bjones
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Blood is like the superhighway of the body. It is used to transport substances to the parts of the body they need to be. For instance, all of the body’s cells require oxygen, so blood picks up oxygen from the lungs and carries it to all the cells of the body. As cells use oxygen, they produce waste in the form of carbon dioxide. Blood transports this gaseous waste back to the lungs so it can be exhaled. Blood also performs several other important duties that keep us alive.
Adult humans have about 5 liters of blood in their body. The blood travels through a 62,000 mile-long network of veins, arteries and capillaries to reach every cell in the body. The blood moves through the vessels from the pumping action of the heart.
Blood is primarily composed of four different substances:
1. Plasma – This liquid makes up most of the blood. It is 90 percent water but also contains the many of the substances that require blood to transport it through the body.
2. Red blood cells – These cells are shaped like discs with flattened centers. They contain a protein called hemoglobin, which it responsible for picking up oxygen from the lungs and carrying it to the body’s other cells.
3. White blood cells – These cells are on the front lines of the body’s immune system. They travel to infected sites of the body and fight microscopic invaders, such as harmful bacteria and viruses.
4. Platelets – These are very small oval-shaped cells. Their job is to seal off broken blood vessels by clotting up sites that are leaking. When you get a cut, platelets rush to the site and, in conjunction with some important proteins, attempt to plug up the cut by becoming a solid.
Blood does not only transport oxygen and carbon dioxide. It is also used to carry nutrients, hormones, proteins and anything else that needs to get from one part of the body to another. Blood also helps the body to maintain a constant temperature, which is the origin of the term warm-blooded.
 Posted 4793 day ago
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