1. Chapter 34 Circulation and Gas Exchange

2. Overview: Trading Places Every organism must exchange materials with its environment Exchanges ultimately occur at the cellular level by crossing the plasma membrane In unicellular organisms, these exchanges occur directly with the environment © 2011 Pearson Education, Inc.

3. For most cells making up multicellular organisms, direct exchange with the environment is not possible Gills are an example of a specialized exchange system in animals –O 2 diffuses from the water into blood vessels –CO 2 diffuses from blood into the water Internal transport and gas exchange are functionally related in most animals © 2011 Pearson Education, Inc.

4. Figure 42.1

5. Circulatory systems link exchange surfaces with cells throughout the body Diffusion time is proportional to the square of the distance Diffusion is only efficient over small distances In small and/or thin animals, cells can exchange materials directly with the surrounding medium In most animals, cells exchange materials with the environment via a fluid-filled circulatory system © 2011 Pearson Education, Inc.

6. Gastrovascular Cavities Some animals lack a circulatory system Some cnidarians, such as jellies, have elaborate gastrovascular cavities A gastrovascular cavity functions in both digestion and distribution of substances throughout the body The body wall that encloses the gastrovascular cavity is only two cells thick Flatworms have a gastrovascular cavity and a large surface area to volume ratio © 2011 Pearson Education, Inc.

7. Figure 42.2 Circular canal Mouth Radial canals 5 cm (a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm Gastrovascular cavity Mouth Pharynx 2 mm

8. Figure 42.2a Circular canal Mouth Radial canals 5 cm (a) The moon jelly Aurelia, a cnidarian

9. Figure 42.2b (b) The planarian Dugesia, a flatworm Gastrovascular cavity Mouth Pharynx 2 mm

10. Evolutionary Variation in Circulatory Systems A circulatory system minimizes the diffusion distance in animals with many cell layers © 2011 Pearson Education, Inc.

11. General Properties of Circulatory Systems A circulatory system has –A circulatory fluid –A set of interconnecting vessels –A muscular pump, the heart The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes Circulatory systems can be open or closed and vary in the number of circuits in the body © 2011 Pearson Education, Inc.

12. Open and Closed Circulatory Systems In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system In an open circulatory system, there is no distinction between blood and interstitial fluid, and this general body fluid is called hemolymph © 2011 Pearson Education, Inc.

13. Figure 42.3 (a) An open circulatory system Heart Hemolymph in sinuses surrounding organs Pores Tubular heart Dorsal vessel (main heart) Auxiliary hearts Small branch vessels in each organ Ventral vessels Blood Interstitial fluid Heart (b) A closed circulatory system

14. Figure 42.3a (a) An open circulatory system Heart Hemolymph in sinuses surrounding organs Pores Tubular heart

15. 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 Annelids, cephalopods, and vertebrates have closed circulatory systems © 2011 Pearson Education, Inc.

16. Figure 42.3b (b) A closed circulatory system Dorsal vessel (main heart) Auxiliary hearts Small branch vessels in each organ Ventral vessels Blood Interstitial fluid Heart

17. Organization of Vertebrate Circulatory Systems Humans and other vertebrates have a closed circulatory system called the cardiovascular system The three main types of blood vessels are arteries, veins, and capillaries Blood flow is one way in these vessels © 2011 Pearson Education, Inc.

18. Arteries branch into arterioles and carry blood away from the heart to capillaries Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid Venules converge into veins and return blood from capillaries to the heart © 2011 Pearson Education, Inc.

19. Arteries and veins are distinguished by the direction of blood flow, not by O 2 content Vertebrate hearts contain two or more chambers Blood enters through an atrium and is pumped out through a ventricle © 2011 Pearson Education, Inc.

20. Single Circulation Bony fishes, rays, and sharks have single circulation with a two-chambered heart In single circulation, blood leaving the heart passes through two capillary beds before returning © 2011 Pearson Education, Inc.

21. Figure 42.4 (a) Single circulation (b) Double circulation Artery Heart: Atrium (A) Ventricle (V) Vein Gill capillaries Body capillaries Key Oxygen-rich blood Oxygen-poor blood Systemic circuit Systemic capillaries RightLeft AA VV Lung capillaries Pulmonary circuit

22. Figure 42.4a (a) Single circulation Artery Heart: Atrium (A) Ventricle (V) Vein Gill capillaries Body capillaries Key Oxygen-rich blood Oxygen-poor blood

23. Double Circulation Amphibian, reptiles, and mammals have double circulation Oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart © 2011 Pearson Education, Inc.

