The heart is the main organ of the circulatory system. The anatomical structure of the human heart is such that it fully ensures the fulfillment by him of the functions of the central organ of the blood supply system of the whole organism.
This organ is located in the chest cavity: behind the sternum in the anterior mediastinum above the diaphragm. 70% of the heart is located in the chest cavity to the left, 30% - to the right of the sternum. Consider the structure of the human heart, starting from its wall. The heart wall has a three-layer structure: the inner layer is the endocardium lined with endotheliocytes; medium - muscle or myocardium, consisting of cardiomyocytes; outer - epicardium and pericardium, formed by a thin shell of connective tissue, the inner surface of which is covered with mesothelium. All cavities of the organ from the inside were expelled by the endocardium; it also forms heart valves. The pericardium, sometimes called the cardiac chemise, covers it from the outside and forms the so-called heart bag. Its main purpose is to reduce friction of the heart during work and protect it from external influences. Between the leaves of the pericardium there is a slit-like space filled with a small volume of fluid.
The heart is divided by a partition into two hollow halves - left and right. Each half consists of the atrium and ventricle. In the right half there is always venous blood, in the left - arterial blood. The structure of the human heart is such that venous blood never mixes with arterial. A tricuspid valve is located between the right chambers , and the pulmonary valve is located at the exit from the right ventricle of the pulmonary artery. A bicuspid or mitral valve is located in the left half of the heart between the atrium and the ventricle, and at the outlet of the aorta from the cavity of the left ventricle is the tricuspid aortic valve with crescent-shaped cusps. The wall thickness of the left ventricle is much greater than in the right. This is because the left ventricle always works more intensively, throwing blood into the aorta, which then goes throughout the body, and the right only into the vessels of the lungs.
Two large veins, called the superior and inferior vena cava, carry blood into the right atrium. They collect venous blood from all organs. Blood from four pulmonary veins enters the left atrium, which, after enrichment with oxygen in the lungs, becomes arterial. The pulmonary artery, also called the pulmonary trunk, through which venous blood flows into the lungs, leaves the right ventricle. The largest aortic artery supplies arterial blood to the entire body, it leaves the left ventricle. From the foregoing, we can conclude that the structure of the human heart is no different from the hearts of other mammals.
The heart itself receives blood from two coronary arteries. The left coronary artery originates at the left aortic sinus or the left sinus of Valsalva, located 1 cm above the attachment site of the lunar valves. It branches into the anterior interventricular and enveloping branches, supplying blood to the anterolateral and part of the posterior wall of the left ventricle, as well as part of the interventricular septum, the apex of the heart, and the left atrium. From the right sinus of the aorta or the right sinus of Valsalva, the right coronary artery begins. This vessel delivers blood to the myocardium of the right atrium and right ventricle, a small part of the interventricular septum.
The human heart, the structure of which we have examined, performs the functions of automatism, conductivity, excitability and contractility. The work of this body is supervised by the heart centers located in the medulla oblongata and the bridge. They affect heart rate, atrioventricular conduction speed, heart rate.
The physiology of the human heart is such that its vital activity consists in constantly alternating contractions and relaxation, that is, systoles and diastoles that provide blood movement, and with it a continuous supply of oxygen and nutrition to all cells of the body.