery and the accompanying vein, an arteriovenous fistula is likely to occur, the essence of which is that through the cavity formed in the tissues, communication between the lumens of the main artery and vein occurs. This is a serious complication, fraught with serious hemodynamic changes due to shunting of the arteriovenous bed. Subsequently, with such injuries, an arteriovenous false aneurysm is formed. Looking ahead somewhat, it can be noted that post-traumatic aneurysms, especially those of gunshot origin, have a tendency to suppurate. It’s easy to imagine the consequences of opening such a phlegmon!

An arterial injury can remain unrecognized for a long time, and only the formation of a false aneurysm, which, due to the entry of thrombotic masses into the peripheral segment of the artery, can cause acute occlusion, allows a correct diagnosis to be made.

The occurrence of arteriovenous fistulas is not very rare. These fistulas are especially dangerous in the neck, since heart failure can actually occur due to the discharge of arterial blood into the superior vena cava. Unrecognized damage, for example to the popliteal artery, inevitably leads to ischemic gangrene of the leg.

It should be emphasized that the compensatory capabilities of collaterals in case of damage to the main arteries, accompanied by soft tissue damage, are significantly reduced. Therefore, the period that is considered acceptable in case of injury to the main arteries - 5 hours from the moment of injury, in cases of severe injuries may be too long. That is why such victims should be helped as quickly as possible.

During the Great Patriotic War, damage to blood vessels was not recognized in approximately 1/3 of cases. In peacetime, this figure is no less, despite the obvious advantages of diagnostics compared to wartime.

Symptoms of Damage to Great Blood Vessels

Wound in the projection of a blood vessel. This fact should always be taken into account by the doctor examining the patient. You should take it as a rule: at the slightest suspicion of damage to the main artery, use all the necessary diagnostic techniques to remove or confirm this diagnosis.

Bleeding. External bleeding naturally occurs only with open injuries. It can be considered almost beyond doubt that only on the basis of external bleeding, with the exception of those cases when a stream of arterial blood pulsates in the wound, it cannot be said whether there is damage to the main artery or not. This especially applies to gunshot wounds and injuries caused by the explosion of anti-personnel mines, which are always accompanied by massive widespread damage to soft tissues.

Of course, external bleeding from an artery or vein is the most obvious symptom of damage. It should be borne in mind that pulsating bleeding with scarlet blood is not always observed, and with closed damage to the arteries it naturally does not exist. Even with severe fractures with damage to the artery, gunshot and shrapnel wounds, external pulsating bleeding is rarely observed. Therefore, from the point of view of further tactics, in any case of intense external bleeding, damage to the main artery or vein should be suspected. Viewing damage to the main artery is fraught with severe and irreversible consequences.

Determination of arterial pulsation distal to the wound site. The preserved clear pulsation on the dorsal artery of the foot and the radial artery indicates the integrity of the main trunk proximal to the site of injury. But not always.

In the absence of pulsation in the periphery, there is reason to think about the cessation of blood flow in the damaged area, but this is also not always the case. If the victim is in a state of shock, collapse due to blood loss, and systolic blood pressure is up to 80 mm Hg. Art. or less, arterial pulsation may not be detected while maintaining the integrity of the main artery. In addition, with a gunshot wound to soft tissue and the anatomical integrity of the artery, a vascular spasm necessarily occurs as a result of the effect of the so-called side impact, essentially a hydrodynamic wave that occurs when a bullet or shrapnel hits the tissue of the human body.

V. L. Khenkin, with injuries to the axillary, brachial, iliac, femoral and popliteal arteries, found the absence of a pulse in only 38% of cases; in the rest, the pulse was either weakened or preserved.

An important sign of injury to a large arterial trunk is swelling caused by a hematoma, but an even more important sign is the pulsation of such swelling, which is relatively easy to detect by eye.

When an arterioveous fistula has formed, the symptom of “cat purring” can be identified.

A pulsating hematoma, and later a false aneurysm, is usually expressed quite clearly in the form of a relatively well-defined swelling. In the case of an arteriovenous aneurysm, the swelling is less; with an arteriovenous fistula, it may be absent.

In no case should one forget such a simple method of examination as auscultation around the circumference of a wound that is at least somewhat suspicious of possible damage to the artery. Systolic blowing noise when an artery is injured is very characteristic.

The pallor of the skin of the limb on the periphery of the wound site should not be ignored. Injuries to large arterial lines may be accompanied by such signs as paresthesia, paresis; at a later date, ischemic contracture develops.

With vascular injuries in peacetime, blood loss is the most common symptom of acute injury to the main blood vessels, especially with injuries to the subclavian, iliac, femoral and popliteal arteries. Clinical signs of acute blood loss are observed in almost all cases of injuries to the listed vessels, however, with injuries to vessels located more distally, clinical signs of acute blood loss are not detected in approximately 40% of cases.

The absolute sign of damage to the main artery is ischemic gangrene of the limb - a late and unfavorable symptom.

Diagnosis of Damage to the Great Blood Vessels

An indisputable diagnosis can be made with a vasographic X-ray contrast study. It should be emphasized that vasography is mandatory at the slightest suspicion of injury to the main artery.

In a specialized hospital, capillaroscopy, contact and remote thermography methods can be used for diagnostic purposes.

Paradoxically, ischemic pain in case of damage to the main artery is not as intense as in case of segmental occlusion of the artery by a thrombus. It is possible that they are to a certain extent masked by pain in the damaged area. Nevertheless, pain in the periphery in relation to the area of ​​injury, which was not previously present and which is clearly related in time to the moment of injury, must be taken into account during the clinical examination of the patient.

Peripheral blood examination indicates blood loss. Hemodynamic changes in arterial damage are also directly related to blood loss and intoxication from the primary lesion in the first hours after injury, and later from ischemic tissues.

Biochemical indicators indicate a focus of ischemia and necrosis, but these data can hardly be attributed to pathognomonic signs.

As noted, arteriography is mandatory both in case of an undoubted clinical diagnosis of arterial damage, and in case of suspicion of such. Arteriographic examination can be performed with sufficient reliability using any, including ward, X-ray machine.

If the main artery of the lower limb is damaged, the following sequence of actions may be recommended.

The victim is placed on the table. The femoral artery is exposed with a projection vertical incision 50-60 mm long under local anesthesia with a 0.5% novocaine solution. Premedication should consist of an injection of 2 ml of a 1% morphine solution and 0.5 ml of a 0.1% atropine solution. Any water-soluble drug with a concentration of no more than 50-60% can be used as a radiopaque contrast agent. We strongly recommend not to catheterize the artery through the skin, but to expose it, primarily because this eliminates the possibility of paravasal hematoma and subsequent bleeding from the puncture of the vessel, especially if postoperative heparin therapy is necessary. The open method allows you to very accurately insert a catheter into the lumen of the artery, which is important for atherosclerotic changes in the arterial wall in an elderly victim. With the open method, paravasal blockade is very well carried out, which should definitely be done by injecting 15-20 ml of 1% or 2% novocaine solution. This is necessary both from the point of view of spasm of the most superficial femoral artery, and from the point of view of the opening of the peripheral arterial collateral network. And finally, which is also very important, with the open method, at the time of administration of the contrast agent, you can clamp the central segment of the artery with a tourniquet or a soft vascular clamp to temporarily stop the blood flow. This significantly improves the quality of the image. Before introducing a contrast agent into the arterial bed, it is imperative to inject 20-25 ml of a 0.5% novocaine solution through a catheter into the lumen of the artery to relieve unwanted, including interoceptive, pain effects.

