1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 42 Circulation and Gas Exchange

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Every organism must exchange materials with its environment Exchanges ultimately occur at the cellular level In unicellular organisms, these exchanges occur directly with the environment A salmon’s feathery gills are an example of a specialized exchange system in animals Overview: Trading with the Environment

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.1: Circulatory systems reflect phylogeny Transport systems connect the organs of exchange with the body cells Most complex animals have internal transport systems that circulate fluid

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastrovascular Cavities Simple animals, such as cnidarians, have a body wall only two cells thick that encloses a gastrovascular cavity This cavity functions in both digestion and distribution of substances throughout the body Some cnidarians, such as jellies, have elaborate gastrovascular cavities

5. LE 42-2 Mouth Radial canal Circular canal 5 cm

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Open and Closed Circulatory Systems More complex animals have either open or closed circulatory systems Both systems have three basic components: – A circulatory fluid (blood or hemolymph) – A set of tubes (blood vessels) – A muscular pump (the heart)

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In insects, other arthropods, and most molluscs blood bathes the organs directly in an open circulatory system There is no distinction between blood and interstitial fluid, and this general body fluid is more correctly called hemolymph

8. LE 42-3 Hemolymph in sinuses surrounding organs Heart Anterior vessel Ostia Tubular heart An open circulatory system. Lateral vessel A closed circulatory system. Auxiliary hearts Ventral vessels Dorsal vessel (main heart) Small branch vessels in each organ Interstitial fluid Heart

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a closed circulatory system, blood is confined to vessels and is distinct from the interstitial fluid Closed systems are more efficient at transporting circulatory fluids to tissues and cells

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Survey of Vertebrate Circulation Humans and other vertebrates have a closed circulatory system, often called the cardiovascular system Blood flows in a closed cardiovascular system, consisting of blood vessels and a two- to four- chambered heart Arteries carry blood to capillaries, the sites of chemical exchange between the blood and interstitial fluid Veins return blood from capillaries to the heart

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fishes A fish heart has two main chambers: one ventricle and one atrium Blood pumped from the ventricle travels to the gills, where it picks up O 2 and disposes of CO 2

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amphibians Frogs and other amphibians have a three- chambered heart: two atria and one ventricle The ventricle pumps blood into a forked artery that splits the ventricle’s output into the pulmocutaneous circuit and the systemic circuit

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reptiles (Except Birds) Reptiles have double circulation, with a pulmonary circuit (lungs) and a systemic circuit Turtles, snakes, and lizards have a three- chambered heart

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mammals and Birds In all mammals and birds, the ventricle is divided into separate right and left chambers The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A powerful four-chambered heart was an essential adaptation of the endothermic way of life characteristic of mammals and birds

16. LE 42-4 FISHES Gill capillaries AMPHIBIANS Lung and skin capillaries REPTILES (EXCEPT BIRDS) Lung capillaries MAMMALS AND BIRDS Lung capillaries Gill circulation Heart: Ventricle (V) Atrium (A) Artery Vein Systemic circulation Systemic capillaries Systemic circuit Pulmocutaneous circuit Right Left A A V A V A V Systemic capillaries Right Left Pulmonary circuit Right systemic aorta V A V Systemic capillaries RightLeft Pulmonary circuit A Systemic circuit Left systemic aorta Systemic circuits include all body tissues except lungs. Note that circulatory systems are depicted as if the animal is facing you: with the right side of the heart shown at the left and vice-versa.

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.2: Double circulation in mammals depends on the anatomy and pumping cycle of the heart The human circulatory system serves as a model for exploring mammalian circulation

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mammalian Circulation: The Pathway Heart valves dictate a one-way flow of blood through the heart Blood begins its flow with the right ventricle pumping blood to the lungs In the lungs, the blood loads O 2 and unloads CO 2 Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle Blood returns to the heart through the right atrium

19. LE 42-5 Anterior vena cava Pulmonary artery Capillaries of right lung Aorta Pulmonary vein Right atrium Right ventricle Posterior vena cava Capillaries of abdominal organs and hind limbs Pulmonary vein Left ventricle Left atrium Aorta Pulmonary artery Capillaries of head and forelimbs Capillaries of left lung

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Mammalian Heart: A Closer Look A closer look at the mammalian heart provides a better understanding of double circulation

21. LE 42-6 Right atrium Posterior vena cava Pulmonary veins Anterior vena cava Pulmonary artery Pulmonary veins Right ventricle Aorta Semilunar valve Atrioventricular valve Pulmonary artery Left atrium Semilunar valve Atrioventricular valve Left ventricle

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.5: Gas exchange occurs across specialized respiratory surfaces Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide Animals require large, moist respiratory surfaces for adequate diffusion of gases between their cells and the respiratory medium, either air or water

23. LE 42-19 Respiratory medium (air or water) Organismal level Cellular level Energy-rich fuel molecules from food Respiratory surface Circulatory system Cellular respiration CO 2 O2O2 ATP

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gills in Aquatic Animals Gills are outfoldings of the body surface specialized for gas exchange

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In some invertebrates, gills have a simple shape and are distributed over much of the body

26. LE 42-20a Gills Coelom Tube foot Sea star

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many segmented worms have flaplike gills that extend from each segment of their body

28. LE 42-20b Gill Parapodia Marine worm

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The gills of clams, crayfish, and many other animals are restricted to a local body region

30. LE 42-20c Gills Scallop

31. LE 42-20d Gills Crayfish

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Effectiveness of gas exchange in some gills, including those of fishes, is increased by ventilation and the countercurrent flow of blood and water