24. Figure 42.4b (b) Double circulation Systemic circuit Systemic capillaries RightLeft A A VV Lung capillaries Pulmonary circuit Key Oxygen-rich blood Oxygen-poor blood

25. In reptiles and mammals, oxygen-poor blood flows through the pulmonary circuit to pick up oxygen through the lungs In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin Oxygen-rich blood delivers oxygen through the systemic circuit Double circulation maintains higher blood pressure in the organs than does single circulation © 2011 Pearson Education, Inc.

26. Adaptations of Double Circulatory Systems Hearts vary in different vertebrate groups © 2011 Pearson Education, Inc.

27. 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 When underwater, blood flow to the lungs is nearly shut off © 2011 Pearson Education, Inc.

28. Amphibians Pulmocutaneous circuit Lung and skin capillaries Atrium (A) Atrium (A) LeftRight Ventricle (V) Systemic capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood Figure 42.5a

29. Reptiles (Except Birds) Turtles, snakes, and lizards have a three- chambered heart: two atria and one ventricle In alligators, caimans, and other crocodilians a septum divides the ventricle Reptiles have double circulation, with a pulmonary circuit (lungs) and a systemic circuit © 2011 Pearson Education, Inc.

30. Figure 42.5b Reptiles (Except Birds) Pulmonary circuit Systemic circuit Systemic capillaries Incomplete septum Left systemic aorta Left Right systemic aorta A V Lung capillaries Atrium (A) Ventricle (V) Key Oxygen-rich blood Oxygen-poor blood

31. Mammals and Birds Mammals and birds have a four-chambered heart with two atria and two ventricles The left side of the heart pumps and receives only oxygen-rich blood, while the right side receives and pumps only oxygen-poor blood Mammals and birds are endotherms and require more O 2 than ectotherms © 2011 Pearson Education, Inc.

32. Systemic circuit Lung capillaries Pulmonary circuit A V Left Right Systemic capillaries Mammals and Birds Atrium (A) Ventricle (V) Key Oxygen-rich blood Oxygen-poor blood Figure 42.5c

33. Figure 42.5 AmphibiansReptiles (Except Birds) Pulmocutaneous circuit Pulmonary circuit Lung and skin capillaries Atrium (A) Atrium (A) LeftRight Ventricle (V) Systemic capillaries Systemic circuit Systemic capillaries Incomplete septum Incomplete septum Left systemic aorta LeftRight systemic aorta A A VV Lung capillaries Lung capillaries Pulmonary circuit AA V V Left Right Systemic capillaries Key Oxygen-rich blood Oxygen-poor blood Mammals and Birds

34. Coordinated cycles of heart contraction drive double circulation in mammals The mammalian cardiovascular system meets the body’s continuous demand for O 2 © 2011 Pearson Education, Inc.

35. Mammalian Circulation 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 through the aorta to the body tissues by the left ventricle The aorta provides blood to the heart through the coronary arteries © 2011 Pearson Education, Inc.

36. Blood returns to the heart through the superior vena cava (blood from head, neck, and forelimbs) and inferior vena cava (blood from trunk and hind limbs) The superior vena cava and inferior vena cava flow into the right atrium © 2011 Pearson Education, Inc.

37. Superior vena cava Pulmonary artery Capillaries of right lung Pulmonary vein Aorta Inferior vena cava Right ventricle Capillaries of abdominal organs and hind limbs Right atrium Aorta Left ventricle Left atrium Pulmonary vein Pulmonary artery Capillaries of left lung Capillaries of head and forelimbs Figure 42.6

38. The Mammalian Heart: A Closer Look A closer look at the mammalian heart provides a better understanding of double circulation © 2011 Pearson Education, Inc.

39. Figure 42.7 Pulmonary artery Right atrium Semilunar valve Atrioventricular valve Right ventricle Left ventricle Atrioventricular valve Semilunar valve Left atrium Pulmonary artery Aorta

40. The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle The contraction, or pumping, phase is called systole The relaxation, or filling, phase is called diastole © 2011 Pearson Education, Inc.