An X-ray is taken at the height of the contrast agent injection; the catheter is not removed, but the image is awaited to develop. If the radiograph is sufficiently informative, the catheter is removed and it is best if the surgeon applies a superficial suture to the adventitia of the artery using atraumatic suture material. It is possible to stop bleeding from a puncture of the arterial wall by pressing it with a gauze ball for several minutes. After stopping the bleeding, the wound is either sutured, if no confirmation of arterial damage is received, or left open, keeping the previously applied tourniquet.

Arteriograms are the most reliable diagnostic document, which confirms not only the fact, level and extent of damage, but also allows us to judge the degree of viability of the collaterals.

Among non-invasive methods for diagnosing lesions of the great vessels, the main role is currently played by ultrasound flowmetry - Dopplerography. The method, based on the registration of moving objects, makes it possible to determine the presence of blood flow in a given section of an artery or vein, its direction and speed in various phases of the cardiac cycle, and the nature of the flow, depending on the properties of the vascular wall. According to various authors, the diagnostic accuracy of the Doppler ultrasound method for occlusive lesions of the arteries of the extremities is 85-95%, for diseases of the veins - from 50 to 100%.

The standard examination scheme includes the location of the main vessels at certain points of the upper and lower extremities, characterizing blood flow in various segments of the vascular bed. Analysis of Dopplerograms consists of a qualitative assessment of the curve and calculation of quantitative parameters. To increase diagnostic accuracy, regional systolic pressure is measured at the level of various segments.

The use of Doppler ultrasound in traumatology includes the diagnosis of thrombotic vascular lesions, acute and chronic traumatic injuries, and dynamic monitoring during treatment. In cases of massive soft tissue injuries of the extremities, accompanied by swelling of the distal parts, clinical diagnosis of vascular damage is difficult, especially in patients with prolonged crush syndrome. In two of these patients, there was no palpation of pulsation in the posterior tibial artery and dorsalis pedis artery, but Doppler ultrasound was able to determine antegrade blood flow in both arteries, which indicated the preservation of vascular patency. The parameters of the curve were significantly changed as a result of compression of the arteries by edematous tissue and bone fragments, but clear positive dynamics were noted during treatment. In one patient with an open fracture of the leg bones and long-term crush syndrome, examination of the dorsal artery of the foot revealed retrograde blood flow, caused by a complete interruption of the anterior tibial artery and the flow of blood from the arterial anastomoses of the foot. Subsequently, as a result of the purulent process and arterial ischemia, necrosis of the foot tissue occurred, leading to amputation.

Doppler sonography is also of great importance in case of chronic arterial injuries for choosing tactics of surgical intervention and prognosis of the postoperative course. In these cases, data on the state of individual arteries are successfully supplemented with integral indicators of blood supply to a limb segment, obtained using rheography, thermography and other methods

Treatment of Damage to Great Blood Vessels

Medical care for injuries to blood vessels:

Measures for injury to blood vessels should be divided into urgent, urgent and definitive. The first, in the form of stopping bleeding by applying a tourniquet, a pressure bandage, pressing a vessel, or forced flexion of a limb, is carried out, as a rule, at the scene of the incident or in a vehicle in which the victim is evacuated.

In almost all cases, hemostasis is carried out using natural mechanisms, and the condition for stopping bleeding is the fastest delivery of the wounded person to the stage of qualified surgical care. To reduce the negative effect of the tourniquet, it is recommended to apply plywood splints on the side opposite to the location of the vessels, and apply the tourniquet as close as possible to the area of ​​the damaged vessel.

Thus, when providing first medical aid, it is advisable to further temporarily stop bleeding not with the help of a tourniquet, but with other methods, for example, tight tamponade of the wound, using a pressure bandage. For vein injuries, a pressure bandage is usually sufficient to stop bleeding.

In a person admitted with a tourniquet, the authenticity of damage to a large vessel and the possibility of replacing the tourniquet with another method of temporarily stopping bleeding should be determined; applying a hemostatic clamp, ligature, suturing a vessel in the wound. If this fails, then the vessel is pressed for 10-15 minutes with a finger, and then, placing a piece of plywood splint or thick cardboard under the tourniquet on the surface of the limb opposite to the projection of the vascular bundle, the tourniquet is tightened again. When bleeding from wounds of the gluteal region or popliteal fossa, you can resort to tight wound tamponade with suturing of the skin over the inserted tampon with several knotted silk sutures. When evacuating a wounded person with a tourniquet in the cold season, the possibility of hypothermia of the limb should be prevented. In conditions of a massive flow of wounded, the scope of assistance is reduced to the provision of first medical aid for life-saving indications and is limited to stopping bleeding using tourniquets or pressure bandages.

Urgent measures are most often carried out at a stage where there is no vascular surgeon and specialized care cannot be provided. In this case, temporary bypass of the artery or, in extreme cases, ligation of it in the wound or throughout it can be used.

In a specialized hospital, care is provided using all modern diagnostic and treatment tools, which are designed to restore blood flow in the most appropriate way for a given specific situation.

In any case of temporary stoppage of bleeding, it is necessary to indicate the exact time when this procedure was performed. In a wound that is known to be infected, when an artery is injured, a vascular suture should be applied, subsequently ensuring good reliable drainage in the anastomosis area, the introduction of powerful antibacterial agents, and good immobilization of the operated limb.

Determination of the degree of ischemia is essential in preoperative diagnosis.

From a practical point of view, it is advisable to divide limb ischemia into two groups - compensated and decompensated. In the first case, surgical restoration of arterial patency is indicated, which will lead to complete restoration of blood flow and almost complete restoration of limb function.

For decompensation of blood flow: loss of active movements, loss of pain and tactile sensitivity - even immediate restoration of blood flow by surgery does not guarantee the anatomical integrity of the limb.

In cases of clearly necrotic changes in the limb, amputation is indicated. The demarcation line most clearly appears 24-48 hours after the cessation of blood flow and the development of symptoms of circulatory decompensation in the limb.

B.V. Petrovsky (1975) distinguishes 4 stages of ischemia:

• acute ischemic disorders;
• relative compensation of blood circulation;
• circulatory decompensation and
• irreversible changes in tissues.

V. A. Kornilov (1971) suggests taking into account two degrees of ischemia in case of vascular damage: compensated ischemia, characterized by the absence of sensory and motor disorders; uncompensated, which is divided into stage I (there are motor and sensory disorders, but no ischemic contracture) and stage II - with the development of ischemic contracture.

Restoration of blood flow should be carried out in case of uncompensated stage I ischemia no later than 6-8 hours; in case of stage II ischemia, restoration of blood flow is contraindicated.

V. G. Bobovnikov (1975) proposed his classification of limb ischemia. The experience of Yaroslavl vascular surgery specialists convincingly suggests that it is advisable to operate on victims with damage to the main arteries using mobile teams where the patient was taken. This makes it possible to operate on about 50% of victims in the first 6 hours.

