The structure of the systemic circulation. Large and small circles of blood circulation

After all, it is a shame for future doctors not to know the basis of the basics - circles of blood circulation. Without this information and understanding of how blood moves through the body, it is impossible to understand the mechanism of development of vascular and heart diseases, to explain pathological processes that occur in the heart with a particular lesion. Without knowing the circles of blood circulation it is impossible to work as a doctor. This information will not interfere with a simple layman, because knowledge about one's own body is never superfluous.

1 Big trip

To better imagine how a large circle of blood circulation works, let's fantasize a little? Imagine that all the vessels of the body are rivers, and the heart is a bay, into the bay of which all the channels of the rivers fall. We set off on a journey: our ship begins a great voyage. From the left ventricle we swim into the aorta - the main vessel human body. This is where the systemic circulation begins.

Oxygenated blood flows in the aorta, because aortic blood is distributed throughout the human body. The aorta gives off branches, like a river, tributaries that supply blood to the brain, all organs. Arteries branch to arterioles, which in turn give off capillaries. bright, arterial blood gives cells oxygen, nutrients, and takes the metabolic products of cellular life.

Capillaries are organized into venules that carry dark, cherry-colored blood, because it has given oxygen to the cells. Venules gather in more large veins. Our ship completes its journey along the two largest "rivers" - the upper and lower vena cava - enters right atrium. The path is over. You can schematically represent a large circle as follows: the beginning is the left ventricle and aorta, the end is the vena cava and the right atrium.

2 Small Journey

What is the pulmonary circulation? Let's go on our second trip! Our ship originates from the right ventricle, from which the pulmonary trunk departs. Remember that completing the systemic circulation, we moored in the right atrium? Out of him deoxygenated blood flows into the right ventricle, and then, with heart contraction, is pushed into the vessel, departing from it - the pulmonary trunk. This vessel travels to the lungs, where it bifurcates into the pulmonary arteries and then into the capillaries.

Capillaries envelop the bronchi and alveoli of the lungs, give carbon dioxide and metabolic products and are enriched with life-giving oxygen. Capillaries organize into venules as they leave the lungs and then into the larger pulmonary veins. We are accustomed to the fact that venous blood flows in the veins. Just not in the lungs! These veins are rich in arterial, bright scarlet, O2 rich blood. Through the pulmonary veins, our ship sails to the bay, where its journey ends - to the left atrium.

So, the beginning of the small circle is the right ventricle and the pulmonary trunk, the end is the pulmonary veins and the left atrium. More detailed description the following: the pulmonary trunk is divided into two pulmonary arteries, which in turn branch into a network of capillaries, like a cobweb enveloping the alveoli, where gas exchange occurs, then the capillaries gather into venules and pulmonary veins that flow into the left upper cardiac chamber of the heart.

3 Historical facts

Having dealt with the departments of blood circulation, it seems that there is nothing complicated in their structure. Everything is simple, logical, understandable. Blood leaves the heart, collects metabolic products and CO2 from the cells of the whole body, saturates them with oxygen, returns to the heart again already venous blood, which, passing through the natural "filters" of the body - the lungs, becomes arterial again. But it took many centuries to study and understand the movement of blood flow in the body. Galen mistakenly assumed that the arteries do not contain blood, but air.

This position today can be explained by the fact that at that time vessels were studied only on corpses, and in dead body the arteries are bloodless, and the veins, on the contrary, are full-blooded. It was believed that blood is produced in the liver, and it is consumed in the organs. Miguel Servet in the 16th century suggested that “the spirit of life originates in the left heart ventricle, the lungs contribute to this, where the air and blood coming from the right are mixed. cardiac ventricle”, thus, the scientist recognized and described for the first time a small circle.

But little attention was paid to the discovery of Servetus. The father of the circulatory system is considered to be Harvey, who already in 1616 wrote in his writings that the blood "circulates through the body." For many years he studied the movement of blood, and in 1628 he published a work that became a classic, and crossed out all ideas about the blood circulation of Galen, in this work the circles of blood circulation were outlined.

