Shells of the heart. Structure of the human heart

The heart is the main organ of the system of blood supply and lymphogenesis in the body. It is presented in the form of a large muscle with several hollow chambers. Due to its ability to contract, it causes the blood to move. In total, three cores of the heart are represented: epicardium, endocardium and myocardium. The structure, purpose and functions of each of them will be considered in this material.

Structure of the human heart - anatomy

The heart muscle consists of 4 chambers - 2 auricles 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. On the contrary, the right ventricle and right atrium make up the venous part of the heart.

The circulatory organ is presented in the form of a flat cone. It distinguishes the base, the tip, the lower and the front surface, and two edges - left and right. The apex of the heart has a rounded shape and is entirely formed by the left ventricle. In the base area there are atria, and in its anterior part there is a pulmonary trunk and aorta.

Sizes of heart

It is believed that in an adult, a formed human individual, the dimensions of the cardiac muscle are equal to the dimensions of the compressed fist. In fact, on average, the length of this organ in a mature person is 12-13 cm. In the diameter, the heart is 9-11 cm.

The mass of the heart of an adult male is about 300 g. For women, the heart weighs an average of about 220 g.

The phases of the heart

There are several separate phases of contraction of the heart muscle:

1. In the beginning, atrial contraction occurs. Then, with some delay, the contraction of the ventricles starts. During the course of this process, the blood naturally tends to fill the chambers with reduced pressure. Why after this does not happen its reverse outflow into the atrium? The fact is that the blood block the way of the gastric valves. Therefore, she can only move in the direction of the aorta, as well as the vessels of the pulmonary trunk.
2. The second phase is relaxation of the ventricles and atria. The process is characterized by a short-term decrease in the tone of the muscular 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 the closing pulmonary and arterial valves. During relaxation, the ventricles are filled with blood that comes from the atria. On the contrary, the atria are filled with bodily fluid from the large and small circle of blood circulation.

What is responsible for the work of the heart?

As you know, the functioning of the heart muscle is not an arbitrary act. The organ remains active continuously, even when the person is in a state of deep sleep. It's unlikely that there are people who pay attention to heart rate in the process of activity. But this is achieved due to a special structure built into the heart muscle itself - the system of generation of biological impulses. It is noteworthy that the formation of this mechanism occurs in the first weeks of intrauterine fetal origin. 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 cardiac muscle for a minute is about 70 beats. Within one hour the number reaches 4,200 beats. Given that in one cut the heart throws 70 ml of fluid into the circulatory system, it is easy to guess that in an hour through it passes up to 300 liters of blood. How much does this body pump blood for life? 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

A total of 3 separate shells of the heart muscle:

1. Endocardium is the inner shell of the heart.
2. Myocardium is an internal muscular complex formed by a thick layer of threadlike fibers.
3. Epicardium is a thin outer shell of the heart.
4. Pericardium - an auxiliary heart shell, which is a kind of bag, which contains the heart entirely.

Next, let's talk about the above-mentioned heart membranes in order, consider their anatomy.

Myocardium

Myocardium is a multi-tissue muscularis of the heart that is formed by striated fibers, loose connective structures, nervous processes, and a branched network of capillaries. Here P-cells are represented, which form and conduct nerve impulses. In addition, the myocardium contains cells of myocytes and cardiomyocytes, which are responsible for the reduction of the circulatory organ.

Myocardium consists of several layers: inner, middle and outer. The internal structure consists of muscle bundles, which are arranged longitudinally in relation to each other. In the outer layer, the bundles of muscle tissue are oblique. The latter go to the very top of the heart, where they form the so-called curl. The middle layer consists of circular muscular bundles, separate for each of the ventricles of the heart.

Epicardium

The presented shell of the heart muscle has the most smooth, thin and somewhat transparent structure. Epicardium forms the outer tissues of the organ. In fact, the shell acts as an inner layer of the pericardium - the so-called heart bag.

The surface of the epicardium is formed from mesothelium cells, under which is a connecting, loose structure, represented by connective fibers. In the region of the apex of the heart and in its furrows, the envelope under consideration includes adipose tissue. The epicardium fuses with the myocardium in the places of the smallest accumulation of fat cells.

Endocardium

Continuing to examine 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 lining all the inner chambers of the heart. Elements that depart from the blood organ: aorta, pulmonary veins, pulmonary trunk of the endocardium tissue go smoothly, without distinct boundaries. In the most thin sections of the atria, the endocardium fuses with the epicardium.

Pericardium

Pericardium is the outer mucosa of the heart, which is also called a pericardial sac. This structure is represented in the form of a cut-off cone. The lower base of the pericardium is located on the diaphragm. To the top, the shell extends 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 the adjacent veins.

Pericardium is formed in human individuals at early stages of intrauterine development. This occurs approximately 3-4 weeks after the embryo is formed. Violations of the structure of this shell, its partial or complete absence often leads to congenital heart defects.

Finally

In the presented material, we considered the structure of the human heart, the anatomy of its chambers and shells. As you can see, the heart muscle has an extremely complex structure. Surprisingly, despite its intricate structure, this organ continuously functions throughout life, giving failures only in the case of the development of serious pathologies.