The place of treatment for such patients is a trauma hospital.

There is no doubt that in patients with combined injuries, surgical intervention should be carried out by two teams of surgeons - traumatologists and specialists in vascular surgery.

In some cases, with severe injuries, it is advisable to catheterize one of the collaterals for regional perfusion. In preparation for surgery, the skin must be treated: in case of damage to the axillary or subclavian blood vessels from the fingertips to the anterior surface of the chest; if the femoral artery is injured in the upper third, the entire limb and abdominal skin are treated.

It is rational to put a sterile plastic bag on the foot or hand, which allows you to monitor the condition of the skin color and pulse. It is necessary to remember about the likely need to take a free venous autograft, so the second, healthy lower limb should be prepared in the same way.

The most important condition for the success of restorative intervention on a main artery or vein is a sufficiently wide projection access, since in cases of complete rupture of the artery, its ends diverge far to the sides and it is not easy to find them in the altered tissues imbibed with blood. This is typical for bullet and especially shrapnel wounds.

Therefore, in principle, the arterial trunks, regardless of the level of damage, must be exposed with projection incisions. This is also important because with the anatomical approach of the artery there are more conditions for preserving collaterals, which must be spared in every possible way. With any type of arterial repair (autovein, synthetic prosthesis), it is necessary to excise the ends of the damaged vessel in order to refresh them and create conditions for an ideal comparison of all three elements of the blood vessel wall. This is the main and decisive condition for the success of surgery on an artery or vein. Naturally, such measures increase the defect of the vascular trunk and create certain technical difficulties.

The need for vascular reconstruction for emergency reasons may arise in any surgical or trauma hospital. Surgery of a main artery or vein, or artery repair with an autovenous vein in case of a large defect, can be performed using only general surgical instruments, but with the obligatory presence of atraumatic suture material. First, the central end should be isolated, mobilized and placed on the tourniquets. The ends of an artery or vein isolated and taken on clamps or tourniquets should be handled with the utmost care, even if we are talking only about parietal damage, since this largely determines whether postoperative thrombosis will occur at the suture site or in the graft or not. It is better to use tourniquets rather than clamps at the central and peripheral ends of the vessel, since they cause less damage to the vessel wall and provide the surgeon with greater freedom of manipulation in the wound.

In case of parietal damage to the artery, separate sutures should be placed in the longitudinal direction relative to the vessels, trying to deform the lumen of the artery or vein as little as possible. You should carefully ensure that the intima is not damaged or wrapped in the lumen of the vessel. If, when suturing a parietal wound of an artery or vein, gross deformation occurs, the vessel should be completely dissected, a circular vascular suture should be performed, and an end-to-end anastomosis should be applied.

During emergency operations on blood vessels, it is better to use predominantly the Carrel suture as it is the most easy to perform and quite reliable. It is advisable to perform the same suture when implanting an autovenous graft into an artery defect.

The suture material should be selected according to the diameter of the blood vessels being sutured. It is better to use monofilamental atraumatic suture material. After performing the anastomosis or anastomoses, in the case of a venous insertion, the peripheral clamp or tourniquet is first removed so that retrograde blood flow completes the area of ​​anastomosis or plastic reconstruction. The center clamp or turnstile can then be removed. Almost always after this there is bleeding from individual punctures in the wall. This bleeding, as a rule, stops quickly; there is no need to rush to apply additional stitches. In case of intense bleeding in a stream of 1-2 injections, a superficial atraumatic suture should be carefully applied.

To replace part of the arterial wall, the great saphenous vein is used predominantly. It is carefully dissected, tying the side branches, otherwise intense bleeding occurs from them, which can only be stopped by ligating the side branches. The vein should be turned 180° before transplantation - valves! The calibers of the transplanted vein and artery rarely coincide completely, so quite often it is necessary to “bring the vein and artery to the same diameter” with the help of sutures.

When treating the ends of an artery, it is advisable to perform a thrombectomy to remove the blood clots that have formed there, best using a Fogarty-type balloon catheter. An autovenous graft can be used as follows. End-to-end anastomosis is, in principle, the best, since it does not create any side pockets. However, if there is no confidence in the reliability of the end-to-end anastomosis, if the operation is performed in a known infected wound, it is possible to perform a bypass shunt from the autovein with an anastomosis of the type end of the vein to the side of the artery.

If the vein of the same name is damaged and there is a suitable size of venous autograft (which is unlikely), it is possible to perform a veno-venous anastomosis.

A synthetic vascular prosthesis is not used in cases of open and closed vein damage. Thanks to the vast experience of vascular surgeons in many countries, it can be considered reliable that any synthetic vascular prosthesis with a diameter of 7 mm or less inevitably thromboses. With open injuries, there is a high risk of microbial contamination of the prosthesis and subsequent, albeit slight, suppuration. This, in turn, will lead to the inevitable removal of the prosthesis, since today there is no method of preserving it in a purulent wound, and the danger of its rupture in these conditions with profuse bleeding is quite high.

In the postoperative period in this category of patients, suppuration can cause sudden profuse arrosive bleeding, which within a few minutes leads to bleeding of the patient and requires the most energetic efforts from the medical staff on duty.

In a certain percentage of cases, with slowly developing thrombosis, therefore, with the blood flow gradually stopping in the main arterial line, collateral blood flow has time to open, which successfully takes on the function of blood supply to the limb. It is also known that simple ligation of the artery does not always lead to necrosis of the limb.

At one time, special rigid endovasal prostheses were developed from special types of plastics, which, in the case of acute injury to the main artery and if, for one reason or another, it was impossible to carry out a vascular suture or vessel plastic surgery at this stage of emergency surgical care, they were inserted into the freshened ends of the artery and they were fixed there with two ligatures on each side. Blood flow through such a tube is maintained for several hours or days, which allows either the victim to be transported to where he will receive specialized care, or it may not be required if a sufficient collateral network develops with gradually developing thrombosis of the endoprosthesis.

Surgery on the arteries should be accompanied by the introduction of a 0.5% novocaine solution into the vascular sheath, constant irrigation of the surgical field and especially the inner lining of the vessels.

In case of a pulsating aneurysm or a formed arteriovenous fistula, operations are performed, as a rule, not for urgent reasons, certainly within the walls of specialized hospitals.

Surgeries for a pulsatile aneurysm or arteriovenous fistula should be provided with a sufficient amount of preferably single-group blood; the surgeon must have at least two assistants. The intervention begins with the obligatory isolation of the artery and accompanying vein proximal and distal to the aneurysm, the vessels are exposed with projection incisions.

The distal and proximal parts of the artery are taken with reliable tourniquets or vascular clamps. After this, they begin careful preparation of the aneurysmal sac, which, as a rule, contains liquid blood, clots with elements of their organization, and wound detritus. It is mandatory to take material from the aneurysm cavity for histological and microbiological studies. Gradually separating the artery trunk and immediately ligating the bleeding vessels, they reach the main lines, which are isolated and also taken with vascular clamps.