41. Figure 42.8-1 Atrial and ventricular diastole 0.4 sec 1

42. Figure 42.8-2 Atrial and ventricular diastole Atrial systole and ventricular diastole 0.1 sec 0.4 sec 2 1

43. Figure 42.8-3 Atrial and ventricular diastole Atrial systole and ventricular diastole Ventricular systole and atrial diastole 0.1 sec 0.4 sec 0.3 sec 2 1 3

44. The heart rate, also called the pulse, is the number of beats per minute The stroke volume is the amount of blood pumped in a single contraction The cardiac output is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume © 2011 Pearson Education, Inc.

45. Four valves prevent backflow of blood in the heart The atrioventricular (AV) valves separate each atrium and ventricle The semilunar valves control blood flow to the aorta and the pulmonary artery © 2011 Pearson Education, Inc.

46. The “lub-dup” sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves Backflow of blood through a defective valve causes a heart murmur © 2011 Pearson Education, Inc.

47. Maintaining the Heart’s Rhythmic Beat Some cardiac muscle cells are self-excitable, meaning they contract without any signal from the nervous system The sinoatrial (SA) node, or pacemaker, sets the rate and timing at which cardiac muscle cells contract Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG) © 2011 Pearson Education, Inc.

48. Figure 42.9-1 SA node (pacemaker) ECG 1

49. Figure 42.9-2 SA node (pacemaker) AV node ECG 12

50. Figure 42.9-3 SA node (pacemaker) AV node Bundle branches Heart apex ECG 123

51. Figure 42.9-4 SA node (pacemaker) AV node Bundle branches Heart apex Purkinje fibers ECG 1234

52. Impulses from the SA node travel to the atrioventricular (AV) node At the AV node, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract © 2011 Pearson Education, Inc.

53. The pacemaker is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisions The sympathetic division speeds up the pacemaker The parasympathetic division slows down the pacemaker The pacemaker is also regulated by hormones and temperature © 2011 Pearson Education, Inc.

54. Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels The physical principles that govern movement of water in plumbing systems also influence the functioning of animal circulatory systems © 2011 Pearson Education, Inc.

55. Blood Vessel Structure and Function A vessel’s cavity is called the central lumen The epithelial layer that lines blood vessels is called the endothelium The endothelium is smooth and minimizes resistance © 2011 Pearson Education, Inc.

56. Figure 42.10 Artery Red blood cells Endothelium Artery Smooth muscle Connective tissue Capillary Valve Vein Basal lamina Endothelium Smooth muscle Connective tissue 100  m LM Venule 15  m LM Arteriole Red blood cell Capillary

57. Figure 42.10a Endothelium Artery Smooth muscle Connective tissue Capillary Valve Vein Basal lamina Endothelium Smooth muscle Connective tissue Venule Arteriole

58. Figure 42.10b Artery Red blood cells Vein 100  m LM

59. Figure 42.10c 15  m LM Red blood cell Capillary

60. Capillaries have thin walls, the endothelium plus its basal lamina, to facilitate the exchange of materials Arteries and veins have an endothelium, smooth muscle, and connective tissue Arteries have thicker walls than veins to accommodate the high pressure of blood pumped from the heart In the thinner-walled veins, blood flows back to the heart mainly as a result of muscle action © 2011 Pearson Education, Inc.

61. Blood Flow Velocity Physical laws governing movement of fluids through pipes affect blood flow and blood pressure Velocity of blood flow is slowest in the capillary beds, as a result of the high resistance and large total cross-sectional area Blood flow in capillaries is necessarily slow for exchange of materials © 2011 Pearson Education, Inc.

62. Figure 42.11 Aorta Arteries Arterioles Capillaries Venules Veins Venae cavae Systolic pressure Diastolic pressure 0 20 40 60 80 100 120 0 10 20 30 40 50 Pressure (mm Hg) Velocity (cm/sec) Area (cm 2 ) 0 1,000 2,000 3,000 4,000 5,000

63. Blood Pressure Blood flows from areas of higher pressure to areas of lower pressure Blood pressure is the pressure that blood exerts against the wall of a vessel In rigid vessels blood pressure is maintained; less rigid vessels deform and blood pressure is lost © 2011 Pearson Education, Inc.

