What is the pulmonary circulation?

From the right ventricle, blood is pumped into the capillaries of the lungs. Here it “gives” carbon dioxide and “takes” oxygen, after which it goes back to the heart, namely the left atrium.

moves along a closed circuit which consists of the large and small circles of blood circulation. The path in the pulmonary circulation is from the heart to the lungs and back. In the pulmonary circulation, venous blood from the right ventricle of the heart enters the pulmonary circulation, where it gets rid of carbon dioxide and is saturated with oxygen and flows through the pulmonary veins into the left atrium. After this, the blood is pumped into the systemic circulation and flows to all organs of the body.

Why is the pulmonary circulation needed?

Dividing the human circulatory system into two circulation circles has one significant advantage: oxygen-enriched blood is separated from “used” blood, saturated with carbon dioxide. Thus, it is subjected to significantly less load than if, in general, it pumped both oxygen-saturated and carbon dioxide-saturated. This structure of the pulmonary circulation is due to the presence of a closed arterial and venous system connecting the heart and lungs. In addition, precisely due to the presence of the pulmonary circulation, it consists of four chambers: two atria and two ventricles.

How does the pulmonary circulation function?

Blood enters the right atrium through two venous trunks: the superior vena cava, which brings blood from the upper parts of the body, and the inferior vena cava, which brings blood from the lower parts. From the right atrium, blood enters the right ventricle, from where it is pumped through the pulmonary artery into the lungs.

Heart valves:

In the heart there are: one between the atria and the ventricles, the second between the ventricles and the arteries emerging from them. prevent backflow of blood and provide direction of blood flow.

Positive and negative pressure:

Alveoli are located on branches of the bronchial tree (bronchioles).

Under high pressure, blood is pumped into the lungs; under negative pressure, it enters the left atrium. Therefore, blood moves through the capillaries of the lungs at the same speed all the time. Thanks to the slow flow of blood in the capillaries, oxygen has time to penetrate the cells and carbon dioxide enters the blood. When oxygen demand increases, such as during intense or strenuous exercise, the pressure created by the heart increases and blood flow accelerates. Due to the fact that blood enters the lungs at a lower pressure than into the systemic circulation, the pulmonary circulation is also called the low-pressure system. : Its left half, which does the heavier work, is usually somewhat thicker than the right.

How is blood flow regulated in the pulmonary circulation?

Nerve cells, acting as a kind of sensors, constantly monitor various indicators, for example, acidity (pH), concentration of liquids, oxygen and carbon dioxide, content, etc. All information is processed in the brain. From it, corresponding impulses are sent to the heart and blood vessels. In addition, each artery has its own internal lumen, ensuring a constant blood flow rate. When the heartbeat speeds up, the arteries widen; when the heartbeat slows down, they narrow.

What is the systemic circulation?

Circulatory system: through the arteries, oxygenated blood is carried from the heart and supplied to the organs; Through the veins, blood saturated with carbon dioxide returns to the heart.

Oxygenated blood travels through the blood vessels of the systemic circulation to all human organs. The diameter of the largest artery, the aorta, is 2.5 cm. The diameter of the smallest blood vessels, capillaries, is 0.008 mm. The systemic circulation begins from, from here arterial blood enters the arteries, arterioles and capillaries. Through the walls of the capillaries, the blood releases nutrients and oxygen into the tissue fluid. And the waste products of cells enter the blood. From the capillaries, blood flows into small veins, which form larger veins and empty into the superior and inferior vena cava. The veins bring venous blood to the right atrium, where the systemic circulation ends.

100,000 km of blood vessels:

If you take all the arteries and veins of an adult of average height and connect them into one, then its length would be 100,000 km, and its area would be 6000-7000 m2. Such a large amount in the human body is necessary for the normal implementation of metabolic processes.

How does the systemic circulation work?

From the lungs, oxygenated blood flows into the left atrium and then into the left ventricle. When the left ventricle contracts, blood is ejected into the aorta. The aorta divides into two large iliac arteries, which run down and supply blood to the limbs. Blood vessels branch off from the aorta and its arch, supplying blood to the head, chest wall, arms and torso.

Where are the blood vessels located?

Blood vessels of the extremities are visible in the folds, for example, veins can be seen in the elbow bends. The arteries are located somewhat deeper, so they are not visible. Some blood vessels are quite elastic, so when you bend an arm or leg they are not pinched.