When operating for an aneurysm, it is quite rarely possible to perform an end-to-end anastomosis, so most often you have to resort to autovenous grafting. If the defect is in the wall of the accompanying vein, it should be carefully ligated, as far as possible from the aneurysm. It has been established that the suture of the accompanying vein at the level of the middle and lower thirds of the thigh, on the lower leg, if performed insufficiently carefully, inevitably leads to thrombosis at the site of the anastomosis. After washing the aneurysm cavity with a 0.25% solution of novocaine, it is irrigated with antibiotic solutions (kanamycin), the wound is sutured tightly in layers, leaving in it reliable silicone graduates or, better, corrugated drains made of a thin polymer film. The need for mandatory closure of the anastomotic line or autograft with soft tissue should be emphasized. The optimal period for surgery for complications of vascular wounds should be considered to be from 2 to 4 months after injury.

After intervention on the subclavian and carotid arteries, it is advisable to place the victim in the Fowler position in the postoperative period.

The issue of prescribing anticoagulants in the postoperative period is not an easy one. It should be noted that if the vascular suture is carefully performed and the internal walls of the vessels being sutured are completely aligned, anticoagulants, in particular heparin, may not be used in the postoperative period.

An important condition is maintaining stable hemodynamic parameters, since a decrease in blood pressure to 90-80 mm Hg. Art. is fraught with the formation of blood clots at the site of the anastomosis.

Mandatory in this category of patients is a study of peripheral blood for coagulation, which should be performed every 4 hours. If the blood clotting time decreases to 2-3 minutes, intravenous drip administration of heparin with one of the transfusion drugs is necessary at the rate of 20,000 units of heparin per 500 ml of isotonic sodium chloride solution, Ringer-Locke solution. Heparin is administered until the blood clotting time increases to 12-17 minutes, maintaining this indicator at this level for 3-4 days. The use of coumarin anticoagulants in patients who have undergone reconstructive surgery on the blood vessels of the extremities is undesirable. The main danger in this case is the occurrence of a paravasal hematoma with its subsequent suppuration.

Damage to the arteries of the neck, chest, abdominal cavity. If the surgeon finds a completely damaged external carotid artery, which inevitably leads to an ischemic stroke, the artery in this case should not be restored, since the renewed blood flow will turn the ischemic stroke into a hemorrhagic stroke with all the ensuing consequences.

In cases of neck injury with continued bleeding, the carotid arteries should be inspected, which is best done by making an incision along the anterior edge of the sternocleidomastoid muscle.

When large blood vessels of the chest are injured, especially in its upper parts, access through a median sternotomy is advisable. Vertebral arteries are extremely difficult to suture, so it is advisable to ligate them. Longitudinal sternotomy is indicated for wounds of the heart or ascending aorta; if the descending aorta is damaged, a thoracotomy is performed with the patient positioned on the right side. In case of injury to the celiac trunk, surgical treatment is possible only through a thoracoabdominal incision with dissection of the diaphragm. The celiac trunk can rarely be restored; more often it has to be ligated. The superior mesenteric and renal arteries should be repaired; most often, however, this can only be done using a venous autograft. The inferior mesenteric artery can be ligated, although today, with the possibilities of microsurgical wound treatment techniques, it is quite possible to raise the question of its restoration.

Damage to the arteries and veins of the shoulder girdle, upper and lower extremities. Injuries to the axillary artery are rarely isolated. Possible combined damage to the elements of the axillary plexus: veins, large nerve trunks. In any case, first of all it is necessary to restore blood flow through the main arteries. The greatest difficulties arise when isolating and stopping bleeding from the central ends of veins and arteries; sometimes it is necessary to resort to exposing the axillary artery.

It is quite difficult to connect the ends of the axillary artery with direct anastomosis. Most often, you have to use an autovenous insert, which should be taken from the great saphenous vein of the thigh. It should be remembered that the axillary vein is unlikely to be sutured, so you should try in every possible way to maintain collateral blood flow.

Restoring blood flow in the brachial artery is relatively easy; here, more often than in other situations, it is possible to perform an end-to-end anastomosis.

In the case of a simultaneous fracture of the humerus and damage to the artery, the bone fragments should first be fixed. Better fixation can be achieved with a “clean” fracture using the CITO-SOAN plate. To prevent ischemic disorders, we can recommend temporary bypassing of the central and peripheral sections of the artery with a polyvinyl chloride tube, followed by suturing of the artery or its autovenous grafting. Restoration of blood flow should be completed last, after osteosynthesis, suturing of nerve trunks (if necessary), ligation or suture of the accompanying vein if it is damaged.

Forearm. The need for a vascular suture in case of injury to the forearm arises only in case of simultaneous damage to the radial and ulnar arteries. And in this case, you should start with osteosynthesis using the most appropriate method. In principle, for “clean” fractures, CITO-SOAN plates should be used, and for infected injuries, extrafocal osteosynthesis should be used.

Considering the small diameter of the arteries of the forearm, it is highly desirable to use microsurgical techniques and perform anastomoses under a microscope. This guarantees against subsequent postoperative thrombosis.

A significant role, from the point of view of timely diagnosis of rethrombosis, is played by continuous monitoring of the limb and the use of special monitors that respond to changes in the temperature of the skin distal to the anastomosis. These systems have an alarm signal that warns the duty personnel about a deficiency of arterial blood flow. If both arteries of the forearm are damaged, it is best to suture both arterial trunks, but if this is not possible, the patency of the radial or ulnar artery should be restored. Associated veins are usually ligated.

Thigh, shin. The greatest difficulties arise during suturing, which is rarely possible, or plastic surgery of the popliteal artery. In case of damage to the artery due to a dislocation in the knee joint or in case of open damage to the artery, one should begin by isolating the artery in the adductor (Hunter) canal. The projection incision should be continued into the popliteal fossa on the back surface of the leg. The greatest difficulties arise if the damage extends to the bifurcation of the popliteal artery. In this case, it is difficult to do without plastic material, and the need to restore arterial blood flow in the popliteal artery is absolute, because its thrombosis inevitably leads to necrosis of the leg and foot.

N 02/18/2019

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Vessels in the body perform various functions. Experts distinguish six main functional groups of vessels: shock-absorbing, resistive, sphincters, exchange, capacitive and shunting.

Shock absorbing vessels

The shock-absorbing group includes elastic vessels: the aorta, pulmonary artery, and adjacent sections of large arteries. The high percentage of elastic fibers allows these vessels to smooth (cushion) the periodic systolic waves of blood flow. This property is called the Windkessel effect. In German the word means "compression chamber".

The ability of elastic vessels to equalize and increase blood flow is determined by the emergence of elastic tension energy at the moment of stretching the walls with a portion of liquid, that is, the transition of a certain fraction of the kinetic energy of the blood pressure that the heart creates during systole into the potential energy of elastic tension of the aorta and large arteries extending from it , which performs the function of maintaining blood flow during diastole.

More distally located arteries are classified as muscular type vessels, as they contain more smooth muscle fibers. Smooth muscles in large arteries determine their elastic properties, without changing the lumen and hydrodynamic resistance of these vessels.

