Blood pressure in the aorta. Arterial pressure

Level blood pressure measured in mmHg and determined by a combination of different factors:

1. The pumping force of the heart.

2. Peripheral resistance.

3. Volume of circulating blood.

Pumping force of the heart. The main factor in maintaining blood pressure levels is the work of the heart. Blood pressure in the arteries fluctuates constantly. Its rise during systole determines maximum (systolic) pressure. In a middle-aged person, in the brachial artery (and in the aorta) it is 110–120 mm Hg. The drop in pressure during diastole corresponds to minimum (diastolic) pressure, which averages 80 mm Hg. It depends on peripheral resistance and heart rate. The amplitude of oscillations, i.e. the difference between systolic and diastolic pressure is pulse pressure is 40–50 mm Hg. It is proportional to the volume of blood ejected. These values ​​are the most important indicators of the functional state of the entire cardiovascular vascular system.

Time average cardiac cycle Blood pressure, which is the driving force of blood flow, is called average pressure. For peripheral vessels it is equal to the sum of diastolic pressure + 1/3 of pulse pressure. For the central arteries it is equal to the sum of diastolic + 1/2 pulse pressure. The average pressure decreases along the way vascular bed. As you move away from the aorta, systolic pressure gradually increases. In the femoral artery it increases by 20 mm Hg, in the dorsal artery of the foot by 40 mm Hg more than in the ascending aorta. Diastolic pressure, on the contrary, decreases. Accordingly, pulse pressure increases, which is caused by peripheral vascular resistance.

In the terminal branches of the arteries and in the arterioles, the pressure decreases sharply (to 30–35 mmHg at the end of the arterioles). Pulse fluctuations significantly decrease and disappear, which is due to the high hydrodynamic resistance of these vessels. In the vena cava, the pressure fluctuates around zero.

mm. Hg Art.

The normal level of systolic pressure in the brachial artery for an adult is usually in the range of 110-139 mm. Hg Art. The normal limit for diastolic pressure in the brachial artery is 60-89. Cardiologists distinguish the concepts:

optimal level Blood pressure when systolic pressure is slightly less than 120 mm. Hg Art. and diastolic – less than 80 mm. Hg Art.

normal level– systolic less than 130 mm. Hg Art. and diastolic less than 85 mm. Hg Art.

high normal level– systolic 130-139 mm. Hg Art. and diastolic 85-89 mm. Hg Art.

Despite the fact that with age, especially in people over 50 years of age, blood pressure usually gradually increases, at present it is not customary to talk about the age-related rate of increase in blood pressure. When systolic pressure increases above 140 mm. Hg Art., and diastolic above 90 mm. Hg Art. It is recommended to take measures to reduce it.

An increase in blood pressure relative to values ​​​​defined for a particular organism is called hypertension(140–160 mm Hg), reduction - hypotension(90–100 mmHg). Under the influence of various factors, blood pressure can change significantly. Thus, with emotions, a reactive increase in blood pressure is observed (passing exams, sports competitions). So-called advanced (pre-start) hypertension occurs. There are daily fluctuations in blood pressure; during the day it is higher; during restful sleep it is slightly lower (by 20 mm Hg). When eating food, systolic pressure increases moderately, diastolic pressure decreases moderately. Pain is accompanied by an increase in blood pressure, but with prolonged exposure to a painful stimulus, a decrease in blood pressure is possible.

During physical activity, systolic increases, diastolic can increase, decrease, or remain unchanged.

Hypertension occurs:

When increasing cardiac output;

When increasing peripheral resistance;

An increase in the mass of circulating blood;

When both factors are combined.

In the clinic, it is customary to distinguish between primary (essential) hypertension, which occurs in 85% of cases, the causes are difficult to determine, and secondary (symptomatic) hypertension - 15% of cases, it accompanies various diseases. Hypotension is also distinguished between primary and secondary.

When a person moves to a vertical position from a horizontal position, a redistribution of blood occurs in the body. Temporarily decreased: venous return, central venous pressure (CVP), stroke volume, systolic pressure. This causes active adaptive hemodynamic reactions: narrowing of resistive and capacitive vessels, increased heart rate, increased secretion of catecholamines, renin, vosopressin, angiotensin II, aldosterone. In some people with low blood pressure, these mechanisms may be insufficient to maintain normal blood pressure levels when the body is upright, and blood pressure drops below acceptable levels. Orthostatic hypotension occurs: dizziness, darkening of the eyes, possible loss of consciousness - orthostatic collapse (fainting). This can happen when the ambient temperature increases.

Peripheral resistance. The second factor determining blood pressure is peripheral resistance, which is determined by the state of resistive vessels (arteries and arterioles).

The amount of circulating blood and its viscosity. When large amounts of blood are transfused, blood pressure increases, and when blood loss occurs, it decreases. Blood pressure depends on venous return (for example, during muscular work). Blood pressure constantly fluctuates from a certain average level. When recording these oscillations on the curve, the following are distinguished: first order waves (pulse), the most frequent, reflect the systole and diastole of the ventricles. Second order waves (respiratory). As you inhale, blood pressure decreases and as you exhale, it increases. Third-order waves reflect the influence of the central nervous system; they are more rare, perhaps due to fluctuations in the tone of peripheral vessels.

Methods for measuring blood pressure

In practice, two methods of measuring blood pressure are used: direct and indirect.

Direct (bloody, intravascular) is carried out by introducing a cannula or catheter into the vessel connected to a recording device. It was first carried out in 1733 by Stefan Health.

Indirect (indirect or palpatory), proposed by Riva-Rocci (1896). Used clinically in humans.

The main device for measuring blood pressure is sphygmomanometer. A rubber inflatable cuff is placed on the shoulder, which, when air is pumped into it, compresses the brachial artery, stopping blood flow in it. The pulse in the radial artery disappears. By releasing air from the cuff, monitor the appearance of the pulse, recording the pressure value at the moment of its appearance using a pressure gauge. This method ( palpable) allows you to determine only systolic pressure.

In 1905 I.S. Korotkov suggested auscultatory method by listening to sounds (Korotkoff sounds) in the brachial artery below the cuff using a stethoscope or phonendoscope. When the valve opens, the pressure in the cuff decreases and, when it drops below systolic pressure, short, clear tones appear in the artery. The systolic pressure is noted on the manometer. Then the tones become louder and then fade, and the diastolic pressure is determined. The tones may be constant or rise again after fading. The appearance of tones is associated with turbulent blood movement. When laminar blood flow is restored, the sounds disappear. With increased activity of the cardiovascular system, the sounds may not disappear.

Only half of people with high blood pressure receive treatment for hypertension.

The state cardiology program includes the detection of hypertension at early stages. That's why clinics can measure blood pressure in the pre-doctor's office. Prevention days are held in pharmacies, and advertising has appeared in television programs.

How is blood pressure formed?

Blood flows as a liquid and fills the vascular bed. According to the laws of physics, the pressure inside the vessels must be constantly higher than atmospheric pressure. This is an indispensable condition of life.

Most often we think about blood pressure, but we should not forget that there are also indicators of intracardiac, venous and capillary levels.

A heartbeat is caused by the contraction of the ventricles and the release of blood into the arteries. Due to their elasticity, they spread the wave from larger vessels to the smallest capillaries.

Measuring blood pressure on the ulnar artery shows 2 numbers:

• the upper one determines the systolic or “cardiac” pressure (indeed, it depends on the strength of the heart muscle);
• lower - diastolic (it shows the ability of the vascular bed to maintain tone during a short period of the cardiac relaxation phase).

The highest pressure is created in the cavity of the left ventricle. When leaving it in the aorta and large vessels, it is slightly lower (by 5–10 mm Hg), but exceeds the figures at the level of the ulnar artery.

The diagram shows two circles of blood circulation, showing areas of maximum pressure (highest pressure) and lowest (lowest pressure)

What does upper and lower pressure depend on?

Not only strong muscle the heart is able to maintain systolic pressure. This is facilitated by:

• the number of contractions or rhythm per minute (with tachycardia, increased cardiac pressure is observed);
• wall resistance force blood vessels, their elasticity.

