Circulatory organs: features, functions. Diseases of the circulatory system

Inside the human body there are digestive organs, blood circulation, hearing, etc. They all participate in the normal functioning of the body. However, it is believed that the key tasks are performed by the circulatory system. Let's consider it in more detail.

General information

Blood circulation is a continuous movement of blood through a closed system. It ensures the supply of oxygen to tissues and cells. However, this is not all the functions of the circulatory system. Due to their activity, nutrients, vitamins, salts, water, hormones enter the cells and tissues. They also participate in the removal of the final products of metabolic processes, maintain a constant body temperature.

Biology, Grade 8: circulatory system

The first acquaintance with the internal structure of the body occurs in school. Students not only learn that there are circulatory organs. Grade 8 implies the study of their characteristics, interaction with other elements of the human body. For a better understanding of the subject, children are offered simple schemes. They clearly show what organs of blood circulation a person has. Schemes simulate the internal structure of the body.

What concerns to bodies of a circulation?

First of all, this heart. It is considered the main body of the system. However, his activity would be useless in the absence of blood vessels present in all tissues of the body. It is through them that nutrients and other essential substances are transferred with blood. Vessels have a different size and diameter. There are large - veins and arteries, and there are small - capillaries.

A heart

It is represented by a hollow muscular organ. In the heart there are four chambers: two atriums (left and right) and the same number of ventricles. All these spaces are separated from one another by partitions. The right atrium and ventricle communicate with each other through the tricuspid, and the left atrium through the two-leaf valve. The weight of the adult's heart is on average about 250 g (in women) and 330 g (in males). The length of the organ is about 10-15 cm, and its transverse dimension is 8-11 cm, from the anterior to the posterior wall the distance is about 6-8.5 cm. The average heart volume of the man is 700-900 cm ³ , the female is 500-600 cm ³ .

Specificity of the heart

The external walls of the organ are formed by the muscle. Its structure is similar to the structure of striated muscle. The heart muscle, however, is capable of rhythmically contracting regardless of external influence. This is due to the impulses that arise in the organ itself.

Cycle

The heart's task is to inject arterial blood through the veins. The organ is reduced approximately 70-75 times / min. at rest. This is approximately once every 0.8 sec. Continuous work of the body consists of cycles. Each of them suggests a reduction (systole) and relaxation (diastole). There are three phases of the heart:

1. Atrial systole. It lasts 0.1 sec.
2. Ventricular contraction. It lasts 0.3 seconds.
3. General relaxation is diastole. It lasts 0.4 sec.

Throughout the cycle, thus, the work of the atria lasts 0.1 seconds, and their relaxation is 0.7 sec. Ventricles contract 0.3 seconds, and rest - 0.5 seconds. This determines the ability of the muscle to work throughout life.

Vessels

High performance of the heart is associated with increased blood supply. It occurs at the expense of the vessels that leave it. Approximately 10% of the blood entering the aorta from the left ventricle penetrates into the arteries that feed the heart. Almost all of them carry oxygen to tissues and other elements of the body. Venous blood carries only the pulmonary artery. The wall of the vessel consists of three layers:

1. External connective tissue envelope.
2. Medium, which is formed by smooth muscles and elastic fibers.
3. Internal, formed by connective tissue and endothelium.

The diameter of the human arteries is within 0.4-2.5 cm. On average, the total volume of blood in them is 950 ml. Arteries branch into smaller arterioles. They, in turn, pass into capillaries. These circulatory organs are considered to be the smallest. The diameter of the capillaries is not more than 0.005 mm. They permeate all tissues and organs. Capillaries provide the connection of arterioles with venules. The walls of the smallest vessels consist of endothelial cells. Through them, gases and other substances are exchanged. The veins carry blood enriched with carbon dioxide, containing metabolic products, hormones and other elements from the organs to the heart. The walls of these vessels are delicate and elastic. Medium and small veins have valves. They prevent the reverse flow of blood.

Circles

Blood and circulatory system were described back in 1628. The cardiovascular scheme of mammals and man was studied by the English physician W. Harvey at that time. He found out that the circulatory system forms two circles - small and large. They differ in their tasks. In addition, there is a third circle, the so-called heart. It serves the heart directly. The circle of coronary arteries starting from the aorta begins. The third circle ends with the heart veins. They converge in the coronary sinus, which flows into the right atrium. Other veins enter his cavity directly.