Main blood vessels:

The heart is supplied with blood by the coronary vessels belonging to the systemic circulation. The aorta branches into a large number of arteries, and as a result, the blood flow is distributed over several parallel vascular networks, each of which supplies blood to a separate organ. The aorta, rushing down, enters the abdominal cavity. Arteries that supply the digestive tract and spleen depart from the aorta. Thus, organs actively involved in metabolism are directly “connected” to the circulatory system. In the area of ​​the lumbar spine, just above the pelvis, the aorta branches: one of its branches supplies blood to the genitals, and the other to the lower extremities. Veins carry oxygen-depleted blood to the heart. From the lower extremities, venous blood collects in the femoral veins, which unite to form the iliac vein, which gives rise to the inferior vena cava. Venous blood flows from the head through the jugular veins, one on each side, and from the upper extremities through the subclavian veins; the latter, merging with the jugular veins, form the innominate veins on each side, which unite to form the superior vena cava.

Portal vein:

The portal vein system is a circulatory system that receives oxygen-depleted blood from the blood vessels of the digestive tract. Before entering the inferior vena cava and the heart, this blood passes through the capillary network

Connections:

In the fingers and toes, intestines and anus there are anastomoses - connections between the afferent and efferent vessels. Rapid heat transfer is possible through such connections.

Air embolism:

If air enters the bloodstream when drugs are given intravenously, it can cause an air embolism and lead to death. Air bubbles clog the capillaries of the lungs.

NOTE:

The opinion that arteries carry only oxygenated blood, and veins carry blood containing carbon dioxide, is not entirely correct. The fact is that in the pulmonary circulation the opposite is true - used blood is carried by arteries, and fresh blood is carried by veins.

Most people do not know how many circulations a person has. Below is detailed information about the authorities responsible for the operation of the system and other nuances.

People have long been interested in the blood flow system and studied it many centuries ago. There are many scientific works by famous scientists on this topic. Around the middle of the 17th century, it was proven that human blood circulates. Further research into the circulatory system and organs involved in this process continued. Over time, they learned to treat ailments associated with blood flow.

There are two important circles of blood circulation in humans - this is big and small. They interact with each other, since the human body is integral.

Circulatory organs

We include:

• vessels.

Heart is very important organ for life, as well as in the human blood circulation stage. Therefore, it is so important to monitor its activity and promptly consult a doctor in case of malfunctions. The most important organ includes four chambers, it consists of two ventricles and how many atria. They are connected by partitions. You can put it this way: the heart is a big muscle. It constantly pulsates or, as we say, beats.

Important! If your limbs go numb or your speech becomes sluggish, you should call an ambulance as quickly as possible. Perhaps it's a stroke.

Vessels are important participants in the blood flow process; they, like pipes, transport nutrients and fluid to all organs and tissues. The vessels consist of three layers of tissue. They all perform their important function.

Circulatory organs interconnected.

Vessel groups

Divided into three groups:

• arteries;
• veins;
• capillaries.

An artery is the largest type of vessels. They are very elastic. The movement of liquid through them occurs at a certain rhythm and under a certain pressure. Normal blood pressure for a person should be 120/80 mm. mercury column.

If there are pathologies in the body, then the rhythm may be disrupted, the pressure may drop, or, on the contrary, increase. Some people's blood pressure regularly rises, a condition called hypertension. There are people with chronically low blood pressure - hypotensive people.

Arterial injuries are very dangerous and pose a threat to human life; it is necessary to urgently call an ambulance. It is important to stop the bleeding in time. We need to apply a tourniquet. From damaged arteries blood flows like a fountain.

Capillaries – arise from the arteries, they are much thinner. Also elastic. Through them, blood flows directly to the organs, to the skin. Capillaries are very fragile, and because they are located in the upper layers of the skin, they are easily damaged and injured. Damage to capillaries for an ordinary body without disturbances in the circulatory system does not pose a danger and does not require the help of doctors.

Veins are vessels through which blood comes back, ending the cycle. Through the veins, fluid enriched with all the necessary nutrients moves back to the heart. Veins are medium-thick vessels. Like other vessels, they are elastic. Vein injuries also require medical attention, although they are less dangerous than arterial injuries.