Diastolic pressure is maintained only by the tone of small arteries in the periphery.

As you move away from the heart, the difference between the upper and lower pressure decreases, and the venous and capillary pressures no longer depend on the strength of the myocardium.

The difference between systolic and diastolic levels is called pulse pressure. It is equal to normal conditions 30–40 mm Hg. Art.

What standards has WHO established for the definition of hypertension? Should high blood pressure be considered a symptom or hypertension? What causes the disease? You can learn this and much more on our website from the article “Hypertension: what is this disease?”

The dependence of systolic and diastolic blood pressure levels on physiological conditions is shown in the table.

What is the danger of high blood pressure?

This significantly increases the risk of diseases such as cerebrovascular accident (stroke), acute heart attack myocardium, contributes to the early formation of heart failure and irreversible kidney pathology.

In cases where hypertension is detected even in the presence of these diseases, it is appropriate to support scientists who figuratively call hypertension a “silent killer.”

A particularly severe form of the disease is malignant hypertension. It is detected in one in 200 hypertensive patients, more often in men. The course is extremely severe. Hypertension cannot be treated medications. Medicines even worsen the patient's condition. The patient dies from complications after 3–6 months.

Can only systolic blood pressure increase?

Most often, with hypertension, an increase in both the upper and lower levels above 140/90 mmHg is detected. Art. But there are cases when only systolic high pressure is determined with normal diastolic numbers.

Reasons for increased heart pressure associated with the adaptation of the myocardium with age to work in conditions of arteries affected by atherosclerosis.

It has been established that systolic pressure normally increases up to 80 years, and diastolic pressure only up to 60, then it stabilizes and can even decrease on its own.

With a lack of collagen, blood vessels lose elasticity, which means they are not able to bring a wave of blood to the periphery, and the oxygen supply is disrupted. The situation worsens even more when the lumen of the arteries is narrowed by atherosclerotic plaques or atherosclerosis of the aorta.

In older people, the heart must contract with greater force to “push” blood through the altered vessels

How does high blood pressure manifest?

Symptoms of hypertension often cannot be distinguished from other conditions unless measured arterial pressure. Most often a person feels:

• headaches in the back of the head and crown;
• dizziness;
• tendency to nosebleeds;
• rush of blood and heat in the upper parts of the body.

With a sharp rise in pressure (hypertensive crisis), symptoms appear suddenly:

• severe headache;
• nausea and vomiting;
• impaired vision, “darkening” in the eyes;
• trembling in the body;
• shortness of breath, lack of air at rest;
• increased heart rate, arrhythmias.

What examination needs to be done?

To prescribe treatment, the doctor needs to know how affected the target organs (heart, kidneys, brain) are, since medications have side properties, and undesirable effects on the heart rate and renal blood flow cannot be allowed.

Hypertension should be confirmed by a recorded elevated blood pressure within 2–3 days if the person is at rest.

The picture of the fundus “tells” about the tone of the blood vessels, so all hypertensive patients are referred to an ophthalmologist. An ophthalmologist not only helps diagnose hypertension, but also establishes its stage of progression.

An electrocardiogram (ECG) reveals a malnutrition of the heart muscle, arrhythmias, and hypertrophy (overload) of the myocardium.

Ultrasound of the heart allows you to examine and measure blood flow through the cardiac chambers, the volume and force of systolic ejection, and the size of the heart.

The increase in the size of the left ventricle is seen by the radiologist when interpreting the fluorogram. If there are pronounced changes, he calls the patient through a therapist for further examination and checks the size of the heart and large vessels in more detail using radiography.

Damage to the kidney tissue is indicated by the presence of protein and red blood cells in the urine test (normally they should not be present). This indicates impaired filtration through the renal tubules.

The examination should help determine the cause of hypertension. This is necessary for therapy.

What you will have to give up, how to change your diet and diet

This also relates to one of the problems early mortality population.

If you have high blood pressure, you must stop working night shifts and beware of excessive nervous and physical stress. In your daily routine, you need to devote time to rest, walks, and ensure good sleep with herbal tea with honey, lemon balm or mint.

Smoking should be stopped; alcohol is allowed in a dose of no more than 150 ml of dry red wine once a month. Steam rooms and saunas are contraindicated. Physical exercise are limited morning exercises, walking, swimming.

The diet is aimed at preventing heart pathology and atherosclerosis. It is necessary to avoid salty and spicy foods; hot sauces, fried and smoked fatty meats, sweets, soda, and coffee are not recommended. It is better to switch to fish, vegetables and fruits, vegetable oils, cereals, dairy products, green tea.

If you are overweight, you should arrange low-calorie fasting days.

You can independently control your blood pressure both at home and in the country.

How to treat high blood pressure?

When prescribing therapy for hypertension, the doctor must use drugs that protect the vessels of the heart and brain and improve their nutrition. The patient’s age, existing other diseases, and risk factors are taken into account.

Drugs from the group of adrenergic blockers remove the unnecessary effect of sympathetic impulses on the vessels. Currently, there are long-acting medications that allow you to take one tablet only in the morning.

Diuretics or diuretics are prescribed depending on the condition of the kidneys. For this purpose, potassium-sparing drugs or stronger ones are chosen, which are not taken constantly, but according to a schedule.

A group of ACE inhibitors and calcium antagonists allow you to dilate blood vessels by acting on muscle cells and nerve endings.

In the absence of symptoms of decompensation, hypertension should be treated in sanatoriums. Physiotherapeutic procedures, baths, acupuncture, and massage are used here.

You can get rid of hypertension only if it is secondary and the underlying disease responds well to treatment. Hypertension has not yet been cured; constant monitoring is necessary. But it is possible to avoid dangerous complications with the help of treatment and a positive attitude of the patient.

What is the highest blood pressure a person can have?

Blood pressure is the pressure that blood exerts on the walls of blood vessels. This parameter, reflecting the condition of the vascular walls, the functioning of the heart and kidneys, is one of the most important for human health. Maintaining it at a constant level is one of the main tasks of the body, since adequate blood supply to the organs, commensurate with the load, occurs only under conditions of optimal blood pressure.

Normal pressure is defined as the range within which adequate blood supply to organs and tissues is ensured. Each organism has its own range, but in most cases it ranges from 100 to 139 mmHg. Conditions in which the systolic pressure level falls below 90 mmHg are called arterial hypotension. And those conditions in which this level rises above 140 mm Hg are called arterial hypertension.

This is an increase in blood pressure, which is important symptom pathological conditions accompanied by either an increase in vascular resistance, or an increase in cardiac output, or a combination of both. WHO (World Health Organization) recommends calling arterial hypertension a level of systolic pressure above 140 mm Hg, and a diastolic pressure above 90 mm Hg. provided that the person was not taking antihypertensive medications at the time of measurement.

Table 1. Physiological and pathological blood pressure values.

Initially, arterial hypertension (AH) is divided into two large groups: primary and secondary. Primary hypertension is called hypertension, the causes of which still remain unclear. Secondary hypertension occurs due to specific reason- pathologies in one of the blood pressure regulation systems.

Table 2. Causes of secondary hypertension.

Even though the reasons hypertension are not fully understood, there are risk factors that contribute to its development:

1. 1. Heredity. By this we mean genetic predisposition to the appearance of this disease.
2. 2. Features of the neonatal period. This refers to persons who were premature at birth. The lower the child's body weight, the higher the risk.
3. 3. Body weight. Excess weight is a key risk factor for developing hypertension. There is evidence that every extra 10 kg increases systolic blood pressure by 5 mmHg.
4. 4. Nutritional factors. Excessive daily consumption of table salt increases the risk of developing arterial hypertension. Consuming more than 5 grams of salt per day is considered excessive.
5. 5. Bad habits. Both smoking and excessive alcohol consumption have a detrimental effect on the condition of the vascular walls, which leads to an increase in their resistance and a rise in pressure.
6. 6. Low physical activity. In people who lead an insufficiently active lifestyle, the risk increases by 50%.
7. 7. Factors environment. Excessive noise, environmental pollution, chronic stress always lead to an increase in blood pressure.

