How Does External & Internal Respiration Work?
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What is Respiration?
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When most people think of respiration, they think of breathing. This is a very basic understanding of the term. Actually, respiration refers to a living creature's exchange of gases with its surroundings. In the animal kingdom, this means the intake of oxygen and output of carbon dioxide. This has all to do with a process known as cellular respiration, by which the individual cells of the living body use oxygen as part of a chemical reaction wherein glucose (sugar) is converted into a chemical known as ATP (adenosine triphosphate), which can then be used to power the continuous functioning of the cell. Carbon dioxide is a byproduct of this. But for cellular respiration to begin, two functions must first occur: external and internal respiration.
External Respiration
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External respiration is the act of breathing. The medulla oblongata in the brain sends a series of impulses to the central nervous system. The central nervous system affects the thoracic diaphragm, a sheet of muscle separating the interior of the torso from the gastrointestinal system. The diaphragm pulls away from the lungs, giving room for the lungs to expand. This is coupled with the expansion of the trachea, sinuses and alveoli in the lungs. The alveoli are spongy tissues which make up the interior of the lungs. They contain many tiny capillaries through which two types of red blood cell pass. Hemoglobin alpha and beta are physically no different except that beta comes to the lungs bearing carbon dioxide molecules attached to spots on its structure called binding sites. They exchange these molecules in favor of oxygen molecules in the lungs, becoming alpha cells.
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Internal Respiration
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Internal respiration picks up where external respiration leaves off. The oxygen-laden alpha cells pass throughout the body's cardiovascular system and diffuse through all the veins and capillaries. As they do so, they come into contact with other cells such as muscle cells, skin cells and organ cells. These cells, as they perform cellular respiration, dispose of carbon dioxide by forcing it out of their exterior membranes, the endothelia. The alpha cell has a large iron molecule in it. When an oxygen molecule is connected to an alpha cell's binding site, it interacts in such a way with the iron molecule as to cause the cell to change shape, exposing a different binding site. Carbon dioxide molecules connect to these new binding sites, breaking the bonds of the oxygen molecules. The living cells of the body take in oxygen molecules through the endothelia, and the alpha cells have now become beta cells, which pass back to the lungs to repeat the process.
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