Harvey did not discover only the capillaries discovered later by the scientist Malpighi, who supplemented the knowledge of the "circles of life" with a connecting capillary link between arterioles and venules. The microscope helped the scientist to open the capillaries, which gave an increase of up to 180 times. Harvey's discovery was met with criticism and challenge by the great minds of those times, many scientists did not agree with Harvey's discovery.

But even today, reading his works, you are surprised how accurately and in detail for that time the scientist described the work of the heart and the movement of blood through the vessels: “The heart, doing work, first makes a movement, and then rests in all animals while they are still alive. At the moment of contraction, it squeezes out blood from itself, the heart is emptied at the moment of contraction. The circulatory circles were also described in detail, with the exception that Harvey could not observe the capillaries, but he accurately described that the blood is collected from the organs and flows back to the heart?

But how does the transition from arteries to veins take place? This question haunted Harvey. malpighi revealed given secret human body, discovering capillary circulation. It's a shame that Harvey did not live several years before this discovery, because the discovery of capillaries with 100% certainty confirmed the veracity of Harvey's teachings. The great scientist did not have a chance to feel the fullness of the triumph of his discovery, but we remember him and his huge contribution to the development of anatomy and knowledge of nature. human body.

4 Largest to smallest

I would like to dwell on the main elements of the circles of blood circulation, which are their framework, along which the blood moves - the vessels. Arteries are blood vessels carrying blood from the heart. The aorta is the most important and important artery of the body, it is the largest - about 25 mm in diameter, it is through it that blood enters other vessels that depart from it and is delivered to organs, tissues, cells.

Exception: the pulmonary arteries carry not O2-rich blood, but CO2-rich blood to the lungs.

Veins are vessels that carry blood to the heart, their walls are easily extensible, the diameter of the vena cava is about 30 mm, and the small ones are 4-5 mm. The blood in them is dark, the color of ripe cherries, saturated with products exchange.

Exception: the pulmonary veins are the only ones in the body through which arterial blood flows.

Capillaries - the thinnest vessels consisting of only one layer of cells. Single layer structure allows gas exchange, exchange of useful and harmful products between cells and directly capillaries.

The diameter of these vessels is only 0.006 mm on average, and the length is not more than 1 mm. That's how small they are! However, if we sum up the length of all the capillaries together, we will get a very significant figure - 100 thousand km ... Our body inside is shrouded in them like a cobweb. And no wonder - after all, every cell of the body needs oxygen and nutrients, and capillaries can ensure the supply of these substances. All vessels, both the largest and smallest capillaries, form closed system, or rather two systems - the aforementioned circles of blood circulation.

5 Important features

What are circulatory circles for? Their role cannot be overestimated. How life on Earth is impossible without water resources and human life is impossible without the circulatory system. Main role great circle is:

Providing oxygen to every cell of the human body;
The flow of nutrients from the digestive system into the blood;
Filtration from blood to excretory organs life products.

The role of the small circle is no less important than those described above: the removal of CO2 from the body and metabolic products.

Building knowledge own body are never superfluous, knowledge of how the circulatory departments function leads to a better understanding of the work of the body, and also forms an idea of the unity and integrity of organs and systems, the connecting link of which is undoubtedly bloodstream organized into circulation circles.

The regularity of the movement of blood in the circles of blood circulation was discovered by Harvey (1628). Subsequently, the doctrine of physiology and anatomy blood vessels enriched with numerous data that revealed the mechanism of general and regional blood supply to organs.

In goblin animals and humans with a four-chambered heart, there are large, small and cardiac circles of blood circulation (Fig. 367). The heart plays a central role in circulation.

367. Scheme of blood circulation (according to Kishsh, Sentagotai).

1 - total carotid artery;
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 - total iliac artery;
13 - total iliac vein;
14 - femoral vein. 15 - portal vein;
16 - hepatic veins;
17 - subclavian vein;
18 - superior vena cava;
19 - internal jugular vein.

