Nutrition of tissues with oxygen, important elements, as well as the removal of carbon dioxide and metabolic products from the cells in the body - blood functions. The process is a closed vascular path - human blood circulation circles, through which a continuous flow of vital fluid passes, its sequence of movement is ensured by special valves.
There are several circles of blood circulation in the human body
How many circles of blood circulation does a person have?
Human blood circulation or hemodynamics is continuous flow plasma fluid through the vessels of the body. This is a closed path of a closed type, that is, it does not come into contact with external factors.
Hemodynamics has:
- main circles – large and small;
- additional loops - placental, coronal and Willis.
The circulation cycle is always complete, which means that mixing of arterial and venous blood does not occur.
The heart, the main organ of hemodynamics, is responsible for plasma circulation. It is divided into 2 halves (right and left), where the internal sections are located - the ventricles and atria.
Heart - main body in the human circulatory system
Direction of liquid moving current connective tissue identify cardiac bridges or valves. They control the flow of plasma from the atria (cuspid) and prevent arterial blood from returning back into the ventricle (lunate).
The blood moves in circles in a certain order - first the plasma circulates in a small loop (5-10 seconds), and then in a large ring. Manage the work circulatory system specific regulators – humoral and nervous.
Big circle
On big circle hemodynamics has 2 functions:
- saturate the entire body with oxygen, distribute the necessary elements into the tissues;
- remove gas dioxide and toxic substances.
Here pass the superior and inferior vena cava, venules, arteries and artioles, as well as the largest artery, the aorta, which emerges from the left ventricle of the heart.
The placental circulation saturates the baby’s organs with oxygen and necessary elements
Heart circle
Due to the fact that the heart continuously pumps blood, it needs increased blood supply. Therefore, an integral part of the great circle is the coronal circle. It begins with the coronary arteries, which surround the main organ like a crown (hence the name of the additional ring).
The cardiac circle supplies the muscular organ with blood
The role of the heart circle is increased nutrition hollow muscular organ with blood. A special feature of the crown ring is that the contraction coronary vessels influences nervus vagus, while on contractility other arteries and veins are affected by the sympathetic nerve.
The circle of Willis is responsible for the complete supply of blood to the brain. The purpose of such a loop is to compensate for the lack of blood circulation in case of blockage of blood vessels. in such a situation, blood from other arterial basins will be used.
The structure of the arterial ring of the brain includes such arteries as:
- anterior and posterior brain;
- front and back connecting.
The circle of Willis circulation supplies the brain with blood
In the normal state, the Willis ring is always closed.The human circulatory system has 5 circles, of which 2 are main and 3 are additional, thanks to which the body is supplied with blood. The small ring carries out gas exchange, and the large one is responsible for transporting oxygen and nutrients to all tissues and cells. Additional circles are performed important role during pregnancy, reduce the load on the heart and compensate for the lack of blood supply to the brain.
The regular movement of blood flow in circles was discovered in the 17th century. Since then, the study of the heart and blood vessels has undergone significant changes due to the acquisition of new data and numerous studies. Today there are rarely people who do not know what circulatory circles are human body. However, not everyone has detailed information.
In this review, we will try to briefly but succinctly describe the importance of blood circulation, consider the main features and functions of blood circulation in the fetus, and the reader will also receive information about what the circle of Willis is. The data presented will allow everyone to understand how the body works.
Additional questions that may arise as you read will be answered by competent portal specialists.
Consultations are carried out online and free of charge.
Historical reference
In 1628, a physician from England, William Harvey, made the discovery that blood moves along a circular path - the systemic circulation and the pulmonary circulation. The latter includes blood flow to easy respiratory system, and the large one circulates throughout the body. In view of this, the scientist Harvey is a pioneer and made the discovery of blood circulation. Of course, Hippocrates, M. Malpighi, as well as other famous scientists made their contribution. Thanks to their work, the foundation was laid, which became the beginning of further discoveries in this area.
general information
The human circulatory system consists of: the heart (4 chambers) and two circulatory circles.
