BIOL 118 1st Edition Lecture 24 Outline of Last Lecture I Introduction II Form Function Adaptation III Tissue IV Organ Organ Systems V Surface Area Volume Relationships VI Homeostasis VII Heat Exchange Outline of Current Lecture I Introduction II Respiratory Circulatory Systems III O2 CO2 Behavior IV Gills V Insect Trachae VI Vertebrate Lungs VII Blood VIII Circulatory Systems Current Lecture Introduction Oxygen required for carbon dioxide produced by cellular respiration must be continuously exchanged with the environment o These gases must be transported throughout the body o Cells must obtain oxygen expel carbon dioxide continuously to support ATP production by mitochondria Gas exchange involves 4 steps These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o Ventilation occurs when air or water moves through a specialized gas exchange organ such as lungs or gills o Gas exchange takes place as CO2 O2 diffuse between air or water and the blood at the ventilator surface o Circulation dissolved O2 CO2 are transported throughout the body o Cellular respiration gas exchange between blood cells occurs in tissues where respiration occurs O2 CO2 diffuse between blood cells Respiratory Circulatory Systems Respiratory system accomplishes ventilation gas exchange Circulatory system responsible for moving O2 CO2 other materials around the body In some animals gas exchange surface is the skin but in most species it is located in a specialized organ O2 CO2 Behavior Gas exchange between environment cells is based on diffusion o Oxygen is high in the environment low in tissues o Carbon dioxide is high in tissues low in the environment o Partial pressure pressure of a particular gas in a mixture of gases To calculate multiply the fractional composition of that gas by the total pressure exerted by the entire mixture Dalton s law The diffusion of oxygen carbon dioxide is dependent upon the partial pressure gradient move from high partial pressure to regions of low partial pressure Water has less available oxygen than air o Is about a thousand times denser than air flows less easily o Water breathers have to expend more energy to ventilate their respiratory surfaces than do air breathers Amount of gas that dissolves depends on several factors o The solubility of the gas in water o The temperature of the water o Presence of other solutes o Partial pressure of the gas in contact with the water Partial pressure of oxygen varies in different types of aquatic habitats o Habitats with large numbers of photosynthetic organisms tend to be relatively oxygen rich o Habitats where most organisms live off existing organic material tend to be oxygen poor Many small animals exchange gases by direct diffusion across the body surface o Mainly live in wet environments Large animals or those that live in dry environments need a specialized organ for gas exchange o Respiratory organs provide a greater surface area for gas exchange Fick s law o States that rate of diffusion of a gas depends on Solubility of the gas Temperature Surface available for diffusion Differences in partial pressures of the gas across the gas exchange surface Thickness of the barrier in diffusion o Identifies traits that allow animals to maximize the rate at which oxygen carbon dioxide diffuse across surfaces Surface area for gas exchange is large Respiratory surface is extremely thin Partial pressure gradient of the gas across the surface is large Gills Gills Outgrowths of the body surface or throat used for gas exchange in aquatic animals o Present an extremely large surface area for oxygen to diffuse across an extremely thin epithelium Structure can be extremely diverse can be internal or external o Fish gills are located on both sides of head is teleosts consisting of four arches Bony fish have internal gills water must be driven over them by ventilation Most fish ventilate gills by opening closing their mouths the operculum stiff flap over the gills Particularly fast swimmers force water through their gills by swimming with their mouths open ram ventilation Structure o Movement of water over gills is in one direction water must flow over gills in order for gases to be exchanged o Gill filaments long thin structures the extend from each gill arch o Each gill filament is composed of hundreds or thousands of gill lamellae sheetlike structures Bed of small blood vessels called capillaries runs through Countercurrent system o Flow of blood through the capillaries is in the opposite direction to the flow of water over gill surface countercurrent exchange in each lamella o Creates large partial pressure of oxygen the carbon dioxide in water over blood efficient gas exchange Insect Trachae Trachea air filled tubes o Open to the outside through pores called spiracles Air moves into trachea then by diffusion into cells o Sufficient to exchange gases in small insects Vertebrate Lungs In terrestrial animals air enters the body through the mouth nose o Trachea carries inhaled air to narrow tubes called bronchi Bronchi branch off into even narrower tubes called bronchioles o Organ for gas exchange is the lung Encloses the bronchioles portions of the bronchi Frogs amphibians simple sac lined with blood vessels Mammals divided into tiny sacs called alveoli greatly increase surface area for gas exchange Alveoli provide an interface between air blood that consists of o Thin aqueous film o Layer of epithelial cells o Some extracellular matrix material o Wall of a capillary Actively ventilate lungs by pumping air via muscular contractions o Positive pressure ventilation Frogs o Negative pressure ventilation Humans other mammals Pumping achieved by diaphragm muscle Human Lungs o When diaphragm moves down air in chest cavity is lowered air moves in o As diaphragm relaxes chest cavity decreases air is exhaled Passive process driven by elastic recoil of the lungs chest wall as the diaphragm rib muscles relax o 450 mL of air moves in out of lungs in average breath 150 mL of this occupy dead space portions of air passages that do not have respiratory surface Bird lungs o Able to extract enough oxygen for extremely long flights flights at high elevations o 4 General steps During inhalation air flows through trachea into 2 large air sacs During exhalation air flows from the air sacs into the posterior of the lung parabronchi During the second inhalation air moves to
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