In adolescence, due to hormonal changes, fluctuations in blood pressure are possible. Thus, by the age of 15, a maximum surge in hormone levels occurs, so symptoms of hypertension may appear. At the age of 20, this peak usually ends, so if blood pressure remains high, it is necessary to exclude secondary arterial hypertension.

The highest blood pressure figures are observed during a hypertensive crisis. This is an acute, pronounced increase in pressure with characteristic clinical symptoms, requiring immediate, controlled reduction in order to prevent multiple organ failure. Most often, a crisis appears when the numbers rise above 180/120 mmHg. Indicators from 240 to 260 systolic and from 130 to 160 mmHg diastolic pressure are critical.

When the upper level reaches 300 mm Hg. a chain of irreversible events occurs that leads the body to death.

An optimal level of pressure maintains sufficient blood supply to organs and tissues. During a hypertensive crisis, the indicators can be so high and the level of blood supply so low that hypoxia and failure of all organs begin to develop. The most sensitive to this is the brain with its unique circulatory system, which has no analogues in any other organ.

It is noteworthy that the blood reservoir here is the vascular ring, and it is this type of blood supply that is evolutionarily the most developed. He also has his own weak sides- such a ring can function only in a strictly defined range of systolic pressure - from 80 to 180 mm Hg. If the pressure rises above these figures, the automatic regulation of the tone of the vascular ring is disrupted, gas exchange is severely disrupted, vascular permeability rapidly increases, and acute brain hypoxia occurs, followed by ischemia. If the pressure remains at the same level, the most dangerous event develops - ischemic stroke. Therefore, relative to the brain, the highest pressure in a person should not exceed 180 mm Hg.

Hypertension implies the presence of certain symptoms, but at the very beginning the disease can be asymptomatic, hidden:

1. 1. Symptoms caused directly by high blood pressure. These include: headaches of various localizations, most often in the back of the head, appearing, as a rule, in the morning; dizziness of varying intensity and duration; feeling of heartbeat; excessive fatigue; noise in the head.
2. 2. Symptoms caused by vascular damage in arterial hypertension. This may include nosebleeds, blood in the urine, visual disturbances, shortness of breath, chest pain, etc.
3. 3. Symptoms of secondary arterial hypertension. Frequent urination, thirst, muscle weakness (with kidney disease); weight gain, emotional instability (for example, with Itsenko-Cushing syndrome), etc.

It is important to understand that with arterial hypertension, not only blood vessels are affected, but also almost all internal organs. With prolonged persistent progression, the retina, kidneys, brain and heart are affected.

When the above symptoms appear, as well as when the readings increase above 140/90 mmHg. you need to consult a general practitioner. During the consultation, the doctor will definitely assess risk factors that can be eliminated, rule out the possibility of secondary arterial hypertension and select the right drug for treatment. The goal of therapy is to reduce the long-term risk of developing vascular accidents (heart attacks, strokes) as much as possible. It must be remembered that the target level in in this case are numbers less than 140/90 mmHg.

The therapist will prescribe an additional examination, which includes a study of blood counts, electrocardiography, consultation with an ophthalmologist to examine the fundus of the eye, submitting urine for a general analysis and a special study (detection of microalbuminuria as an indicator of target organ damage in hypertension), ultrasound of the vessels of the neck, etc. Then Taking into account the data obtained, the doctor will select the correct treatment regimen.

If, at the first appointment, figures above 180 mm Hg are detected, treatment is prescribed immediately.

The first key link in the treatment of arterial hypertension is lifestyle changes, which include:

• to give up smoking;
• reduction and stabilization of body weight;
• reducing alcohol consumption;
• reducing table salt consumption;
• physical activity - regular dynamic exercise for at least 30 minutes a day;
• increasing the consumption of fruits and vegetables, reducing the consumption of fatty foods.

The second link is the prescription of drug therapy. Among the many antihypertensive drugs, the doctor will choose the optimal one based on blood pressure numbers, examination data and the presence of concomitant pathologies.

If you suspect a hypertensive crisis, you must immediately call an ambulance medical care. In an uncomplicated version of the crisis, it is very important to reduce the pressure carefully and slowly. Even the highest blood pressure in a person must be reduced by no more than 25% in 2 hours. If you reduce it quickly, there is a high risk of developing circulatory disorders in organs and tissues, called hypoperfusion. You can take Captopril (Capoten) or Nifedipine sublingually on your own. The widely known clonidine is currently used less and less, however, it is also effective in this type of crisis.

A complicated hypertensive crisis always occurs with life-threatening complications, which include cerebral stroke, acute coronary syndrome, developing edema lungs and other conditions. In pregnant women, a crisis can be complicated by preeclampsia or eclampsia with a characteristic picture. A complicated version of the crisis requires immediate controlled reduction with drugs administered parenterally, therefore, if it develops, it is necessary to wait for the ambulance to arrive, and then decide on hospitalization.

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The aorta has the highest pressure

Blood pressure is created by contraction of the ventricles of the heart; under the influence of this pressure, blood flows through the vessels. Pressure energy is spent on friction of blood against itself and the walls of blood vessels, so that along the bloodstream the pressure constantly decreases:

• in the aortic arch the systolic pressure is 140 mmHg. Art. (this is the highest pressure in the circulatory system),
• in the brachial artery – 120,
• in capillaries 30,
• in the vena cava -10 (below atmospheric).

The speed of blood depends on the total lumen of the vessel: the larger the total lumen, the lower the speed.

• The narrowest point of the circulatory system is the aorta, its lumen is 8 square meters. see, so here is the most high speed blood – 0.5 m/s.
• The total lumen of all capillaries is 1000 times larger, so the blood speed in them is 1000 times less - 0.5 mm/s.
• The total lumen of the vena cava is 15 square meters. cm, speed – 0.25 m/s.

Tests

849-01. Where does blood move at the slowest speed?

A) in the brachial artery

B) in the inferior vena cava

D) in the superior vena cava

849-02. In which vessels of the systemic circulation of the human body is the highest blood pressure recorded?

D) large veins

849-03. Blood pressure on the walls of large arteries occurs as a result of contraction

B) left ventricle

B) leaf valves

D) semilunar valves

849-04. In which human blood vessel is the maximum pressure achieved?

A) pulmonary artery

B) pulmonary vein

D) inferior vena cava

849-05. Of the listed blood vessels, the lowest speed of blood movement is observed in

A) skin capillary

B) inferior vena cava

B) femoral artery

D) pulmonary vein

849-06. At what stage of the cardiac cycle does maximum blood pressure occur?

A) relaxation of the ventricles

B) contraction of the ventricles

B) atrial relaxation

D) atrial contraction

849-07. The lowest blood pressure is observed in

Relationship between high blood pressure and vascular condition

Problems with blood pressure are observed in the majority of residents of the country and their number is only growing every year.

If low blood pressure only brings discomfort and unpleasant symptoms, then high blood pressure can lead to adverse consequences and possibly death.

The main causes of high blood pressure are the condition of the blood vessels. So do blood vessels dilate or contract when blood pressure is high?

To reduce blood pressure while preserving blood vessels, it is better to add it to tea in the morning before breakfast.

What does blood pressure depend on?

There are a number of reasons that can destabilize blood pressure. One of them is incorrect lifestyle.

It is the consequences of an unhealthy lifestyle that gradually worsen the condition of the blood vessels and the entire cardiovascular system as a whole:

1. constant stressful situations. They are the ones who deplete the nervous system and, as a result, the vascular system;
2. genetic predisposition. This does not mean that if one of the family members has hypertension, it will necessarily manifest itself. This is only possible when the disease is provoked. In conditions modern life, it’s not difficult at all;
3. poor quality food. Excessively fatty or salty foods can cause hypertension. This also applies to drinking alcohol, including wine and beer, smoking, taking drugs;
4. sedentary lifestyle, emotional or physical stress.

All these factors provoke wear and tear of blood vessels, their elasticity decreases. The result is high blood pressure.

