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

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The heart is fastened in a pericardial sac that is lined v the parietal great of a serous membrane. The visceral great of the serous membrane develops the epicardium.

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Layers that the love Wall

Three layers of tissue kind the heart wall. The external layer the the heart wall is the epicardium, the center layer is the myocardium, and the inner class is the endocardium.

Chambers of the Heart

The interior cavity of the heart is split into four chambers:

Right atriumRight ventricleLeft atriumLeft ventricle

The two atria space thin-walled chambers that receive blood indigenous the veins. The 2 ventricles room thick-walled chambers the forcefully pump blood the end of the heart. Distinctions in thickness that the love chamber wall surfaces are as result of variations in the lot of myocardium present, which shows the amount of force each room is forced to generate.

The ideal atrium obtain deoxygenated blood native systemic veins; the left atrium receive oxygenated blood indigenous the pulmonary veins.

Valves of the Heart

Pumps need a collection of valves to save the liquid flowing in one direction and also the love is no exception. The heart has actually two varieties of valves that save the blood flow in the correct direction. The valves between the atria and also ventricles are dubbed atrioventricular valves (also called cuspid valves), while those in ~ the bases of the large vessels leaving the ventricles are dubbed semilunar valves.

The appropriate atrioventricular valve is the tricuspid valve. The left atrioventricular valve is the bicuspid, or mitral, valve. The valve in between the ideal ventricle and 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 near to protect against blood from flowing earlier into the atria. When the ventricles relax, semilunar valves nearby to stop blood from flowing ago into the ventricles.

Pathway the Blood v the Heart

While it is practically to describe the circulation of blood with the right side that the heart and also then with the left side, the is important to realize the both atria and also ventricles contract in ~ the same time. The heart functions as 2 pumps, one ~ above the right and one top top the left, functioning simultaneously. Blood operation from the right atrium to the right ventricle, and also then is pumped to the lungs to obtain oxygen. Native the lungs, the blood flows to the left atrium, climate to the left ventricle. From over there it is pumped come the systemic circulation.

Blood supply to the Myocardium

The myocardium that the heart wall surface is a working muscle that needs a constant supply of oxygen and also nutrients to function efficiently. For this reason, cardiac muscle has considerable network of blood ship to lug oxygen come the contracting cells and also to remove waste products.

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The right and left coronary arteries, branches of the ascending aorta, it is provided blood come the walls of the myocardium. After blood passes with the capillaries in the myocardium, that enters a system of cardiac (coronary) veins. Most of the cardiac veins drain into the coronary sinus, i beg your pardon opens into the best atrium.