Briefly about the blood flow system

Already mentioned above, there is big and small circle of blood circulation. In other words, corporeal (large) and pulmonary (respectively small). The systemic circulation begins in the left ventricle.

The blood enters the widest artery in diameter - the aorta, then spreads through other arteries, then through the capillaries and goes to the peripheral tissues and all organs.

The blood is saturated with useful substances, after which it is released into the veins. Through the veins, blood returns to the heart, namely, to the right atrium. This blood flow system is called the bodily system because the vessels supply blood to areas of the body. Veins of the systemic circulation come from all organs. Where the systemic circulation begins, there is an increased pulse, because the aorta is the thickest of all vessels.

Attention! More and more people have problems with the cardiovascular system. Now even children suffer from vascular diseases. Stroke is no longer a problem for adults!

The arteries of the systemic circulation diverge into all parts of the body.

The human body is penetrated by countless capillaries, which are kilometers long. The veins of the systemic circulation complete the cycle.

In the diagram you can clearly see how the human circulatory system works and what happens, where the systemic circulation begins, where the boundaries between veins and arteries are.

Pulmonary circulation

It is also called pulmonary. The name is such because the blood in this circle is supplied to the respiratory system, in particular the lungs. The pulmonary circulation starts in the right ventricle, then goes to the respiratory organs. Its purpose is saturate the blood with oxygen and remove CO2.

What is a small circle?

The pulmonary circulation includes the following elements:

1. Right ventricle;
2. Left atrium;
3. Lungs;
4. Arteries;
5. Capillaries;
6. Vienna.

Those small vessels that diverge from the arteries penetrate the lungs, passing through all the alveoli - these are bubbles with pure. The paradox of the system of this circle - venous blood is pumped through the arteries, and arterial blood flows through the veins.

Strong emotions always lead to increased blood pressure and increased blood flow. In different vessels the speed of liquid movement is different. The wider the vessel, the higher the speed, and vice versa. It turns out that in the aorta the speed of movement is very high. In capillaries it is ten times lower.

If there is not enough pressure, then blood poorly supplies distant areas, for example, it does not flow to the limbs. This leads to discomfort, sometimes to serious health problems. For example, Reine's syndrome is associated precisely with the lack of blood flow to the fingers. The simplest thing that bothers people with poor blood flow is constantly cold extremities. Nerve endings constantly suffer from this, not receiving enough nutrients.

Heartbeat

It’s interesting that when we’re at rest, we don’t notice how our heart beats. Moreover, it does not bring us discomfort. And after physical activity, we hear this organ knocking. He pumps blood more intensely and quickly.

People with different physical fitness respond differently to exercise. In some students the pulse is very strong, in others it is not so pronounced. For some groups of the planet's inhabitants, sports are contraindicated due to heart problems.

And for those who are allowed physical activity, you need to remember that the heart is a muscle, which means it requires constant training. Exercise has a great effect on the functioning of the cardiovascular system. It gives you a boost of energy for the whole day. You can join a gym or work out at home. Swimming is great for training your heart.

Attention! In smokers, the blood is enriched with oxygen much worse, this negatively affects the entire functioning of the body. They suffer much more often from heart diseases!

In addition to the above-mentioned circles, there are even less well-known circles of blood circulation - the cardiac and the circle of Willis. The first one ensures blood flow around the heart.

Its origins come from the aorta. Then the blood goes through its cycle through the coronary arteries. This is called coronary circulation. It has an accelerated pace. The excitability of the nervous system has a direct influence on coronary circulation. When irritated, the pulse increases greatly.

The Circle of Willis is little known to most people. Its importance is very great. Blood vessels of this circle supplies blood to the brain. The difference is that it is closed.

You should always pay attention to how the heart and blood flow in general work. Ideally, the heart rhythm is monotonous. If there are any diseases, then it is disrupted. There may be interruptions, stops, or just a rapid heartbeat. All these diagnoses: arrhythmias, tachycardia, hypoxia - cannot be left to chance.

Another common illness that causes a lot of inconvenience is vegetative-vascular dystonia. These are disturbances in blood flow in the vessels. Vessels with VSD are often narrowed.

The human body is permeated with vessels through which blood continuously circulates. This is an important condition for the life of tissues and organs. The movement of blood through the vessels depends on nervous regulation and is ensured by the heart, which acts as a pump.