WITH physiological point vision, increased blood pressure occurs for the following reasons:

• increasing the number of platelets in the blood (increasing its viscosity);
• increased blood volume (for example, during pregnancy);
• disruptions in the functioning of the heart (the strength of contractions and the pace changes, which leads to an increase in blood pressure);
• pathological changes that led to a narrowing of the lumen.

Blood vessels and high blood pressure

There is ignorance among people that with high blood pressure, blood vessels are dilated or narrowed. In various sources you can find information that drinking, for example, alcohol, increases the pressure in a person’s blood vessels. Is it so?

Stages of vasoconstriction

An increase in blood pressure can occur due to a significant decrease in the lumen of small and large blood vessels. Blood pressure can also increase due to prolonged narrowing of the arterial muscles, which provokes the development of hypertension.

Veins are much more likely to undergo narrowing than arterial ones. This can be noticed in people belonging to risk groups: patients diabetes mellitus, thrombophlebitis, having heart problems.

It is extremely dangerous for hypertensive patients to provoke situations where a rapid increase in blood pressure is possible, and later it a sharp decline.

This is explained by the fact that insufficiently elastic vessels may not withstand the pressure of the blood flow. This may manifest itself in a rupture of its wall or subsequent stroke.

The situation gets worse if cholesterol is deposited on the inner walls. It is a fat that, when deposited, is converted into cholesterol plaque.

The plaque also contains blood cells and scar tissue. The more such plaques there are inside the vessels, the smaller their lumen. A dangerous condition is when cholesterol completely clogs their lumen. This entails many adverse consequences, one of which is death.

Blood pressure control

Constant monitoring of blood pressure helps to identify this disease at the earliest stages of development. This is necessary in cases where deviations were previously noticed during pressure measurements.

If there are problems with indicators in intravascular pressure (increased or decreased), systemic blood pressure is additionally determined.

This is the force that acts on the large arteries when the heart contracts. Determining this indicator is also used to monitor the effect of medications and anesthesia on blood pressure. It is also measured if there has been trauma or sepsis.

Diagnostic measures

The most reliable information about the condition of blood vessels from the inside will be provided by an invasive diagnostic method - angiography.

It consists of an X-ray examination with contrast. This method gives a picture of blood flow inside an organ or in certain sections (for example, cervical, abdominal, etc.).

The non-invasive method is also popular. It is based on an MRI examination. More suitable for examining the brain, internal organs, and limbs. Gives a complete picture of the state of blood flow throughout the body.

Doppler ultrasound (ultrasound with Doppler) is used less frequently. Suitable for primary examinations of the cervical spine, as well as organs that are abundantly supplied with blood.

Consequences of narrowing or blockage of blood vessels

A narrow clearance has dangerous consequences. Cholesterol plaques can clog it completely.

With an increased level of platelets in the blood, there is a risk of blood clots.

Blockage of the lumen can occur with it. An additional danger to life may be the detachment of a blood clot from the vessel wall.

Moving through narrow vessels (and even with cholesterol deposits), it can block the lumen anywhere. For example, if a blood clot enters the brain, an embolism develops, which is a harbinger of an ischemic stroke.

Serious complications throughout cardiovascular system may cause deterioration of the aorta. Which vessel has the highest blood pressure? It is in the aorta. It is 140/90 mmHg. Art. Deterioration can manifest itself both in the form of the appearance of cholesterol plaques and thickening of its wall on the inside and outside (aneurysm). This phenomenon requires constant monitoring and, if necessary, surgical intervention.

Narrow vessels not only provoke an increase in blood pressure, but can also reduce performance, giving painful sensations in the limbs. With narrow vessels, the symptoms appear as follows:

• frequent numbness of the limbs, weak pulsation of the arteries;
• the skin of the lower extremities becomes dry, bluish in color, sometimes pale with a marbled pattern;
• the appearance of muscle pain, which intensifies at night;
• trophic ulcers, which may appear on the lower extremities.

As a rule, specialists prescribe blood-thinning drugs, as well as those that improve the elasticity of the walls of blood vessels. These are also medications that clear them of cholesterol plaques (if any). Traditional medicine also takes place. But there is no need to talk about its effectiveness, except in cases where the methods are recognized by traditional medicine.

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Giving up bad habits and coffee, physical activity and regular consumption of garlic are simple measures that will help clean blood vessels. More useful tips in the video:

The narrowing of the walls of blood vessels leads to a number of problems, one of them is increased blood pressure. Abnormally elevated blood pressure leads to hypertensive crisis and pre-infarction conditions. Also, narrowing of the walls leads to more serious consequences: stroke (partial or complete paralysis is possible), thrombophlebitis and trophic ulcers, hemorrhages, heart attack, ischemic disease heart and other problems with both the cardiovascular system and other internal organs.

How to beat HYPERTENSION at home?

To get rid of hypertension and cleanse blood vessels, you need.

• Eliminates the causes of pressure disorders
• Normalizes blood pressure within 10 minutes after administration

The first symptoms of high blood pressure in humans

Blood pressure is the force with which the flow of blood, passing through blood vessels, presses on their walls. With its help, blood circulates throughout the human circulatory system, thereby ensuring the supply of nutrients to the tissues and cells of the body, and also removes their decay products.

Types of Blood Pressure

There are arterial, venous and capillary blood pressure. The highest blood pressure in humans is found in the aorta. When diagnosing various diseases, the concept of blood pressure (BP) is mainly used.

When the left cardiac ventricle contracts, the flow of oxygenated blood is forcefully pushed into the lumen of the bloodstream, but this force is not enough for arterial blood to enter all blood vessels. But nature is wise; under the pressure of blood, the walls of the arteries first stretch, then return to normal sizes.

When the muscles are stretched, the blood pressure in the vessels increases, then the muscles of the artery contract, resulting in such a flow force that the blood is able to pass through the smallest capillaries. During the pause between two contractions, the aortic muscles return to normal and reach a minimum. Highest value Blood pressure is observed at the beginning of the artery, and the pressure in the vena cava fluctuates around zero.

For the first time, instruments capable of measuring blood pressure began to be used in the 18th century, and in the 19th century, the tonometer took on the form that is already familiar to us. The principle of operation of the tonometer is based on the Korotkoff measurement method: using a rubber bulb, air is pumped into a cuff placed on the forearm, which compresses the blood vessels in the arm. The stethoscope should be placed in the crook of the elbow, instead of where the pulse sounds of the blood artery will be most audible. Then the air from the cuff is slowly released, when the first pulse sounds are heard, the value is recorded on the pressure gauge and then the last tone heard is recorded.

The first value of blood pressure, created by the force of contraction of the aortic walls, will mean the value of systolic pressure, the second – diastolic. In some cases, it is possible to measure blood pressure on the leg (for example, when overweight patient). As can be seen from the description, with this measurement method, it is necessary to listen to pulse noise. The concepts of blood pressure in this method and pulse are inextricably linked, since blood flows through the vessels unevenly, but in jerks, the number of contractions of the muscles of the vessel walls per minute is called the pulse rate.

Attention! In practice, there are such methods of measuring blood pressure as invasive (or direct, a needle connected to a pressure gauge is inserted directly into the bloodstream) and non-invasive (indirect). Measuring blood pressure with invasive methods is more accurate, it is used during operations, rather than invasive or indirect in another way, when measured with a tonometer.

To obtain accurate data about a person’s health, when recording blood pressure, you should adhere to certain instructions:

• Before the procedure you should sit for about 10 minutes;
• blood pressure measurements are taken while a person is sitting or lying down;
• Half an hour before the procedure, you should not smoke or overeat;
• The blood pressure value is recorded on both arms;
• When measuring blood pressure, you should not move or talk.

Normal blood pressure in humans

A person's blood pressure should be within 120/70 mm Hg. Art. fluctuations within 10 units are allowed. If all conditions for measurement are met, and blood pressure is lower or higher by 20 units or more. normal values pressure, this indicates the onset of hypotension or hypertension, respectively. An interesting fact is that blood pressure in children under one year of age is normally 80/50, and increases over time, reaching 120/70 in adulthood.