Small circle of blood circulation (pulmonary)

Venous blood from the right atrium through the right atrioventricular opening passes into the right ventricle, which, contracting, pushes the blood into the pulmonary trunk. It divides into the right and left pulmonary arteries, which enter the lungs. IN lung tissue the pulmonary arteries divide into capillaries surrounding each alveolus. After the erythrocytes release carbon dioxide and enrich them with oxygen, venous blood turns into arterial blood. Arterial blood flows through four pulmonary veins (two veins in each lung) into the left atrium, then through the left atrioventricular opening passes into the left ventricle. The systemic circulation begins from the left ventricle.

Systemic circulation

Arterial blood from the left ventricle during its contraction is ejected into the aorta. The aorta splits into arteries that supply blood to the limbs, torso, and. All internal organs and ending in capillaries. From the blood capillaries to tissues nutrients, water, salts and oxygen, metabolic products and carbon dioxide are resorbed. Capillaries gather into venules, where it begins venous system vessels 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 enters all layers and parts of the heart, and then is collected through small veins into the venous coronary sinus. This vessel with a wide mouth opens into the right atrium. Part of the small veins of the heart wall directly opens into the cavity of the right atrium and ventricle of the heart.

Supplying tissues with oxygen important elements, as well as the removal of carbon dioxide from the cells and metabolic products in the body - the functions of the blood. The process is a closed vascular path - human circulation circles through which an uninterrupted current of vital important fluid, its movement sequence is provided by special valves.

There are several circulations in the human body.

How many circles of blood circulation does a person have?

Human circulation or hemodynamics is a continuous flow of 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, coronary and Willisian.

The circulation cycle is always complete, which means that there is no mixing of arterial and venous blood.

The heart, the main organ of hemodynamics, is responsible for the circulation of plasma. It is divided into 2 halves (right and left), where are located internal departments- ventricles and atria.

Heart - main body in the human circulatory system

The direction of the flow of liquid mobile connective tissue is determined by cardiac bridges or valves. They control the flow of plasma from the atria (valve) and prevent arterial blood from returning back to the ventricle (lunate).

Blood moves in circles in a certain order - first, the plasma circulates along a small loop (5–10 seconds), and then along big ring. Manage work circulatory system specific regulators - humoral and nervous.

big circle

The large circle of hemodynamics is assigned 2 functions:

saturate the entire body with oxygen, carry the necessary elements into the tissues;
remove gas and toxic substances.

Here are the superior vena cava and inferior vena cava, venules, arteries and artioles, as well as the largest artery - the aorta, it comes out of the left heart of the ventricle.

A large circle of blood circulation saturates the organs with oxygen and removes toxic substances.

In the extensive ring, the flow of blood fluid begins in the left ventricle. The purified plasma exits through the aorta and is carried to all organs by moving through the arteries, arterioles, reaching smallest vessels- capillary network, where it gives oxygen to tissues and useful components. Instead, hazardous waste and carbon dioxide are removed. The return path of plasma to the heart lies through venules, which smoothly flow into the vena cava - this is venous blood. The circulation along the large loop ends in the right atrium. Duration full circle- 20-25 seconds.

Small circle (pulmonary)

The primary role of the pulmonary ring is to carry out gas exchange in the alveoli of the lungs and to produce heat transfer. During the cycle, venous blood is saturated with oxygen, being cleansed of carbon dioxide. There is a small circle and additional functions. It blocks the further progress of embolism and thrombi that have penetrated from the large circle. And if the volume of blood changes, then it accumulates in separate vascular reservoirs, which in normal conditions do not participate in circulation.

The pulmonary circle has the following structure:

pulmonary vein;
capillaries;
pulmonary artery;
arterioles.

Venous blood, due to ejection from the atrium of the right side of the heart, passes into the large pulmonary trunk and enters the central organ of the small ring - the lungs. IN capillary network there is a process of plasma enrichment with oxygen and release of carbon dioxide. Already arterial blood flows into the pulmonary veins, the ultimate goal of which is to reach the left heart section (atrium). At this, the cycle along the small ring closes.

