Heart and blood vessels

The heart is a hollow muscle organ located in the center of the chest. The right and left sides of the heart each have an upper chamber (the atrium that collects blood and the lower chamber (ventricle) that draws blood.To blood just flow in one direction, the ventricle has one valve at the entrance and one valve on the exit.

The main function of the heart is to provide oxygen throughout the body and cleanse the body of the metabolism (carbon dioxide).

The heart performs this function by collecting oxygen-depleted blood from the rest of the body and pumping it into the lungs, where the blood will take up oxygen and dispose of carbon dioxide; the heart then collects oxygen-rich blood from the lungs and pumps it into tissues throughout the body.


At the time of pulsation, every chamber of the heart relaxes and is filled with blood (called diastole); then the heart contracts and pumps blood out of the heart chamber (called systole). Both atria relax and contract simultaneously, and both ventricles also relax and contract simultaneously.

Blood that runs out of oxygen and contains a lot of carbon dioxide from the whole body flows through two large veins (vena cava) into the right atrium. After the right atrium is filled with blood, he will push the blood into the right ventricle. The blood from the right ventricle will be pumped through the pulmonary valve into the pulmonary artery, leading to the lungs. Blood will flow through the very small vessels (capillaries) that encircle the air bag in the lungs, absorb oxygen and release the carbon dioxide which is then exhaled.

Oxygen-rich blood flows in the pulmonary vein leading to the left atrium. The circulation of blood between the right part of the heart, lungs and the left atrium is called pulmonary circulation. Blood in the left atrium will be pushed into the left ventricle, which will then pump the oxygen-rich blood through the aortic valve into the aorta (the largest artery in the body).

This oxygen-rich blood is reserved for the whole body, except the lungs.


The entire circulatory system (the cardiovascular system) consists of arteries, arterioles, capillaries, venules and veins. Arteries (strong and supple) carry blood from the heart and bear the highest blood pressure. Flexibility helps maintain blood pressure between heartbeats.

Smaller arteries and arterioles have muscular walls that adjust their diameter to increase or decrease blood flow to certain areas. Capillaries are fine blood vessels with very thin walls, which act as a bridge between arteries (carrying blood from the heart) and veins (bringing blood back to the heart).

The capillaries allow oxygen and nutrients to move from the blood into the tissues and allow the metabolism to move from tissues into the blood. From the capillaries, blood flows into the venule then into the veins, which will bring blood back to the heart.

The veins have thin walls, but they usually are larger in diameter than the arteries; so the vein carries blood in the same volume but at a lower speed and less under pressure.

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