- The heart has two atria and two ventricles.
- The systemic circulation begins from the ventricle of the left chamber, and the blood is called arterial. From this point, blood flows through the arteries to each organ. As they travel through the body, the arteries transform into capillaries, which exchange gases. Next, the blood flow turns into venous. Then it enters the atrium of the right chamber and ends in the ventricle.
- The pulmonary circulation is formed in the ventricle of the right chamber and goes through the arteries to the lungs. There the blood exchanges, giving off gas and taking up oxygen, exits through the veins into the atrium of the left chamber, and ends in the ventricle.
Diagram No. 1 clearly shows how the blood circulation operates.
It is also necessary to pay attention to the organs and clarify the basic concepts that have important in the functioning of the body.
The circulatory organs are as follows:
- atria;
- ventricles;
- aorta;
- capillaries, incl. pulmonary;
- veins: hollow, pulmonary, blood;
- arteries: pulmonary, coronary, blood;
- alveolus.
Circulatory system
In addition to the minor and major pathways of blood circulation, there is also a peripheral pathway.
Peripheral circulation is responsible for the continuous process of blood flow between the heart and blood vessels. The muscle of the organ, contracting and relaxing, moves blood throughout the body. Of course, the pumped volume, blood structure and other nuances are important. The circulatory system works due to the pressure and impulses created in the organ. The way the heart pulsates depends on the systolic state and its change to diastolic.
The vessels of the systemic circulation carry blood flow to organs and tissues.
Types of vessels of the circulatory system:
- Arteries leaving the heart carry blood circulation. Arterioles perform a similar function.
- Veins, like venules, help return blood to the heart.
Arteries are tubes through which a large circle of blood flows. They have a fairly large diameter. Capable of withstanding high pressure due to thickness and ductility. They have three shells: inner, middle and outer. Thanks to their elasticity, they independently regulate depending on the physiology and anatomy of each organ, its needs and the temperature of the external environment.
The system of arteries can be imagined as a bush-like bundle, which becomes smaller the further from the heart. As a result, in the limbs they look like capillaries. Their diameter is no larger than a hair, and they are connected by arterioles and venules. Capillaries have thin walls and have one epithelial layer. This is where the exchange of nutrients takes place.
Therefore, the importance of each element should not be underestimated. Violation of the functions of one leads to diseases of the entire system. Therefore, in order to maintain the functionality of the body, you should maintain healthy image life.
Heart third circle
As we found out, the pulmonary circulation and the large circulation are not all components of the cardiovascular system. There is also a third path along which blood flow occurs and it is called the cardiac circulation circle.
This circle originates from the aorta, or rather from the point where it divides into two coronary arteries. The blood penetrates through them through the layers of the organ, then through small veins it passes into the coronary sinus, which opens into the atrium of the chamber of the right section. And some of the veins are directed to the ventricle. The path of blood flow through the coronary arteries is called the coronary circulation. Together, these circles are a system that supplies blood and nutrients to the organs.
Coronary circulation has the following properties:
- increased blood circulation;
- supply occurs in the diastolic state of the ventricles;
- There are few arteries here, so dysfunction of one gives rise to myocardial diseases;
- excitability of the central nervous system increases blood flow.
Diagram No. 2 shows how the coronary circulation functions.
The circulatory system includes the little-known circle of Willis. Its anatomy is such that it is presented in the form of a system of vessels that are located at the base of the brain. Its importance is difficult to overestimate, because... its main function is to compensate for the blood that it transfers from other “pools”. Vascular system The Willis circle is closed.
Normal development of the Willis pathway occurs in only 55%. A common pathology is an aneurysm and underdevelopment of the arteries connecting it.
At the same time, underdevelopment does not affect the human condition in any way, provided that there are no violations in other pools. May be detected during MRI. Aneurysm of the arteries of the Willis circulation is performed as surgical intervention in the form of its dressing. If the aneurysm has opened, the doctor prescribes conservative methods treatment.
