The structure of the human heart
Blood is the internal environment of the body, providing communication between its organs. It flows through the arteries, veins and capillaries. And it is the heart that directs it. What the blood and blood vessels look like is easy to imagine, but the structure of the heart remains a mystery to many. This is a complex organ with a unique design, which we will talk about today.
External structure of the human heart
In form and shape, the heart is not at all like the figures that depict such pictures: ♥ or ☜ ♡ ☞. It has the appearance of a hollow cone-like organ that is flattened in the anteroposterior direction. Mentally, the heart can be divided into two parts: the top and the base. The tip is pointed, and the base is an expanded part of the heart. On its surface you can see the coronal sulcus running across the longitudinal axis. It seems to show the boundary between the ventricles and the atria. This organ is usually located behind the sternum and slightly shifted to the left. But in people whose body has a transposition (mirror arrangement) of internal organs with dextrocardia, it is on the right, and their heart structure is slightly different.Usually its weight is about 250-360 grams.
Internal structure of the heart
This is a hollow muscular organ, the wall of which consists of three layers:
- internal - endothelial;
- middle - myocardium;
- external - connective tissue.
Outside, the heart is surrounded by an elastic pericardium, a pericardium sac that protects it from overdistension during the filling with blood. The inner walls of the pericardial sac secrete fluid that moisturizes the heart and reduces its friction against the walls of the pericardium during contractions. Like other mammals, the human heart has four chambers: it has two atria (upper part of the heart) and two ventricles (lower part of the heart). Auricles are the sections in which blood builds up from the veins, and from the ventricles the blood enters the arteries. In the heart there are four valves: two hinged and two crescent. The leaf valves are located between the ventricles and the atria. In the left half of the heart, the valve is double, and in the right half it is tricuspid. Because of the pressure of the blood, they open up and let it pass into the ventricles. When the ventricles contract, the valves close and do not pass it back to the atrium. Due to this, blood in the heart flows in a single direction - from the atria to the ventricles.Semilunar (pocket) valves are located in different parts of the heart: one - at the exit of the aorta (from the left ventricle), and the other - at the end of the pulmonary artery (from the right ventricle). They do not pass blood from vessels after relaxation of the ventricles.
How does the heart maintain its performance?
A feature of the heart is the rhythm of his work. Its relaxation (diastole) alternates with contraction (systole). The contractions and relaxation of the ventricles and atria under standard conditions are mutually consistent and constitute a single cycle of the heart, which is very well adapted to the needs of the body due to the mechanisms of self-regulation, as well as nervous and humoral regulation. Its self-regulation is provided by intracardiac mechanisms: the more the heart cavity fills with blood, the more it contracts. Adaptation of the heart to the needs of the body is achieved by mutually agreed activity of the nervous and endocrine systems. During physical exertion, the work of the heart becomes more intense.
The heart is the most important organ in the human body, so it must be protected.