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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What is Gas Exchange? Gas exchange -> supplies oxygen for cellular respiration.

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Presentation on theme: "Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What is Gas Exchange? Gas exchange -> supplies oxygen for cellular respiration."— Presentation transcript:

1 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What is Gas Exchange? Gas exchange -> supplies oxygen for cellular respiration -> disposes of carbon dioxide Gases diffuse down pressure gradients in the lungs and other organs b/c of differences in partial pressure. Ok… but what is Partial Pressure? Partial pressure -> the pressure exerted by a particular gas in a mixture of gases A gas diffuses from a region of higher partial pressure to a region of lower partial pressure In the lungs and tissues -> O2 and CO2 diffuse from areas of higher partial pressure to lower partial pressure

2 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Where does an organism’s O 2 come from? Respiratory Media Animals can use air or water as a source of O 2, or respiratory medium. In a given volume, there is less O 2 available in water than in air. So… Obtaining O 2 from water requires greater efficiency than air breathing.

3 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What are respiratory surfaces? Large, thin, moist tissue used for gas exchange Gases diffuse across respiratory surfaces

4 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How do cnidarians perform gas exchange? Cnidarians (i.e. jellies) -> gas exchange occurs in all cells -> no specific respiratory tissue

5 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What about annelids? Gas exchange performed through the skin Hemoglobin present in circulatory system

6 Gills -> outfoldings of the body that create a large surface area for gas exchange Parapodium (functions as gill) (a) Marine worm Gills (b) Crayfish (c) Sea star Tube foot Coelom Gills

7 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ventilation moves the respiratory medium (i.e. air or water) over the respiratory surface. Aquatic animals move through water or move water over their gills for ventilation. Fish gills -> countercurrent exchange -> is when blood flows in opposite direction to water passing over gills -> blood always has less O2 than the water moving over it

8 How do fish gills work? Anatomy of gills Gil l arch Water flow Operculum Gill arch Gill filament organization Blood vessels Oxygen-poor blood Oxygen-rich blood Fluid flow through gill filament Lamella Blood flow through capillaries in lamella Water flow between lamellae Countercurrent exchange P O 2 (mm Hg) in water P O 2 (mm Hg) in blood Net diffusion of O 2 from water to blood 150120906030 1108020 Gill filaments 50 140

9 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How do insects do gas exchange? Tracheal system -> tiny branching tubes that penetrate the body. Tracheal tubes supply O 2 directly to all body cells Also… Respiratory and circulatory systems are separate. Larger insects must ventilate their tracheal system to meet O 2 demands, i.e. in flight

10 Air sacs Tracheae = air tubes External opening: spiracles Body cell Air sac Tracheole TracheolesMitochondriaMuscle fiber 2.5 µm Body wall Trachea Air external openings spiracles

11 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The circulatory system (open or closed) transports gases between the lungs and the rest of the body. Lungs=infolding of body surface Size and complexity of lungs increases with organism’s metabolic rate. How do terrestrial vertebrates do gas exchange?

12 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How about mammals, specifically? System of branching ducts/air tubes conveys air to the lungs. Air inhaled through the nostrils --> pharynx - -> larynx --> trachea --> bronchi --> bronchioles --> alveoli = site of gas exchange. Alveoli -> sacs of thin epithelium wrapped in capillaries Exhaled air passes over the vocal cords to create sounds.

13 Human Respiratory System Pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm Heart SEM Left lung Nasal cavity Terminal bronchiole Branch of pulmonary vein (oxygen-rich blood) Branch of pulmonary artery (oxygen-poor blood) Alveoli Colorized SEM 50 µm

14 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How does breathing ventilate the lungs? Amphibians -> positive pressure breathing, ->forces air down the trachea. Mammals -> negative pressure breathing, ->pulls air into the lungs by varying volume/air pressure. Lung volume increases as the rib muscles and diaphragm contract. Tidal volume -> volume of air inhaled/breath Maximum tidal volume -> vital capacity. Residual volume -> volume of air that remains in the lungs after exhalation

15 Negative pressure breathing: H --> L Lung Diaphragm Air inhaled Rib cage expands as rib muscles contract Rib cage gets smaller as rib muscles relax Air exhaled EXHALATION Diaphragm relaxes (moves up) Volume decreases Pressure increases Air rushes out INHALATION Diaphragm contracts (moves down) Volume increases Pressure decreases Air rushes in

16 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How do birds breathe? Eight-nine air sacs function as bellows that keep air flowing through the lungs. Air passes through the lungs in one direction only. Also… Every exhalation completely renews the air in the lungs.

