The heart is the main organ of the blood supply system and lymph formation in the body. It is presented in the form of a large muscle with several hollow chambers. Due to its ability to contract, it sets the blood in motion. There are three layers of the heart: epicardium, endocardium and myocardium. The structure, purpose and functions of each of them will be considered in this material.
The structure of the human heart - anatomy
The heart muscle consists of 4 chambers - 2 atria and 2 ventricles. The left ventricle and the left atrium form the so-called arterial part of the organ, based on the nature of the blood located here. In contrast, the right ventricle and right atrium make up the venous portion of the heart.
The circulatory organ is presented in the form of a flattened cone. It distinguishes the base, apex, lower and anteroposterior surfaces, as well as two edges - left and right. The apex of the heart has a rounded shape and is entirely formed by the left ventricle. At the base are the atria, and in its front part lies the pulmonary trunk and aorta.
Heart measurements
It is believed thatin an adult, mature human individual, the dimensions of the heart muscle are equal to the dimensions of a clenched fist. In fact, the average length of this organ in a mature person is 12-13 cm. The diameter of the heart is 9-11 cm.
The weight of an adult male heart is about 300 g. In women, the heart weighs an average of about 220 g.
Phases of the heart
There are several separate phases of contraction of the heart muscle:
- Atrial contraction occurs at the beginning. Then, with some slowdown, the contraction of the ventricles starts. During this process, the blood naturally tends to fill the chambers with reduced pressure. Why does it not return to the atria after this? The fact is that the gastric valves block the path of blood. Therefore, she only has to move in the direction of the aorta, as well as the vessels of the pulmonary trunk.
- Second phase - relaxation of the ventricles and atria. The process is characterized by a short-term decrease in the tone of the muscle structures from which these chambers are formed. The process causes a decrease in pressure in the ventricles. Thus, the blood begins to move in the opposite direction. However, this is prevented by closing pulmonary and arterial valves. During relaxation, the ventricles fill with blood, which comes from the atria. In contrast, the atria fill with bodily fluid from the systemic and pulmonary circulations.
What is responsible for the work of the heart?
As you know, the functioning of the heartmuscle is not an arbitrary act. The organ remains active continuously even when the person is in deep sleep. There are hardly any people who pay attention to the heart rate in the process of activity. But this is achieved due to a special structure built into the heart muscle itself - a system for generating biological impulses. It is noteworthy that the formation of this mechanism occurs in the first weeks of intrauterine gestation. Subsequently, the pulse generation system does not allow the heart to stop throughout life.
Interesting facts about the work of the heart
In a calm state, the number of contractions of the heart muscle for a minute is about 70 beats. Within one hour, the number reaches 4200 beats. Given that during one contraction, the heart ejects 70 ml of fluid into the circulatory system, it is easy to guess that up to 300 liters of blood passes through it in an hour. How much blood does this organ pump in a lifetime? This figure averages 175 million liters. Therefore, it is not surprising that the heart is called the ideal engine, which practically does not fail.
Heart shells
In total, there are 3 separate shells of the heart muscle:
- Endocardium is the inner lining of the heart.
- Myocardium is an internal muscle complex formed by a thick layer of filamentous fibers.
- Epicardium is the thin outer shell of the heart.
- Pericardium is an auxiliary heart membrane that representsa kind of bag that contains the whole heart.
Next, let's talk about the above shells of the heart in order, consider their anatomy.
Myocardium
Myocardium is a multi-tissue muscular membrane of the heart, which is formed by striated fibers, loose connective structures, nerve processes, and an extensive network of capillaries. Here are the P-cells that form and conduct nerve impulses. In addition, there are myocytes and cardiomyocytes in the myocardium, which are responsible for the contraction of the blood organ.
Myocardium consists of several layers: inner, middle and outer. The internal structure consists of muscle bundles that are located longitudinally in relation to each other. In the outer layer, the bundles of muscle tissue are located obliquely. The latter go to the very top of the heart, where they form the so-called curl. The middle layer consists of circular muscle bundles, separate for each of the ventricles of the heart.
Epicardium
The presented shell of the heart muscle has the smoothest, thinnest and somewhat transparent structure. The epicardium forms the outer tissues of the organ. In fact, the shell acts as the inner layer of the pericardium - the so-called heart sac.
The surface of the epicardium is formed from mesothelial cells, under which there is a connective, loose structure represented by connective fibers. In the region of the apex of the heart and in its furrows, consideredsheath includes adipose tissue. The epicardium fuses with the myocardium in places where there is the least accumulation of fat cells.
Endocardium
Continuing to consider the membranes of the heart, let's talk about the endocardium. The presented structure is formed by elastic fibers, which consist of smooth muscle and connective cells. Endocardial tissues line all the internal chambers of the heart. On the elements extending from the blood organ: aorta, pulmonary veins, pulmonary trunk, endocardial tissues pass smoothly, without clearly distinguishable boundaries. In the thinnest parts of the atria, the endocardium fuses with the epicardium.
Pericardium
The pericardium is the outer lining of the heart, also called the pericardial sac. This structure is presented in the form of a cone cut at an angle. The lower base of the pericardium is placed on the diaphragm. Towards the top, the shell goes more to the left than to the right. This peculiar bag surrounds not only the heart muscle, but also the aorta, the mouth of the pulmonary trunk and adjacent veins.
The pericardium is formed in human individuals in the early stages of fetal development. This happens approximately 3-4 weeks after the formation of the embryo. Violations of the structure of this shell, its partial or complete absence often leads to congenital heart defects.
In closing
In the presented material, we examined the structure of the human heart, the anatomy of its chambers and membranes. As you can see, the heart muscle has an extremely complex structure. Surprisingly, despiteintricate structure, this organ functions continuously throughout life, failing only in the event of the development of serious pathologies.
