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How does blood flow through the heart during different phases of cardic cycle

Answer» The heart is roughly triangular in shape. It has four compartments called chambers inside it. The upper two chambers of the heart are called atria and the lower two chambers are called ventricles. The atria receive blood from the two main veins. The left atrium is connected to the left ventricle through a valve V1 and the right atrium is connected to the right ventricle through another valve V2. These valves prevent the backflow of blood into atria when the ventricles contract to pump blood out of the heart to the rest of the body because when the ventricles contract, the valves V1 and V2 close automatically so that the blood may not go back into the atria. The job of heart is to pump blood around our body. All the atria and ventricles of the heart contract and relax at appropriate times and make the heart behave like a pump. A sheath of tissue called pericardium protects the muscular heart.Working of Human blood circulatory system takes place in the steps below:(i) When the muscles of all the four chambers are relaxed, the pulmonary vein brings the oxygenated blood from the lungs in the left atrium of the heart.(ii) When the left atrium contracts, the oxygenated blood is pushed into the left ventricle through valve V1.(iii) When the left ventricle contracts, the oxygenated blood enters the main artery called aorta from which it goes to the different body organs through small branches called arterioles and capillaries.(iv) The main artery carries the blood to all the organs of the body head, arms etc except the lungs. The oxygenated blood gives off oxygen, digested food and dissolved materials to the body cells. The carbon dioxide produced in the cells enters the blood. The deoxygenated blood enters main vein called vena cava which carried it to the right atrium of the heart.(v) When the right atrium contracts, the deoxygenated blood enters right ventricle through valve V2.(vi) When the right ventricle contracts, the deoxygenated blood enters the lungs through pulmonary artery and releases carbon dioxide and absorbs fresh oxygen from air. The blood becomes oxygenated again and is sent to the left atrium of heart by pulmonary vein for circulation in the body. This whole process is repeated continuously.


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