Structure of the circulatory system

The circulatory system includes:

• veins;
• arteries;
• capillaries.

The liquid constantly circulates in two closed circles. The small one supplies the vascular tubes of the brain, neck, and upper parts of the body. Large - vessels of the lower body, legs. In addition, placental (present during fetal development) and coronary circulation are distinguished.

Structure of the heart

The heart is a hollow cone made of muscle tissue. All people have slightly different organs in shape and sometimes in structure.. It has 4 sections - the right ventricle (RV), left ventricle (LV), right atrium (RA) and left atrium (LA), which communicate with each other through openings.

The holes are closed by valves. Between the left sections is the mitral valve, between the right sections is the tricuspid valve.

The pancreas pushes fluid into the pulmonary circulation - through the pulmonary valve to the pulmonary trunk. The LV has denser walls, since it pushes blood into the systemic circulation, through the aortic valve, i.e. it must create sufficient pressure.

After a portion of liquid is ejected from the compartment, the valve closes, which ensures the movement of liquid in one direction.

Functions of arteries

The arteries receive oxygenated blood. Through them it is transported to all tissues and internal organs. The walls of the vessels are thick and highly elastic. The fluid is ejected into the artery under high pressure - 110 mmHg. Art., and elasticity is a vital quality that keeps the vascular tubes intact.

The artery has three membranes that ensure its ability to perform its functions. The middle shell consists of smooth muscle tissue, which allows the walls to change their lumen depending on body temperature, the needs of individual tissues, or under high pressure. Penetrating into the tissue, the arteries narrow, turning into capillaries.

Functions of capillaries

Capillaries penetrate all tissues of the body, except the cornea and epidermis, carrying oxygen and nutrients to them. The exchange is possible due to the very thin wall of the blood vessels. Their diameter does not exceed the thickness of a hair. Gradually, the arterial capillaries turn into venous ones.

Functions of veins

Veins carry blood to the heart. They are larger than arteries and contain about 70% of the total blood volume. Along the venous system there are valves that operate on the principle of heart valves. They allow blood to pass through and close behind it to prevent its outflow. Veins are divided into superficial, located directly under the skin, and deep, located in the muscles.

The main task of the veins is to transport blood to the heart, which no longer contains oxygen and contains decay products. Only the pulmonary veins carry oxygenated blood to the heart. There is a movement from bottom to top. When the normal functioning of the valves is disrupted, blood stagnates in the vessels, stretching them and deforming the walls.

What are the reasons for the movement of blood in the vessels:

• myocardial contraction;
• contraction of the smooth muscle layer of blood vessels;
• difference in blood pressure in arteries and veins.

Movement of blood through vessels

Blood moves through the vessels continuously. Somewhere faster, somewhere slower, it depends on the diameter of the vessel and the pressure under which the blood is ejected from the heart. The speed of movement through the capillaries is very low, due to which metabolic processes are possible.

The blood moves in a whirlwind, carrying oxygen along the entire diameter of the vessel wall. Due to such movements, oxygen bubbles seem to be pushed beyond the boundaries of the vascular tube.

The blood of a healthy person flows in one direction, the outflow volume is always equal to the inflow volume. The reason for the continuous movement is explained by the elasticity of the vascular tubes and the resistance that the fluid has to overcome. When blood enters, the aorta and artery stretch, then narrow, gradually allowing fluid to pass further. Thus, it does not move jerkily, like the heart contracts.

Pulmonary circulation

The small circle diagram is shown below. Where, RV - right ventricle, LS - pulmonary trunk, RPA - right pulmonary artery, LPA - left pulmonary artery, PH - pulmonary veins, LA - left atrium.

Through the pulmonary circulation, the fluid passes to the pulmonary capillaries, where it receives oxygen bubbles. The oxygen-rich fluid is called arterial fluid. From the LA it passes to the LV, where the bodily circulation originates.

Systemic circulation

Scheme of the bodily circle of blood circulation, where: 1. LV - left ventricle.

2. Ao - aorta.

3. Art - arteries of the trunk and limbs.

4. B - veins.

5. PV - vena cava (right and left).

6. RA - right atrium.

The body circle aims to distribute fluid full of oxygen bubbles throughout the body. It carries O 2 and nutrients to tissues, collecting decay products and CO 2 along the way. After this, movement occurs along the route: RV - LP. And then it starts again through the pulmonary circulation.

