Vertebrate Respiration Bi 150/150.1

Functions Intake and distribution of oxygen, elimination of carbon dioxide Passive diffusion: simplest form Dependent on surface area and difference in partial pressures Ventilation – passage of air or water over respiratory surface Perfusion – driving of blood through capillaries Differ with regard to habitat Unidirectional vs. bidirectional

Basic: Origins of the Organs Gills: from pharyngeal slits Lungs: endodermal outpocketings from the gut Gas bladders: may be homologous to lungs

Ventilatory Mechanisms Ciliatory mechanisms Muscular mechanisms Dual Pump (water ventilation) – in most fishes Buccal Pump (air ventilation) Two-stroke – in air-breathing fishes and most amphibians Four-stroke – in some salamanders Aspiration Pump (air ventilation) – in amniotes

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http://upload. wikimedia http://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Two_stroke_buccal_pumping.jpg/400px-Two_stroke_buccal_pumping.jpg http://upload.wikimedia.org/wikipedia/commons/thumb/f/f4/Four_stroke_buccal_pumping.jpg/800px-Four_stroke_buccal_pumping.jpg

http://www. cvphysiology http://www.cvphysiology.com/Cardiac%20Function/abdominothoracic%20pump%20animated.gif

Phylogeny of the System Elasmobranchii Countercurrent flow across gills Ram ventilation (obligate in some) First gill slit reduced to spiracle http://www.shark-info.com/images/respiration.jpg

Osteichthyes Operculum covers the gills Some use gas bladders (sometimes connected to the buccal cavity via the pneumatic duct) http://www.goldfishworld.com/images/gill_gross_view.jpg

Amphibia Gill ventilation as juveniles Cutaneous respiration and lung ventilation as adults

Reptilia Single central air chamber with faveoli (compartments that increase surface area and are sites of gas exchange) Aspiration (exhalation sometimes passive) Snake lungs singular and divided into respiratory and saccular portions Crocodile livers act as pistons. Limb movement important in turtles

Journal Article* Farmer CG, Sanders K. 2010. Unidirectional airflow in the lungs of alligators. Science 327:338-340.

Birds Passageways branch off into parabronchi (unidirectional) With 6-12 (usually nine) avascular air sacs, which extend into the cores of large bones Crosscurrent flow

Mammals Extensive use of diaphragm and intercostals With alveoli (bidirectional) Viscera also assist in respiration.

Functional considerations Types of flow Ventilation and perfusion rates should be balanced (ratios depend on ecology) Metabolic costs of living in water vs. air Regulation of blood pH levels