What are the chambers of the heart

Electrocardiogram - Structure and Function of the Heart

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Structure of the heart


The chambers and atria

The picture on the left shows a cross-section through the ventricles: the left ventricle on the right, the right ventricle on the left, and the main artery cut above.

The heart consists of a left and a right half. The left half is the stronger part because it is from here that the blood has to be pumped into the body's great circulation. The right part supplies the pulmonary circulation. Each of the two halves of the heart has a small atrium and a larger chamber, also called a ventricle. The atria can hold about 40 ml of blood each, the chambers about 100 ml each. The left and right parts of the heart are separated from each other by a septum that is very thin between the atria, but consists of thick muscle layers between the chambers.


The heart valves

The picture on the right shows the heart valves: the two-lobed leaflet valve at the bottom left, the three-lobed leaflet valve at the bottom right, the pulmonary valve in the upper middle and the aortic valve in the lower middle. The left ventricle on the right, the right ventricle on the left, the main artery incised at the top.

A heart valve is located between the atrium and the ventricle to control the blood flow; in the left half of the heart the mitral valve (so called because its shape resembles the two-lobed miter), in the right half of the heart the tricuspid valve (three-lobed miter). They work on the principle of the check valve, which means that the blood can only flow in one direction. At the exit of the large chambers there are two heart valves, the aortic valve in the left half of the heart and the pulmonary valve in the right half. They also serve to control the blood flow in certain directions, namely in the body and in the pulmonary circulation.


The coronary vessels

The heart itself needs large amounts of energy for its vital functions. This is supplied to the heart muscle via the coronary arteries, also known as the coronary arteries.


The pericardium

The pericardium, also known as the pericardium, is a double-walled sack into which the heart is everted from above. Its inner layer is connected to the heart muscle and separated from the outer layer by a narrow cavity filled with about 30 cm³ of fluid. This fluid is the pericardial water. The pericardium is, so to speak, a protective cover that is intended to prevent diseases from surrounding the heart and also mechanical overstretching of the heart muscle.


How the heart works

Duties of the left heart

The bright red blood flowing in from the lungs and enriched with oxygen collects in the left, stronger part of the heart. It first reaches the left atrium and from there through the mitral valve into the left ventricle. The heart contracts for a third of a second - this phase is called systole - and presses the bright red blood, which is not only oxygen but also nutrients such as fat, sugar, minerals and hormones, through the aorta, which measures 15 to 20 millimeters in the great body circulation. After the systole, the contraction of the heart muscle, the heart has two thirds of a second to rest from the previous exertion. This resting phase is called the diastole.

diastole (left picture)
During diastole, the atrium contracts and blood flows through the open leaflet valves into the chamber.

Systole (right picture)
In systole, the chamber contracts, the leaflet valves close, the pocket valves open, and blood flows into the pulmonary artery.

The "valve level" moves deeper due to the contraction of the chamber. This is shown by dashed lines on the left at the level of the sail and on the right at the level of the pocket flaps. This sucks blood into the atrium (arrows).

While both heart chambers contract synchronously and pump the blood into the body and pulmonary circulation, the two overlying atria relax. The filling of the four different heart cavities with blood and their emptying takes place in regular alternation.

Tasks of the right heart

The dark red venous blood flowing back from the body collects in the right ventricle and is pumped from there with the muscle contraction of the heart through the pulmonary valve and through the pulmonary artery into the lungs. There, in the capillaries of the two lungs, the so-called gas exchange takes place, i.e. the carbonic acid is released and exhaled, and the red blood cells are loaded with freshly inhaled oxygen. The blood turns bright red again. Starting from the hair vessels of the lungs, the blood collects in smaller and larger vessels and finally reaches the left atrium and the left ventricle via the four pulmonary veins. There the cycle begins again. The contractions of the two halves of the heart do not occur one after the other, but absolutely synchronously and simultaneously. This results in the steady heart rhythm and the constant alternation of systole and diastole.

Contraction of the heart

The contraction of the heart, which we can also feel as pulse beats and even see in some places, comes about through the complex interaction of the autonomic nervous system with the sympathetic and parasympathetic (vagus), the hormones adrenaline and noradrenaline and the heart's own control mechanisms. The sympathetic nervous system accelerates the heartbeat, while the parasympathetic nervous system acts as a brake, reducing the heart's activity and helping the entire system to avoid wasting energy. This unconscious nervous system is also involved in regulating the flow of blood through the blood vessels by making them narrow and wide as needed. Hormones, especially adrenaline and noradrenaline, are also involved in this control function. So the heart works independently of the human mind and will. But it is very sensitive to physical exertion and emotions. When we climb stairs and the leg muscles require more energy for this activity, the heart pumps faster so that the currently increased energy requirement can be met. When we get very excited or when we are frightened, the heart also beats faster.

Phase 1: The slack atria fill with blood.

Phase 2: When the atria contract, the blood flows through the leaflet valves into the heart chambers.

Phase 3: During the tension phase of the chambers, the leaflet flaps close.

Phase 4: When contracting (systole), the chambers push the blood through the opened pocket flaps into the main artery (red) or pulmonary artery (blue), at the same time the atria begin to fill with blood.


The circulation

The task of the blood circulation is to supply every body cell with the substances necessary for its metabolism, to transport away metabolic degradation products, to convey messenger substances (hormones), enzymes and heat.

The Arteries have the task of distributing oxygen-rich blood (high pressure with supply function: 120/80 mmHg Torr, that is 16 / 10.7 kPa).

The Veins have the task of guiding the "collected" oxygen-poor blood back to the heart (low pressure with reservoir function: 25/10 mmHg Torr, that is 3.3 / 1.3 kPa).

From the aorta, the main artery, arteries branch off to the upper body circulation, which supplies the head region, brain and upper extremities; also to the lower body circulation with large-volume branches to all abdominal organs and to the right and left leg. All arteries branch out into ever smaller and thinner branches up to the capillaries, the finest hair vessels, which then have a diameter of about a tenth of a millimeter. The small picture shows a red blood cell that makes itself small to fit through the finest capillaries. The blood pressure emanating from the pumping work of the heart ensures that oxygen-rich blood reaches the most distant areas of the body and supplies every cell there. The nutrients are exchanged through the walls of the cells, i.e. oxygen and nutrients are absorbed and carbonic acid and metabolic waste products are released. The blood, which is now dark red, is now transported via the so-called venous side, again starting from the finest hair vessels, then via the larger venules and the lower and upper vena cava to the right atrium and the right ventricle. All blood vessels that carry blood from the heart into the body are called arteries or arteries; all vessels that carry blood from the body to the heart are called veins or blood vessels.

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