Personal circulation of the heart

The heart is the “autonomous republic” of the body. It has its own innervation system, which moves the muscles of the organ. And its own circulation, which consists of coronary arteries and veins. The coronary arteries independently regulate the blood supply to the heart tissue, which is important for the continuous functioning of the organ.

The structure of the vascular tubes is not identical. Most people have two coronary arteries, but it is possible to have a third. The heart can be supplied from the right or left coronary artery. Because of this, it is difficult to establish cardiac circulation standards. depends on the load, physical fitness, and age of the person.

Placental circulation

Placental circulation is inherent in every person at the stage of fetal development. The fetus receives blood from the mother through the placenta, which is formed after conception. From the placenta it moves to the baby's umbilical vein, from where it goes to the liver. This explains the large size of the latter.

The arterial fluid enters the vena cava, where it mixes with the venous fluid, and then goes to the left atrium. From it, blood flows to the left ventricle through a special opening, after which it flows directly to the aorta.

The movement of blood in the human body in a small circle begins only after birth. With the first breath, the blood vessels of the lungs dilate, and they develop for a couple of days. An oval hole in the heart can persist for up to a year.

Circulatory pathologies

Blood circulation is carried out in a closed system. Changes and pathologies in the capillaries can negatively affect the functioning of the heart. Gradually, the problem will worsen and develop into a serious disease. Factors affecting blood flow:

1. Pathologies of the heart and large vessels lead to insufficient blood flowing to the periphery. Toxins stagnate in the tissues, they do not receive proper oxygen supply and gradually begin to break down.
2. Blood pathologies, such as thrombosis, stasis, embolism, lead to blockage of blood vessels. Movement through arteries and veins becomes difficult, which deforms the walls of blood vessels and slows down the flow of blood.
3. Deformation of blood vessels. The walls can become thinner, stretch, change their permeability and lose elasticity.
4. Hormonal pathologies. Hormones can increase blood flow, which leads to strong filling of blood vessels.
5. Compression of blood vessels. When the vessels are compressed, the blood supply to the tissues stops, which leads to cell death.
6. Disturbances in the innervation of organs and injuries can lead to destruction of the walls of arterioles and provoke bleeding. Also, disruption of normal innervation leads to disorder of the entire circulatory system.
7. Infectious heart diseases. For example, endocarditis, which affects the heart valves. The valves do not close tightly, which promotes the reverse flow of blood.
8. Damage to cerebral vessels.
9. Vein diseases that affect the valves.

The movement of blood is also affected by a person’s lifestyle. Athletes have a more stable circulatory system, so they are more resilient, and even running fast will not immediately speed up the heart rate.

The average person can experience changes in blood circulation even from smoking a cigarette. In case of injuries and ruptures of blood vessels, the circulatory system is capable of creating new anastomoses to provide blood to the “lost” areas.

Regulation of blood circulation

Any process in the body is controlled. There is also regulation of blood circulation. The activity of the heart is activated by two pairs of nerves - sympathetic and vagus. The first excite the heart, the second slow down, as if controlling each other. Severe irritation of the vagus nerve can stop the heart.

A change in the diameter of blood vessels also occurs due to nerve impulses from the medulla oblongata. The heart rate increases or decreases depending on signals received from external stimuli, such as pain, temperature changes, etc.

In addition, the regulation of cardiac function occurs due to substances contained in the blood. For example, adrenaline increases the frequency of myocardial contractions and at the same time constricts blood vessels. Acetylcholine has the opposite effect.

All these mechanisms are needed to maintain constant uninterrupted functioning in the body, regardless of changes in the external environment.

Cardiovascular system

The above is only a brief description of the human circulatory system. The body contains a huge number of vessels. The circulation of blood in a large circle passes throughout the body, providing blood to every organ.

The cardiovascular system also includes the organs of the lymphatic system. This mechanism works in concert, under the control of neuro-reflex regulation. The type of movement in the vessels can be direct, which excludes the possibility of metabolic processes, or vortex.

The movement of blood depends on the operation of each system in the human body and cannot be described by a constant value. It changes depending on many external and internal factors. For different organisms existing in different conditions, there are their own norms of blood circulation, under which normal life activity will not be in danger.

