Chapter 42 Respiratory System

Biology, 7th Edition (Book & CD-ROM)

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Chapter 42 Respiratory System I. Gas exchange A. Introduction 1. Gas exchange- the uptake of oxygen and discharge of carbon dioxide (exchange of gas) a. Necessary to produce ATP 2. Respiratory medium- the air for terrestrial animals and water for most aquatic animals a. There is always much more oxygen in air than there is in water 3. Respiratory surface- the part of an animal’s body where gasses are exchanged a. Tends to be thin and have a lot of surface area b. All living cells must be bathed in water to maintain their plasma membrane, so the lungs need to be kept moist 4. Many simple animals use the outer skin as a respiratory system, but for others it lacks enough surface area for it to be efficient B. Gills 1. Gills- outfoldings of the body surface that are suspended in the water a. Sea starrs- simple shape and distributed over much of body b. Marine worms- flaplike gills all over their body or long feathery gills clustered at the head or tial c. Scallops, crayfish, etc- restricted to a local body region d. Total surface area of gills much greater than rest of body area 2. Advantage/Disadvantage a. Water is always present, there’s no problem of keeping the plasma membranes moist b. Water has low oxygen concentrations c. The warmer and saltier the water, the less oxygen present 3. Ventilation- increasing the flow of the respiratory medium over the respiratory surface (keeping water moving) 4. Countercurrent exchange a. Blood moves in opposite direction nof water (oxygen) b. As blood moves through the capillary, it becomes more and more loaded with O 2 and at the same time encounters water with a higher O 2 concentration c. Diffusion gradient transfers O 2 from water to blood d. Gills remove 80% of O 2 in water through countercurrent exchange 5. When fish are caught and brought to land, their gills dry out and therefore collapse on each other so they suffocate to death. C. Tracheal Systems
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Chapter 42 Respiratory System - Chapter 42 Respiratory...

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