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What the difference between a lung and a gill?
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Default What the difference between a lung and a gill? - 12-20-2008, 02:49 PM

How does a gill work that's different from a lung so that only one can breathe air and the other can only breathe water? Is there a third choice?
   
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Default 12-24-2008, 08:35 PM

Fish can pull oxygen from water, they have gills madeto do this when moving water is going through them.Both use the basicprinciples of concentrations/partial pressures of oxygen and a carriermolecule (hemoglobin) to bind the oxygen and carry it to the tissues. Itis also a requirement to bind carbon dioxide and carry it away from thetissues and release it in the lungs of gills.
   
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Default 12-29-2008, 06:33 PM

The lung and the gill are both organs of respiration. The lung is the organ of respiration of humans while the gill is the organ of respiration of fish.In the respiration of fish, they use the countercurrent flow mechanism. This mechanism is where the blood of the fish travels in the opposite direction as the direction of water. This mechanism is useful so that the absorption of oxygen in the water would be maximized. How? If the blood of the fish were to travel along with the water's direction, the blood of the fish will not only absorb oxygen from the water but also lose oxygen to it.
   
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Default 02-22-2009, 05:52 PM

They are different in structure and also in the way that gas exchange occurs.In gills, the water flows in a single direction, and the blood flow in the blood vessels occurs in the opposite direction. Thus optimal gas exchange is achieved (there are good illustrations in textbooks to understand this better). However, to take up oxygen effectively, gills need an enormous surface area, because oxygen is relatively scarce in water. Thus, the gill lamellae are subdivided into smaller lamellae, and these in turn into even smaller projections; these extremely thin laminas are supported in water, but collapse onto each other in air, because of surface tension and gravity.Lungs can be of 2 types: the basic model comprises paired sacs, with more or less elaborate inner walls for greater surface area, but also with a surfactant substance that decreases surface tension so that these sacs do not collapse. The air goes in and out of the lungs by way of a single duct, thus there isn't a continuous flow of oxygenated air. Less efficient, but air has so much oxygen that it works anyway. The exception are the lungs of birds, in which the blood vessels are at right angles with respect to air flow, and the latter is continuous and unidirectional.All respiratory surfaces need to be moist, and lungs are no exception. However, in this case the moisture is _inside_ the body, and the body surface is still mostly impermeable.Third choice... that would be perhaps the tracheae of insects. Aquatic arthropods have lungs of different types, and terrestrial chelicerates do have special gills too. But insects have a different system: ducts that pierce the body wall and project inwards, taking oxygenated air directly to the tissues (no participation of the circulatory system).
   
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Default 02-24-2009, 08:49 PM

Two other"third"choices:Spiders and arachnids in general have"book lungs". These are essentially gills modified to work on land.Many terrestrial animals do not bother with lungs, simply exchanging oxygen for carbon dioxide along the surface of the skin. Earthworms are a prime example of this. Modern amphibians also exchange oxygen this way, but most of them also have lungs. Ancient amphibians had scales, so could not exhange much oxygen through the skin, but these have all been extinct since the Mesozoic.
   
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