Small Circle

With its help, respiratory and circulatory organs interact. A small circle is also called pulmonary. It provides enrichment of blood in the lungs with oxygen. A circle starts from the right ventricle. Venous blood moves to the pulmonary trunk. It is divided into two branches. Each of them carries blood, respectively, to the right and left lungs. Inside them, the arteries divide into capillaries. In the vasculature, which ruptures the pulmonary vesicles, the blood gives off carbon dioxide and receives oxygen. She becomes scarlet and walks through the capillaries into the veins. They then join into four pulmonary vessels and flow into the left atrium. Here, in fact, the small circle ends. Atrial blood enters the atrioventricular orifice into the left ventricle. Hence a great circle begins. Thus, the pulmonary arteries carry the venous, and the veins - the arterial blood.

Great Circle

It involves all the circulatory system, except the pulmonary vessels. A large circle is also called bodily. He collects blood from the veins of the upper and lower parts of the trunk and distributes the arterial blood. A circle starts from the left ventricle. From it, blood flows into the aorta. It is considered to be the largest vessel. The arterial blood contains all the substances necessary for the life of the body, as well as oxygen. The aorta diverges into arteries. They go to all the tissues of the body, pass into the arterioles and then into the capillaries. The latter, in turn, combine into venules and then into the veins. Through the capillary walls, gases and substances are exchanged. Arterial blood gives oxygen and takes the products of metabolism and carbon dioxide. Venous fluid has a dark red color. Vessels are connected in hollow veins - large trunks. They fall into the right atrium. Here a large circle ends.

Movement along the vessels

The flow of any liquid occurs due to the difference in pressure. The higher it is, the higher the speed. Similarly, blood moves through the vessels of small and large circles. The pressure in this case is created by contractions of the heart. In the aorta and left ventricle, it is higher than in the right atrium and hollow veins. Due to this, the liquid moves through the vessels of a large circle. In the pulmonary artery and right ventricle, the pressure is high, and in the left atrium and pulmonary veins - low. Due to the difference, there is movement in a small circle. The greatest pressure in the large arteries and aorta. This indicator is unstable. During the flow of blood, part of the energy from the pressure is spent on reducing blood friction against the vascular walls. In this regard, it begins to decline gradually. This process is especially evident in capillaries and small arteries. This is due to the fact that these vessels have the greatest resistance. In the veins, the pressure continues to decrease and in hollow vessels it becomes as atmospheric or even lower.

Traveling speed

Features of the circulatory system are their internal structure and size. For example, if we talk about vessels, then the speed of the fluid will depend on the width of their channel. The largest, as mentioned above, is the aorta. This is the only vessel with the widest channel. Through it passes all the blood coming out of the left ventricle. This determines the maximum speed in this vessel - 500 mm / sec. Arteries branch into smaller ones. Accordingly, the speed in them is reduced to 0.5 mm / sec. In the capillaries. Due to this, the blood manages to give nutritional compounds and oxygen and to take the products of metabolism. The movement of fluid through the capillaries is caused by a change in the lumen of the small arteries. When they expand, the current increases, with constriction - it weakens. The smallest circulatory organs - the capillaries - are represented in huge numbers. At the person of them it is totaled about 40 billion At that their total lumen is more than aortal in 800 times. Nevertheless, the velocity of the fluid along them is very low. The veins, approaching the heart, become larger and merge. Their total lumen decreases, but the blood flow velocity in comparison with capillaries increases. Movement in the veins is due to the difference in pressure. The blood flow is directed to the heart, which is facilitated by the reduction of skeletal muscles and the activity of the thorax. So, when you inhale, the difference in pressure at the beginning and end of the venous system increases. When the skeletal muscles contract, veins contract. It also promotes blood flow to the heart.

Pathological conditions

Diseases of the circulatory system today occupy one of the first places in statistics. Often, pathological conditions lead to a complete loss of ability to work. The reasons for which these or other violations occur are very diverse. Lesions can appear in the most different parts of the heart and in the vessels. Diseases of the circulatory system are diagnosed in people of different age and sex. According to statistics, however, some pathological conditions can occur more often in women, and others in men.