64. Changes in Blood Pressure During the Cardiac Cycle Systolic pressure is the pressure in the arteries during ventricular systole; it is the highest pressure in the arteries Diastolic pressure is the pressure in the arteries during diastole; it is lower than systolic pressure A pulse is the rhythmic bulging of artery walls with each heartbeat © 2011 Pearson Education, Inc.

65. Regulation of Blood Pressure Blood pressure is determined by cardiac output and peripheral resistance due to constriction of arterioles Vasoconstriction is the contraction of smooth muscle in arteriole walls; it increases blood pressure Vasodilation is the relaxation of smooth muscles in the arterioles; it causes blood pressure to fall © 2011 Pearson Education, Inc.

66. Vasoconstriction and vasodilation help maintain adequate blood flow as the body’s demands change Nitric oxide is a major inducer of vasodilation The peptide endothelin is an important inducer of vasoconstriction © 2011 Pearson Education, Inc.

67. Blood Pressure and Gravity Blood pressure is generally measured for an artery in the arm at the same height as the heart Blood pressure for a healthy 20-year-old at rest is 120 mm Hg at systole and 70 mm Hg at diastole © 2011 Pearson Education, Inc.

68. Blood pressure reading: 120/70 120 70 Sounds stop Sounds audible in stethoscope 120 Artery closed 1 2 3 Figure 42.12

69. Fainting is caused by inadequate blood flow to the head Animals with longer necks require a higher systolic pressure to pump blood a greater distance against gravity Blood is moved through veins by smooth muscle contraction, skeletal muscle contraction, and expansion of the vena cava with inhalation One-way valves in veins prevent backflow of blood © 2011 Pearson Education, Inc.

70. Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed) Figure 42.13

71. Capillary Function Blood flows through only 5  10% of the body’s capillaries at a time Capillaries in major organs are usually filled to capacity Blood supply varies in many other sites © 2011 Pearson Education, Inc.

72. Two mechanisms regulate distribution of blood in capillary beds –Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel –Precapillary sphincters control flow of blood between arterioles and venules Blood flow is regulated by nerve impulses, hormones, and other chemicals © 2011 Pearson Education, Inc.

73. Figure 42.14 Precapillary sphincters Thoroughfare channel Arteriole Capillaries Venule (a) Sphincters relaxed ArterioleVenule (b) Sphincters contracted

74. The exchange of substances between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries The difference between blood pressure and osmotic pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end Most blood proteins and all blood cells are too large to pass through the endothelium © 2011 Pearson Education, Inc.

75. Figure 42.15 INTERSTITIAL FLUID Net fluid movement out Blood pressure Osmotic pressure Arterial end of capillary Direction of blood flow Venous end of capillary Body cell

76. Fluid Return by the Lymphatic System The lymphatic system returns fluid that leaks out from the capillary beds Fluid, called lymph, reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system The lymphatic system drains into veins in the neck Valves in lymph vessels prevent the backflow of fluid © 2011 Pearson Education, Inc.

77. Lymph nodes are organs that filter lymph and play an important role in the body’s defense Edema is swelling caused by disruptions in the flow of lymph © 2011 Pearson Education, Inc.

78. Figure 42.16

79. Blood components contribute to exchange, transport, and defense With open circulation, the fluid that is pumped comes into direct contact with all cells The closed circulatory systems of vertebrates contain blood, a specialized connective tissue © 2011 Pearson Education, Inc.

80. Blood Composition and Function Blood consists of several kinds of cells suspended in a liquid matrix called plasma The cellular elements occupy about 45% of the volume of blood © 2011 Pearson Education, Inc.

81. Figure 42.17 Plasma 55% ConstituentMajor functions Water Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Solvent for carrying other substances Osmotic balance, pH buffering, and regulation of membrane permeability Plasma proteins Osmotic balance, pH buffering Albumin Fibrinogen Immunoglobulins (antibodies) Clotting Defense Substances transported by blood Nutrients Waste products Respiratory gases Hormones Separated blood elements Basophils Neutrophils Monocytes Lymphocytes Eosinophils Platelets Erythrocytes (red blood cells) 5–6 million 250,000–400,000Blood clotting Transport of O 2 and some CO 2 Defense and immunity Functions Number per  L (mm 3 ) of blood Cell type Cellular elements 45% Leukocytes (white blood cells)5,000–10,000