The Willis vascular system is designed not only to supply blood flow to the brain, but also to compensate for thrombosis. In view of this, treatment of the Willis pathway is practically not carried out, because no health hazard.
Blood supply in the human fetus
Fetal circulation is the following system. Blood flow with a high content of carbon dioxide from the upper region enters the atrium of the right chamber through the vena cava. Through the hole, blood enters the ventricle and then into the pulmonary trunk. Unlike the human blood supply, the fetal pulmonary circulation does not go to the lungs Airways, and into the duct of the arteries, and only then into the aorta.
Diagram No. 3 shows how blood flows in the fetus.
Features of fetal blood circulation:
- Blood moves due to the contractile function of the organ.
- Starting from the 11th week, breathing affects blood flow.
- Great importance is given to the placenta.
- The fetal pulmonary circulation does not function.
- Mixed blood flow enters the organs.
- Identical pressure in the arteries and aorta.
To summarize the article, it should be emphasized how many circles are involved in supplying blood to the entire body. Information about how each of them works allows the reader to independently understand the intricacies of anatomy and functionality human body. Don’t forget that you can ask a question online and get an answer from competent specialists with medical education.
In the human body, there are two circles of blood circulation: large (systemic) and small (pulmonary). The systemic circle originates in the left ventricle and ends in the right atrium. The arteries of the systemic circulation carry out metabolism, carry oxygen and nutrition. In turn, the arteries of the pulmonary circulation enrich the blood with oxygen. Metabolic products are removed through the veins.
Arteries of the systemic circulation moves blood from the left ventricle first through the aorta, then through the arteries to all organs of the body, and this circle ends in the right atrium. The main purpose of this system is to deliver oxygen and nutrients to the organs and tissues of the body. Metabolic products are removed through veins and capillaries. The main function of the pulmonary circulation is the process of gas exchange in the lungs.
Arterial blood, which moves through the arteries, having passed its path, passes into the venous. After most of the oxygen has been given away and carbon dioxide has passed from the tissues into the blood, it becomes venous. All small vessels (venules) are collected in large veins systemic circulation. They are the superior and inferior vena cava.
They flow into the right atrium, and here the systemic circulation ends.Ascending aorta
Blood from the left ventricle begins its circulation. First it enters the aorta. This is the most significant vessel of the large circle.
It is divided into:
- ascending part
- aortic arch,
- descending part.
These are the liver, kidneys, stomach, intestines, brain, skeletal muscles etc.
The carotid arteries send blood to the head, the vertebral arteries - to the upper limbs. Then the aorta passes down along the spine, and here it enters the lower limbs and organs abdominal cavity and torso muscles.
At rest it is 20-30 cm/s, and at physical activity increases by 4-5 times. Arterial blood is rich in oxygen, it passes through the vessels and enriches all organs, and then through the veins, carbon dioxide and cellular metabolic products again enter the heart, then into the lungs and, passing through the pulmonary circulation, are removed from the body.
Location of the ascending aorta in the body:
- begins with an extension, the so-called onion;
- exits the left ventricle at the level of the third intercostal space on the left;
- goes up and behind the sternum;
- at the level of the second costal cartilage it passes into the aortic arch.
They are moving away from her right and left coronary arteries which supply blood to the heart.
Aortic arch
Three large vessels depart from the aortic arch:
- brachiocephalic trunk;
- left common carotid artery;
- left subclavian artery.
They bleed enters the upper torso, head, neck, upper limbs.
Starting from the second costal cartilage, the aortic arch turns left and back to the fourth thoracic vertebra and passes into the descending aorta.
This is the longest part of this vessel, which is divided into thoracic and abdominal sections.Brachiocephalic trunk
One of the large vessels, 4 cm long, goes up and to the right from the right sternal-clavicular joint. This vessel is located deep in the tissues and has two branches:
- right common carotid artery;
- right subclavian artery.
They supply blood to the organs of the upper body.
