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 bronchioles 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 Gradients o Portion of atmospheric pressure contributed by a gas o 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 pressure Fig 42 28 Alveolus PO2 100 mm Hg Alveolus PCO2 40 mm Hg PO2 40PO2 100 PCO2 46 PCO2 40 Circulatory Circulatory system system PO2 40 PO2 100 PCO2 46PCO2 40 PO2 40 mm Hg PCO2 46 mm Hg Body tissue Body tissue b Carbon dioxide a Oxygen Respiratory 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 Asthma Bronchial tubes inflamed and sensitive to irritants Increased rates due to pollutants Chronic obstructive pulmonary disease Limitation of airflow not fully reversible Chronic bronchitis emphysema Tobacco smoking 90 of cases in US and airborne irritants
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