17 The Avian Respiratory System Anterior air sacs Posterior air sacs Lungs Air Lungs Air 1 mm Trachea Air tubes (parabronchi) in lung EXHALATION Air sacs empty; Lungs Fill INHALATION Air sacs fill

18 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How do humans control their breathing? Breathing control -> two regions of the brain, medulla oblongata & pons Medulla -> regulates the rate and depth of breathing in response to pH changes: CO 2 levels in the cerebrospinal fluid -> adjusts breathing rate and depth to match metabolic demands Pons -> regulates the tempo

19 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sensors in the aorta and carotid arteries monitor O 2 and CO 2 concentrations in the blood -> secondary control over breathing Also…

20 Automatic control of breathing Breathing control centers Cerebrospinal fluid Pons Medulla oblongata Carotid arteries Aorta Diaphragm Rib muscles

21 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How are gases transported in the circulatory system? In many organisms, blood must transport large amounts of O2 and CO2 Blood arriving in lungs -> low O2, high CO2 relative to air in alveoli In the alveoli -> O 2 diffuses into the blood and CO 2 diffuses into the air. In tissue capillaries -> partial pressure gradients favor diffusion of O 2 into the fluid around cells (interstitial fluid) and CO 2 into the blood.

22 Loading and unloading of respiratory gases Alveolus P O 2 = 100 mm Hg P O 2 = 40 P O 2 = 100 P O 2 = 40 Circulatory system Body tissue P O 2 ≤ 40 mm HgP CO 2 ≥ 46 mm Hg Body tissue P CO 2 = 46 P CO 2 = 40 P CO 2 = 46 Circulatory system P CO 2 = 40 mm Hg Alveolus (b) Carbon dioxide (a ) Oxygen

23 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings What are respiratory pigments? Respiratory pigments -> proteins that transport oxygen Greatly increase the amount of oxygen blood can carry Arthropods and many molluscs have hemocyanin -> copper = oxygen-binding component. Most vertebrates and some invertebrates use hemoglobin -> iron = oxygen-binding component contained within erythrocytes.

24 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How does hemoglobin work? 1 hemoglobin carries 4 O 2 Hemoglobin dissociation curve -> shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O 2 Bohr Shift -> CO 2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O 2

25  Chains Iron Heme  Chains Hemoglobin

26 Hemoglobin Dissociation Curves (37ºC) O 2 unloaded to tissues at rest O 2 unloaded to tissues during exercise 100 40 0 20 60 80 0 4080100 O 2 saturation of hemoglobin (%) 2060 Tissues during exercise Tissues at rest Lungs P O 2 (mm Hg) (a) P O 2 and hemoglobin dissociation at pH 7.4 O 2 saturation of hemoglobin (%) 40 0 20 60 80 0 40801002060 100 P O 2 (mm Hg) (b) pH and hemoglobin dissociation pH 7.4 pH 7.2 Hemoglobin retains less O 2 at lower pH (higher CO 2 concentration)

27 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How is carbon dioxide transported? Hemoglobin -> helps transport CO 2 -> assists in buffering CO 2 diffuses into the blood & is transported either in blood plasma, bound to hemoglobin, or as bicarbonate ions (HCO 3 –.)

28 Carbon dioxide transport in the blood Body tissue CO 2 produced CO 2 transport from tissues Capillary wall Interstitial fluid Plasma within capillary CO 2 Red blood cell H2OH2O H 2 CO 3 Hb Carbonic acid Hemoglobin picks up CO 2 and H + CO 2 transport to lungs HCO 3 – Bicarbonate H+H+ + Hemoglobin releases CO 2 and H + To lungs HCO 3 – Hb H+H+ + HCO 3 – H 2 CO 3 H2OH2O CO 2 Alveolar space in lung

29 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings How has gas exchange evolved? Evolutionary adaptations in gas exchange help animals do extraordinary things. Pronghorn Antelope -> runs extremely fast for long distances b/c of increased O2 consumption Deep-diving air breathers -> stockpile O 2 and deplete it slowly. Weddell seals -> high blood/ body volume ratio -> can store oxygen in their muscles in myoglobin proteins.

30 Summary Inhaled airExhaled air Alveolar epithelial cells Lungs - Alveolar Air Spaces GAS EXCHANGE CO 2 O2O2 O2O2 Alveolar capillaries of lung Pulmonary veins Pulmonary arteries Systemic veinsSystemic arteries Heart Systemic capillaries CO 2 O2O2 O2O2 Body tissue - GAS EXCHANGE

31 What is cystic fibrosis? Genetic disease -> autosomal recessive Faulty gene for a protein that pumps Na+ in lung cells Causes mucous buildup in respiratory tract Symptoms include: delayed growth, weight loss, fatigue, nausea, frequent pneumonia, coughing/sinus pressure due to mucous Diagnosed through blood test or sweat chloride test Currently no cure, average lifespan 37 years Treated through specialized diet, frequent exercise, clearing mucous multiple times daily

32 What is bronchitis? Inflammation of the bronchi -> main air tubules to lungs Can be acute, i.e. due to viral infection, or chronic Symptoms include: cough, chest pain, shortness of breath, fatigue Treatment -> acute goes away on its own in 1 week -> chronic doesn’t usually go away, but smoking cessation can help


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