Descending aorta
The descending aorta is divided into a thoracic (up to the diaphragm) and an abdominal (below the diaphragm) part. It is located in front of the spine, starting from the 3rd-4th thoracic vertebra to the level of the 4th lumbar vertebra. This is the longest part of the aorta; at the lumbar vertebra it divides into.
CIRCLES OF BLOOD CIRCULATION
Arterial and venous vessels are not isolated and independent, but are interconnected as one system blood vessels. The circulatory system forms two circles of blood circulation: LARGE and SMALL.
The movement of blood through the vessels is also possible due to the difference in pressure at the beginning (artery) and end (vein) of each circle of blood circulation, which is created by the work of the heart. The pressure in arteries is higher than in veins. During contractions (systole), the ventricle ejects an average of 70-80 ml of blood each. Blood pressure rises and their walls stretch. During diastole (relaxation), the walls return to their original position, pushing the blood further, ensuring its uniform flow through the vessels.
Speaking about blood circulation circles, it is necessary to answer the questions: (WHERE? and WHAT?). For example: WHERE does it end?, begin? – (in which ventricle or atrium).
WHAT does it end with?, begins with? - (with what vessels) ..
The small circle of blood circulation delivers blood to the lungs where gas exchange occurs.
It begins in the right ventricle of the heart with the pulmonary trunk, into which venous blood enters during ventricular systole. The pulmonary trunk is divided into right and left pulmonary arteries. Each artery enters the lung through its gate and, accompanying the structures " bronchial tree"reaches the structural and functional units of the lung - (acnus) - dividing to blood capillaries. Gas exchange occurs between the blood and the contents of the alveoli. Venous vessels form two lungs in each lung
veins that carry arterial blood to the heart. The pulmonary circulation ends in the left atrium with four pulmonary veins.
right ventricle of the heart --- pulmonary trunk --- pulmonary arteries ---
division of intrapulmonary arteries --- arterioles --- blood capillaries ---
venules --- confluence of intrapulmonary veins --- pulmonary veins --- left atrium.
Which vessel and in which chamber of the heart does the pulmonary circulation begin:
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truncus pulmonalis
,Towith which vessels the pulmonary circulation begins and endsI.
originates from the right ventricle through the pulmonary trunk
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vessels forming the pulmonary circulation:
truncus pulmonalis
What vessels and in what chamber of the heart does the pulmonary circulation end:
Atrium sinistrum
The circulatory system delivers blood to all organs of the body.
From the left ventricle of the heart arterial blood during systole it is directed to the aorta. The elastic and muscle types, intraorgan arteries that divide into arterioles and blood capillaries. Venous blood flows through the system of venules, then intraorgan veins, extraorgan veins form the superior and inferior vena cava. They head towards the heart and empty into the right atrium.
sequentially it looks like this:
left ventricle of the heart --- aorta --- arteries (elastic and muscular) ---
intraorgan arteries --- arterioles --- blood capillaries --- venules ---
intraorgan veins ---veins---superior and inferior vena cava---
in which chamber of the heartbeginssystemic circulationand how
vesselohm .
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v. cava superior
v. cava inferior
Which vessels and in which chamber of the heart will the systemic circulation end:
v. cava inferior
The pattern of blood movement in circulatory circles was discovered by Harvey (1628). Subsequently, the doctrine of the physiology and anatomy of blood vessels was enriched with numerous data that revealed the mechanism of general and regional blood supply to organs.
In goblin animals and humans, which have a four-chambered heart, a distinction is made between the greater, lesser and cardiac circles of blood circulation (Fig. 367). The heart occupies a central place in blood circulation.
367. Blood circulation diagram (according to Kishsh, Sentagotai).
1 - general;
2 - aortic arch;
3 - pulmonary artery;
4 - pulmonary vein;
5 - left ventricle;
6 - right ventricle;
7 - celiac trunk;
8 - top mesenteric artery;
9 - inferior mesenteric artery;
10 - inferior vena cava;
11 - aorta;
12 - common iliac artery;
13 - common iliac vein;
14 - femoral vein. 15 - portal vein;
16 - hepatic veins;
17 - subclavian vein;
18 - superior vena cava;
19 - internal jugular vein.
