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respiration - Respiratory System Chapter 13 External...

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11/8/2011 1 External Respiration exchange of O 2 and CO 2 between vascular system and external environment Internal Respiration exchange of O 2 and CO 2 between vascular system and tissues of the body Respiratory System Chapter 13 External Respiration Involves skin (cutaneous respiration), gills and/or lungs Mechanism = passive diffusion In order for gases to diffuse across a membrane, the membrane must be moist Although most vertebrates have some type of hemoglobin, oxygen movement is still passive GILLS Specialized respiratory organs - highly variable Primitive anatomy: Gill slits (internal & external) Gill bar Supported by visceral arch Supplied with blood by afferent branchial artery Covered on one or both sides by gill lamellae Holobranch, demibranch & pseudobranch
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11/8/2011 2 Variation in gill structures: Agnatha have "marsipobranchs" supported by branchial basket cartilage Lampreys - 7 pairs of gill pouches Hagfish - 6-14 pairs of gill pouches utilize buccal force pump Chondrichthyes have "naked" gill slits gill formula = spiracle + demibranch + 4 holobranchs Variation in gill structures: Actinopterygians & Crossopterygians operculate gills spiracle variable - becomes involved with ear structures typically 4 holobranchs gill rakers in two rows Dipnoi also operculate but gill lamellae greatly reduced Austrailian lungfish - similar to other bony fish African & S. American lunfish - obligate lung breathers » no lamellae on gill bars 1 or 2
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