The Human Circulatory System

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The Human Circulatory System

The human circulatory is one of, if not the, most important system in the body. “It consists of such organs as the heart, and lungs” (Dunbar 4). “However every organ and organ system in the body is nourished and kept alive through the use of the circulatory system” (2-4). The main organ in the circulatory system is the heart. “Basically, the heart is a pump that keeps fresh blood coursing through your body, bringing oxygen and nutrients to all your organs and cells” (2). “A mathematical description of what the heart accomplishes is astonishing. Your heart keeps approximately ten pints (4.73 liters) of blood constantly circulating through seventy –five –thousand miles (one –hundred –thousand kilometers) of blood vessels” (2). Those thousands of miles of blood vessels reach every organ in your body. “Once they reach the organ they deliver much needed oxygen and take away carbon dioxide and other waste products that your body cannot use. This must be done without interruption if you are to remain healthy and alive” (2).

“Every living cell in your body depends on oxygen for life. Any cell deprived of oxygen for more than thirty minutes will die. The cells in your brain are even more dependent on fresh oxygen. If your brain cells are deprived of oxygen for only five seconds it will cause you to become unconscious. If your brain is deprived of oxygen for more than four minutes your brain will die” (2).

But where does all of this oxygen come from? , You may ask yourself. The lungs, I believe, are the second most important organs in the circulatory system. For one reason they are the only way for oxygen to be received into the body. It is in the lungs that cells absorb fresh oxygen, and where carbon dioxide is released to be expelled from the body. The transfer of these two gasses takes place in the alveoli in the lungs. “Alveoli are ‘small cavities’ or ‘air sacs in the lungs’” (Marieb G-2). “Blood entering the lungs through the pulmonary circulation is dark colored, low on oxygen, and high in carbon dioxide. The blood is pumped by the right side of the heart into the pulmonary arteries, which leads to the lungs. The pulmonary arteries divide into smaller and smaller blood vessels, which ending with pulmonary capillaries in the walls of the alveoli”(World Book L 528). These alveoli are the smallest o...

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Platelets are disk like structures that develop from cells found in the marrow. They help prevent the loss of blood from damaged vessels. If a small blood vessel is cut or broken, platelets stick to the damaged surface and to one another. As they pile up, they form a temporary seal over the injury. At the same time, the platelets release substances that start the process of blood clotting. Platelets are the smallest of the formed elements. They measure only about two to four microns in diameter. A micro liter of blood contains one –hundred –fifty –thousand to four –hundred –thousand platelets” (425).

Bibliography

“Blood” The World Book Encyclopedia: Scott Fetzer Company. 1990.

Dunbar, Robert E. The Heart and Circulatory System New York: Franklin Watts, 1984

Hildebrant, Jack and Modell, Harold I.

“Lung” The World Book Encyclopedia: Scott Fetzer Company. 1990.

“How the Heart Works” The World Book Encyclopedia: Scott Fetzer Company. 1990.

Marieb, Elaine N. Essentials of Human Anatomy and Physiology New York: The

Benjamin/Cummings Publishing Company, Inc., 1994

“The Circulatory System.” The World Book Encyclopedia: Scott Fetzer Company. 1990.

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