Pulmonary circulation (pulmonary)
Venous blood from the right atrium passes through the right atrioventricular orifice into the right ventricle, which contracts and pushes blood into the pulmonary trunk. It divides into the right and left pulmonary arteries, which enter the lungs. In the lung tissue, the pulmonary arteries are divided into capillaries surrounding each alveolus. After red blood cells release carbon dioxide and enrich them with oxygen, venous blood turns into arterial blood. Arterial blood flows through four pulmonary veins (there are two veins in each lung) into the left atrium, then passes through the left atrioventricular orifice into the left ventricle. The systemic circulation begins from the left ventricle.
Systemic circulation
Arterial blood from the left ventricle is ejected into the aorta during its contraction. The aorta splits into arteries that supply blood to the limbs and torso. all internal organs and ending with capillaries. Nutrients, water, salts and oxygen are released from the blood capillaries into the tissues, metabolic products and carbon dioxide are resorbed. The capillaries gather into venules, where the venous system of vessels begins, representing the roots of the superior and inferior vena cava. Venous blood through these veins enters the right atrium, where the systemic circulation ends.
Cardiac circulation
This circle of blood circulation begins from the aorta with two coronary cardiac arteries, through which blood flows to all layers and parts of the heart, and then collects through small veins into the venous coronary sinus. This vessel opens with a wide mouth into the right atrium. Some of the small veins of the heart wall directly open into the cavity of the right atrium and ventricle of the heart.
In mammals and humans, the circulatory system is the most complex. This is a closed system consisting of two circles of blood circulation. Providing warm-bloodedness, it is more energetically beneficial and allows a person to occupy the habitat niche in which he is currently located.
The circulatory system is a group of hollow muscular organs responsible for circulating blood through the vessels of the body. It is represented by the heart and vessels of different sizes. These are muscular organs that form blood circulation circles. Their diagram is offered in all anatomy textbooks and is described in this publication.
The concept of blood circulation
The circulatory system consists of two circles - the bodily (large) and pulmonary (small). The circulatory system is a system of blood vessels of the arterial, capillary, lymphatic and venous type, which supplies blood from the heart to the vessels and its movement in the opposite direction. The heart is central, since two circles of blood circulation intersect in it without mixing arterial and venous blood.
Systemic circulation
The systemic circulation is the system of supplying peripheral tissues and its return to the heart. It starts from the left ventricle, from where blood exits into the aorta through the aortic orifice with the tricuspid valve. From the aorta, blood is directed to smaller bodily arteries and reaches the capillaries. This is a set of organs that forms the adductor link.
Here oxygen enters the tissues, and from them carbon dioxide is captured by red blood cells. Blood also transports amino acids, lipoproteins, and glucose into tissues, the metabolic products of which are carried out from capillaries into venules and further into larger veins. They drain into the vena cava, which returns blood directly to the heart into the right atrium.
The right atrium ends the systemic circulation. The diagram looks like this (along the blood circulation): left ventricle, aorta, elastic arteries, muscular elastic arteries, muscular arteries, arterioles, capillaries, venules, veins and vena cava, returning blood to the heart into the right atrium. The brain, all skin, and bones are nourished from the systemic circulation. In general, all human tissues are nourished by the vessels of the systemic circulation, and the small one is only a place of blood oxygenation.
Pulmonary circulation
The pulmonary (lesser) circulation, the diagram of which is presented below, originates from the right ventricle. Blood enters it from the right atrium through the atrioventricular opening. From the cavity of the right ventricle, oxygen-depleted (venous) blood flows through the outlet (pulmonary) tract into the pulmonary trunk. This artery is thinner than the aorta. It divides into two branches that go to both lungs.
