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Concept 42.5: Gas exchange occurs across specialized respiratory surfaces page 915
Gas exchange supplies O2 for cellular respiration and disposes of CO2 © 2011 Pearson Education, Inc.
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Some comparisons we will be making
Bacteria Protists Worms Insects Fish Amphibians Reptiles Mammals
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Partial Pressure Gradients in Gas Exchange
A gas diffuses from a region of higher partial pressure to a region of lower partial pressure Partial pressure is the pressure exerted by a particular gas in a mixture of gases Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in partial pressure © 2011 Pearson Education, Inc.
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Partial Pressure Gradients in Gas Exchange
A gas diffuses from a region of higher partial pressure to a region of lower partial pressure Partial pressure is the pressure exerted by a particular gas in a mixture of gases Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in partial pressure What gas is most prevalent in air? What percent of air is oxygen? © 2011 Pearson Education, Inc.
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Composition of Air Air contains:
Air at sea level is at a pressure of 760 mmHg. What is the partial pressure of O2 at sea level? 760 mmHg X 20.95=159.2 mmHg
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How can organisms take in needed oxygen and expel CO2?
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Respiratory Surfaces Animals require large, moist respiratory surfaces for exchange of gases between their cells and the respiratory medium, either air or water Gas exchange across respiratory surfaces takes place by diffusion Respiratory surfaces vary by animal and can include the outer surface, skin, gills, tracheae, and lungs © 2011 Pearson Education, Inc.
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6 mechanisms for gas exchange
1. Diffusion through cell membrane Ex: Single Cell 2. Diffusion through skin Ex: Earthworm 3. Papillae- Increased folds in skin Ex: Echinoderms 4. Spiracles and tracheae Ex: Insects 5. Gills Ex: Fish 6. Alveoli of Lungs Ex: Mammals
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Gills in Aquatic Animals
Gills are outfoldings of the body that create a large surface area for gas exchange © 2011 Pearson Education, Inc.
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Figure 42.22 Gills are Shown In Pink
Coelom Gills Gills Figure Diversity in the structure of gills, external body surfaces that function in gas exchange. Tube foot Parapodium (functions as gill) (a) Marine worm (b) Crayfish (c) Sea star
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Ventilation moves the respiratory medium over the respiratory surface
Aquatic animals move through water or move water over their gills for ventilation Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets © 2011 Pearson Education, Inc.
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Countercurrent exchange PO (mm Hg) in water 2
Figure 42.23 O2-poor blood Gill arch O2-rich blood Lamella Blood vessels Gill arch Water flow Operculum Water flow Blood flow Countercurrent exchange Figure The structure and function of fish gills. PO (mm Hg) in water 2 150 120 90 60 30 Gill filaments Net diffu- sion of O2 140 110 80 50 20 PO (mm Hg) in blood 2
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Tracheal Systems in Insects
The tracheal system of insects consists of tiny branching tubes that penetrate the body The tracheal tubes supply O2 directly to body cells The respiratory and circulatory systems are separate Larger insects must ventilate their tracheal system to meet O2 demands © 2011 Pearson Education, Inc.
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Tracheoles Mitochondria Muscle fiber 2.5 m Body cell Tracheae Air sac
Figure 42.24 Tracheoles Mitochondria Muscle fiber 2.5 m Body cell Tracheae Air sac Tracheole Figure Tracheal systems. Air sacs Trachea Air External opening
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Amphibians and Reptiles
Amphibians have lungs but also supplement their respiration through moist skin- cutaneous respiration. Reptiles have a partially divided ventricle that more efficiently separates oxygenated from deoxygenated blood, reducing the need for cutaneous respiration. Turtles supplement their respiration through skin on their ____!
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What structures are involved in mammal gas exchange?
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Mammalian Respiratory Systems: A Closer Look
A system of branching ducts conveys air to the lungs Air inhaled through the nostrils is warmed, humidified, and sampled for odors The pharynx directs air to the lungs and food to the stomach Swallowing tips the epiglottis over the glottis in the pharynx to prevent food from entering the trachea © 2011 Pearson Education, Inc.
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enveloping alveoli (SEM)
Figure 42.25 Branch of pulmonary vein (oxygen-rich blood) Branch of pulmonary artery (oxygen-poor blood) Terminal bronchiole Nasal cavity Pharynx Left lung Larynx (Esophagus) Alveoli Trachea 50 m Right lung Capillaries Bronchus Figure The mammalian respiratory system. Bronchiole Diaphragm (Heart) Dense capillary bed enveloping alveoli (SEM)
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Exhaled air passes over the vocal cords in the larynx to create sounds
Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs Exhaled air passes over the vocal cords in the larynx to create sounds Cilia and mucus line the epithelium of the air ducts and move particles up to the pharynx © 2011 Pearson Education, Inc.
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Gas exchange takes place in alveoli, air sacs at the tips of bronchioles
Oxygen diffuses through the moist film of the epithelium and into capillaries Carbon dioxide diffuses from the capillaries across the epithelium and into the air space © 2011 Pearson Education, Inc.
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Let’s model how the blood gets oxygen to every body cell.
Oxygen in the blood is affixed to _______ The more that the tissue needs oxygen, the lower the affinity of hemoglobin for oxygen.
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Modeling O2 Delivery 8 students are hemoglobin- cups with 4 O
Each table is a body cell- 1 cup with 4 O Body cells are digestive, brain, skeletal muscle Every hemoglobin has a route, one row. Body Cells use O2 Warm up- Every cell uses 1/ 20 sec Raise hand when need an oxygen Active tissue uses 1/10 sec, vary which tissue is active
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Figure 42.31 Oxyhemoglobin dissociation curve
100 100 O2 unloaded to tissues at rest pH 7.4 80 80 pH 7.2 O2 unloaded to tissues during exercise Hemoglobin retains less O2 at lower pH (higher CO2 concentration) 60 60 O2 saturation of hemoglobin (%) O2 saturation of hemoglobin (%) 40 40 20 20 20 40 60 80 100 20 40 60 80 100 Figure Dissociation curves for hemoglobin at 37°C. PO (mm Hg) Tissues during exercise Tissues at rest Lungs 2 (b) pH and hemoglobin dissociation PO (mm Hg) 2 2 (a) PO and hemoglobin dissociation at pH 7.4
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O2 saturation of hemoglobin (%)
Figure 42.31b 100 pH 7.4 80 pH 7.2 Hemoglobin retains less O2 at lower pH (higher CO2 concentration) 60 O2 saturation of hemoglobin (%) 40 20 Figure Dissociation curves for hemoglobin at 37°C. 20 40 60 80 100 PO (mm Hg) 2 (b) pH and hemoglobin dissociation
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Oxyhemoglobin dissociation curve
What effect does exercise have on the curve? How do you think a fetus’ curve would look (shift left or shift right?).
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