The heart is located in the chest, behind the sternum, at its anterior, lower part, slightly to the left of the midline of the chest. It is made up of myocardial fibres, which are capable of continuous, strong contractions against our will, but due to neural and hormonal effects, the frequency of contractions adapts to changing loads. Its size is approximately proportional to body weight, averaging 4 grams per kilogram body weight. In healthy adults, the average size is 250-350 grams.
In terms of the structure of the heart, it is a hose with muscular walls and a complex cavity system. It consists of two atria and two ventricles, where the atria receive blood from the veins and the ventricles continue to pump it into the arteries.
Arteries and veins are also structurally different because blood flows in different directions in them. It flows from the heart to the peripheries through the arteries and back to the heart through the veins from the peripheries.
The connective tissue of the arteries is a dense fibrous connective tissue made up of elastic fibres, the veins are thinner and less elastic-walled, however, the pulmonary valves in them help the blood flow.