The peculiarity of the small ring is that the plasma movement along it has a reverse sequence. Here, blood rich in carbon dioxide and cellular waste flows through the arteries, and oxygenated fluid moves through the veins.

Additional circles

Based on the characteristics of human physiology, in addition to the 2 main ones, there are 3 more auxiliary hemodynamic rings - placental, cardiac or coronary and willis.

Placental

The period of development in the uterus of the fetus implies the presence of a circle of blood circulation in the embryo. Its main task is to saturate with oxygen and useful elements all body tissues of the unborn child. Liquid connective tissue enters the fetal organ system through the mother's placenta along the capillary network of the umbilical vein.

The sequence of movement is as follows:

the arterial blood of the mother, entering the body of the fetus, mixes with its venous blood from the lower body;
fluid moves to the right atrium through the inferior vena cava;
more plasma enters the left side of the heart through atrial septum(a small circle is bypassed, since it does not yet function in the embryo) and passes into the aorta;
the remaining amount of undistributed blood flows into the right ventricle, where, through the superior vena cava, having collected all the venous blood from the head, it enters right side heart, and from there to the pulmonary trunk and aorta;
from the aorta, blood spreads to all tissues of the embryo.

After the birth of a child, the need for a placental circle disappears, and the connecting veins are emptied and do not function.

The placental circle of blood circulation saturates the child's organs with oxygen and the necessary elements.

heart circle

Since the heart pumps blood continuously, it needs an increased blood supply. Therefore, an integral part of the large circle is the crown circle. It starts with coronary arteries, which surround the main organ as if with a crown (hence the name of the additional ring).

The heart circle nourishes the muscular organ with blood

The role of the heart circle is increased nutrition gently muscular organ blood. A feature of the coronal ring is that the contraction coronary vessels affects nervus vagus, while on contractility other arteries and veins are affected by the sympathetic nerve.

The circle of Willis is responsible for the proper 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 pools will be used.

The structure of the arterial ring of the brain includes arteries such as:

anterior and posterior cerebral;
front and back connecting.

The circle of Willis supplies the brain with blood

IN normal condition the ring of willis is always closed.

The human circulatory system has 5 circles, of which 2 are main and 3 are additional, thanks to them 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 perform important role during pregnancy, reduce the load on the heart and compensate for the lack of blood supply to the brain.

arterial blood is oxygenated blood.
Deoxygenated blood- saturated with carbon dioxide.

arteries are vessels that carry blood away from the heart.
Vienna are the vessels that carry blood to the heart.
(In the pulmonary circulation, venous blood flows through the arteries, and arterial blood flows through the veins.)

In humans, in all other mammals, as well as in birds four-chambered heart, consists of two atria and two ventricles (in the left half of the heart, blood is arterial, in the right - venous, mixing does not occur due to a complete septum in the ventricle).

Between the ventricles and atria are flap valves, and between arteries and ventricles - semilunar. The valves prevent blood from flowing backwards (from the ventricle to the atrium, from the aorta to the ventricle).

The thickest wall is in the left ventricle, because it pushes blood through the systemic circulation. With the contraction of the left ventricle, a pulse wave is created, as well as maximum blood pressure.

Blood pressure: largest in arteries, medium in capillaries, smallest in veins. Blood speed: largest in arteries, smallest in capillaries, medium in veins.

big circle blood circulation: from the left ventricle, arterial blood travels through the arteries to all organs of the body. In the capillaries of the great circle, gas exchange occurs: oxygen passes from the blood to the tissues, and carbon dioxide from the tissues into the blood. The blood becomes venous, through the vena cava enters the right atrium, and from there - into the right ventricle.

Small circle: From the right ventricle, venous blood flows through the pulmonary arteries to the lungs. In the capillaries of the lungs, gas exchange occurs: carbon dioxide passes from the blood into the air, and oxygen from the air into the blood, the blood becomes arterial and enters the left atrium through the pulmonary veins, and from there into the left ventricle.