Resistive vessels

The group of resistive vessels includes terminal arteries and arterioles, as well as capillaries and venules, but to a lesser extent. Precapillary vessels (terminal arteries and arterioles) have a relatively small lumen; their walls are sufficiently thick and have well-developed smooth muscles, therefore they are able to provide the greatest resistance to blood flow.

In numerous arterioles, along with a change in the force of contraction of muscle fibers, the diameter of the vessels and, accordingly, the total cross-sectional area, on which the hydrodynamic resistance depends, changes. In this regard, we can conclude that the main mechanism for distributing systemic blood flow (cardiac output) among organs and regulating the volumetric velocity of blood flow in different vascular areas is the contraction of the smooth muscles of precapillary vessels.

The resistance force of the postcapillary bed is influenced by the condition of the veins and venules. The hydrostatic pressure in the capillaries and, accordingly, the quality of filtration and reabsorption depend on the ratio of precapillary and postcapillary resistance.

Sphincter vessels

The diagram of the microvasculature is as follows: meta-arterioles, wider than true capillaries, branch off from the arteriole, which continue with the main channel. In the area of ​​the branch from the arteriole, the wall of the metaarteriole contains smooth muscle fibers. The same fibers are present in the area where capillaries arise from precapillary sphincters and in the walls of arteriovenous anastomoses.

Thus, sphincter vessels, which are the final sections of precapillary arterioles, regulate the number of functioning capillaries through narrowing and expansion, that is, the exchange surface area of ​​these vessels depends on their activity.

Exchange vessels

Exchange vessels include capillaries and venules, in which diffusion and filtration occur. These processes play an important role in the body. Capillaries cannot contract on their own; their diameter changes due to pressure fluctuations in sphincter vessels, as well as pre- and postcapillaries, which are resistive vessels.

Capacitive vessels

In the human body there are no so-called true depots, in which blood is retained and released as needed. For example, in a dog, such an organ is the spleen. In humans, the function of blood reservoirs is performed by capacitive vessels, which mainly include veins. In a closed vascular system, when the capacity of any section changes, a redistribution of blood volume occurs.

Veins have high distensibility, therefore, when containing or releasing a large volume of blood, they do not change the parameters of blood flow, although they directly or indirectly affect the overall function of blood circulation. Some veins with low intravascular pressure have an oval-shaped lumen. This allows them to hold additional blood volume without stretching, but changing their flattened shape to a more cylindrical one.

The hepatic veins, large veins in the abdominal area and veins of the subpapillary plexus of the skin have the greatest capacity. In total, they hold over 1000 ml of blood, which is discarded if necessary. The pulmonary veins, which are connected in parallel to the systemic circulation, also have the ability to temporarily deposit and eject large amounts of blood.

Shunt vessels

Shunt vessels include arteriovenous anastomoses, which are present in some tissues. When open, they help to reduce or completely stop blood flow through the capillaries.

In addition, all vessels in the body are divided into pericardial, main and organ. The pericardial vessels begin and end the systemic and pulmonary circulation. These include elastic arteries - the aorta and pulmonary trunk, as well as the pulmonary and vena cava.

The function of the great vessels is to distribute blood throughout the body. Vessels of this type include large and medium-sized muscular extraorgan arteries and extraorgan veins.

Organ blood vessels are designed to ensure metabolic reactions between the blood and the main functioning elements of the internal organs (parenchyma). These include intraorgan arteries, intraorgan veins and capillaries.

Video about the human vascular system:

With high blood pressure, are the blood vessels dilated or narrowed?

All organs of the human body are nourished by the circulatory system, the main “workers” of which are blood vessels. Their work is interconnected with blood pressure, since blood pressure is an indicator of the force with which blood presses on the walls of blood vessels in the process of pumping it. In case of problems with blood pressure (hypotension, hypertension), the walls of blood vessels dilate or narrow, so it is important to find out: are the vessels dilated or narrowed at high or low pressure?

What does blood pressure depend on?

Blood pressure is a value that is quite dependent on external factors and is not constant. Among the reasons that influence the level of pressure are the following:

• presence of bad habits (alcohol, smoking);
• lack of healthy, full sleep;
• eating food that contains a lot of salt;
• excess weight;
• presence of chronic diseases;
• frequent stress.

Lifestyle, determined by all of the above reasons, affects the health and functioning of the human body, and this, in turn, causes:

• violation of the resistance of the vascular walls;
• deterioration of the elasticity of arteries, capillaries and veins;
• changes in the speed at which the heart beats;
• decrease in the intensity of blood supply to the body's organs.

What happens to the vessels?

There are important mechanisms and reflexes in the body that ensure constant blood pressure. So, in response to increases in blood pressure, in some vessels there are receptors that send corresponding signals and nerve impulses to the brain along the depressor nerve and vagus nerves. The activity of pressor zone neurons in response to these impulses decreases, which leads to an increase in the lumen of the vessel walls. This mechanism lowers blood pressure and stabilizes it. That is, when pressure increases, narrowed vessels expand due to receptors. In response to too low pressure, mechanoreceptors send signals to the brain that activate the sympathetic nerve, the blood vessel constricts, the pressure rises to a normal value and stabilizes. It is this regulatory mechanism that ensures the stability of blood pressure, so if it malfunctions, problems arise with pressure surges, and as a result, with the functioning of blood vessels.

High blood pressure and blood vessels

A jump in blood pressure down or up is reflected in the vessels. With increased pressure, blood vessels narrow. That is, the walls of the vessels narrow, the lumen for the passage of blood becomes smaller, and, accordingly, there is less space for its flow through the vessels. Under the influence of the regulatory mechanism, the walls of blood vessels should expand, and blood pressure, accordingly, should normalize.

Low pressure and blood vessels

Low pressure means that the walls of the vessels will expand, the lumen for the passage of blood will become wider, and the speed of its flow into the organs will decrease.

Blood pressure control

Blood pressure is controlled by measuring it with a tonometer. Measure your blood pressure three times in a row at intervals of 3–5 minutes to track changes in readings. The highest values ​​are taken into account.

If there is a slight fluctuation in blood pressure in the absence of other diseases that could cause them, you can adjust and control the pressure by following the following rules:

• reduction of excess weight (obesity provokes an increase in blood pressure);
• moderate but regular physical activity is required;
• smoking and alcohol cause disturbances in the functioning of the heart;
• maintaining a proper diet (reducing the amount of cholesterol and fat, increasing the amount of potassium);
• limiting caffeine consumption;
• it is necessary to avoid stressful situations;
• regular consultation with a cardiologist.

Diagnostic measures

If surges in blood pressure are detected, you must consult your doctor or therapist. The therapist, having completed the initial examination, will suggest, if necessary, examination by a cardiologist or endocrinologist.

Possible diagnostic measures may include:

• blood tests;
• urine tests;
• Ultrasound of the kidneys.

How to normalize blood pressure?

Vascular high blood pressure is normalized with the help of blood thinning medications prescribed by a doctor. More fluid blood circulates better through narrowed vessels. Thinners are often prescribed along with diuretics.

If the vessels dilate, the pressure drops. Low blood pressure is stabilized with the help of tinctures and decoctions based on natural stimulants - eleutherococcus, lemongrass, ginseng, and hawthorn. These drugs help the blood vessels to tone and thus stabilize blood pressure. However, possible individual intolerance to the components of these drugs should be taken into account.

