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HUMAN CARDIOVASCULAR SYSTEM
As with most animals, the human cardiovascular (circulatory) system consists of
a heart and blood vessels of various diameters.
The main function of the cardiovascular system is to ensure the movement of
blood through the body. Moreover, if we are talking about a closed circulatory system,
so that venous and arterial blood do not mix. The remaining functions of the
cardiovascular system are related to the functions of the blood itself.
The structure of the heart and circulatory circles
The key organ of the cardiovascular system is the heart (figure 16). The beating
of the heart ensures the movement of blood through the vessels, and a special structure
plays a regulatory role, dividing blood currents into those passing through the whole
body and through the lungs, in which blood is enriched with oxygen.
The human heart, like all mammals, is four-chambered. It consists of the left and
right halves, which do not communicate with each other. In other words, normally the
blood from the left half of the heart can not get into the right. The left half of the heart
contains arterial blood, and the right half contains venous blood.
In turn, each half of the heart consists of its atrium and its ventricle. Blood flows
from the atria to the ventricles through valves: tricuspid on the right and mitral on the
left (sometimes both valves are called valvular). Usually, in drawings, the left half of
the heart is depicted on the right, and the right – on the left (imagine you are looking at
the person standing in front of you).

Figure 16. The structure of the heart

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