Chapter 22 Gas Exchange PowerPoint Lectures for Biology: Concepts & Connections, Sixth Edition Campbell, Reece, Taylor, Simon, and Dickey Lecture by Edward J. Zalisko
Introduction: Surviving in Thin Air People cannot survive in the air at the world s highest peaks in the Himalayan Mountains Twice a year, flocks of geese migrate over the Himalayas How can geese fly where people cannot breathe? Geese have more efficient lungs than humans Geese hemoglobin has a very high affinity for oxygen
Introduction: Surviving in Thin Air The process of gas exchange is called respiration, the interchange of O 2 and the waste product CO 2 Between an organism and its environment
MECHANISMS OF GAS EXCHANGE
22.1 Overview: Gas exchange in an animal with lungs involves breathing, transport of gases, and exchange of gases with tissue cells Three phases of gas exchange Breathing Transport of oxygen and carbon dioxide in blood Body tissues take up oxygen and release carbon dioxide Cellular respiration requires a continuous supply of oxygen and the disposal of carbon dioxide
O 2 1 CO 2 Breathing Lung 2 Circulatory system Transport of gases by the circulatory system 3 Exchange of gases with body cells Mitochondria O 2 CO 2 Capillary Cell
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 Earthworms and other animals use their skin for gas exchange
Cut Cross section of respiratory surface (the outer skin) CO 2 Capillaries O 2
22.2 Animals exchange O 2 and CO 2 across moist body surfaces Most animals have specialized body parts that promote gas exchange Gills in fish and amphibians Tracheal systems in arthropods Lungs in tetrapods that live on land Amphibians Reptiles Birds Mammals
Body surface Respiratory surface (gill) CO 2 Capillary O 2
Body surface Respiratory surface (air tubes) O 2 CO 2 Body cells (no capillaries)
CO 2 O 2 Body surface Respiratory surface (within lung) CO 2 O 2 Capillary
22.3 Gills are adapted for gas exchange in aquatic environments Gills Are extensions of the body Increase the surface to volume ratio Increase the surface area for gas exchange Oxygen absorbed Carbon dioxide released
22.3 Gills are adapted for gas exchange in aquatic environments In a fish, gas exchange is enhanced by Ventilation of the gills (moving water past the gills) Countercurrent flow of water and blood
22.3 Gills are adapted for gas exchange in aquatic environments Cold water holds more oxygen than warm water Fresh water holds more oxygen than salt water Turbulent water holds more oxygen than still water
Gill arch Oxygen-poor blood Direction of water flow Gill arch Blood vessels Oxygen-rich blood Lamella Operculum (gill cover) Water flow between lamellae Gill filaments Blood flow through capillaries in lamella Countercurrent exchange Diffusion of O 2 from water to blood Water flow, showing % O 2 100 70 40 15 80 60 30 5 Blood flow in simplified capillary, showing % O 2
Direction of water flow Gill arch Direction of water flow Gill arch Gill arch Gill arch Blood vessels Oxygen-rich blood Oxygen-poor blood Blood vessels Lamella Operculum (gill cover) Operculum (gill cover) Diffusion of O 2 from water to blood Water flow between lamellae Gill filaments Blood flow through capillaries in lamella Countercurrent exchange Water flow, showing % O Gill 2 100 70 40 15 80 60 30 5 Blood flow in simplified capillary, showing % O 2 filaments
Oxygen-rich blood Oxygen-poor blood Lamella Gill arch Blood vessels Water flow between lamellae Gill filaments Blood flow through capillaries in lamella Countercurrent exchange Diffusion of O 2 from water to blood Water flow, showing % O 2 100 70 40 15 80 60 30 5 Blood flow in simplified capillary, showing % O 2
22.4 The tracheal system of insects provides direct exchange between the air and body cells Compared to water, using air to breathe has two big advantages Air contains higher concentrations of O 2 Air is lighter and easier to move
22.4 The tracheal system of insects provides direct exchange between the air and body cells Air-breathing animals lose water through their respiratory surfaces Insect tracheal systems use tiny branching tubes This reduces water loss Air is piped directly to cells
Air sacs Tracheae Opening for air Body cell Tracheole Air sac Trachea O 2 CO 2 Body wall
22.5 EVOLUTION CONNECTION: The evolution of lungs facilitated the movement of tetrapods onto land Tetrapods seem to have evolved in shallow water Fossil fish with legs had lungs and gills Legs may have helped them lift up to gulp air The fossil fish Tiktaalik illustrates these air-breathing adaptations
22.5 EVOLUTION CONNECTION: The evolution of lungs facilitated the movement of tetrapods onto land The first tetrapods on land diverged into three major lineages Amphibians use small lungs and their body surfaces Nonbird reptiles have lower metabolic rates and simpler lungs Birds and mammals have higher metabolic rates and more complex lungs
22.6 In the human respiratory system, branching tubes convey air to lungs located in the chest cavity In mammals, air is inhaled through the nostrils into the nasal cavity Air is filtered by hairs and mucus surfaces Air is warmed and moisturized Air is sampled for odors
22.6 In the human respiratory system, branching tubes convey air to lungs located in the chest cavity From the nasal cavity, air next passes To the pharynx Then larynx, past the vocal cords Into the trachea, held open by cartilage rings Into the paired bronchi Into bronchioles And finally to the alveoli, grapelike clusters of air sacs, where gas exchange occurs
Oxygen-rich blood Oxygen-poor blood Nasal cavity Bronchiole Pharynx (Esophagus) Larynx Trachea Right lung Left lung Alveoli Bronchus Bronchiole Blood capillaries Diaphragm (Heart)