In general, any changes in blood pressure should be analyzed by a doctor, who will correctly prescribe medication and will definitely advise you to adjust your lifestyle, since complex treatment has the greatest effect.

Vasoconstrictor drugs

Low pressure means dilated vessel walls. If the body's blood pressure regulation system does not work, sometimes it is necessary to help it with medication. For this purpose, vasoconstrictor medications are used. They restore the functioning of the walls of blood vessels and stabilize the pressure to normal. They prescribe Midodrine, Phenylephrine, etc.

Vasodilators

For hypertension, vasodilators are prescribed because, by expanding the walls of blood vessels, they reduce the degree of blood pressure on them, and, therefore, help reduce blood pressure.

Vasodilator drugs have different types of action:

• diuretics – “Veroshpiron”, “Trifas”;
• calcium antagonists (calcium channel blockers) - Amlodipine, Verapamil;
• ACE inhibitors – “Enalapril”, “Lisinopril”;
• beta blockers – “Nebivalol”;
• angiotensin II receptor antagonists - Valsartan, Candesartan.

With high pressure, the walls of blood vessels must be expanded with the help of vasodilators. With a high degree of obstruction of blood vessels clogged with cholesterol, which results in increased blood pressure, a vasodilator will work better together with statins. That is, the drug will have a very good effect on a healthy area of ​​the vessel that is not clogged, for example, with cholesterol plaques, and will expand it, which will lead to the outflow of blood into this vessel. Therefore, vasodilating drugs are recommended to be used together with additional therapy and consultation with a doctor.

Conclusion

Blood pressure and blood vessels are directly interconnected, therefore, if you observe changes in blood pressure, you should immediately contact a specialist. Only an integrated approach (drug treatment and lifestyle changes) will help in the fight against cardiovascular diseases and surges in blood pressure.

How does pulmonary artery hypoplasia manifest?

Pulmonary artery hypoplasia is a malformation of the pulmonary vessels. It is expressed in underdevelopment of the branches of the pulmonary artery or branches. Very often, this defect occurs in combination with pulmonary hypoplasia, as well as heart defects.

• Types of anomaly
• How an anomaly is detected
• How does vice manifest itself?
• Treatment options

Narrowing of the pulmonary artery or its branches is a congenital defect that forms during intrauterine development of the fetus. Such disorders can be in any part of them that extends from the pulmonary trunk, and appear in a limited area or have a large extent.

Vasoconstrictions can be numerous. In this case, at the ends of small arteries in which narrowings have arisen, aneurysmal dilatations, the so-called “blind sacs,” appear. Places of narrowing of blood vessels are accompanied by thickening of their walls.

There are three forms of narrowing of the arteries:

• local narrowing or local compression;
• segmental narrowing or elongated;
• diffuse narrowing

Typically, hypoplasia is combined with hypertrophy of the right ventricle of the heart. This is because extra force is required to push blood through the narrowed part of the blood vessel. This forces the right ventricular muscle to work harder. The consequence of this is an increase in pressure in the right ventricle.

Pulmonary valve normal and defective

The defect leads to changes in the structure of the lung tissue. At the same time, the final sections of the lung increase. Air retention occurs, it fills the alveoli. This leads to increased pressure inside the lungs and thinning of the walls of the alveoli. Due to overfilling with air, the proportion of the lung increases significantly, and the elasticity of the lung tissue decreases.

The increased proportion puts pressure on healthy areas of the lung, they collapse and lose their ability to participate in air exchange.

Types of anomaly

The anomaly is divided into several types, based on anatomical features:

1. Type I It includes an anomaly in which there is a narrowing or fusion of the pulmonary artery valve, and its trunk and branches are normally developed. Pulmonary blood flow passes through the ductus arteriosus. Almost all branches of the arterial vessel are developed normally.
2. Type II The pulmonary artery trunk is susceptible to hypoplasia, and its branches are normally developed.
3. III type.
   • III A. The anomaly consists of hypoplasia of the valve, trunk, and left branch of the pulmonary artery. Its right branch is in normal condition and usually connects directly with the patent ductus arteriosus.
   • III B. The anomaly consists of hypoplasia of the trunk and right branch, as well as the valve of the blood vessel. At the same time, the level of development of the left branch is normal; it is connected directly to the patent ductus arteriosus. At the same time, the lungs provide blood to the aortopulmonary collaterals.
4. IV type. There is no communication between the artery and the right ventricle. The pulmonary arteries do not participate in the blood supply. It is provided by collaterals. Remnants of the arteries are preserved in the lung parenchyma.

How an anomaly is detected

A defect in the pulmonary blood vessel that carries blood from the heart is an intrauterine abnormality of the fetus. It is genetic in nature. The development of hypoplasia is promoted by pathogenic factors that affect the development of the fetus in the first trimester of pregnancy. The development of the anomaly is provoked by rubella disease, radiation exposure, certain medications, and a pregnant woman’s tendency to drink alcohol.

A doctor may suspect the presence of a defect by listening to a systolic murmur over the base of the heart and changes in heart sounds. An X-ray during a routine medical examination may show excessive transparency of one lung and at the same time underdevelopment or absence of the pulmonary veins, when the blood supply goes through the bronchial arteries, branches of the aorta. You can confirm the presence of an anomaly using the following methods.

How does vice manifest itself?

Hypoplasia of the blood vessel carrying blood from the heart, developed to a slight extent, usually does not cause trouble to a person. He is not in pain and leads a normal life. If the anomaly is developed to a significant extent, the person suffers from shortness of breath, which is especially severe during physical exertion. He gets tired quickly and often suffers from respiratory diseases and pneumonia.

Treatment options

Narrowing of the pulmonary artery accounts for 4% of heart defects. Thanks to the methods of angiocardiography and cardiac catheterization, this developmental anomaly is being detected more and more often. Children diagnosed with hypoplasia should undergo general health activities and engage in physical therapy.

Surgical correction of the defect is the only effective treatment. Specialists use surgical intervention in cases where vasoconstriction is detected in a size greater than half the diameter of the cavity, and the difference in pressure reaches 30%. If the narrowing of the pulmonary arteries is numerous, they are not operated on. During the operation, the problem area of ​​the vessel is dissected and its lumen is increased by means of a patch made from the patient's pericardium.

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With anatomically correct development, the aorta communicates with the left ventricle and distributes oxygen-enriched blood throughout the systemic circulation. And the pulmonary trunk branches off from the right ventricle and delivers blood to the lungs, where it is enriched with oxygen and returns to the left atrium. The oxygenated blood then enters the left ventricle.

However, under the influence of a number of unfavorable factors, cardiogenesis may occur incorrectly, and the fetus will develop such as complete transposition of the great vessels (TMS). With this anomaly, the aorta and pulmonary artery change places - the aorta branches off from the right ventricle, and the pulmonary artery from the left ventricle. As a result, blood not enriched with oxygen enters the systemic circulation, and oxygenated blood is again delivered to the pulmonary circulation (i.e., to the lungs). In this way, the blood circulation circles are separated, and they represent two closed rings that do not communicate with each other in any way.