82. Plasma 55% ConstituentMajor functions Water Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Solvent for carrying other substances Osmotic balance, pH buffering, and regulation of membrane permeablity Plasma proteins Osmotic balance, pH bufferingAlbumin Fibrinogen Immunoglobulins (antibodies) Clotting Defense Substances transported by blood Nutrients Waste products Separated blood elements Respiratory gases Hormones Figure 42.17a

83. Separated blood elements Basophils Neutrophils Monocytes Lymphocytes Eosinophils Platelets Erythrocytes (red blood cells) 5–6 million 250,000–400,000Blood clotting Transport of O 2 and some CO 2 Defense and immunity Functions Number per  L (mm 3 ) of blood Cell type Cellular elements 45% Leukocytes (white blood cells)5,000–10,000 Figure 42.17b

84. Plasma Blood plasma is about 90% water Among its solutes are inorganic salts in the form of dissolved ions, sometimes called electrolytes Another important class of solutes is the plasma proteins, which influence blood pH, osmotic pressure, and viscosity Various plasma proteins function in lipid transport, immunity, and blood clotting © 2011 Pearson Education, Inc.

85. Cellular Elements Suspended in blood plasma are two types of cells –Red blood cells (erythrocytes) transport oxygen O 2 –White blood cells (leukocytes) function in defense Platelets, a third cellular element, are fragments of cells that are involved in clotting © 2011 Pearson Education, Inc.

86. Red blood cells, or erythrocytes, are by far the most numerous blood cells They contain hemoglobin, the iron-containing protein that transports O 2 Each molecule of hemoglobin binds up to four molecules of O 2 In mammals, mature erythrocytes lack nuclei and mitochondria Erythrocytes © 2011 Pearson Education, Inc.

87. Sickle-cell disease is caused by abnormal hemoglobin proteins that form aggregates The aggregates can deform an erythrocyte into a sickle shape Sickled cells can rupture or block blood vessels © 2011 Pearson Education, Inc.

88. Leukocytes There are five major types of white blood cells, or leukocytes: monocytes, neutrophils, basophils, eosinophils, and lymphocytes They function in defense by phagocytizing bacteria and debris or by producing antibodies They are found both in and outside of the circulatory system © 2011 Pearson Education, Inc.

89. Platelets Platelets are fragments of cells and function in blood clotting © 2011 Pearson Education, Inc.

90. Blood Clotting Coagulation is the formation of a solid clot from liquid blood A cascade of complex reactions converts inactive fibrinogen to fibrin, forming a clot A blood clot formed within a blood vessel is called a thrombus and can block blood flow © 2011 Pearson Education, Inc.

91. Figure 42.18 Collagen fibers 1 23 Platelet plug Fibrin clot Fibrin clot formation Red blood cell 5  m Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Enzymatic cascade ProthrombinThrombin FibrinogenFibrin 

92. Collagen fibers 1 Platelet plug Fibrin clot Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Enzymatic cascade ProthrombinThrombin FibrinogenFibrin  Fibrin clot formation 2 3 Figure 42.18a

93. Figure 42.18b Fibrin clot Red blood cell 5  m

94. Stem Cells and the Replacement of Cellular Elements The cellular elements of blood wear out and are being replaced constantly Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones, especially ribs, vertebrae, sternum, and pelvis The hormone erythropoietin (EPO) stimulates erythrocyte production when O 2 delivery is low © 2011 Pearson Education, Inc.

95. Stem cells (in bone marrow) Myeloid stem cells Lymphoid stem cells B cellsT cells Lymphocytes Erythrocytes Neutrophils Basophils Eosinophils Platelets Monocytes Figure 42.19

96. Cardiovascular Disease Cardiovascular diseases are disorders of the heart and the blood vessels Cardiovascular diseases account for more than half the deaths in the United States Cholesterol, a steroid, helps maintain membrane fluidity © 2011 Pearson Education, Inc.

97. Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production High-density lipoprotein (HDL) scavenges cholesterol for return to the liver Risk for heart disease increases with a high LDL to HDL ratio Inflammation is also a factor in cardiovascular disease © 2011 Pearson Education, Inc.

98. Atherosclerosis, Heart Attacks, and Stroke One type of cardiovascular disease, atherosclerosis, is caused by the buildup of plaque deposits within arteries © 2011 Pearson Education, Inc.

