Question

How blood circulation occurs in our body

Answer 1

There are three circulatory processes occurring simultaneously within the body. Firstly systemic circulation carries blood around the body, pulmonary circulation carries blood to the lungs and coronary circulation provides the heart with its own supply of blood.

At the start of the blood circulatory cycle the heart pumps oxygenated blood out of the left ventricle, through the Aorta (the largest artery in the body). The aorta divides into smaller arteries, then arterioles and finally into microscopic capillaries, found deep within muscles and organs. Here the Oxygen (and other nutrients) passes through the thin capillary walls, into the tissues where it can be used to produce the energy muscles require to contract.

A waste product of energy production (metabolism) is Carbon dioxide and in order to be removed, it too passes across the walls of the capillaries, into the blood stream. The blood continues back towards the heart, through venules and then veins, into the right atrium.

Once blood returns to the heart it is then pumped from the right ventricle through the Pulmonary arteries to the lungs, where the waste carbon dioxide can be expelled and more Oxygen collected. The Pulmonary vein carries oxygenated blood back to the left atrium of the heart, where the cycle starts again.

Answer 2

Blood flows through our body in two ways:
Systemic circulation
pulmonary circulation

Now, systemic circulation is a long route circulation which involves flow of oxygenated blood from the aorta to different parts of the body and returning of the blood back to the heart through posterior and anterior vena cavas.

The blood which returns to the heart through the veins is deoxygenated. So now, pulmonary circulation takes place. The blood flows to the lungs from the right auricle of the heart through the pulmonary artery for oxygenation. This blood after oxygenation is then returned back to the heart through the pulmonary veins.
Again the systemic circulation starts.

Thus, ours is a closed circulation, i.e., blood flows through arteries, veins and capillaries only in a closed pathway.

The heart also needs oxygen for doing its work. So, an artery called coronary artery supplies blood to the heart muscles. Coronary sinus is a vein which brings back deoxygenated blood from the heart muscles to the right auricle.

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