Symptoms of lesions

Diseases of the circulatory system are accompanied by different complaints of patients. Often the symptoms are common to all pathological conditions and do not refer to any particular disorder. Sufficiently common are cases where in the early stages of the occurrence of violations a person does not make any complaints at all. Some diseases of the circulatory system are diagnosed accidentally. However, knowledge of the most common symptoms makes it possible to identify the pathology in time and eliminate it at an early stage. Diseases can be accompanied by:

• Shortness of breath.
• Pain in the heart.
• Puffiness.
• Cyanosis, etc.

Palpitation

It is known that healthy people do not feel cuts in their heart at rest. You can not feel the heartbeat and with a moderate fiznagruzke. However, with its increase, even a healthy person will feel the sound of a heart. His heartbeat can increase with running, agitation, at high temperature. The situation is different for people who have heart or vessel problems. Strong palpitation, they can feel and with little load, and in some cases even at rest. The main cause of this condition is a violation of the contractile function of the body. Palpitation in this case is a compensatory mechanism. The fact is that with this violation for one reduction, the organ throws a smaller amount of blood into the aorta than necessary. Therefore, the heart goes into an intensive mode of operation. This has an extremely unfavorable effect on it, since the relaxation phase is substantially shortened. Thus, the heart relaxes less than it should. During a short relaxation, the biochemical processes necessary for recovery do not have time to pass. A rapid heartbeat is called tachycardia.

Pain

This symptom is accompanied by many diseases. In some cases, the pain in the heart can be the main symptom (for example, with ischemia), and in others - not have a determining value. With IHD, the pain is caused by insufficient blood supply to the heart muscle. The manifestation of pathology is quite clear. The pain is compressive, short-term (3-5 minutes), paroxysmal, occurs, as a rule, at a physical load, with a low air temperature. A similar state can arise in a dream. Usually a person who feels such pain takes a sitting position, and it resembles. Such an attack is called stenocardia of rest. With other diseases, pains do not have such a clear manifestation. Usually they are aching and continue at different times. They are not of high intensity. At the same time, there is no stopping effect from taking any medications. Such pains accompany different pathologies. Among them are heart defects, pericarditis, myocarditis, hypertension and so on. Pain in the area of the heart may not be associated with diseases of the circulatory system. For example, they are diagnosed with left-sided pneumonia, cervical and thoracic osteochondrosis, intercostal neuralgia, myositis and so on.

Interruptions in the activity of the heart

With this condition, a person feels the irregularity of the body's work. It manifests itself in the form of fading, a strong short stroke, a stop, etc. Some people have such interruptions, others - more durable and sometimes constant. As a rule, such sensations are accompanied by tachycardia. In a number of cases, irregularities are noted and with a rare rhythm. The causes are extrasystoles (extraordinary shortening), atrial fibrillation (loss of rhythmic function of the heart). In addition, there may be a violation of the conduction system and the muscle of the organ.

Hygiene of the heart

Normal stable activity of the body is possible only with a well-developed healthy circulatory system. Current speed determines the degree of supply of tissues with the necessary compounds and the intensity of removal of metabolic products from them. In the process of physical activity, the need for oxygen increases simultaneously with the increase in heart contractions. To avoid interruptions and violations, it is necessary to train the muscle of the organ. For this purpose, experts recommend doing exercises in the mornings. This is especially important for those people whose activities are not connected with the fiznagruzkoy. The greater effect of exercise comes when they are done in the fresh air. In general, doctors recommend more walking. Along with this, it should be remembered that excessive psycho-emotional and physical activities can disrupt the normal functioning of the heart. In this regard, stress and anxiety should be avoided whenever possible. While engaging in physical work, it is necessary to choose loads commensurate with the capabilities of the body. Extremely negative effect on the work of the body nicotine, alcohol, drugs. They poison the central nervous system and heart, cause serious disturbances in the regulation of vascular tone. As a result, serious diseases of the circulatory system may develop, some of which end in a fatal outcome. People who drink and smoke often have vascular spasms. In this regard, it is necessary to abandon bad habits and in every possible way to help your heart.