The lungs are the central organ that forms the pulmonary circulation. The human diagram described in anatomy textbooks explains that pulmonary blood flow is necessary for oxygenation of the blood. Here it gives off carbon dioxide and takes in oxygen. In the sinusoidal capillaries of the lungs, with a diameter atypical for the body of about 30 microns, gas exchange occurs.
Subsequently, oxygenated blood is sent through the intrapulmonary venous system and collected in the 4 pulmonary veins. All of them are attached to the left atrium and carry oxygen-rich blood there. This is where the blood circulation ends. The diagram of the small pulmonary circle looks like this (in the direction of blood flow): right ventricle, pulmonary artery, intrapulmonary arteries, pulmonary arterioles, pulmonary sinusoids, venules, pulmonary veins, left atrium.
Features of the circulatory system
A key feature of the circulatory system, which consists of two circles, is the need for a heart with two or more chambers. Fish have only one blood circulation, because they do not have lungs, and all gas exchange takes place in the vessels of the gills. As a result, the fish heart is single-chambered - it is a pump that pushes blood in only one direction.
Amphibians and reptiles have respiratory organs and, accordingly, blood circulation. The scheme of their work is simple: from the ventricle blood is sent to the vessels of the systemic circle, from the arteries to the capillaries and veins. Venous return to the heart is also realized, but from the right atrium the blood enters the ventricle common to the two circulations. Since these animals have a three-chambered heart, blood from both circles (venous and arterial) mixes.
In humans (and mammals), the heart has a 4-chamber structure. It contains two ventricles and two atria separated by septa. The absence of mixing of two types of blood (arterial and venous) became a gigantic evolutionary invention that ensured the warm-bloodedness of mammals.
Blood supply to the lungs and heart
In the circulatory system, which consists of two circles, nutrition of the lungs and heart is of particular importance. These are the most important organs that ensure the closure of the bloodstream and the integrity of the respiratory and circulatory systems. So, the lungs have two circles of blood circulation in their thickness. But their tissue is nourished by the vessels of the systemic circle: bronchial and pulmonary vessels branch off from the aorta and intrathoracic arteries, carrying blood to the lung parenchyma. And the organ cannot receive nutrition from the right sections, although some of the oxygen diffuses from there. This means that the large and small circles of blood circulation, the diagram of which is described above, perform different functions (one enriches the blood with oxygen, and the second sends it to the organs, taking deoxygenated blood from them).
The heart is also fed by the vessels of the systemic circle, but the blood in its cavities is capable of providing oxygen to the endocardium. In this case, part of the myocardial veins, mainly small ones, flow directly into the It is noteworthy that the pulse wave does not propagate into cardiac diastole. Therefore, the organ is supplied with blood only when it is “resting”.
The human blood circulation, the diagram of which is presented above in the relevant sections, provides both warm-bloodedness and high endurance. Even though humans are not an animal that often uses their strength to survive, this has allowed other mammals to populate certain habitats. Previously, they were inaccessible to amphibians and reptiles, and even more so to fish.
In phylogeny, the large circle appeared earlier and was characteristic of fish. And the small circle supplemented it only in those animals that entirely or completely came to land and populated it. Since its inception, the respiratory and circulatory systems have been considered together. They are connected functionally and structurally.
This is an important and already indestructible evolutionary mechanism for leaving and settling the land. Therefore, the ongoing complication of mammalian organisms will now be directed not along the path of complication of the respiratory and circulatory system, but in the direction of strengthening the oxygen-binding system and increasing the area of the lungs.
Heart is central authority blood circulation It is a hollow muscular organ consisting of two halves: the left - arterial and the right - venous. Each half consists of an interconnected atrium and ventricle of the heart.
The central circulatory organ is heart. It is a hollow muscular organ consisting of two halves: the left - arterial and the right - venous. Each half consists of an interconnected atrium and ventricle of the heart.
Venous blood flows through the veins into the right atrium and then into the right ventricle of the heart, from the latter into the pulmonary trunk, from where it flows through the pulmonary arteries to the right and left lungs. Here the branches of the pulmonary arteries branch into the smallest vessels - capillaries.