99. Lumen of artery Smooth muscle Endothelium Plaque Smooth muscle cell T lymphocyte Extra- cellular matrix Foam cell Macrophage Plaque rupture LDL Cholesterol Fibrous cap 12 4 3 Figure 42.20

100. A heart attack, or myocardial infarction, is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries Coronary arteries supply oxygen-rich blood to the heart muscle A stroke is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head Angina pectoris is caused by partial blockage of the coronary arteries and results in chest pains © 2011 Pearson Education, Inc.

101. Risk Factors and Treatment of Cardiovascular Disease A high LDL to HDL ratio increases the risk of cardiovascular disease The proportion of LDL relative to HDL can be decreased by exercise, not smoking, and avoiding foods with trans fats Drugs called statins reduce LDL levels and risk of heart attacks © 2011 Pearson Education, Inc.

102. Figure 42.21 Individuals with two functional copies of PCSK9 gene (control group) Plasma LDL cholesterol (mg/dL) Individuals with an inactivating mutation in one copy of PCSK9 gene Plasma LDL cholesterol (mg/dL) Average  63 mg/dL Average  105 mg/dL 30 20 10 0 0501001502002503000 0 10 20 30 50100150200250300 Percent of individuals RESULTS Percent of individuals

103. Inflammation plays a role in atherosclerosis and thrombus formation Aspirin inhibits inflammation and reduces the risk of heart attacks and stroke Hypertension, or high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke Hypertension can be reduced by dietary changes, exercise, and/or medication © 2011 Pearson Education, Inc.

104. Gas exchange occurs across specialized respiratory surfaces Gas exchange supplies O 2 for cellular respiration and disposes of CO 2 © 2011 Pearson Education, Inc.

105. 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.

106. 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 Obtaining O 2 from water requires greater efficiency than air breathing © 2011 Pearson Education, Inc.

107. 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.

108. Gills in Aquatic Animals Gills are outfoldings of the body that create a large surface area for gas exchange © 2011 Pearson Education, Inc.

109. Figure 42.22 Parapodium (functions as gill) (a) Marine worm (b) Crayfish Gills Tube foot (c) Sea star Coelom

110. Figure 42.22a Parapodium (functions as gill) (a) Marine worm

111. Figure 42.22b (b) Crayfish Gills

112. Figure 42.22c Gills Tube foot (c) Sea star Coelom

113. 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 O 2 than the water it meets © 2011 Pearson Education, Inc.

114. Figure 42.23 Gill arch O 2 -poor blood O 2 -rich blood Blood vessels Gill arch Operculum Water flow Water flow Blood flow Countercurrent exchange P O (mm Hg) in water 2 150 P O (mm Hg) in blood 2 120906030 140110805020 Net diffu- sion of O 2 Lamella Gill filaments

115. Gill arch Operculum Water flow Blood vessels Gill arch Gill filaments Figure 42.23a

116. O 2 -poor blood Water flow Blood flow Countercurrent exchange P O (mm Hg) in water 2 150 P O (mm Hg) in blood 2 140 Net diffu- sion of O 2 Lamella O 2 -rich blood 120906030 110805020 Figure 42.23b

117. Tracheal Systems in Insects The tracheal system of insects consists of tiny branching tubes that penetrate the body The tracheal tubes supply O 2 directly to body cells The respiratory and circulatory systems are separate Larger insects must ventilate their tracheal system to meet O 2 demands © 2011 Pearson Education, Inc.

118. Tracheoles Mitochondria Muscle fiber 2.5  m Tracheae Air sacs External opening Trachea Air sac Tracheole Body cell Air Figure 42.24

119. Figure 42.24a TracheolesMitochondria Muscle fiber 2.5  m

120. Lungs Lungs are an infolding of the body surface The circulatory system (open or closed) transports gases between the lungs and the rest of the body The size and complexity of lungs correlate with an animal’s metabolic rate © 2011 Pearson Education, Inc.

121. 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.

