The human being heart is a four-chambered muscular organ, shaped and sized around like a man"s closed fist through two-thirds the the mass come the left of midline.

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The heart is fastened in a pericardial sac that is lined through the parietal class of a serous membrane. The visceral great of the serous membrane forms the epicardium.

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Layers that the love Wall

Three great of tissue kind the love wall. The external layer that the heart wall is the epicardium, the middle layer is the myocardium, and also the inner class is the endocardium.

Chambers that the Heart

The interior cavity the the heart is divided into 4 chambers:

Right atriumRight ventricleLeft atriumLeft ventricle

The 2 atria are thin-walled chambers that receive blood native the veins. The two ventricles are thick-walled chambers the forcefully pump blood the end of the heart. Differences in thickness the the love chamber walls are because of variations in the lot of myocardium present, which shows the lot of force each chamber is compelled to generate.

The best atrium obtain deoxygenated blood native systemic veins; the left atrium receives oxygenated blood from the pulmonary veins.

Valves that the Heart

Pumps need a collection of valves to save the fluid flowing in one direction and the love is no exception. The heart has two types of valves that store the blood flow in the exactly direction. The valves between the atria and also ventricles are dubbed atrioventricular valves (also dubbed cuspid valves), when those at the bases the the huge vessels leaving the ventricles are dubbed semilunar valves.

The right atrioventricular valve is the tricuspid valve. The left atrioventricular valve is the bicuspid, or mitral, valve. The valve in between the ideal ventricle and also pulmonary trunk is the pulmonary semilunar valve. The valve in between the left ventricle and also the aorta is the aortic semilunar valve.

When the ventricles contract, atrioventricular valves close to protect against blood indigenous flowing ago into the atria. Once the ventricles relax, semilunar valves close to stop blood native flowing back into the ventricles.

Pathway of Blood through the Heart

While the is practically to explain the circulation of blood through the appropriate side the the heart and also then with the left side, the is vital to realize the both atria and also ventricles contract at the same time. The heart functions as two pumps, one ~ above the right and one on the left, functioning simultaneously. Blood operation from the appropriate atrium to the right ventricle, and then is pumped come the lung to obtain oxygen. Indigenous the lungs, the blood flows to the left atrium, then to the left ventricle. From over there it is pumped to the systemic circulation.

Blood supply to the Myocardium

The myocardium the the heart wall is a working muscle that requirements a constant supply of oxygen and nutrients to function efficiently. For this reason, cardiac muscle has an extensive network that blood vessels to lug oxygen to the contracting cells and also to remove waste products.

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The right and left coronary arteries, branches the the ascending aorta, supply blood to the wall surfaces of the myocardium. After ~ blood passes with the capillaries in the myocardium, it enters a mechanism of cardiac (coronary) veins. Most of the cardiac veins drainpipe into the coronary sinus, i m sorry opens into the ideal atrium.