Answer:
The normal heart is composed of four chambers. The two upper chambers (called atriums or atria) are reservoirs which collect blood as it flows back to the heart. From the atriums, blood flows into the lower two chambers (called ventricles) which pump blood, with each heart beat, into the main arteries. From the right side of the heart one of these arteries (the pulmonary artery) carries blood to the lungs for re-oxygenation. The left side of the heart pumps blood into the other main artery (the aorta), which takes blood to the rest of the body.
The two ventricles and the two atriums are separated by partitions called 'septums'. The partition between the atriums is called the 'atrial septum' and the one separating the two ventricles is the 'ventricular septum'. Dark red deoxygenated blood (shown blue in diagram) returns to the right atrium from the body through the two main veins called the 'superior vena cava' and 'inferior vena cava'. It is pumped by the right ventricle to the lungs for replenishment with oxygen. The dark blood becomes bright red (shown red in diagram) in the lungs when oxygen is taken up. This red blood returns through two veins from each lung, to the left atrium and is pumped by the left ventricle to the body again.
The heart has its own internal pacemaker which controls its rhythmical beating. It creates an electrical impulse which causes firstly the atriums, and secondly the ventricles, to contract in turn. With each contraction the blood is pumped, then the heart muscle relaxes and the chambers refill with blood, ready for the next contraction.
The two ventricles and the two atriums are separated by partitions called 'septums'. The partition between the atriums is called the 'atrial septum' and the one separating the two ventricles is the 'ventricular septum'. Dark red deoxygenated blood (shown blue in diagram) returns to the right atrium from the body through the two main veins called the 'superior vena cava' and 'inferior vena cava'. It is pumped by the right ventricle to the lungs for replenishment with oxygen. The dark blood becomes bright red (shown red in diagram) in the lungs when oxygen is taken up. This red blood returns through two veins from each lung, to the left atrium and is pumped by the left ventricle to the body again.
The heart has its own internal pacemaker which controls its rhythmical beating. It creates an electrical impulse which causes firstly the atriums, and secondly the ventricles, to contract in turn. With each contraction the blood is pumped, then the heart muscle relaxes and the chambers refill with blood, ready for the next contraction.
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