122. Figure 42.25 Pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Capillaries Left lung Dense capillary bed enveloping alveoli (SEM) 50  m Alveoli Branch of pulmonary artery (oxygen-poor blood) Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity

123. Pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Left lung Nasal cavity Figure 42.25a

124. Capillaries Alveoli Branch of pulmonary artery (oxygen-poor blood) Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Figure 42.25b

125. Figure 42.25c Dense capillary bed enveloping alveoli (SEM) 50  m

126. 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 This “mucus escalator” cleans the respiratory system and allows particles to be swallowed into the esophagus © 2011 Pearson Education, Inc.

127. 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.

128. Alveoli lack cilia and are susceptible to contamination Secretions called surfactants coat the surface of the alveoli Preterm babies lack surfactant and are vulnerable to respiratory distress syndrome; treatment is provided by artificial surfactants © 2011 Pearson Education, Inc.

129. RDS deaths Deaths from other causes RESULTS 40 30 20 10 0 08001,6002,4003,2004,000 Body mass of infant (g) Surface tension (dynes/cm) Figure 42.26

130. Breathing ventilates the lungs The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air © 2011 Pearson Education, Inc.

131. How an Amphibian Breathes An amphibian such as a frog ventilates its lungs by positive pressure breathing, which forces air down the trachea © 2011 Pearson Education, Inc.

132. 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 © 2011 Pearson Education, Inc.

133. Anterior air sacs Posterior air sacs Lungs 1 mm Airflow Air tubes (parabronchi) in lung Anterior air sacs Lungs Second inhalation First inhalation Posterior air sacs 3 2 4 1 4 3 1 2 Second exhalation First exhalation Figure 42.27

134. Figure 42.27a 1 mm Airflow Air tubes (parabronchi) in lung

135. 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 The tidal volume is the volume of air inhaled with each breath © 2011 Pearson Education, Inc.

136. Figure 42.28 Rib cage expands. Air inhaled. Air exhaled. Rib cage gets smaller. 12 Lung Diaphragm

137. The maximum tidal volume is the vital capacity After exhalation, a residual volume of air remains in the lungs © 2011 Pearson Education, Inc.

138. 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 The pons regulates the tempo © 2011 Pearson Education, Inc.

139. Sensors in the aorta and carotid arteries monitor O 2 and CO 2 concentrations in the blood These sensors exert secondary control over breathing © 2011 Pearson Education, Inc.

140. Homeostasis: Blood pH of about 7.4 CO 2 level decreases. Stimulus: Rising level of CO 2 in tissues lowers blood pH. Response: Rib muscles and diaphragm increase rate and depth of ventilation. Carotid arteries Aorta Sensor/control center: Cerebrospinal fluid Medulla oblongata Figure 42.29

141. Adaptations for gas exchange include pigments that bind and transport gases The metabolic demands of many organisms require that the blood transport large quantities of O 2 and CO 2 © 2011 Pearson Education, Inc.

142. Coordination of Circulation and Gas Exchange Blood arriving in the lungs has a low partial pressure of O 2 and a high partial pressure of CO 2 relative to air in the 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 interstitial fluids and CO 2 into the blood © 2011 Pearson Education, Inc.

143. Exhaled air Inhaled air Pulmonary arteries Systemic veins Systemic arteries Pulmonary veins Alveolar capillaries Alveolar spaces Alveolar epithelial cells Inhaled air 160 120 80 40 0 Heart 81 2 3 4 6 7 CO 2 O2O2 Systemic capillaries CO 2 O2O2 Body tissue5 (a) The path of respiratory gases in the circulatory system (b) Partial pressure of O 2 and CO 2 at different points in the circulatory system numbered in (a) 4321567 Exhaled air Partial pressure (mm Hg) POPO 2 P CO 2 8 Figure 42.30

144. Figure 42.30a Exhaled air Inhaled air Pulmonary arteries Systemic veins Systemic arteries Pulmonary veins Alveolar capillaries Alveolar spaces Alveolar epithelial cells Heart Systemic capillaries CO 2 O2O2 Body tissue (a) The path of respiratory gases in the circulatory system CO 2 O2O2 8 1 2 3 7 64 5

145. Inhaled air 160 (b) Partial pressure of O 2 and CO 2 at different points in the circulatory system numbered in (a) 1 Exhaled air Partial pressure (mm Hg) POPO 2 120 80 40 0 2345678 P CO 2 Figure 42.30b

146. Respiratory Pigments Respiratory pigments, proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry Arthropods and many molluscs have hemocyanin with copper as the oxygen-binding component Most vertebrates and some invertebrates use hemoglobin In vertebrates, hemoglobin is contained within erythrocytes © 2011 Pearson Education, Inc.

