Arterial blood flows through the veins in what circle. Veins of the systemic circulation

Blood constantly circulates throughout the body, providing transport various substances. It consists of plasma and suspension various cells(the main ones are red blood cells, leukocytes and platelets) and moves along a strict route - the system of blood vessels.

Venous blood - what is it?

Venous – blood that returns to the heart and lungs from organs and tissues. It circulates through the pulmonary circulation. The veins through which it flows lie close to the surface of the skin, so the venous pattern is clearly visible.

This is partly due to a number of factors:

1. It is thicker, rich in platelets, and when damaged venous bleeding easier to stop.
2. The pressure in the veins is lower, so if a vessel is damaged, the amount of blood loss is lower.
3. Its temperature is higher, so it additionally prevents rapid loss heat through the skin.

The same blood flows in both arteries and veins. But its composition is changing. From the heart it enters the lungs, where it is enriched with oxygen, which carries it to internal organs providing them with food. The veins that carry arterial blood are called arteries. They are more elastic, blood moves through them in spurts.

Arterial and venous blood do not mix in the heart. The first passes along the left side of the heart, the second - along the right. They mix only when serious pathologies heart, which entails a significant deterioration in well-being.

What is the systemic and pulmonary circulation?

Contents are expelled from the left ventricle and enter the pulmonary artery, where it is saturated with oxygen. Then it is carried throughout the body through arteries and capillaries, carrying oxygen and nutrients.

The aorta is the largest artery, which is then divided into superior and inferior. Each of them supplies blood to the upper and bottom part bodies accordingly. Since the arterial system “flows around” absolutely all organs and is supplied to them with the help of a branched system of capillaries, this circle of blood circulation is called large. But the arterial volume is about 1/3 of the total.

Blood flows through the pulmonary circulation, which has given up all the oxygen and “taken away” metabolic products from the organs. It flows through the veins. The pressure in them is lower, the blood flows evenly. It returns through the veins to the heart, from where it is then pumped to the lungs.

How are veins different from arteries?

Arteries are more elastic. This is due to the fact that they need to maintain a certain speed of blood flow in order to deliver oxygen to the organs as quickly as possible. The walls of the veins are thinner and more elastic. This is due to the lower speed of blood flow, as well as the large volume (venous is about 2/3 of the total volume).

What kind of blood is in the pulmonary vein?

The pulmonary arteries ensure the flow of oxygenated blood into the aorta and its further circulation throughout the systemic circulation. The pulmonary vein returns some of the oxygenated blood to the heart to nourish the heart muscle. It is called a vein because it supplies blood to the heart.

What is venous blood rich in?

Entering the organs, the blood gives them oxygen, in return it is saturated with metabolic products and carbon dioxide, takes on a dark red hue.

A large amount of carbon dioxide is the answer to the question why venous blood is darker than arterial blood and why veins are blue. It also contains nutrients that are absorbed in the digestive tract, hormones and other substances synthesized by the body.

Its saturation and density depend on the vessels through which venous blood flows. The closer to the heart, the thicker it is.

Why are tests taken from a vein?

This is due to the type of blood in the veins - rich in products metabolism and vital functions of organs. If a person is sick, it contains certain groups of substances, remains of bacteria and other pathogenic cells. U healthy person these impurities are not detected. By the nature of the impurities, as well as by the level of concentration of carbon dioxide and other gases, the nature of the pathogenic process can be determined.

The second reason is that venous bleeding when a vessel is punctured is much easier to stop. But there are times when bleeding from a vein for a long time doesn't stop. This is a sign of hemophilia, low content platelets. In this case, even a minor injury can be very dangerous for a person.

How to distinguish venous bleeding from arterial bleeding:

1. Assess the volume and nature of leaking blood. The venous flows out in a uniform stream, the arterial flows out in portions and even in “fountains”.
2. Determine what color the blood is. Bright scarlet points to arterial bleeding, dark burgundy - for venous.
3. Arterial is more liquid, venous is thicker.

Why does venous clot faster?

It is thicker and contains a large number of platelets. The low speed of blood flow allows the formation of a fibrin mesh at the site of vessel damage, to which platelets “cling.”

How to stop venous bleeding?

With minor damage to the veins of the extremities, it is often enough to create an artificial outflow of blood by raising an arm or leg above the level of the heart. A tight bandage should be applied to the wound itself to minimize blood loss.

