The heart is the main organ of the human body. It is a muscular organ, hollow inside and having the shape of a cone. In newborns, the heart weighs about thirty grams, and in an adult - about three hundred.
The topography of the heart is as follows: it is located in the chest cavity, moreover, one third of it is located on the right side of the mediastinum, and two thirds on the left. The base of the organ is directed upwards and somewhat backwards, and the narrow part, that is, the apex, is directed downwards, to the left and anteriorly.
Organ borders
The borders of the heart allow you to determine the location of the organ. There are several of them:
- Top. It corresponds to the cartilage of the third rib.
- Lower. This border connects the right side to the top.
- Top. This border is located in the fifth intercostal space, towards the left midclavicular line.
- Right. Between the third and fifth ribs, a couple of centimeters to the right of the edge of the sternum.
- Left. The topography of the heart at this border has its own characteristics. It connects the apex with the upper border, and itself passes through the left ventricle, which faces the lefteasy.
Topographically, the heart is behind and just below half of the sternum. The largest vessels are placed behind, in the upper part.
Changes in topography
The topography and structure of the human heart change with age. In childhood, the body makes two turns around its axis. The boundaries of the heart change during breathing and depending on the position of the body. So, when lying on the left side and when bending over, the heart approaches the chest wall. When a person is standing, it is lower than when he is lying down. Because of this feature, the apical impulse is displaced. According to anatomy, the topography of the heart also changes as a result of respiratory movements. So, on inspiration, the organ moves away from the chest, and on exhalation it returns back.
Changes in the function, structure, topography of the heart are observed in different phases of cardiac activity. These indicators depend on gender, age, as well as on the individual characteristics of the body: the location of the digestive organs.
Structure of the heart
The heart has a top and a base. The latter is turned up, to the right and back. Behind the base is formed by the atria, and in front - by the pulmonary trunk and a large artery - the aorta.
The top of the organ is turned down, forward and to the left. According to the topography of the heart, it reaches the fifth intercostal space. The apex is usually located eight centimeters from the mediastinum.
The walls of the organ have several layers:
- Endocardium.
- Myocardium.
- Epicardium.
- Pericardium.
Endocardium linedorgan from the inside. This fabric forms flaps.
Myocardium is a heart muscle that contracts involuntarily. The ventricles and atria also consist of muscles, with the former having more developed muscles. The surface layer of the atrial muscles consists of longitudinal and circular fibers. They are independent for each atrium. And in the ventricles there are the following layers of muscle tissue: deep, superficial and middle circular. From the deepest, fleshy bridges and papillary muscles are formed.
The epicardium is epithelial cells covering the outer surface of both the organ and the nearest vessels: the aorta, vein, and also the pulmonary trunk.
The pericardium is the outer layer of the pericardial sac. Between the sheets there is a slit-like formation - the pericardial cavity.
Holes
The heart has several holes, chambers. The organ has a longitudinal partition that divides it into two parts: left and right. At the top of each part are the atria, and below - the ventricles. There are openings between the atria and ventricles.
The first of them have some protrusion that forms the heart eye. The walls of the atria have different thicknesses: the left one is more developed than the right one.
Inside the ventricles there are papillary muscles. Moreover, there are three of them in the left, and two in the right.
The right atrium receives fluid from the superior and inferior pudendal veins, the sinus veins of the heart. Four pulmonary veins lead to the left. The pulmonary trunk departs from the right ventricle, and from the left -aorta.
Valves
The heart has tricuspid and bicuspid valves that close the gastro-atrial openings. The absence of reverse blood flow and eversion of the walls is ensured by tendon threads passing from the edge of the valves to the papillary muscles.
The bicuspid or mitral valve closes the left ventricular-atrial opening. Tricuspid - right ventricular-atrial opening.
In addition, there are semilunar valves in the heart. One closes the opening of the aorta, and the other - the pulmonary trunk. Valve defects are defined as heart defects.
circulation circles
There are several circulations in the human body. Consider them:
- The great circle (BCC) starts from the left ventricle and ends at the right atrium. Through it, blood flows through the aorta, then through the arteries, which diverge into precapillaries. After that, the blood enters the capillaries, and from there to the tissues and organs. In these small vessels, nutrients are exchanged between tissue cells and blood. After that, the reverse flow of blood begins. From the capillaries, it enters the postcapillaries. They form venules, from which venous blood enters the veins. Through them, it approaches the heart, where the vascular beds converge into the vena cava and enter the right atrium. This is how the blood supply to all organs and tissues occurs.
- Lesser circle (ICC) starts from the right ventricle and ends at the left atrium. Its beginning is the pulmonary trunk, which is divided into a pair of pulmonaryarteries. They carry venous blood. It enters the lungs and is enriched with oxygen, turning into arterial. Then the blood is collected in the pulmonary veins and flows into the left atrium. ICC is intended to enrich the blood with oxygen.
- There is also a crown circle. It starts from the aortic bulb and the right coronary artery, passes through the capillary network of the heart and returns through the venules and coronary veins, first to the coronary sinus, and then to the right atrium. This circle supplies nutrients to the heart.
The heart, as you can see, is a complex organ that has its own circulation. Its boundaries change, and the heart itself changes its angle of inclination with age, turning around its axis twice.