Establish a correspondence between the sections of the circulatory system and the circle of blood circulation to which they belong: 1) the systemic circle of blood circulation, 2) the small circle of blood circulation. Write the numbers 1 and 2 in the correct order.
A) right ventricle
B) carotid artery
B) pulmonary artery
D) superior vena cava
D) left atrium
E) left ventricle

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. The systemic circulation in the human body
1) begins in the left ventricle
2) originates in the right ventricle
3) saturated with oxygen in the alveoli of the lungs
4) supplies organs and tissues with oxygen and nutrients
5) ends in the right atrium
6) brings blood to the left half of the heart

Answer

1. Set the sequence of human blood vessels in decreasing order in them blood pressure. Write down the corresponding sequence of numbers.
1) inferior vena cava
2) aorta
3) pulmonary capillaries
4) pulmonary artery

Answer

2. Establish the sequence in which blood vessels should be arranged in order of decreasing blood pressure in them
1) Veins
2) Aorta
3) Arteries
4) Capillaries

Answer

Establish a correspondence between the vessels and circles of human circulation: 1) pulmonary circulation, 2) systemic circulation. Write the numbers 1 and 2 in the correct order.
A) aorta
B) pulmonary veins
B) carotid arteries
D) capillaries in the lungs
D) pulmonary arteries
E) hepatic artery

Answer

Choose the one most correct option. Why can't blood get from the aorta to the left ventricle of the heart?
1) the ventricle contracts with great strength and creates high pressure
2) the semilunar valves fill with blood and close tightly
3) leaf valves are pressed against the walls of the aorta
4) the cuspid valves are closed and the semilunar valves are open

Answer

Choose one, the most correct option. Blood enters the pulmonary circulation from the right ventricle through
1) pulmonary veins
2) pulmonary arteries
3) carotid arteries
4) aorta

Answer

Choose one, the most correct option. Arterial blood in the human body flows through
1) renal veins
2) pulmonary veins
3) vena cava
4) pulmonary arteries

Answer

Choose one, the most correct option. In mammals, oxygenation of the blood occurs in
1) arteries of the pulmonary circulation
2) capillaries of a large circle
3) arteries of the great circle
4) small circle capillaries

Answer

1. Establish the sequence of blood flow through the vessels of the systemic circulation. Write down the corresponding sequence of numbers.
1) portal vein of the liver
2) aorta
3) gastric artery
4) left ventricle
5) right atrium
6) inferior vena cava

Answer

2. Determine correct sequence blood circulation in the systemic circulation, starting from the left ventricle. Write down the corresponding sequence of numbers.
1) Aorta
2) Superior and inferior vena cava
3) Right atrium
4) Left ventricle
5) Right ventricle
6) Tissue fluid

Answer

3. Establish the correct sequence of blood flow through the systemic circulation. Write down the corresponding sequence of numbers in the table.
1) right atrium
2) left ventricle
3) arteries of the head, limbs and trunk
4) aorta
5) inferior and superior vena cava
6) capillaries

Answer

4. Establish the sequence of blood movement in the human body, starting from the left ventricle. Write down the corresponding sequence of numbers.
1) left ventricle
2) vena cava
3) aorta
4) pulmonary veins
5) right atrium

Answer

5. Establish the sequence of passage of a portion of blood in a person, starting from the left ventricle of the heart. Write down the corresponding sequence of numbers.
1) right atrium
2) aorta
3) left ventricle
4) lungs
5) left atrium
6) right ventricle

Answer

Arrange the blood vessels in order of decreasing speed of blood flow in them.
1) superior vena cava
2) aorta
3) brachial artery
4) capillaries

Answer

Choose one, the most correct option. The vena cava in the human body drains into
1) left atrium
2) right ventricle
3) left ventricle
4) right atrium

Answer

Choose one, the most correct option. Backflow of blood from the pulmonary artery and aorta to the ventricles is prevented by valves
1) tricuspid
2) venous
3) double-leaf
4) semilunar