For older people, an increased blood pressure of 135/90 can be considered normal. This phenomenon is explained by the state of the muscle tone of the arteries, so in infants the muscles do not need to strain much to push blood, and with age, the lumen in the arteries decreases due to deposits on the walls of the vessels, which is why in the elderly we see high blood pressure or hypertension.

During artificial (hardware) circulation (for example, during surgical interventions), blood pressure is maintained at 60 mm Hg. Art. using a special apparatus.

Many factors influence a person's blood pressure:

1. With an active lifestyle, lower blood pressure is noted.
2. In women, this pressure indicator is lower than in men.
3. In pregnant women, a temporary decrease in blood pressure is noted; this phenomenon occurs under the influence of certain hormones, the level of which increases in women in the “position”.
4. If a pregnant woman experiences high blood pressure, protein in the urine and swelling at the end of pregnancy, we are talking about gestosis in pregnant women, in which case the woman is hospitalized, since gestosis is one of the reasons for an emergency cesarean section.
5. Obese people most often suffer from high blood pressure, as their blood vessels are susceptible to atherosclerosis.
6. In some cases, high lower pressure (diastolic) is noted, which indicates disorders within the body, for example, with diseases of the thyroid gland;
7. The highest blood pressure is observed in older people.

Your blood pressure will always be 120/80 if you drink in the morning.

Hypertension and hypotension

When describing the value of blood pressure, concepts such as hypertension and hypotension are used.

Hypertension is high blood pressure in a person. This is how we usually talk about it when an individual’s blood pressure exceeds the norm by more than 20 units.

The main signs of high blood pressure:

• headache;
• pain in the heart area;
• hard breath;
• insomnia;
• nose bleed;
• decreased vision;
• increased platelet count in the blood and thick blood;
• Sometimes with hypertension, loss of consciousness can be observed.

There are 3 degrees of hypertension, so in grade I there is an occasional slight increase in blood pressure, which normalizes with rest; headache, dizziness and occasionally nosebleeds may begin. Stage II hypertension is characterized by sudden changes in blood pressure, pain in the heart area, dizziness, and nausea may occur. Rest no longer brings relief; cerebral circulation may be impaired and, as a result, mental impairment may occur. If you don't resort to medication assistance, then a so-called pre-stroke condition may develop and, as a consequence, a stroke.

As a result III degree hypertension, irreversible conditions develop: stroke, myocardial infarction, heart failure, renal failure, damage to the fundus vessels. This degree of hypertension cannot be normalized at home; the sick person must be urgently hospitalized. Sometimes there are conditions in which, without a diagnosis of hypertension, blood pressure still rises. For example, “white coat disease” is known, in which a person’s blood pressure rises when they see a doctor in a white coat.

The causes of hypertension include:

• passive lifestyle;
• frequent smoking;
• exposure to stress;
• consumption of alcoholic beverages and drugs;
• excessive consumption of coffee and energy drinks;
• increased body weight;
• eating unhealthy food for hypertension;
• addiction to table salt (first, osmotic pressure increases, which leads to increased blood pressure);
• if you spend a long time at the computer, your blood pressure may increase because the person remains motionless for a long time;
• There are diseases characterized by constant high blood pressure. For example, kidney failure.

At mild degree hypertension, in order to avoid worsening the condition, it is recommended to follow a diet and monitor your weight. If you have high blood pressure, give preference to walking fresh air, and avoid stressful situations as much as possible. There are a number food products, which, when used wisely, reduce the risk of hypertensive conditions and a sharp jump in blood pressure. The beneficial effects of eating cabbage, legumes, dairy products and red fish are noted. Lemon, orange, pomegranate, kiwi perfectly regulate blood pressure.

IN folk medicine To normalize the condition, blood-thinning herbs are used. These herbs not only lower blood pressure, but also thin the blood. Acetylsalicylic acid(aspirin) is also a good blood thinner. It is usually prescribed to hypertensive patients initial stage hypertension to avoid the risk of heart attack or stroke. Some conditions require normalization of blood sugar levels. A berry like cranberry perfectly reduces blood pressure, this is due to its diuretic properties.

Hypotension is a blood pressure level that is lower than normal. When diagnosing hypotension, note:

• memory problems;
• increased sweating with low blood pressure;
• pale skin;
• dizziness and fainting;
• general weakness;
• feeling of lack of air;
• with low blood pressure, nausea and sometimes vomiting;
• at laboratory research, the partial pressure of oxygen (this value measures the ability of hemoglobin to attach oxygen) in arterial blood will be low.

Although hypotension does not cause such harm to the body as hypertension, it still requires close attention to itself, as it often accompanies more serious illnesses. With low blood pressure the following is diagnosed:

• vegetative-vascular dystonia;
• hypothyroidism;
• adrenal insufficiency;
• develops against the background of anemia;
• tuberculosis;
• peptic ulcer.

Hypotension can also develop with alcohol consumption, as a result of chronic infections and asthenia. Stressful situations can also lead to a sharp decrease in blood pressure.

Treatment

Treatment depends on the course of the disease, which resulted in a decrease in blood pressure. For example, they can be assigned hormonal drugs if the decrease in blood pressure is caused by endocrine disorders. To prevent hypertension, it is recommended to consume foods high in heme iron, establish a work schedule, and avoid overwork. Walking in the fresh air and physical exercise will have a beneficial effect on raising blood pressure. In the treatment of neurotic causes, medications that stimulate the nervous system are used.

Blood pressure is the pressure in the blood vessels. Without it, it is impossible to fully carry out metabolic processes in the tissues of the body. Thanks to it, blood moves through the circulatory system.

Power of heart contractions;

The amount of blood it throws out at a time with each successive contraction;

The resistance that the walls of blood vessels (peripheral) provide to the moving flow of blood;

The number of heart contractions per one accepted unit of time.

Secondary factors affecting blood pressure are its quantity and viscosity. It is also a difference in pressure in the abdominal cavity and in the thoracic cavity, which occurs due to movements during breathing.

Blood pressure is at its maximum when the left ventricle of the heart contracts (systole). At the same time, approximately 70 ml of blood is pushed out of it at a time. Such an amount cannot immediately pass through capillaries and other small vessels. The aorta, due to its elasticity, stretches, and at the same time its systolic pressure increases. In a (healthy) person over 16 years of age, it can range from 110 to 130 mm Hg. Art.

During diastole - the pause between two contractions of the left and right ventricles - the stretched walls of the large arteries and the aorta begin to contract. Thus, they push blood into the capillaries. Its pressure drops and at the end of diastole in the aorta drops to 90 mm Hg. Art., and in large arteries - up to 70 mm Hg. Art. The difference between systole and diastole is perceived by a person in the form of a pulse.

How longer distance from blood vessels to the heart, the less pressure there is. The first, upper number indicates systolic pressure, and the second, lower number indicates diastolic pressure.

In large arteries it is higher, in arterioles it is lower. When moving into the capillary bed, the blood pressure decreases, in the venous bed it drops even more, and in the vena cava it even reaches negative values.

Measuring it in veins or capillaries is technically not very simple. Therefore, the magnitude of pressure is judged on the basis of its determination in the arteries.

Its normal indicators depend on how a person lives, what he does, and what individual characteristics he has. With age, the pressure level changes. It also increases with increased emotional stress and physical work. And at the same time, among athletes, among people who constantly and physically work hard, it may even decrease.

Systolic pressure in children is determined by the formula 80 + 2a, in which a is age (number of years).

The mechanisms that exist in the body and control the level of pressure allow it to return to normal after minor fluctuations as a result of emotional stress or physical labor.

If they are violated, there is a persistent change in the upward direction, then we talk about arterial hypertension, or in the downward direction, then we are talking about

Usually, any person knows his normal blood pressure. And any deviation in one direction or another should be a reason to consult a doctor, because there are many reasons that influence this indicator. For example, with infectious diseases, heart diseases, and poisoning, hypotension often occurs. And with kidney diseases and endocrine disorders - hypertension.