In the lungs, venous blood is saturated with oxygen, becomes arterial and is directed through four pulmonary veins to the left atrium, then enters the left ventricle of the heart. From the left ventricle of the heart, blood enters the largest arterial line - the aorta, and through its branches, which disintegrate in the tissues of the body to the capillaries, is distributed throughout the body. Having given oxygen to the tissues and taken in carbon dioxide from them, the blood becomes venous. The capillaries, again connecting with each other, form veins.
All veins of the body are connected into two large trunks - the superior vena cava and the inferior vena cava. IN superior vena cava Blood is collected from areas and organs of the head and neck, upper extremities and some areas of the walls of the body. The inferior vena cava is filled with blood from the lower extremities, walls and organs of the pelvic and abdominal cavities.
Systemic circulation video.
Both vena cavae bring blood to the right atrium, which also receives venous blood from the heart itself. This closes the circle of blood circulation. This blood path is divided into the pulmonary and systemic circulation.
Pulmonary circulation video
Pulmonary circulation(pulmonary) starts from the right ventricle of the heart with the pulmonary trunk, includes the branches of the pulmonary trunk to the capillary network of the lungs and the pulmonary veins flowing into the left atrium.
Systemic circulation(bodily) starts from the left ventricle of the heart with the aorta, includes all its branches, capillary network and veins of organs and tissues of the whole body and ends in the right atrium.
Consequently, blood circulation occurs through two interconnected circulation circles.
When the human circulatory system is divided into two circulation circles, the heart is subjected to less stress than if the body had general system blood supply In the pulmonary circulation, blood travels from the heart to the lungs and then back thanks to the closed arterial and venous system that connects the heart and lungs. Its path begins in the right ventricle and ends in the left atrium. In the pulmonary circulation, blood with carbon dioxide is carried by arteries, and blood with oxygen is carried by veins.
From the right atrium, blood enters the right ventricle and is then pumped through the pulmonary artery into the lungs. From the right ventricle, venous blood enters the arteries and capillaries of the lungs, where it gets rid of carbon dioxide and is then saturated with oxygen. Through the pulmonary veins, blood flows into the left atrium, then it enters the systemic circulation and then goes to all organs. Since it flows slowly in the capillaries, carbon dioxide has time to enter it, and oxygen has time to penetrate the cells. Because blood enters the lungs at low pressure, the pulmonary circulation is also called the low-pressure system. The time it takes for blood to pass through the pulmonary circulation is 4-5 seconds.
When there is an increased need for oxygen, such as during intense exercise, the pressure generated by the heart increases and blood flow accelerates.
Systemic circulation
The systemic circulation begins from the left ventricle of the heart. Oxygenated blood travels from the lungs to the left atrium and then into the left ventricle. From there, arterial blood enters the arteries and capillaries. Through the walls of the capillaries, the blood releases oxygen and nutrients into the tissue fluid, taking away carbon dioxide and metabolic products. From the capillaries it enters small veins, which form larger veins. Then, through two venous trunks (superior vena cava and inferior vena cava), it enters the right atrium, ending the systemic circulation. The blood circulation in the systemic circulation is 23-27 seconds.
The superior vena cava carries blood from the upper parts of the body, and the inferior vena cava carries blood from the lower parts.
The heart has two pairs of valves. One of them is located between the ventricles and atria. The second pair is located between the ventricles and arteries. These valves direct blood flow and prevent blood from flowing backward. Blood is pumped into the lungs under high pressure, and it enters the left atrium at negative pressure. The human heart has an asymmetrical shape: since its left half does more heavy work, it is slightly thicker than
Blood ensures normal human life, saturating the body with oxygen and energy, while removing carbon dioxide and toxins.
The central organ of the circulatory system is the heart, which consists of four chambers separated from each other by valves and partitions, which act as the main channels for blood circulation.
