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The heart is essentially a muscular pump, which is responsible for moving blood aorund the vessles of the body. It is made up of two halves, separated by the septum, a thick muscular wall. Each half is again divided into an upper and lower chamber.

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Introduction

HEART: The heart is essentially a muscular pump, which is responsible for moving blood aorund the vessles of the body. It is made up of two halves, separated by the septum, a thick muscular wall. Each half is again divided into an upper and lower chamber. The two chambers on the left side of the heart( left atrium and vetricle) are responsible for recieiving oxygen-rich blood from the lungs and pumping it out to the body along its largest artery, the aorta. The two chambers on the right side of the heart ( right atrium and ventricle) are responsible for receiving revatively deoxygenated blood from the body and distributing it via the pulmonary trunk to the lungs for gas exchange to occur. These two circuits of blood flow are called systemic and pulmonary circulations respectively. Within the heart there are four valves that ensure blood flows in one direction: from atrium to ventricle and out through its appropriate artery. The two artrioventricular valves are located between the atria and ventricles on each side of the heart. Between the right atrium and right ventricle lies the tricuspid valve, while the mitral valve lies between the left atrium and left vetnricle. The function of the atrioventricular valves is to prevent back-flow from the ventricles to the atria during ventricular contraction. The other two cardiac valves (semilunar valves) are located at the outlets from the ventricles: the pulmonary valve lies at the point where the right ventricle expels blood to the pulmonary trunk, while the aortic valve lies at the outlet of the left ventricle. ...read more.

Middle

The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle. The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior. The heart's structure makes it an efficient, never-ceasing pump. From the moment of development through the moment of death, the heart pumps. The heart, therefore, has to be strong. The average heart's muscle, called cardiac muscle, contracts and relaxes about 70 to 80 times per minute without you ever having to think about it. As the cardiac muscle contracts it pushes blood through the chambers and into the vessels. ...read more.

Conclusion

If you took all of the blood vessels out of an average child, and laid them out in one line, the line would be over 60,000 miles long! An adult's vessels would be closer to 100,000 miles long! Besides circulating blood, the blood vessels provide two important means of measuring vital health statistics: pulse and blood pressure. We measure heart rate, or pulse, by touching an artery. The rhythmic contraction of the artery keeps pace with the beat of the heart. Since an artery is near the surface of the skin, while the heart is deeply protected, we can easily touch the artery and get an accurate measure of the heart's pulse. When we measure blood pressure, we use the blood flowing through the arteries because it has a higher pressure than the blood in the veins. Your blood pressure is measured using two numbers. The first number, which is higher, is taken when the heart beats during the systole phase. The second number is taken when the heart relaxes during the diastole phase. Those two numbers stand for millimeters. A column of mercury rises and falls with the beat of the heart. The height of the column is measured in millimeters. Normal blood pressure ranges from 110 to 150 millimeters (as the heart beats) over 60 to 80 millimeters (as the heart relaxes). It is normal for your blood pressure to increase when you are exercising and to decrease when you are sleeping. If your blood pressure stays too high or too low, however, you may be at risk of heart disease. ...read more.

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