Circulation is the movement of blood through the vascular system. It ensures gas exchange between the body and the external environment, metabolism between all organs and tissues, humoral regulation various functions of the body and the transfer of heat generated in the body. Blood circulation is a process necessary for the normal functioning of all body systems, primarily the central nervous system. The section of physiology devoted to the patterns of blood flow through vessels is called hemodynamics; the basic laws of hemodynamics are based on the laws of hydrodynamics, i.e. teachings about the movement of liquid in tubes.

The laws of hydrodynamics are applicable to the circulatory system only within certain limits and only with approximate accuracy. Hemodynamics is a branch of physiology about the physical principles underlying the movement of blood through the vessels. Driving force blood flow is the pressure difference between individual sections of the vascular bed. blood flows from an area of ​​higher pressure to an area of ​​lower pressure. This pressure gradient serves as a source of force that overcomes hydrodynamic resistance. Hydrodynamic resistance depends on the size of the vessels and blood viscosity.

Basic hemodynamic parameters .

1. Volumetric blood velocity. Blood flow, i.e. the volume of blood passing per unit time through the blood vessels in any section of the bloodstream is equal to the ratio of the difference in average pressure in the arterial and venous parts of this section (or in any other parts) to the hydrodynamic resistance. The volumetric velocity of blood flow reflects the blood supply to an organ or tissue.

In hemodynamics, this hydrodynamic indicator corresponds to the volumetric velocity of the blood, i.e. the amount of blood flowing through the circulatory system per unit of time, in other words, the minute volume of blood flow. Since the circulatory system is closed, the same amount of blood passes through any cross section of it per unit time. The circulatory system consists of a system of branching vessels, so the total lumen increases, although the lumen of each branch gradually decreases. Through the aorta, as well as through all arteries, all capillaries, all veins, the same volume of blood passes per minute.

2. Second hemodynamic indicator - linear speed blood movement .

You know that the flow rate of a liquid is directly proportional to pressure and inversely proportional to resistance. Consequently, in tubes of different diameters, the speed of blood flow is greater, the smaller the cross-section of the tube. In the circulatory system, the narrowest place is the aorta, the widest is the capillaries (remember that we are dealing with the total lumen of the vessels). Accordingly, blood in the aorta moves much faster - 500 mm/sec, than in the capillaries - 0.5 mm/sec. In the veins, the linear speed of blood flow increases again, since when the veins merge with each other, the total lumen of the bloodstream narrows. In the vena cava, the linear speed of blood flow reaches half the speed in the aorta (Fig.).

The linear speed is different for blood particles moving in the center of the flow (along the longitudinal axis of the vessel) and at vascular wall. In the center of the vessel, the linear velocity is maximum; near the vessel wall it is minimal due to the fact that here the friction of blood particles against the wall is especially high.

The resultant of all linear velocities in various parts the vascular system is expressed blood circulation time . In a healthy person at rest it is equal to 20 seconds. This means that the same particle of blood passes through the heart 3 times every minute. With intense muscle work, the blood circulation time can decrease to 9 seconds.

3. Resistance of the vascular system - third hemodynamic indicator. Flowing through the tube, the liquid overcomes the resistance that arises due to internal friction liquid particles between each other and against the wall of the tube. This friction will be greater the greater the viscosity of the liquid, the narrower its diameter and the greater the flow speed.

Under viscosity usually understand internal friction, i.e. forces affecting the flow of fluid.

However, it should be borne in mind that there is a mechanism that prevents a significant increase in resistance in the capillaries. It is due to the fact that in the smallest vessels (less than 1 mm in diameter), red blood cells line up in so-called coin columns and, like a snake, move along the capillary in a plasma shell, with almost no contact with the walls of the capillary. As a result, blood flow conditions are improved, and this mechanism partially prevents a significant increase in resistance.

Hydrodynamic resistance also depends on the size of the vessels, their length and cross-section. In summary, the equation describing vascular resistance is the following (Poiseuille formula):

R = 8ŋL/πr 4

where ŋ is the viscosity, L is the length, π = 3.14 (pi), r is the radius of the vessel.

Blood vessels provide significant resistance to blood flow, and the heart has to spend most of its work overcoming this resistance. The main resistance of the vascular system is concentrated in the part where the arterial trunks branch into the smallest vessels. However, the smallest arterioles present the maximum resistance. The reason is that arterioles, having almost the same diameter as capillaries, are generally longer and the speed of blood flow in them is higher. In this case, the amount of internal friction increases. In addition, arterioles are capable of spasms. The total resistance of the vascular system increases all the time with distance from the base of the aorta.

Blood pressure in vessels. This is the fourth and most important hemodynamic indicator, as it is easy to measure.

If you insert a pressure gauge sensor into a large artery of an animal, the device will detect a pressure that fluctuates in the rhythm of the heartbeat around an average value of approximately 100 mm Hg. The pressure existing inside the vessels is created by the work of the heart, pumping blood into the arterial system during systole. However, even during diastole, when the heart is relaxed and does not produce work, the pressure in the arteries does not drop to zero, but only drops slightly, giving way to a new rise during the next systole. Thus, the pressure ensures a continuous flow of blood, despite the intermittent work of the heart. The reason is the elasticity of the arteries.

Blood pressure value determined by two factors: the amount of blood pumped by the heart and the resistance existing in the system:

It is clear that the pressure distribution curve in the vascular system should be a mirror image of the resistance curve. So, in the subclavian artery of a dog P = 123 mm Hg. Art. in the brachial vein - 118 mm, in the capillaries of the muscles 10 mm, in the facial vein 5 mm, in the jugular vein - 0.4 mm, in the superior vena cava -2.8 mm Hg.

Among these data, the negative value of pressure in the superior vena cava attracts attention. It means that in the large venous trunks immediately adjacent to the atrium, the pressure is less than atmospheric. It is created by a suction action chest and the heart itself during diastole and promotes the movement of blood to the heart.

Basic principles of hemodynamics

Other from the section: ▼

The study of the movement of blood in vessels is based on the laws of hydrodynamics - the study of the movement of liquids. The movement of liquid through pipes depends on: a) the pressure at the beginning and end of the pipe b) the resistance in this pipe. The first of these factors promotes, and the second hinders, the movement of fluid. The amount of liquid flowing through a pipe is directly proportional to the pressure difference at the beginning and end of it and inversely proportional to the resistance.

In the circulatory system, the volume of blood that flows through the vessels also depends on the pressure at the beginning of the vascular system (in the aorta - P1) and at the end (in the veins flowing into the heart - P2), as well as on vascular resistance.

The volume of blood flowing through each section of the vascular bed per unit time is the same. This means that in 1 minute the same amount of blood flows through the aorta, or pulmonary arteries, or the total cross-section drawn at any level of all arteries, capillaries, veins. This is the IOC. The volume of blood flowing through the vessels is expressed in milliliters per minute.

The resistance of the vessel depends, according to the Poiseuille formula, on the length of the vessel (l), the viscosity of the blood (n) and the radius of the vessel (r).

According to the equation, the maximum resistance to blood flow should be in the thinnest blood vessels - arterioles and capillaries, namely: about 50% of the total peripheral resistance is in the arterioles and 25% in the capillaries. The lower resistance in capillaries is explained by the fact that they are much shorter than arterioles.

Resistance is also affected by blood viscosity, which is determined primarily by formed elements and, to a lesser extent, by proteins. In humans it is “C-5. The formed elements are localized near the walls of blood vessels and move due to friction between themselves and the wall at a lower speed than those concentrated in the center. They play a role in the development of blood resistance and pressure.

Hydrodynamic resistance the entire vascular system cannot be directly measured. However, it can be easily calculated using the formula, remembering that P1 in the aorta is 100 mm Hg. Art. (13.3 kPa), and P2 in the vena cava is about 0.

Basic principles of hemodynamics. Classification of vessels

Hemodynamics is a branch of science that studies the mechanisms of blood movement in the cardiovascular system. It is part of hydrodynamics, a branch of physics that studies the movement of fluids.