If the injury is deep, a tourniquet should be placed above the damaged vein to limit the amount of blood flowing to the injury site. In summer you can keep it for about 2 hours, in winter - for an hour, maximum one and a half. During this time, you need to have time to deliver the victim to the hospital. If you hold the tourniquet longer than the specified time, tissue nutrition will be disrupted, which threatens necrosis.

It is advisable to apply ice to the area around the wound. This will help slow down your blood circulation.

Video

Ensures the flow of lymph and blood to the heart.

Vienna great circle blood circulation is closed system vessels that collect oxygen-depleted blood from all body cells and tissues, united by the following subsystems:

• cardiac veins;
• superior vena cava;
• inferior vena cava.

Difference between venous and arterial blood

Deoxygenated blood is the blood that flows back from everyone cellular systems and tissues, saturated with carbon dioxide, containing metabolic products.

Medical manipulations and studies are carried out mainly with blood that contains metabolic end products and a smaller amount of glucose.

This is the blood that flows to all cells and tissues from the heart muscle, saturated with oxygen and hemoglobin, containing nutrients.

Oxygenated arterial blood circulates through the arteries of the systemic circulation and the veins of the pulmonary circulation.

Vein structure

The walls are much thinner than arterial ones, since the blood flow speed and pressure in them is lower. Their elasticity is lower than that of arteries. The valves of the vessels are usually located opposite, which prevents the reverse flow of blood. IN large quantities The valves of the veins are located in the lower extremities. The veins are also located from the folds of the inner membrane, which have special elasticity. In the arms and legs there are venous vessels located between the muscles, this, when muscle contraction, allows blood to return back to the heart.

The large circle originates in the left ventricle of the heart, and the aorta emerges from it with a diameter of up to three centimeters. Next, the oxygenated blood of the arteries flows through vessels of decreasing diameter to all organs. Having given everything useful material, the blood is saturated with carbon dioxide and goes back through the venous system through the smallest vessels - venules, while the diameter gradually increases, approaching the heart. Venous blood from the right atrium is pushed into the right ventricle, and the pulmonary circulation begins. Entering the lungs, the blood is filled with oxygen again. Arterial blood enters the left atrium through the veins, which is then pushed into the left ventricle of the heart, and the circle repeats again.

The arteries and veins of the systemic circulation include the aorta, as well as the smaller, superior and inferior hollow vessels branching from it.

Small capillaries make up an area of ​​about one and a half thousand square meters in the human body.

The veins of the systemic circulation carry depleted blood, except for the umbilical and pulmonary veins, which carry arterial, oxygenated blood.

Cardiac vein system

These include:

• cardiac veins, which go directly into the heart cavity;
• coronary sinus;
• great cardiac vein;
• left gastric posterior vein;
• left atrial oblique vein;
• anterior vessels of the heart;
• average and small vein;
• atrial and ventricular;
• the smallest venous vessels of the heart;
• atrioventricular.

The driving force of blood flow is the energy given by the heart, as well as the pressure difference in the sections of the vessels.

Superior vena cava system

The superior vena cava takes venous blood from the upper part of the body - head, neck, sternum and partially abdominal cavity and gets into right atrium. There are no vascular valves. The process is as follows: blood saturated with carbon dioxide superior vein flows into the pericardial region, lower - into the region of the right atrium. The superior vena cava system is divided into the following parts:

1. The upper hollow is a small vessel, 5-8 cm long, 2.5 cm in diameter.
2. The azygos is a continuation of the right ascending lumbar vein.
3. Hemizygos is a continuation of the left ascending lumbar vein.
4. Posterior intercostal - collection of the veins of the back, its muscles, external and internal vertebral plexuses.
5. Intravertebral venous connections - located inside spinal canal.
6. Brachiocephalic - roots of the upper hollow.
7. Vertebral - location in the diametrical foramina of the cervical vertebrae.
8. Deep cervical - collection of venous blood from the occipital region along the carotid artery.
9. Inner chest.

Inferior vena cava system

The inferior vena cava is a connection of the iliac veins on both sides in the area of ​​4 - 5 lumbar vertebrae, takes venous blood lower sections bodies. The inferior vena cava is one of the largest veins in the body. It is about 20 cm long, up to 3.5 cm in diameter. Thus, from the lower hollow there is an outflow of blood from the legs, pelvis and abdomen. The system is divided into the following components:

Portal vein

The portal vein got its name due to the entry of the trunk into the portal of the liver, as well as the collection of venous blood from the digestive organs - the stomach, spleen, large and small intestines. Its vessels are located behind the pancreas. The length of the vessel is 500-600 mm, in diameter - 110-180 mm.

The tributaries of the visceral trunk are the superior mesenteric, inferior mesenteric and splenic vessels.

