Structure and topography of the heart. Boundaries of the heart. Anatomy
The heart is the main organ of the bodyrights. It is a muscular organ, hollow inside and shaped like a cone. In newborns, the heart weighs about thirty grams, and for an adult human - about three hundred.
The topography of the heart is as follows: it is located in the thoracic cavity, with the third part located on the right side of the mediastinum, and two thirds on the left side. The base of the organ is directed upwards and somewhat posteriorly, and the narrow part, that is, the apex, is directed downward, to the left and anteriorly.
Borders of the organ
The boundaries of the heart allow you to determine the location of the organ. There are several of them:
- Upper. It corresponds to the cartilage of the third rib.
- Lower. This border connects the right side with the top.
- Top. This border is located in the fifth intercostal space, in the direction of the left sredneklyuchichnoy straight.
- Right. Between the third and fifth rib, a couple of centimeters to the right of the edge of the sternum.
- The left one. The topography of the heart on this border has its own peculiarities. It connects the top with the upper border, and itself passes along the left ventricle, which faces the left lung.
By topography, the heart is behind and just below half of the sternum. The largest vessels are located behind, in the upper part.
Topography and heart structure in humanschange with age. In childhood, the organ makes two turns around its axis. The boundaries of the heart change during breathing and depending on the position of the body. So, lying on the left side and at the slopes, the heart approaches the chest wall. When a person stands, it is located lower than when it is lying. Because of this feature, the apical impulse is displaced. By anatomy, the topography of the heart changes and as a result of respiratory movements. So, on inhalation, the organ moves away from the chest, and on exhalation returns back.
Changes in function, structure, topography of the heartis observed in different phases of cardiac activity. These indicators depend on sex, age, and also on the individual characteristics of the organism: the location of the digestive organs.
Structure of the heart
The heart has a tip and a base. The last is turned up, to the right and back. Behind the base is formed by the atria, and in front - the pulmonary trunk and a large artery - the aorta.
The top of the organ faces down, forward and left. According to the topography of the heart, it reaches the fifth intercostal space. The apex is usually located at a distance of eight centimeters from the mediastinum.
The walls of the organ have several layers:
The endocardium is lined with an organ from the inside. This fabric forms valves.
Myocardium is a heart muscle,which is involuntarily reduced. Ventricles and atria also consist of muscles, and the first musculature is developed more strongly. The superficial layer of 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 medium circular. From the deepest are formed fleshy crosspieces and papillary muscles.
Epicardium is an epithelial cell that covers the outer surface and the organ and the nearest vessels: the aorta, the vein, and the pulmonary trunk.
Pericardium is the outer leaf of the pericardial sac. Between the sheets there is a sliced formation - the pericardial cavity.
The heart has several holes, chambers. The organ has a longitudinal septum that divides it into two parts: the left and the right. At the top of each part are located atriums, and below - ventricles. Between the atria and ventricles there are holes.
The first of them have some protrusion, which forms the ear of the ear. The walls of the atria have different thicknesses: the left is more developed than the right one.
Inside the ventricles there are papillary muscles. And there are three in the left, and two in the right.
In the right atrium fluid comes from the upper and lower genital veins, the veins of the sinus of the heart. Four pulmonary veins lead to the left. From the right ventricle the pulmonary trunk departs, and from the left - the aorta.
In the heart there is a tricuspid and bicuspidvalves that close the gastric atrial openings. The absence of a reverse flow of blood and the inversion of the walls is provided by tendon filaments passing from the edge of the valves to the papillary muscles.
The bivalve or mitral valve closes the left ventricular-atrial orifice. Tri-fold - right ventricular-atrial aperture.
In addition, the heart has semilunar valves. One covers the aortic opening, and the other - the pulmonary trunk. Defects of valves are defined as heart disease.
Circles of blood circulation
In the human body there are several circles of blood circulation. Consider these:
- A large circle (CCB) starts from the left ventricleand ends with the right atrium. Blood flows through it on the aorta, then along the arteries that divide 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 this, the reverse flow of blood begins. From the capillaries, she enters the postcapillaries. They form venules, from which venous blood enters the veins. On them, it comes to the heart, where the vascular beds converge into the hollow veins and enter the right atrium. This is the blood supply of all organs and tissues.
- The small circle (MCC) starts from the right ventricleand ends in the left atrium. Its beginning is a pulmonary trunk, which is divided into a pair of pulmonary arteries. Venous blood flows through them. It enters the lungs and is enriched with oxygen, turning into an arterial one. Then the blood is collected in the pulmonary veins and poured into the left atrium. The ICC is intended to enrich the blood with oxygen.
- There is also a coronet. It starts from the bulb of the aorta and the right coronary artery, passes through the capillary mesh of the heart and returns through the venules and coronary veins first into the coronary sinus and then into the right atrium. This circle supplies the heart with nutrients.
The heart, as you could see, is a complex organ having its own circulatory system. Its borders change, and the heart itself changes its angle of inclination with age, turning twice its axis.