The hemodynamic disturbance that occurs during such TMS is incompatible with life, but often this anomaly is combined with a compensating presence in the interatrial septum. Thanks to this, the two circles can communicate with each other through this shunt, and at least a slight mixing of venous and arterial blood occurs. However, such slightly oxygenated blood cannot fully saturate the body. If the heart also has a defect in the interventricular septum, then the situation is further compensated, but such enrichment of the blood with oxygen is not enough for the normal functioning of the body.

A child born with such a congenital defect quickly falls into a critical condition. manifests itself already in the first hours of life, and in the absence of immediate help, the newborn dies.

Complete TMS is a critical blue-type heart defect that is incompatible with life and always requires immediate cardiac surgery. If there is an open foramen ovale and an atrial septal defect, surgery may be postponed, but it should be performed in the first weeks of the child’s life.

This congenital defect is one of the most common anomalies of the heart and blood vessels. It, along with tetralogy of Fallot, patent foramen ovale, and ventricular septal defect, is one of the “big five” heart anomalies. According to statistics, TMS develops 3 times more often in male fetuses and accounts for 7-15% of all congenital defects.

In children with corrected TMS, the location of the ventricles, rather than the arteries, changes. With this type of defect, venous blood ends up in the left ventricle, and oxygenated blood in the right. However, from the right ventricle it enters the aorta and enters the systemic circulation. Such hemodynamics are also atypical, but blood circulation still occurs. As a rule, this type of anomaly does not affect the condition of the born child and does not pose a threat to his life. Subsequently, such children may experience some developmental delay, since the functionality of the right ventricle is lower than that of the left, and it cannot fully cope with ensuring normal blood supply to the systemic circulation.

In this article we will introduce you to the possible causes, types, symptoms, methods of diagnosis and correction of transposition of the great vessels. This information will help you get a general understanding of the essence of this dangerous blue type congenital heart defect and the principles of its treatment.

Bad habits of a pregnant woman significantly increase the risk of developing congenital heart defects in the fetus.

Like all other congenital heart defects, TMS develops in the prenatal period under the influence of the following unfavorable factors:

• heredity;
• unfavorable environment;
• taking teratogenic drugs;
• viral and bacterial infections suffered by the pregnant woman (measles, mumps, chicken pox, rubella, ARVI, syphilis, etc.);
• toxicosis;
• diseases of the endocrine system (diabetes mellitus);
• the age of the pregnant woman is over 35-40 years;
• polyhypovitaminosis during pregnancy;
• contact of the expectant mother with toxic substances;
• bad habits of a pregnant woman.

An abnormal location of the great vessels is formed in the 2nd month of embryogenesis. The mechanism of formation of this defect has not yet been sufficiently studied. Previously it was assumed that the defect is formed due to improper bending of the aortic-pulmonary septum. Later, scientists began to assume that transposition is formed due to the fact that when the arterial trunk branches, abnormal growth of the subpulmonary and subaortic cone occurs. As a result, the pulmonary valve is located above the left ventricle, and the aortic valve is located above the right ventricle.

Classification

Depending on the accompanying defects that perform the role of shunts compensating for hemodynamics during TMS, a number of variants of this anomaly of the heart and blood vessels are distinguished:

• a defect accompanied by a sufficient volume of pulmonary blood flow and hypervolemia and combined with a patent foramen ovale (or simple TMS), a ventricular septal defect or patent ductus arteriosus and the presence of additional shunts;
• a defect accompanied by insufficient pulmonary blood flow and combined with a ventricular septal defect and stenosis of the outflow tract (complex TMS) or with a narrowing of the outflow tract of the left ventricle.

In approximately 90% of patients, TMS is combined with hypervolemia of the pulmonary circulation. In addition, 80% of patients have one or more additional compensating shunts.

The most favorable option for TMS is in cases where, due to defects of the interatrial and interventricular septa, sufficient mixing of arterial and venous blood is ensured, and moderate narrowing of the pulmonary artery prevents the onset of significant pulmonary hypervolemia.

Normally, the aorta and pulmonary trunk are in a crossed state. During transposition, these vessels are located parallel. Depending on their relative position, the following TMS options are distinguished:

• D-option – aorta to the right of the pulmonary trunk (in 60% of cases);
• L-variant – aorta to the left of the pulmonary trunk (in 40% of cases).

Symptoms

During intrauterine development, TMS hardly manifests itself in any way, since during fetal circulation the pulmonary circulation does not yet function, and blood flow occurs through the oval window and the patent ductus arteriosus. Typically, children with such a heart defect are born at normal times, with sufficient or slightly excess weight.

After the birth of a child, its viability is completely determined by the presence of additional communications that ensure the mixing of arterial and venous blood. In the absence of such compensating shunts - a patent foramen ovale, a ventricular septal defect or a patent ductus arteriosus - the newborn dies after birth.

Typically, TMS can be detected immediately after birth. Exceptions are cases of corrected transposition - the child develops normally, and the anomaly appears a little later.

After birth, the newborn develops the following symptoms:

• total cyanosis;
• rapid pulse.

If this anomaly is combined with coarctation of the aorta and patent ductus arteriosus, then the child has differentiated cyanosis, manifested by greater cyanosis of the upper body.

Later in children with TMS it progresses (the size of the heart and liver increases, ascites develops less often and edema appears). Initially, the child’s body weight is normal or slightly excessive, but later (by 1-3 months of life) malnutrition develops due to cardiac insufficiency and hypoxemia. Such children often suffer from acute respiratory viral infections and pneumonia, and are lagging behind in physical and mental development.

When examining a child, a doctor may identify the following symptoms:

• wheezing in the lungs;
• expanded chest;
• unsplit loud II tone;
• noises of accompanying anomalies;
• rapid pulse;
• heart hump;
• deformation of fingers like “drum sticks”;
• liver enlargement.

With corrected TMS, which is not accompanied by additional congenital anomalies of the heart, the defect can be asymptomatic for a long time. The child develops normally, and complaints appear only when the right ventricle ceases to cope with providing the systemic circulation with a sufficient amount of oxygenated blood. When examined by a cardiologist, such patients are diagnosed with heart murmurs and atrioventricular block. If corrected TMS is combined with other congenital defects, then the patient develops complaints characteristic of the existing anomalies of heart development.

Diagnostics

Most often, TMS is detected in the maternity hospital. When examining the child, the doctor detects a pronounced medially displaced cardiac impulse, cardiac hyperactivity, cyanosis and expansion of the chest. When listening to the sounds, an increase in both tones, the presence of systolic murmur and murmurs characteristic of concomitant cardiac defects are revealed.

For a detailed examination of a child with TMS, the following diagnostic methods are prescribed:

• chest x-ray;
• catheterization of cardiac cavities;
• (aorto-, atrio-, ventriculo- and coronary angiography).

Based on the results of instrumental studies of the heart, the cardiac surgeon draws up a plan for further surgical correction of the anomaly.

Treatment

With complete TMS, all children undergo emergency palliative operations in the first days of life, aimed at creating a defect between the pulmonary and systemic circulation or expanding it. Before such interventions, the child is prescribed a drug that promotes patent ductus arteriosus - prostaglandin E1. This approach allows for mixing of venous and arterial blood and ensures the child’s viability. A contraindication to performing such operations is the development of irreversible pulmonary hypertension.