The system basically includes the vessels of the stomach, large intestine and fine sections, pancreas, gallbladder and spleen. In the liver it divides into right and left and then branches into smaller veins. Eventually they merge into central veins liver, sublobular veins of the liver. And eventually three or four hepatic vessels are formed. Thanks to this system, the blood of the digestive organs passes through the liver, entering the inferior vena cava subsystem.

Upper mesenteric vein accumulates blood in the roots of the mesentery small intestine from ileum, pancreatic, right and middle colon, ileal colon and right ventricular-epiploic veins.

The inferior mesenteric vein is formed from the superior rectal, sigmoid and left colic veins.

The splenic vein combines splenic blood, stomach blood, duodenum and pancreas.

Jugular vein system

The jugular vein vessel runs from the base of the skull to the supraclavicular cavity. The systemic circulation includes these veins, which are the key collectors of blood from the head and neck. In addition to the internal blood, the external one also collects blood from the head and soft tissues. jugular vein. The external one begins in the area of ​​the auricle and goes down along the sternocleidomastoid muscle.

Veins coming from the external jugular:

• posterior ear - collection of venous blood for auricle;
• occipital branch - collection from venous plexus heads;
• suprascapular - receiving blood from formations of the periosteal cavity;
• transverse veins of the neck - satellites of the transverse cervical arteries;
• anterior jugular - consists of the mental veins, veins of the maxillohyoid and sternothyroid muscles.

The internal jugular vein begins in the jugular cavity of the skull, being a companion to the external and internal carotid arteries.

Great circle functions

It is thanks to the continuous movement of blood in the arteries and veins of the systemic circulation that the main functions of the system are ensured:

• transportation of substances to ensure the functions of cells and tissues;
• -transport necessary chemical substances for metabolic reactions in cells;
• sampling of cell and tissue metabolites;
• connection of tissues and organs with each other through blood;
• transport to cells protective equipment;
• fence harmful substances from the body;
• heat exchange.

The vessels of this circulatory circle represent an extensive network that supplies blood to all organs, in contrast to the small circle. Optimal functioning of the system of the superior and inferior vena cava leads to adequate blood supply to all organs and tissues.

Question 1. What kind of blood flows through the arteries of the systemic circle, and what kind of blood flows through the arteries of the small circle?
Arterial blood flows through the arteries of the systemic circle, and venous blood flows through the arteries of the small circle.

Question 2. Where does the systemic circulation begin and end, and where does the pulmonary circulation end?
All vessels form two circles of blood circulation: large and small. The great circle begins in the left ventricle. The aorta departs from it, which forms an arch. Arteries arise from the aortic arch. From the initial part of the aorta they extend coronary vessels, which supply blood to the myocardium. The part of the aorta located in chest, called thoracic aorta, and the part that is in the abdominal cavity is abdominal aorta. The aorta branches into arteries, arteries into arterioles, and arterioles into capillaries. From the capillaries of a large circle, oxygen and nutrients flow to all organs and tissues, and carbon dioxide and metabolic products flow from the cells into the capillaries. Blood turns from arterial to venous.
Cleansing the blood from poisonous products disintegration occurs in the vessels of the liver and kidneys. Blood from digestive tract, pancreas and spleen enters the portal vein of the liver. In the liver portal vein branches into capillaries, which then unite again into common trunk hepatic vein. This vein drains into the inferior vena cava. Thus, all blood from the abdominal organs, before entering the systemic circle, passes through two capillary networks: through the capillaries of these organs themselves and through the capillaries of the liver. The portal system of the liver ensures the neutralization of toxic substances that are formed in the large intestine. The kidneys also have two capillary networks: the network of the renal glomeruli, through which the blood plasma containing harmful products metabolism (urea, uric acid), passes into the cavity of the nephron capsule, and capillary network, entwining convoluted tubules.
Capillaries merge into venules, then into veins. Then, all the blood flows into the superior and inferior vena cava, which drain into the right atrium.
The pulmonary circulation begins in the right ventricle and ends in the left atrium. Venous blood from the right ventricle enters the pulmonary artery, then into the lungs. Gas exchange occurs in the lungs, venous blood turns into arterial blood. The four pulmonary veins carry arterial blood to the left atrium.

Question 3. To a closed or open system refers to the lymphatic system?
The lymphatic system should be classified as open. It blindly begins in the tissues with lymphatic capillaries, which then unite to form lymphatic vessels, and they, in turn, form lymphatic ducts, flowing into the venous system.

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.