According to the laws of hydrodynamics, the amount of liquid (Q) flowing through any pipe is directly proportional to the pressure difference at the beginning (P1) and at the end (P2) of the pipe and inversely proportional to the resistance (P2) to the flow of liquid:

If we apply this equation to the vascular system, we should keep in mind that the pressure at the end of this system, that is, at the point where the vena cava enters the heart, is close to zero. In this case, the equation can be written as follows:

where Q is the amount of blood expelled by the heart per minute; P is the value of the average pressure in the aorta, R is the value of vascular resistance.

From this equation it follows that P = Q*R, i.e. the pressure (P) at the mouth of the aorta is directly proportional to the volume of blood ejected by the heart into the arteries per minute (Q) and the value of peripheral resistance (R). Aortic pressure (P) and minute volume (Q) can be measured directly. Knowing these values, peripheral resistance is calculated - the most important indicator of the state of the vascular system.

The peripheral resistance of the vascular system consists of many individual resistances of each vessel. Any of these vessels can be likened to a tube, the resistance of which (R) is determined by the Poiseuille formula:

where l is the length of the tube; η is the viscosity of the liquid flowing in it; π - ratio of circumference to diameter; r is the radius of the tube.

The vascular system consists of many individual tubes connected in parallel and in series. When tubes are connected in series, their total resistance is equal to the sum of the resistances of each tube:

R=R1+R2+R3+. +Rn

When connecting tubes in parallel, their total resistance is calculated using the formula:

R=1/(1/R1+1/R2+1/R3+. +1/Rn)

It is impossible to accurately determine vascular resistance using these formulas, since the geometry of the vessels changes due to contraction of the vascular muscles. Blood viscosity is also not a constant value. For example, if blood flows through vessels with a diameter of less than 1 mm, the viscosity of the blood decreases significantly. The smaller the diameter of the vessel, the lower the viscosity of the blood flowing in it. This is due to the fact that in the blood, along with plasma, there are shaped elements, which are located in the center of the flow. The parietal layer is plasma, the viscosity of which is much less than the viscosity of whole blood. The thinner the vessel, the larger part of its cross-sectional area is occupied by a layer with minimal viscosity, which reduces the overall value of blood viscosity. Theoretical calculation of capillary resistance is impossible, since normally only part of the capillary bed is open, the remaining capillaries are reserve and open as metabolism in the tissues increases.

From the above equations it is clear that the capillary with a diameter of 5-7 microns should have the highest resistance value. However, due to the fact that a huge number of capillaries are included in the vascular network through which blood flows in parallel, their total resistance is less than the total resistance of the arterioles.

The main resistance to blood flow occurs in the arterioles. The system of arteries and arterioles is called resistance vessels, or resistive vessels.

Arterioles are thin vessels (diameter 15-70 microns). The wall of these vessels contains a thick layer of circularly arranged smooth muscle cells, when contracted, the lumen of the vessel can significantly decrease. At the same time, arteriolar resistance sharply increases. Changing arteriolar resistance changes the level of blood pressure in the arteries. If arteriolar resistance increases, the outflow of blood from the arteries decreases and the pressure in them increases. A decrease in arteriolar tone increases the outflow of blood from the arteries, which leads to a decrease in blood pressure. It is the arterioles that have the greatest resistance among all parts of the vascular system, so changes in their lumen are the main regulator of the level of total blood pressure. Arterioles are “faucets of the cardiovascular system” (I.M. Sechenov). Opening these “taps” increases the outflow of blood into the capillaries of the corresponding area, improving local blood circulation, and closing them sharply worsens the blood circulation of this vascular zone.

So, arterioles play a dual role: they participate in maintaining necessary for the body the level of general blood pressure and in regulating the amount of local blood flow through a particular organ or tissue. The amount of organ blood flow corresponds to the organ’s need for oxygen and nutrients, determined by the level of working activity of the organ.

In a working organ, the tone of the arterioles decreases, which ensures an increase in blood flow. To prevent the overall blood pressure from decreasing in other (non-functioning) organs, the tone of the arterioles increases. The total value of total peripheral resistance and the total level of blood pressure remain approximately constant, despite the continuous redistribution of blood between working and non-working organs.

The resistance in various vessels can be judged by the difference in blood pressure at the beginning and at the end of the vessel: the higher the resistance to blood flow, the greater the force expended on its movement through the vessel and, therefore, the greater the pressure drop along the vessel. As direct measurements of blood pressure in different vessels show, pressure throughout large and medium-sized arteries drops by only 10%, and in arterioles and capillaries - by 85%. This means that 10% of the energy expended by the ventricles on expulsion of blood is spent on moving blood in large and medium-sized arteries, and 85% is spent on moving blood in arterioles and capillaries.

Knowing the volumetric velocity of blood flow (the amount of blood flowing through the cross-section of a vessel), measured in milliliters per second, we can calculate the linear velocity of blood flow, which is expressed in centimeters per second. Linear velocity (V) reflects the speed of movement of blood particles along the vessel and is equal to volumetric velocity (Q) divided by the cross-sectional area of ​​the blood vessel:

The linear speed calculated using this formula is the average speed. In fact, the linear velocity is different for blood particles moving in the center of the flow (along the longitudinal axis of the vessel) and at the vascular wall. In the center of the vessel, the linear velocity is maximum; near the vessel wall it is minimal due to the fact that here the friction of blood particles against the wall is especially high.

The volume of blood flowing in 1 minute through the aorta or vena cava and through the pulmonary artery or pulmonary veins is the same. The outflow of blood from the heart corresponds to its inflow. It follows from this that the volume of blood flowing in 1 minute through the entire arterial and venous systems of the systemic and pulmonary circulation is the same. With a constant volume of blood flowing through any overall cross section vascular system, the linear speed of blood flow cannot be constant. It depends on the total width of a given section of the vascular bed. This follows from the equation expressing the relationship between linear and volumetric velocity: the larger the total cross-sectional area of ​​the vessels, the lower the linear velocity of blood flow. The narrowest point in the circulatory system is the aorta. When arteries branch, despite the fact that each branch of the vessel is narrower than the one from which it originated, an increase in the total channel is observed, since the sum of the lumens of the arterial branches is greater than the lumen of the branched artery. The greatest expansion of the channel is observed in the capillary network: the sum of the lumens of all capillaries is approximately 500-600 times larger than the lumen of the aorta. Accordingly, blood in the capillaries moves 500-600 times slower than in the aorta.

In the veins, the linear speed of blood flow increases again, since when the veins merge with each other, the total lumen of the bloodstream narrows. In the vena cava, the linear speed of blood flow reaches half the speed in the aorta.

Due to the fact that the blood is ejected by the heart in separate portions, the blood flow in the arteries has a pulsating character, therefore the linear and volumetric velocities are constantly changing: they are maximum in the aorta and pulmonary artery at the time of ventricular systole and decrease during diastole. In capillaries and veins, blood flow is constant, that is, its linear speed is constant. The properties of the arterial wall matter in the transformation of pulsating blood flow into constant one.

The continuous flow of blood throughout the vascular system is determined by the pronounced elastic properties of the aorta and large arteries.

In the cardiovascular system, part of the kinetic energy developed by the heart during systole is spent on stretching the aorta and the large arteries extending from it. The latter form an elastic, or compression, chamber into which a significant volume of blood enters, stretching it; in this case, the kinetic energy developed by the heart is converted into the energy of elastic tension of the arterial walls. When systole ends, the stretched arterial walls tend to escape and push blood into the capillaries, maintaining blood flow during diastole.

From the standpoint of functional significance for the circulatory system, vessels are divided into the following groups:

1. Elastic-extensible - the aorta with large arteries in the systemic circulation, the pulmonary artery with its branches in the small circle, i.e. elastic type vessels.

2. Resistance vessels (resistive vessels) - arterioles, including precapillary sphincters, i.e. vessels with a well-defined muscle layer.

3. Exchange (capillaries) - vessels that ensure the exchange of gases and other substances between blood and tissue fluid.

4. Shunting (arteriovenous anastomoses) - vessels that provide “discharge” of blood from the arterial to the venous vascular system, bypassing the capillaries.

5. Capacitive - veins with high distensibility. Thanks to this, the veins contain 75-80% of the blood.

The processes occurring in series-connected vessels that ensure blood circulation (circulation) are called systemic hemodynamics. The processes occurring in the vascular beds connected in parallel to the aorta and vena cava, providing blood supply to organs, are called regional, or organ, hemodynamics.

