1. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chapter 22 Gas Exchange

2. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Surviving in Thin Air The high mountains of the Himalayas –Have claimed the lives of even the world’s top mountain climbers The air at the height of the world’s highest peak, Mt. Everest –Is so low in oxygen that most people would pass out instantly if exposed to it

3. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Twice a year, flocks of geese migrate over the Himalayas –They are able to fly at such a high altitude because of the efficiency of their lungs –These birds have blood with hemoglobin with a very high affinity for oxygen –This adaptation allows them to carry large amounts of oxygen to their tissues to exchange with carbon dioxide

4. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The process of gas exchange, often called respiration –Is the interchange of O 2 and CO 2 between an organism and its environment

5. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.1 Overview: Gas exchange involves breathing, transport of gases, and exchange of gases with tissue cells The three phases of gas exchange MECHANISMS OF GAS EXCHANGE 1 Breathing O2O2 CO 2 Lung Circulatory system 2 Transport of gases by the circulatory system 3 Exchange of gases with body cells Capillary Cell CO 2 O2O2 Mitochondria Figure 22.1

6. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Gas exchange –Provides O 2 for cellular respiration and removes its waste product, CO 2

7. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.2 Animals exchange O 2 and CO 2 across moist body surfaces Respiratory surfaces –Must be thin and moist for diffusion of O 2 and CO 2 to occur

8. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Some animals, like the earthworm –Use their entire skin as a gas-exchange organ Cut Cross section of respiratory surface (the skin covering the body) Capillaries CO 2 O2O2 Figure 22.2A

9. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In most animals –Specialized body parts provide large respiratory surfaces for gas exchange Body surface Respiratory surface (gill) Capillary CO 2 O2O2 Body surface Respiratory surface (air tubes) Body cells (no capillaries) O2O2 CO 2 Body surface Respiratory surface (within lung) Capillary CO 2 O2O2 O2O2 Figure 22.2B Figure 22.2C Figure 22.2D

10. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.3 Gills are adapted for gas exchange in aquatic environments Gills are extensions of the body –That absorb O 2 dissolved in water

11. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In a fish, gas exchange –Is enhanced by ventilation and the countercurrent flow of water and blood Gill arch Direction of water flow Gill arch Blood vessels Gill filaments Oxygen-rich blood Oxygen-poor blood Lamella 15% 40% 70% 100% 60% 80% 30% 5% % O 2 in water flowing over lamellae % O 2 in blood flowing through capillaries in lamellae Countercurrent exchange Figure 22.3

12. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.4 The tracheal system of insects provides direct exchange between the air and body cells Land animals –Exchange gases by breathing air

13. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.5 Terrestrial vertebrates have lungs In mammals, air inhaled through the nostrils –Passes through the pharynx and larynx into the trachea, bronchi, and bronchioles (Heart) Diaphragm Bronchiole Bronchus Right lung Trachea Larynx (Esophagus) Pharynx Nasal cavity Left lung Figure 22.5A

14. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The bronchioles end in clusters of tiny sacs called alveoli –Where gas exchange occurs Colorized SEM 6,200  Oxygen-rich blood Bronchiole Oxygen-poor blood Alveoli Blood capillaries Figure 22.5B, C

15. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 22.6 Smoking is a deadly assaults on our respiratory system Mucus and cilia in the respiratory passages –Protect the lungs –Can be destroyed by smoking

16. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Smoking –Causes lung cancer, heart disease, and emphysema Lung Heart Figure 22.6

17. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.7 Breathing ventilates the lungs Breathing –Is the alternation of inhalation and exhalation

18. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The contraction of rib muscles and the diaphragm –Expands the chest cavity and reduces air pressure in the alveoli (negative pressure breathing) Rib cage expands as rib muscles contract Air inhaled Rib cage gets smaller as rib muscles relax Air exhaled Lung Diaphragm Diaphragm relaxes (moves up) Diaphragm contracts (moves down) Inhalation Exhalation Figure 22.7A

19. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Vital capacity is the maximum volume of air we can inhale and exhale –But our lungs still hold a residual volume

20. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.9 Breathing is automatically controlled Breathing control centers in the brain –Keep breathing in tune with body needs, sensing and responding to the CO 2 level in the blood Brain Cerebrospinal fluid Pons Medulla Nerve signals trigger contraction of muscles Breathing control centers stimulated by: CO 2 increase / pH decrease in blood Nerve signals indicating CO 2 and O 2 levels CO 2 and O 2 sensors in aorta Diaphragm Rib muscles Figure 22.8

21. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A drop in blood pH –Triggers an increase in the rate and depth of breathing

22. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings TRANSPORT OF GASES IN THE BODY 22.9 Blood transports respiratory gases The heart pumps oxygen-poor blood to the lungs –Where it picks up O 2 and drops off CO 2 Then the heart pumps the oxygen-rich blood to body cells –Where it drops off O 2 and picks up CO 2

23. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Gas transport and exchange in the body Exhaled air Inhaled air Air spaces Alveolar epithelial cells CO 2 O2O2 O2O2 CO 2 -rich, O 2 -poor blood O 2 -rich, CO 2 -poor blood Heart Tissue capillaries CO 2 O2O2 Interstitial fluid CO 2 O2O2 Tissue cells throughout body Alveolar capillaries of lung Figure 22.9

24. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Gases diffuse down partial-pressure gradients –In the lungs and the tissues

25. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.10 Hemoglobin carries O 2 and helps transport CO 2 and buffer the blood Hemoglobin in red blood cells –Transports oxygen, helps buffer the blood and carries some CO 2 Iron atom Heme group O 2 loaded in lungs O 2 unloaded in tissues Polypeptide chain Figure 22.10

26. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Most CO 2 in the blood –Is transported as bicarbonate ions in the plasma CO 2 + H2OH2OH 2 CO 3 H+H+ + HCO 3 – Carbon dioxide WaterCarbonic acid Hydrogen ions Bicarbonate

27. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 22.11 The human fetus exchanges gases with the mother’s bloodstream A human fetus –Exchanges gases with maternal blood in the placenta Placenta, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus Figure 22.11

28. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fetal hemoglobin –Enhances oxygen transfer from maternal blood At birth, increasing CO 2 in the fetal blood –Stimulates the breathing control centers to initiate breathing