Answer

1. Establish the sequence of blood flow in a person in the pulmonary circulation. Write down the corresponding sequence of numbers.
1) pulmonary artery
2) right ventricle
3) capillaries
4) left atrium
5) veins

Answer

2. Establish the sequence of blood circulation processes, starting from the moment when blood moves from the lungs to the heart. Write down the corresponding sequence of numbers.
1) blood from the right ventricle enters the pulmonary artery
2) blood moves through the pulmonary vein
3) blood moves through the pulmonary artery
4) oxygen flows from the alveoli to the capillaries
5) blood enters the left atrium
6) blood enters the right atrium

Answer

3. Establish the sequence of movement of arterial blood in a person, starting from the moment of its saturation with oxygen in the capillaries of the small circle. Write down the corresponding sequence of numbers.
1) left ventricle
2) left atrium
3) veins of the small circle
4) small circle capillaries
5) arteries of a large circle

Answer

4. Establish the sequence of movement of arterial blood in the human body, starting with the capillaries of the lungs. Write down the corresponding sequence of numbers.
1) left atrium
2) left ventricle
3) aorta
4) pulmonary veins
5) capillaries of the lungs

Answer

5. Set the correct sequence for the passage of a portion of blood from the right ventricle to the right atrium. Write down the corresponding sequence of numbers.
1) pulmonary vein
2) left ventricle
3) pulmonary artery
4) right ventricle
5) right atrium
6) aorta

Answer

Set the sequence of events that take place in cardiac cycle after blood enters the heart. Write down the corresponding sequence of numbers.
1) contraction of the ventricles
2) general relaxation of the ventricles and atria
3) the flow of blood into the aorta and artery
4) the flow of blood into the ventricles
5) atrial contraction

Answer

Establish a correspondence between human blood vessels and the direction of blood flow in them: 1) from the heart, 2) to the heart
A) veins of the pulmonary circulation
B) veins of the systemic circulation
B) arteries of the pulmonary circulation
D) arteries of the systemic circulation

Answer

Choose three options. A person has blood from the left ventricle of the heart
1) when it contracts, it enters the aorta
2) when it contracts, it enters the left atrium
3) supply the cells of the body with oxygen
4) enters the pulmonary artery
5) under great pressure enters the greater circulation
6) under slight pressure enters the pulmonary circulation

Answer

Choose three options. Blood flows through the arteries of the pulmonary circulation in humans
1) from the heart
2) to the heart

4) oxygenated
5) faster than in pulmonary capillaries
6) slower than in pulmonary capillaries

Answer

Choose three options. Veins are blood vessels through which blood flows
1) from the heart
2) to the heart
3) under greater pressure than in the arteries
4) under less pressure than in the arteries
5) faster than in capillaries
6) slower than in capillaries

Answer

Choose three options. Blood flows through the arteries of the systemic circulation in humans
1) from the heart
2) to the heart
3) saturated with carbon dioxide
4) oxygenated
5) faster than in other blood vessels
6) slower than in other blood vessels

Answer

1. Establish a correspondence between the type of human blood vessels and the type of blood they contain: 1) arterial, 2) venous
A) pulmonary arteries
B) veins of the pulmonary circulation
B) aorta and arteries of the systemic circulation
D) superior and inferior vena cava

Answer

2. Establish a correspondence between the vessel of the human circulatory system and the type of blood that flows through it: 1) arterial, 2) venous. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) femoral vein
B) brachial artery
B) pulmonary vein
D) subclavian artery
D) pulmonary artery
E) aorta

Answer

Choose three options. In mammals and humans, venous blood, in contrast to arterial,
1) poor in oxygen
2) flows in a small circle through the veins
3) fills right half hearts
4) saturated with carbon dioxide
5) enters the left atrium
6) provides body cells with nutrients

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. Veins as opposed to arteries
1) have valves in the walls
2) can subside
3) have walls from one layer of cells
4) carry blood from the organs to the heart
5) withstand high blood pressure
6) always carry blood that is not saturated with oxygen