Depending on the clinical case, one of the methods of such palliative operations is selected:

• balloon atrioseptostomy (endovascular Park-Rushkind technique);
• open atrioseptectomy (resection of the interatrial septum using the Blalock-Hanlon technique).

Such interventions are performed to eliminate life-threatening hemodynamic disorders and are preparation for the necessary cardiac surgical correction.

To eliminate hemodynamic disturbances that occur during TMS, the following operations can be performed:

1. According to Senning's method. The cardiac surgeon, using special patches, redraws the cavities of the atria so that blood from the pulmonary veins begins to flow into the right atrium, and from the vena cava into the left.
2. According to Mustard's method. After opening the right atrium, the surgeon excises most of the interatrial septum. The doctor cuts out a patch in the shape of pants from a piece of pericardium and sews it in such a way that blood from the pulmonary veins flows into the right atrium, and from the vena cava into the left.

To anatomically correct the incorrect location of the great vessels during transposition, the following arterial switching operations can be performed:

1. Crossing and orthotopic replantation of the great vessels, ligation of the PDA (according to Zatena). The pulmonary artery and aorta cross and move to their respective ventricles. In addition, the vessels anastomose their distal sections with the proximal segments of each other. Next, the surgeon transplants the coronary arteries into the neoaorta.
2. Elimination of pulmonary artery stenosis and plastic surgery of ventricular septal defect (according to Rastelli). Such operations are performed when transposition is combined with a ventricular septal defect and pulmonary artery stenosis. The ventricular septal defect is closed with a patch of pericardium or synthetic material. Pulmonary artery stenosis is eliminated by closing its mouth and implanting a vascular graft that provides communication between the right ventricle and the pulmonary trunk. In addition, new blood outflow pathways are formed. Blood flows from the right ventricle to the pulmonary artery through the created extracardiac conduit, and from the left ventricle to the aorta through the intracardial tunnel.
3. Arterial switching and plastic surgery of the interventricular septum. During the intervention, the pulmonary artery is cut off and reimplanted into the right ventricle, and the aorta into the left ventricle. The coronary arteries are sutured to the aorta, and the ventricular septal defect is closed with a synthetic or pericardial patch.

Typically, such operations are performed before 2 weeks of a child’s life. Sometimes their implementation is delayed up to 2-3 months.

Each of the above methods of anatomical correction of TMS has its own indications, contraindications, pros and cons. The tactics of arterial switching are selected depending on the clinical case.

After cardiac surgical correction, patients are recommended to undergo further lifelong monitoring by a cardiac surgeon. Parents are advised to ensure that their child follows a gentle regimen:

• avoiding heavy physical activity and excessive activity;
• good sleep;
• proper organization of the daily routine;
• proper nutrition;
• prophylactic use of antibiotics before dental or surgical procedures to prevent infective endocarditis;
• regular observation by a doctor and compliance with his prescriptions.

In adulthood, the patient must follow the same recommendations and restrictions.

Forecast

In the absence of timely cardiac surgical treatment, the prognosis for the outcome of TMS is always unfavorable. According to statistics, about 50% of children die during the first month of life, and more than 2/3 of children do not survive until the age of 1 year due to severe hypoxia, increasing acidosis and heart failure.

The prognosis after cardiac surgery becomes more favorable. With complex defects, positive long-term results are observed in approximately 70% of patients, with simpler ones - in 85-90%. Regular monitoring by a cardiac surgeon is of no small importance in the outcome of such cases. After corrective operations, patients may develop long-term complications: stenosis, thrombosis and calcification of conduits, heart failure, etc.

Transposition of the great vessels is one of the most dangerous heart defects and can only be corrected surgically. The timeliness of cardiac surgery is of no small importance for its favorable outcome. Such operations are carried out up to 2 weeks of the child’s life, and only in some cases they can be delayed up to 2-3 months. It is desirable that such a developmental anomaly be detected before the baby is born, and that pregnancy and childbirth are planned taking into account the presence of this dangerous congenital heart defect in the unborn child.

Functional classification of blood vessels.

• Main vessels.
• Resistive vessels.
• Exchange vessels.
• Capacitive vessels.
• Shunt vessels.

Main vessels- aorta, large arteries. The wall of these vessels contains many elastic elements and many smooth muscle fibers. Meaning: transform the pulsating ejection of blood from the heart into a continuous flow of blood.

Resistive vessels- pre- and post-capillary. Precapillary vessels - small arteries and arterioles, capillary sphincters - vessels have several layers of smooth muscle cells. Postcapillary vessels - small veins, venules - also contain smooth muscles. Meaning: have the greatest resistance to blood flow. Precapillary vessels regulate blood flow in the microvasculature and maintain a certain blood pressure in large arteries. Post-capillary vessels - maintain a certain level of blood flow and pressure in the capillaries.

Exchange vessels- 1 layer of endothelial cells in the wall - high permeability. They carry out transcapillary exchange.

Capacitive vessels- all venous. They contain 2/3 of all blood. They have the least resistance to blood flow, their wall is easily stretched. Meaning: due to expansion, they deposit blood.

Shunt vessels- connect arteries with veins bypassing capillaries. Meaning: provide unloading of the capillary bed.

Number of anastomoses- the value is not constant. They occur when there is poor circulation or lack of blood supply.

Patterns of blood movement through vessels. The value of elasticity of the vascular wall

Blood movement is subject to physical and physiological laws. Physical:- laws of hydrodynamics.

1st law: the amount of blood flowing through the vessels and the speed of its movement depends on the pressure difference at the beginning and end of the vessel. The greater this difference, the better the blood supply.

2nd law: Peripheral resistance prevents blood flow.

Physiological patterns of blood movement through vessels:

• heart function;
• closedness of the cardiovascular system;
• suction effect of the chest;
• elasticity of blood vessels.

During the systole phase, blood enters the vessels. The wall of blood vessels stretches. During diastole there is no ejection of blood, the elastic vascular wall returns to its original state, and energy accumulates in the wall. When the elasticity of blood vessels decreases, pulsating blood flow appears (normally in the vessels of the pulmonary circulation). In pathological sclerotic vessels - Musset's symptom - head movements in accordance with the pulsation of the blood.

Blood circulation time. Volumetric and linear blood flow velocity

Blood circulation time- the time during which the cow passes through both circles of blood circulation. At a heart rate of 70 per minute, the time is 20 - 23 s, of which 1/5 of the time is for the small circle; 4/5 of the time - for a large circle. Time is determined using control substances and isotopes. - they are injected intravenously into the v.venaris of the right hand and it is determined after how many seconds this substance will appear in the v.venaris of the left hand. Time is affected by volumetric and linear speeds.

Volume velocity- the volume of blood that flows through the vessels per unit time. Vlin. - the speed of movement of any blood particle in the vessels. The highest linear velocity is in the aorta, the lowest is in the capillaries (0.5 m/s and 0.5 mm/s, respectively). Linear velocity depends on the total cross-sectional area of ​​the vessels. Due to the low linear velocity in the capillaries, conditions for transcapillary exchange. This speed in the center of the vessel is greater than at the periphery.