Blood pressure in different parts of the vascular bed is not the same: in arterial system it is higher, in the venous lower. This is clearly visible from the data presented in table. 3 and in Fig. 16.

Table 3. The value of the average dynamic pressure in various parts of the human circulatory system

Rice. 16. Diagram of pressure changes in different parts of the vascular system. A - systolic; B - diastolic; B - medium; 1 - aorta; 2 - large arteries; 3 - small arteries; 4 - arterioles; 5 - capillaries; 6 - venules; 7 - veins; 8 - vena cava

Blood pressure- blood pressure on the walls of blood vessels - measured in pascals (1 Pa = 1 N/m2). Normal blood pressure is necessary for blood circulation and proper blood supply to organs and tissues, for the formation tissue fluid in capillaries, as well as for the processes of secretion and excretion.

The amount of blood pressure depends on three main factors: the frequency and strength of heart contractions; the value of peripheral resistance, i.e. the tone of the walls of blood vessels, mainly arterioles and capillaries; volume of circulating blood.

There are arterial, venous and capillary blood pressure. Blood pressure in a healthy person is fairly constant. However, it is always subject to slight fluctuations depending on the phases of cardiac activity and respiration.

There are systolic, diastolic, pulse and mean arterial pressure.

Systolic(maximum) pressure reflects the state of the myocardium of the left ventricle of the heart. Its value is 13.3-16.0 kPa (100-120 mm Hg).

Diastolic(minimum) pressure characterizes the degree of tone of the arterial walls. It is equal to 7.8-10.7 kPa (60-80 mm Hg).

Pulse pressure is the difference between systolic and diastolic pressure. Pulse pressure is necessary to open the semilunar valves during ventricular systole. Normal pulse pressure is 4.7-7.3 kPa (35-55 mm Hg). If systolic pressure becomes equal to diastolic pressure, blood movement will be impossible and death will occur.

Average blood pressure is equal to the sum of diastolic and 1/3 of pulse pressure. Mean arterial pressure expresses the energy of continuous blood movement and is a constant value for a given vessel and body.

Blood pressure is influenced by various factors: age, time of day, state of the body, central nervous system, etc. In newborns, the maximum blood pressure is 5.3 kPa (40 mm Hg), at the age of 1 month - 10.7 kPa (80 mm Hg . Art.), 10-14 years - 13.3-14.7 kPa (100-110 mm Hg. Art.), 20-40 years - 14.7-17.3 kPa (110-130 mm Hg. Art. .). With age, the maximum pressure increases to a greater extent than the minimum.

During the day, there is a fluctuation in blood pressure: during the day it is higher than at night.

Significant increases in maximum blood pressure may occur in severe physical activity, during sports competitions, etc. After stopping work or finishing competitions, blood pressure quickly returns to its original values. An increase in blood pressure is called hypertension. The decrease in blood pressure is called hypotension. Hypotension can occur as a result of drug poisoning, severe injuries, extensive burns, or large blood losses.

Persistent hypertension and hypotension can cause organ dysfunction, physiological systems and the body as a whole. In these cases, qualified medical assistance is necessary.

In animals, blood pressure is measured using a bloodless and bloody method. In the latter case, one of the large arteries (carotid or femoral) is exposed. An incision is made in the wall of the artery through which a glass cannula (tube) is inserted. The cannula is secured in the vessel using ligatures and connected to one end of a mercury manometer using a system of rubber and glass tubes filled with a solution that prevents blood clotting. At the other end of the pressure gauge, a float with a scribe is lowered. Pressure fluctuations are transmitted through the liquid tubes to a mercury manometer and a float, the movements of which are recorded on the sooty surface of the kymograph drum.

In humans, blood pressure is determined by auscultation using the Korotkov method (Fig. 17). For this purpose, it is necessary to have a Riva-Rocci sphygmomanometer or sphygmotonometer (membrane-type manometer). The sphygmomanometer consists of a mercury manometer, a wide flat rubber cuff bag and a rubber pressure bulb connected to each other by rubber tubes. A person's blood pressure is usually measured in the brachial artery. A rubber cuff, made inextensible by the canvas cover, is wrapped around the shoulder and fastened. Then, using a bulb, air is pumped into the cuff. The cuff inflates and compresses the tissues of the shoulder and the brachial artery. The degree of this pressure can be measured using a pressure gauge. The air is pumped until the pulse in the brachial artery can no longer be felt, which occurs when it is completely compressed. Then, in the area of ​​the elbow bend, i.e., below the point of compression, a phonendoscope is applied to the brachial artery and they begin to gradually release air from the cuff using a screw. When the pressure in the cuff drops so much that the blood during systole is able to overcome it, characteristic sounds - tones - are heard in the brachial artery. These tones are caused by the appearance of blood flow during systole and its absence during diastole. The pressure gauge readings, which correspond to the appearance of tones, characterize the maximum, or systolic, pressure in the brachial artery. With a further decrease in pressure in the cuff, the tones first intensify, and then subside and cease to be audible. The cessation of sound phenomena indicates that now, even during diastole, blood is able to pass through the vessel. The intermittent flow of blood turns into a continuous one. Movement through the vessels in this case is not accompanied by sound phenomena. The pressure gauge readings, which correspond to the moment the sounds disappear, characterize the diastolic, minimum, pressure in the brachial artery.

Rice. 17. Determination of blood pressure in humans

Arterial pulse - these are periodic expansions and lengthenings of the walls of the arteries, caused by the flow of blood into the aorta during systole of the left ventricle. The pulse is characterized by a number of qualities that are determined by palpation, most often of the radial artery in the lower third of the forearm, where it is located most superficially.

The following pulse qualities are determined by palpation: frequency- number of beats in 1 minute, rhythm- correct alternation of pulse beats, filling- degree of change in arterial volume, determined by the strength of the pulse beat, voltage- characterized by the force that must be applied to compress the artery until the pulse completely disappears.

The condition of the artery walls is also determined by palpation: after compression of the artery until the pulse disappears, in the case of sclerotic changes in the vessel, it is felt as a dense cord.

The resulting pulse wave spreads through the arteries. As it progresses, it weakens and fades at the level of the capillaries. The speed of propagation of the pulse wave in different vessels of the same person is not the same, it is greater in the vessels muscular type and less in elastic vessels. Thus, in young and elderly people, the speed of propagation of pulse oscillations in elastic vessels ranges from 4.8 to 5.6 m/s, in large arteries of the muscular type - from 6.0 to 7.0-7.5 m/s With. Thus, the speed of pulse wave propagation through the arteries is much greater than the speed of blood movement through them, which does not exceed 0.5 m/s. With age, when the elasticity of blood vessels decreases, the speed of propagation of the pulse wave increases.

For a more detailed study of the pulse, it is recorded using a sphygmograph. The curve obtained by recording pulse fluctuations is called sphygmogram(Fig. 18).

Rice. 18. Sphygmograms of arteries recorded synchronously. 1 - carotid artery; 2 - radial; 3 - finger

On the sphygmogram of the aorta and large arteries, the ascending limb is distinguished - anacrotic and the descending knee - catacrota. The occurrence of anacrota is explained by the entry of a new portion of blood into the aorta at the beginning of left ventricular systole. As a result, the wall of the vessel expands, and a pulse wave appears that spreads through the vessels, and the sphygmogram shows an increase in the curve. At the end of ventricular systole, when the pressure in it decreases and the walls of the vessels return to their original state, catacrota appears on the sphygmogram. During ventricular diastole, the pressure in their cavity becomes lower than in the arterial system, therefore conditions are created for the return of blood to the ventricles. As a result, the pressure in the arteries drops, which is reflected in the pulse curve in the form of a deep notch - incisura. However, on its way the blood encounters an obstacle - the semilunar valves. Blood is pushed away from them and causes the appearance of a secondary wave of increased pressure. This in turn causes a secondary expansion of the arterial walls, which is recorded on the sphygmogram as a dicrotic rise.

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