Answer

Analyze the table "The work of the human heart." For each cell marked with a letter, select the appropriate term from the list provided.
1) Arterial
2) Superior vena cava
3) Mixed
4) Left atrium
5) Carotid artery
6) Right ventricle
7) Inferior vena cava
8) Pulmonary vein

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. Elements of the human circulatory system that contain venous blood are
1) pulmonary artery
2) aorta
3) vena cava
4) right atrium and right ventricle
5) left atrium and left ventricle
6) pulmonary veins

Answer

Choose three correct answers from six and write down the numbers under which they are indicated. Blood flowing from the right ventricle
1) arterial
2) venous
3) along the arteries
4) through the veins
5) towards the lungs
6) towards the cells of the body

Answer

Establish a correspondence between the processes and circles of blood circulation for which they are characteristic: 1) small, 2) large. Write down the numbers 1 and 2 in the order corresponding to the letters.
A) Arterial blood flows through the veins.
B) The circle ends in the left atrium.
C) Arterial blood flows through the arteries.
D) The circle begins in the left ventricle.
D) Gas exchange occurs in the capillaries of the alveoli.
E) Venous blood is formed from arterial blood.

Answer

Find three errors in the given text. Specify the numbers of proposals in which they are made.(1) The walls of arteries and veins have a three-layer structure. (2) The walls of the arteries are very resilient and elastic; the walls of the veins, on the contrary, are inelastic. (3) When the atria contract, blood is pushed out into the aorta and pulmonary artery. (4) The blood pressure in the aorta and vena cava is the same. (5) The speed of blood movement in the vessels is not the same, in the aorta it is maximum. (6) The speed of blood movement in capillaries is higher than in veins. (7) The blood in the human body moves in two circles of blood circulation.

Answer

Choose three correctly labeled captions for the figure, which depicts internal structure hearts. Write down the numbers under which they are indicated.
1) superior vena cava
2) aorta
3) pulmonary vein
4) left atrium
5) right atrium
6) inferior vena cava

Answer

Choose three correctly marked captions for the picture, which shows the structure of the human heart. Write down the numbers under which they are indicated.
1) superior vena cava
2) flap valves
3) right ventricle
4) semilunar valves
5) left ventricle
6) pulmonary artery

Answer

In humans, as in all mammals and birds, two circles of blood circulation - large and small. Four-chambered heart - two ventricles + two atria.

When looking at a drawing of a heart, imagine that you are looking at a person facing you. Then his left half of the body will be opposite your right, and the right - opposite your left. Left half the heart is closer to the left hand, and the right hand is closer to the middle of the body. Or imagine not a drawing, but yourself. "Feel" where you are left-hand side hearts, and where is the right one.

In turn, each half of the heart - left and right - consists of an atrium and a ventricle. The atria are at the top, the ventricles at the bottom.

Also remember the following thing. The left half of the heart is arterial, and the right half is venous.

One more rule. Blood is expelled from the ventricles and flows into the atria.

Now we turn to the circles of blood circulation themselves.

Small circle. From the right ventricle, blood flows to the lungs, from where it enters the left atrium. In the lungs, the blood turns from venous to arterial, because it gives off carbon dioxide and is saturated with oxygen.

Small circle of blood circulation
right ventricle → lungs → left atrium

Big circle. From the left ventricle, arterial blood flows to all organs and parts of the body, where it becomes venous, after which it is collected and sent to the right atrium.

Systemic circulation
left ventricle → body → right atrium

This is a schematic presentation of the circles of blood circulation in order to explain briefly and clearly. However, it is often also required to know the names of the vessels through which blood is pushed out of the heart and flows into it. Here you should pay attention to the following. The vessels that carry blood from the heart to the lungs are called pulmonary arteries. But venous blood flows through them! The vessels that carry blood from the lungs to the heart are called pulmonary veins. But arterial blood flows through them! That is, in the case of a small circle of blood circulation, the opposite is true.

The large vessel that exits the left ventricle is called the aorta.

The superior and inferior vena cava flow into the right atrium, and not one vessel as in the diagram. One collects blood from the head, the other from the rest of the body.