Today everything is usually divided into two circles - large and small. They are combined into one system and closed on each other. The blood circulation circles consist of arteries - vessels carrying blood from the heart, and veins - vessels delivering blood back to the heart.
Blood in the human body can be arterial and venous. The first carries oxygen into the cells and has the highest pressure and, accordingly, speed. The second removes carbon dioxide and delivers it to the lungs (low pressure and low speed).
Both circles of blood circulation are two loops connected in series. The main circulatory organs can be called the heart - which acts as a pump, the lungs - which exchange oxygen, and which cleanses the blood of harmful substances and toxins.
In the medical literature one can often find more wide list, where human circulation is presented as follows:
- Big
- Small
- Cordial
- Placental
- Willisev
Human circulatory system
The great circle originates from the left ventricle of the heart.
Its main function is the delivery of oxygen and nutrients to organs and tissues through capillaries, the total area of which reaches 1500 square meters. m.
In the process of passing through the arteries, the blood takes up carbon dioxide and returns to the heart through the vessels, closing the blood flow in the right atrium with two vena cava - the lower and the upper.
The entire passage cycle takes from 23 to 27 seconds.
Sometimes the name body circle appears.
Pulmonary circulation
The small circle originates from the right ventricle, then passing through the pulmonary arteries, it delivers venous blood to the lungs.
Through the capillaries, carbon dioxide is displaced (gas exchange) and the blood, becoming arterial, returns to the left atrium.
The main task of the pulmonary circulation is heat exchange and blood circulation
The main task of the small circle is heat exchange and circulation. The average blood circulation time is no more than 5 seconds.
It may also be called the pulmonary circulation.
“Additional” blood circulation in humans
By placental circle the fetus is supplied with oxygen in the womb. It has a biased system and does not belong to any of the main circles. The umbilical cord simultaneously carries arterial-venous blood with a ratio of oxygen and carbon dioxide of 60/40%.
The cardiac circle is part of the body (greater) circle, but due to the importance of the heart muscle, it is often separated into a separate subcategory. At rest, up to 4% of the total participates in the bloodstream cardiac output(0.8 – 0.9 mg/min), with increasing load the value increases up to 5 times. It is in this part of a person’s blood circulation that blockage of blood vessels with a blood clot occurs and a lack of blood in the heart muscle.
The circle of Willis provides blood supply to the human brain and is also distinguished separately from the larger circle due to the importance of its functions. When individual vessels are blocked, it provides additional oxygen delivery through other arteries. Often atrophied and has hypoplasia of individual arteries. A full-fledged circle of Willis is observed only in 25-50% of people.
Features of blood circulation of individual human organs
Although the entire body is supplied with oxygen through the large circulation, some individual organs have their own unique oxygen exchange system.
The lungs have a double capillary network. The first belongs to the bodily circle and nourishes the organ with energy and oxygen, while taking away metabolic products. The second is to the pulmonary - here the displacement (oxygenation) of carbon dioxide from the blood and its enrichment with oxygen occurs.
The heart is one of the main organs of the circulatory system
Venous blood flows from the unpaired organs of the abdominal cavity otherwise, it first passes through portal vein. The vein is so named because of its connection with the porta hepatis. Passing through them, it is cleansed of toxins and only after that it returns through the hepatic veins to the general blood circulation.
The lower third of the rectum in women does not pass through the portal vein and is connected directly to the vagina, bypassing hepatic filtration, which is used to administer some medications.
Heart and brain. Their features were revealed in the section on additional circles.
Some facts
Up to 10,000 liters of blood pass through the heart per day, and it is also the most strong muscle in the human body, compressing up to 2.5 billion times during a lifetime.
The total length of blood vessels in the body reaches 100 thousand kilometers. This may be enough to reach the moon or circle the earth around the equator several times.
The average amount of blood is 8% of the total body weight. With a weight of 80 kg, about 6 liters of blood flow in a person.
Capillaries have such “narrow” (no more than 10 microns) passages that blood cells can only pass through them one at a time.
Watch an educational video about blood circulation:
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