Circles of blood circulation in the human body

The organs of blood circulation in the human body allow the blood to perform all the necessary functions. The essence of blood circulation is the movement of blood through the vessels to ensure the necessary substances of all human organs. The whole system of the circulatory system is composed of blood vessels and the heart. Due to the contraction of the heart muscle, the blood is carried along the vessels. There are two types of vessels: arteries (carry blood from the heart muscle to organs and tissues) and veins, through which blood flows to the heart. Between themselves all the vessels are connected by the smallest blood capillaries.
The following circulatory circles are distinguished in man : small, large. The trunk or large circle originates in the left ventricle of the heart. Then the blood flows into the main artery in the human body - the aorta. From the aorta, the blood spreads along the spine, thanks to the smaller arteries. Having reached the organs, the arteries are divided into arterioles, smaller vessels, which in turn are subdivided into capillaries. So the organs and tissues are saturated with oxygen and nutrients necessary for the normal functioning of the body. Similarly, starting from the capillaries, the venous blood enters the two large veins of the body, the lower and upper. Then it is delivered to the right atrium. The whole cycle is the big circle of blood circulation.
The pulmonary, or otherwise small circle, circulates a shorter path. From the right ventricle of the heart leaves a large artery, which is divided into two pulmonary arteries. So the blood enriched with oxygen is delivered to the lungs. Large arteries are divided into arterioles, and those, in turn, are divided into capillaries. It is they that make it possible to saturate the lungs with oxygen and to purify it of carbon dioxide. This is the exchange of gases in the lungs. Then the venous blood flows through the veins into the left atrium.
Small and large circles of blood circulation are similar functions of all organs. Arteries deliver blood, saturated with nutrients and oxygen, to organs and tissues. The veins, in turn, return the venous blood to the heart. The only difference is the distance: large and small. Circles of blood circulation perform the function of saturation of body cells with oxygen.
But the circulation circles do not transfer all the blood that is in the body. Some blood is retained in the blood depots. They are in the spleen, liver, lungs and in a cluster of vessels under the skin. Such depots are necessary for emergency saturation of organs and tissues with oxygen.
The distribution of blood between individual organs of the body is not uniform. Circles of blood supply deliver blood, depending on the activity of the organ or tissue. This occurs as the vessels expand and contract. Blood to the actively working organ comes in a larger amount due to lower blood flow in other, less active organs.
Circles of blood circulation work due to the system of blood vessels, and of course, the heart muscle. Arteries respond to the delivery to organs and tissues of blood enriched with oxygen and nutritional components. Thanks to them, high blood pressure is maintained, ensuring rapid blood flow through the capillaries and saturation of tissues and organs.

Blood that has passed through the circulation circles, contains the products of the vital activity of the human body and carbon dioxide. Such blood carries vessels, which are called veins.
Capillaries also play an important role in the entire circulatory system. This is a branched network of small vessels, through which the blood, saturated with nutrients and oxygen, flows directly into the muscles and tissues of the organs.
The entire circulatory system is of great importance in the life of the body. The heart, blood vessels and circulation are its main components.