33. LE 42-21 Gill arch Water flow Operculum Gill arch Blood vessel Oxygen-rich blood Water flow over lamellae showing % O 2 Gill filaments O2O2 Oxygen-poor blood Lamella 15% 40% 70% 100% 90% 60% 30% 5% Blood flow through capillaries in lamellae showing % O 2 Countercurrent exchange

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tracheal Systems in Insects The tracheal system of insects consists of tiny branching tubes that penetrate the body

35. LE 42-22a Air sacs Tracheae Spiracle

36. LE 42-22b Body cell Tracheole Air sac Trachea Air Body wall MyofibrilsTracheoles Mitochondria 2.5 µm

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The tracheal tubes supply O 2 directly to body cells

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lungs Spiders, land snails, and most terrestrial vertebrates have internal lungs

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mammalian Respiratory Systems: A Closer Look A system of branching ducts conveys air to the lungs Air inhaled through the nostrils passes through the pharynx into the trachea, bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs

40. LE 42-23 Branch from pulmonary vein (oxygen-rich blood) Terminal bronchiole Branch from pulmonary artery (oxygen-poor blood) Alveoli 50 µm Colorized SEM SEM Nasal cavity 50 µm Left lung Heart Larynx Pharynx Esophagus Trachea Right lung Bronchus Bronchiole Diaphragm

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.6: Breathing ventilates the lungs The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How an Amphibian Breathes An amphibian such as a frog ventilates its lungs by positive pressure breathing, which forces air down the trachea

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How a Mammal Breathes Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs Lung volume increases as the rib muscles and diaphragm contract

44. LE 42-24 Rib cage expands as rib muscles contract Air inhaled Lung Diaphragm INHALATION Diaphragm contracts (moves down) Rib cage gets smaller as rib muscles relax Air exhaled EXHALATION Diaphragm relaxes (moves up)

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How a Bird Breathes Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs Air passes through the lungs in one direction only Every exhalation completely renews the air in the lungs

46. LE 42-25 Anterior air sacs Lungs Posterior air sacs Trachea Air Lungs Air Air tubes (parabronchi) in lung 1 mm EXHALATION Air sacs empty; lungs fill INHALATION Air sacs fill

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Control of Breathing in Humans In humans, the main breathing control centers are in two regions of the brain, the medulla oblongata and the pons The medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid The medulla adjusts breathing rate and depth to match metabolic demands

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sensors in the aorta and carotid arteries monitor O 2 and CO 2 concentrations in the blood These sensors exert secondary control over breathing

49. LE 42-26 Breathing control centers Cerebrospinal fluid Medulla oblongata Pons Carotid arteries Aorta Diaphragm Rib muscles

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.7: Respiratory pigments bind and transport gases The metabolic demands of many organisms require that the blood transport large quantities of O 2 and CO 2

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Role of Partial Pressure Gradients Gases diffuse down pressure gradients in the lungs and other organs Diffusion of a gas depends on differences in a quantity called partial pressure

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A gas diffuses from a region of higher partial pressure to a region of lower partial pressure In the lungs and tissues, O 2 and CO 2 diffuse from where their partial pressures are higher to where they are lower

53. LE 42-27 Inhaled air Blood entering alveolar capillaries Alveolar epithelial cells Alveolar spaces Alveolar capillaries of lung Exhaled air Blood leaving alveolar capillaries Pulmonary veins Pulmonary arteries Tissue capillaries Heart Systemic veins Systemic arteries Blood leaving tissue capillaries Blood entering tissue capillaries Tissue cells CO 2 O2O2 O2O2 O2O2 O2O2 < 40> 45 4045 CO 2 O2O2 10040 CO 2 O2O2 O2O2 4045 CO 2 O2O2 10440 O2O2 CO 2 O2O2 O2O2 O2O2 10440 12027 1600.2

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Respiratory Pigments Respiratory pigments, proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxygen Transport The respiratory pigment of almost all vertebrates is the protein hemoglobin, contained in erythrocytes Like all respiratory pigments, hemoglobin must reversibly bind O 2, loading O 2 in the lungs and unloading it in other parts of the body

56. LE 42-28 Polypeptide chain O 2 unloaded in tissues O 2 loaded in lungs Iron atomHeme group

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Loading and unloading of O 2 depend on cooperation between the subunits of the hemoglobin molecule The binding of O 2 to one subunit induces the other subunits to bind O 2 with more affinity Cooperative O 2 binding and release is evident in the dissociation curve for hemoglobin A drop in pH lowers affinity of hemoglobin for O 2

58. LE 42-29a O 2 unloaded from hemoglobin during normal metabolism O 2 reserve that can be unloaded from hemoglobin to tissues with high metabolism P and hemoglobin dissociation at 37°C and pH 7.4 O2O2 P (mm Hg) O2O2 Tissues during exercise Tissues at rest Lungs 10080 6040200 0 40 60 80 100 O 2 saturation of hemoglobin (%)

59. LE 42-29b Bohr shift: additional O 2 released from hemoglobin at lower pH (higher CO 2 concentration) pH and hemoglobin dissociation P (mm Hg) O2O2 10080 6040200 0 40 60 80 100 O 2 saturation of hemoglobin (%) pH 7.2 pH 7.4

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carbon Dioxide Transport Hemoglobin also helps transport CO 2 and assists in buffering Carbon from respiring cells diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs

61. LE 42-30 CO 2 transport from tissues CO 2 produced Tissue cell CO 2 Interstitial fluid Blood plasma within capillary Capillary wall Hemoglobin picks up CO 2 and H + CO 2 transport to lungs To lungs H 2 CO 3 Carbonic acid H2OH2O Hb HCO 3 – Bicarbonate Red blood cell H+H+ + HCO 3 – Hemoglobin releases CO 2 and H + H+H+ + HCO 3 – CO 2 H 2 CO 3 H2OH2O CO 2 Hb Alveolar space in lung