In human beings, the various organs associated with this system include the heart, lungs, blood vessels, capillaries, and blood. The heart is the pumping organ that squirts out blood. The heart does this with so much pressure that it is capable of squirting blood up to 9 meters high. It never stops and beats continuously so that blood can travel to all parts of the body.

Your blood travels through these blood vessels transporting oxygen, carbon dioxide, digested food, hormones and even waste products. It is amazing to see how transportation in human beings is carried out by the circulatory system, with the heart and the vast network of blood vessels.

Blood

Blood is an important fluid connective tissue. It is mainly composed of plasma and blood cells. There are three types of blood cells, namely, red blood cells, white blood cells, and blood platelets. The RBCs have haemoglobin, an iron-containing complex protein. The WBCs are the cells that help in fighting diseases and attack any foreign bodies in the blood. The blood platelets are the ones that help in clotting of blood.

In human beings, there is a phenomenon calleddouble circulationthat occurs, which is an efficient way. The heart pumps the blood, and through the various blood vessels, it travels to different organs and then comes back again to the heart. Now, this flow of blood in humans occurs in two pathways called the pulmonary pathway and the systemic pathway.

This system ensures that the deoxygenated blood (blood carrying carbon dioxide) from the right side of the heart goes to the lungs, where gaseous exchange occurs. Blood gets filled with oxygen from the lungs and carbon dioxide is given out to the lungs(from where it leaves the body). The oxygenated blood then travels from the left side of the heart to all other parts of the body.

The double circulation seen here ensures that there is no mixing of oxygenated blood and deoxygenated blood. There is also an efficient supply of oxygen to the body cells and a greater rate of blood flow in the body.

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