The cardiovascular system is an important component of any living organism. Blood transports oxygen, various nutrients and hormones to the tissues, and carries the metabolic products of these substances to the excretory organs for their removal and neutralization. It is enriched with oxygen in the lungs and nutrients in the organs of the digestive system. In the liver and kidneys, metabolic products are excreted and neutralized. These processes are carried out through constant blood circulation, which occurs through the systemic and pulmonary circulation.

General information

There were attempts to discover the circulatory system in different centuries, but the English physician William Harvey truly understood the essence of the circulatory system, discovered its circles and described the diagram of their structure. He was the first to prove through experiment that in an animal’s body the same amount of blood constantly moves in a vicious circle due to the pressure created by the contractions of the heart. Harvey published a book in 1628. In it, he outlined his doctrine of the circulatory system, creating the prerequisites for further in-depth study of the anatomy of the cardiovascular system.

In newborn children, blood circulates in both circles, but while the fetus was still in the womb, its blood circulation had its own characteristics and was called placental. This is due to the fact that during the development of the fetus in the womb, the respiratory and digestive systems of the fetus do not function fully, and it receives all the necessary substances from the mother.

The structure of blood circulation

The main component of blood circulation is the heart. The large and small circles of blood circulation are formed by the vessels extending from it and are closed circles. They consist of vessels of various structures and diameters.

According to the function of blood vessels, they are usually divided into the following groups:

1. 1. Pericardial. They begin and end both circles of blood circulation. These include the pulmonary trunk, aorta, vena cava and pulmonary veins.
2. 2. Trunk. They distribute blood throughout the body. These are large and medium-sized extraorgan arteries and veins.
3. 3. Organ. With their help, the exchange of substances between the blood and tissues of the body is ensured. This group includes intraorgan veins and arteries, as well as the microcirculatory unit (arterioles, venules, capillaries).

Small circle

It works to oxygenate the blood, which occurs in the lungs. Therefore, this circle is also called pulmonary. It begins in the right ventricle, into which all venous blood entering the right atrium passes.

The beginning is the pulmonary trunk, which, when approaching the lungs, branches into the right and left pulmonary arteries. They carry venous blood to the alveoli of the lungs, which, having given up carbon dioxide and received oxygen in return, becomes arterial. Oxygenated blood flows through the pulmonary veins (two on each side) into the left atrium, where the pulmonary circle ends. The blood then flows into the left ventricle, where the systemic circulation originates.

Big circle

It originates in the left ventricle by the largest vessel of the human body - the aorta. It carries arterial blood containing substances and oxygen necessary for life. The aorta branches into arteries that go to all tissues and organs, which subsequently become arterioles and then capillaries. Through the wall of the latter, the exchange of substances and gases between tissues and vessels occurs.

Having received metabolic products and carbon dioxide, the blood becomes venous and collects in venules and then into veins. All veins merge into two large vessels - the inferior and superior vena cava, which then flow into the right atrium.

Functioning and meaning

Blood circulation is carried out due to contractions of the heart, the combined operation of its valves and the pressure gradient in the vessels of the organs. With the help of all this, the necessary sequence of blood movement in the body is set.

Thanks to the action of the blood circulation, the body continues to exist. Constant blood circulation is important for life and performs the following functions:

• gas (delivery of oxygen to organs and tissues and removal of carbon dioxide from them through the venous channel);
• transport of nutrients and plastic substances (enter the tissues through the arterial bed);
• delivery of metabolites (processed substances) to excretory organs;
• transport of hormones from the place of their production to target organs;
• circulation of thermal energy;
• delivery of protective substances to the place of requirement (to places of inflammation and other pathological processes).

The coordinated work of all parts of the cardiovascular system, which results in continuous blood flow between the heart and organs, allows for the exchange of substances with the external environment and maintains the constancy of the internal environment for the full functioning of the body for a long time.

Circulation- this is a continuous flow of blood in human vessels, providing all tissues of the body with all the substances necessary for normal life. The migration of blood elements helps remove salts and toxins from the organs.

Purpose of blood circulation– this ensures the flow of metabolism (metabolic processes in the body).