147. Hemoglobin A single hemoglobin molecule can carry four molecules of O 2, one molecule for each iron- containing heme group The 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 CO 2 produced during cellular respiration lowers blood pH and decreases the affinity of hemoglobin for O 2 ; this is called the Bohr shift © 2011 Pearson Education, Inc.

148. Figure 42.UN01 Iron Heme Hemoglobin

149. Figure 42.31 2 (a) P O and hemoglobin dissociation at pH 7.4 Tissues during exercise Tissues at rest Lungs P O (mm Hg) 2 (b) pH and hemoglobin dissociation P O (mm Hg) 2 020406080100 0 20 40 60 80 100 020406080100 0 20 40 60 80 100 Hemoglobin retains less O 2 at lower pH (higher CO 2 concentration) pH 7.2 pH 7.4 O 2 unloaded to tissues during exercise O 2 saturation of hemoglobin (%) O 2 unloaded to tissues at rest O 2 saturation of hemoglobin (%)

150. Figure 42.31a 2 (a) P O and hemoglobin dissociation at pH 7.4 Tissues during exercise Tissues at rest Lungs P O (mm Hg) 2 020406080100 0 20 40 60 80 100 O 2 unloaded to tissues during exercise O 2 unloaded to tissues at rest O 2 saturation of hemoglobin (%)

151. (b) pH and hemoglobin dissociation P O (mm Hg) 2 020406080100 0 20 40 60 80 100 Hemoglobin retains less O 2 at lower pH (higher CO 2 concentration) pH 7.2 pH 7.4 O 2 saturation of hemoglobin (%) Figure 42.31b

152. Carbon Dioxide Transport Hemoglobin also helps transport CO 2 and assists in buffering the blood CO 2 from respiring cells diffuses into the blood and is transported in blood plasma, bound to hemoglobin, or as bicarbonate ions (HCO 3 – ) © 2011 Pearson Education, Inc.

153. Figure 42.32a Body tissue Capillary wall Interstitial fluid Plasma within capillary CO 2 transport from tissues CO 2 produced CO 2 H2OH2O H 2 CO 3 Hb Red blood cell Carbonic acid Hemoglobin (Hb) picks up CO 2 and H +. H+H+ HCO 3  Bicarbonate  HCO 3  To lungs CO 2

154. Figure 42.32b HCO 3  CO 2 transport to lungs H 2 CO 3 H2OH2O H+H+  Hb Hemoglobin releases CO 2 and H +. CO 2 Alveolar space in lung To lungs HCO 3  CO 2

155. Figure 42.32 Body tissue Capillary wall Interstitial fluid Plasma within capillary CO 2 transport from tissues CO 2 produced CO 2 H2OH2O H 2 CO 3 Hb Red blood cell Carbonic acid Hemoglobin (Hb) picks up CO 2 and H +. H+H+ HCO 3  Bicarbonate  HCO 3  To lungs CO 2 transport to lungs HCO 3  H 2 CO 3 H2OH2O CO 2 H+H+  Hb Hemoglobin releases CO 2 and H +. CO 2 Alveolar space in lung

156. Respiratory Adaptations of Diving Mammals Diving mammals have evolutionary adaptations that allow them to perform extraordinary feats –For example, Weddell seals in Antarctica can remain underwater for 20 minutes to an hour –For example, elephant seals can dive to 1,500 m and remain underwater for 2 hours These animals have a high blood to body volume ratio © 2011 Pearson Education, Inc.

157. Deep-diving air breathers stockpile O 2 and deplete it slowly Diving mammals can store oxygen in their muscles in myoglobin proteins Diving mammals also conserve oxygen by –Changing their buoyancy to glide passively –Decreasing blood supply to muscles –Deriving ATP in muscles from fermentation once oxygen is depleted © 2011 Pearson Education, Inc.

158. Figure 42.UN02 Exhaled air Alveolar epithelial cells Pulmonary arteries Systemic veins Heart CO 2 O2O2 Body tissue Systemic capillaries Systemic arteries Pulmonary veins Alveolar capillaries Alveolar spaces Inhaled air CO 2 O2O2