BIOL 152 1st Edition Lecture 25 Outline of Last Lecture - Osmoregulation Outline of Current Lecture - Gas Exchange Current Lecture- Gas Exchange - Gas exchange sustains cell respiration- Cells need O2 and expel CO2 Air and Water are very different mediums for respiration- Air contains more oxygen and is less dense, making ventilation easier Respiratory Surfaces Vary- Size of organism- Aquatic or terrestrial- Metabolic demands- Endo vs ecto- Skin (flatworms, eartworms)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.- Gills (aquatic animals)- Trachea (insects)- Lungs (spiders, snails, vertebrates)How do gills work?- Gills present a large surface area for oxygen to diffuse across a thin epithelium.- Advantages: large surface area, in water, - Disadvantages: oxygen levels are low in water - Movement of water over gills is unidirectional. - Gill filaments extend from each gill arch. - Gill filament composed of hundreds or thousands of gill lamellae—sheetlike with a bed of capillaries.How do tracheae work?- Tracheae – extensive system of tubes within the body of insects - Ventilation not as important - Connect to exterior through spiracles – can be closed to minimize water loss - Open circulatory system – no capillary bed How do lungs work?- The trachea carries inhaled air to narrower tubes called o Bronchi àbronchioles- Lungs are infoldings of the throat or body surface that enclose the bronchioles and part of the bronchi. o Mammalian lungs are divided into tiny sacs called alveoli.How are lungs ventilated?- Diffusion only in the snails and spiders- Frogs and related animals push air into their lungs via positive pressure ventilation.- Humans and other mammals pull air into their lungs via negative pressure ventilation.Avian Respiration - Lungs are dense and spongy with parabronchi instead of alveoli- Air flows in only one direction, but only one trachea??- Elaborate system of interconnected air sacs and no diaphragm - Gas exchange occurs on inhale and exhale- Partial Pressure Gradientso Portion of atmospheric pressure contributed by a gaso Atmospheric pressure = 760mm Hg PO2 = 0.21 x 760 = 160 mm Hg PCO2 = 0.0003 x 760 = 0.23 mm Hg - Gasses diffuse from high to low partial pressureRespiratory Pigments- Oxygen is not transported in dissolved form – would need 555 L of blood/minute!o Hemoglobin decreases this to: 4 subunits Each hemoglobin carries 4 oxygen molecules Oxygen-hemoglobin dissociation Decreases in pH and increases in temperature alter hemoglobin’s conformation it becomes more likely to release O2. Bohr shif.Fig. 42-28AlveolusPO2 = 100 mm HgPO2 = 40PO2 = 100PO2 = 100PO2 = 40CirculatorysystemBody tissuePO2 ≤ 40 mm Hg PCO2 ≥ 46 mm HgBody tissuePCO2 = 46PCO2 = 40PCO2 = 40PCO2 = 46CirculatorysystemPCO2 = 40 mm HgAlveolus(b) Carbon dioxide(a) OxygenAsthma- Bronchial tubes inflamed and sensitive to irritants- Increased rates due to pollutantsChronic obstructive pulmonary disease- Limitation of airflow, not fully reversible- Chronic bronchitis, emphysema- Tobacco smoking (90% of cases in US) and airborne
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