Circulatory organs

The organs that provide blood circulation include such anatomical formations as the heart along with the pericardium covering it and all the vessels passing through the tissues of the body:

Vessels of the circulatory system

All vessels included in the circulatory system are divided into groups:

1. Arterial vessels;
2. Arterioles;
3. Capillaries;
4. Venous vessels.

Arteries

Arteries include those vessels that transport blood from the heart to the internal organs. There is a common misconception among the population that the blood in the arteries always contains a high concentration of oxygen. However, this is not the case; for example, venous blood circulates in the pulmonary artery.

Arteries have a characteristic structure.

Their vascular wall consists of three main layers:

1. Endothelium;
2. Muscle cells located underneath;
3. A membrane consisting of connective tissue (adventitia).

The diameter of the arteries varies widely - from 0.4-0.5 cm to 2.5-3 cm. The entire volume of blood contained in vessels of this type is usually 950-1000 ml.

As they move away from the heart, the arteries divide into smaller vessels, the last of which are the arterioles.

Capillaries

Capillaries are the smallest component of the vascular bed. The diameter of these vessels is 5 microns. They penetrate all tissues of the body, ensuring gas exchange. It is in the capillaries that oxygen leaves the bloodstream and carbon dioxide migrates into the blood. This is where the exchange of nutrients takes place.

Vienna

Passing through organs, capillaries merge into larger vessels, first forming venules and then veins. These vessels carry blood from the organs towards the heart. The structure of their walls differs from the structure of arteries; they are thinner, but much more elastic.

A feature of the structure of veins is the presence of valves - connective tissue formations that block the vessel after the passage of blood and prevent its reverse flow. The venous system contains much more blood than the arterial system - approximately 3.2 liters.

Structure of the systemic circulation

1. Blood is pushed out of the left ventricle, where the systemic circulation begins. The blood is released from here into the aorta, the largest artery of the human body.
2. Immediately after leaving the heart the vessel forms an arch, at the level of which the common carotid artery departs from it, supplying blood to the organs of the head and neck, as well as the subclavian artery, which nourishes the tissues of the shoulder, forearm and hand.
3. The aorta itself goes down. From its upper, thoracic, section, arteries extend to the lungs, esophagus, trachea and other organs contained in the chest cavity.
4. Below aperture The other part of the aorta is located - the abdominal one. It gives branches to the intestines, stomach, liver, pancreas, etc. The aorta then divides into its terminal branches - the right and left iliac arteries, which supply blood to the pelvis and legs.
5. Arterial vessels, dividing into branches, they are transformed into capillaries, where the blood, previously rich in oxygen, organic matter and glucose, gives these substances to the tissues and becomes venous.
6. Great circle sequence blood circulation is such that capillaries are connected to each other in several pieces, initially merging into venules. They, in turn, also gradually connect, forming first small and then large veins.
7. Eventually, two main vessels are formed- superior and inferior vena cava. The blood flows from them directly to the heart. The trunk of the vena cava flows into the right half of the organ (namely, into the right atrium), and the circle closes.

Functions

The main purpose of blood circulation is the following physiological processes:

1. Gas exchange in tissues and in the alveoli of the lungs;
2. Delivery of nutrients to organs;
3. Receipt of special means of protection against pathological influences - immune cells, proteins of the coagulation system, etc.;
4. Removing toxins, waste, metabolic products from tissues;
5. Delivery of hormones that regulate metabolism to organs;
6. Providing thermoregulation of the body.

Such a variety of functions confirms the importance of the circulatory system in the human body.

Features of blood circulation in the fetus

The fetus, being in the mother's body, is directly connected with her through its circulatory system.

It has several main features:

1. Foramen ovale in the interventricular septum, connecting the sides of the heart;
2. The ductus arteriosus passing between the aorta and the pulmonary artery;
3. Duct venosus connecting the placenta and fetal liver.

Such specific anatomical features are based on the fact that the child has pulmonary circulation due to the fact that the work of this organ is impossible.

Blood for the fetus, coming from the body of the mother carrying it, comes from vascular formations included in the anatomical composition of the placenta. From here the blood flows to the liver. From there, through the vena cava, it enters the heart, namely, the right atrium. Through the oval window, blood passes from the right to the left side of the heart. Mixed blood spreads into the arteries of the systemic circulation.

The circulatory system is one of the most important components of the body. Thanks to its functioning in the body, all physiological processes are possible, which are the key to normal and active life.