Pharynx (Esophagus) Larynx Trachea Nasal cavity Left lung Right lung Bronchus Bronchiole Diaphragm (Heart)
Oxygen-rich blood Oxygen-poor blood Bronchiole Alveoli Blood capillaries
22.6 In the human respiratory system, branching tubes convey air to lungs located in the chest cavity Alveoli are well adapted for gas exchange High surface area of capillaries High surface area of alveoli In alveoli O 2 diffuses into the blood CO 2 diffuses out of the blood
22.7 CONNECTION: Smoking is a serious assault on the respiratory system Mucus and cilia in the respiratory passages Protect the lungs Can be damaged by smoking Without healthy cilia, smokers must cough to clear dirty mucus from the trachea
22.7 CONNECTION: Smoking is a serious assault on the respiratory system Smoking can cause Lung cancer Heart disease Emphysema Smoking accounts for 90% of all lung cancer cases Smoking increases the risk of other types of cancer
22.7 CONNECTION: Smoking is a serious assault on the respiratory system Smoking also Increases the risk of heart attacks and strokes Raises blood pressure Increases harmful types of cholesterol Every year in the United States, smoking kills about 440,000 people This is more than all the deaths from accidents, alcohol, drug abuse, HIV, and murders combined Adults who smoke cut 13 14 years from their lifespan
Lung Heart
22.8 Negative pressure breathing ventilates our lungs Breathing is the alternate inhalation and exhalation of air (ventilation) Inhalation occurs when The rib cage expands The diaphragm moves downward The pressure around the lungs decreases And air is drawn into the respiratory tract
22.8 Negative pressure breathing ventilates our lungs Exhalation occurs when The rib cage contracts The diaphragm moves upward The pressure around the lungs increases And air is forced out of the respiratory tract
Rib cage expands as rib muscles contract Air inhaled Rib cage gets smaller as rib muscles relax Air exhaled Lung Diaphragm Diaphragm contracts (moves down) Inhalation Diaphragm relaxes (moves up) Exhalation
22.8 Negative pressure breathing ventilates our lungs Not all air is expelled during exhalation Some air still remains in the trachea, bronchi, bronchioles, and alveoli This remaining air is dead air Thus, inhalation mixes fresh air with dead air One-way flow of air in birds reduces dead air and increases their ability to obtain oxygen
22.9 Breathing is automatically controlled Breathing is usually under automatic control Breathing control centers in the brain sense and respond to CO 2 levels in the blood A drop in blood ph increases the rate and depth of breathing
Brain Cerebrospinal fluid Pons 1 Nerve signals trigger contraction of muscles Medulla Diaphragm Rib muscles
Brain Cerebrospinal fluid Pons 1 Nerve signals trigger contraction of muscles Medulla 2 Breathing control centers respond to ph of blood Diaphragm Rib muscles
Brain Cerebrospinal fluid Pons 1 Nerve signals trigger contraction of muscles Medulla 2 Breathing control centers respond to ph of blood 3 Nerve signals indicating CO 2 and O 2 levels CO 2 and O 2 sensors in aorta Diaphragm Rib muscles
TRANSPORT OF GASES IN THE HUMAN BODY
22.10 Blood transports respiratory gases The heart pumps blood to two regions The right side pumps oxygen-poor blood to the lungs The left side pumps oxygen-rich blood to the body In the lungs, blood picks up O 2 and drops off CO 2 In the body tissues, blood drops off O 2 and picks up CO 2
22.10 Blood transports respiratory gases Gases move from areas of higher concentration to areas of lower concentration Gases in the alveoli of the lungs have more O 2 and less CO 2 than gases the blood O 2 moves from the alveoli of the lungs into the blood CO 2 moves from the blood into the alveoli of the lungs The tissues have more CO 2 and less O 2 than in the blood CO 2 moves from the tissues into the blood O 2 moves from the blood into the tissues
22.10 Blood transports respiratory gases Animation: CO 2 from Blood to Lungs Animation: CO 2 from Tissues to Blood Animation: O 2 from Blood to Tissues Animation: O 2 from Lungs to Blood
Exhaled air Inhaled air Alveolar epithelial cells Air spaces CO 2 O 2 Alveolar capillaries CO 2 -rich, O 2 -poor blood O 2 -rich, CO 2 -poor blood Tissue capillaries Heart Tissue cells throughout body CO 2 O 2 Interstitial fluid
22.11 Hemoglobin carries O 2, helps transport CO 2, and buffers the blood Most animals transport O 2 bound to proteins called respiratory pigments Copper-containing pigment is used by Molluscs Arthropods Iron-containing hemoglobin Is used by almost all vertebrates and many invertebrates Transports oxygen, buffers blood, and transports CO 2
Iron atom O 2 loaded in lungs O 2 O 2 unloaded in tissues Heme group Polypeptide chain O 2
22.11 Hemoglobin carries O 2, helps transport CO 2, and buffers the blood Most CO 2 in the blood is transported as bicarbonate ions in the plasma
22.11 Hemoglobin carries O 2, helps transport CO 2, and buffers the blood CO + H O H CO H + HCO + 2 2 2 3 3- Carbon Water Carbonic Hydrogen Bicarbonate Dioxide Acid Ions
22.12 CONNECTION: The human fetus exchanges gases with the mother s bloodstream A human fetus Does not breathe with its lungs Instead, it exchanges gases with maternal blood in the placenta In the placenta, capillaries of maternal blood and fetal blood run next to each other The fetus and mother do not share the same blood
22.12 CONNECTION: The human fetus exchanges gases with the mother s bloodstream Fetal hemoglobin Attracts O 2 more strongly than adult hemoglobin Thus, fetal blood takes oxygen from maternal blood At birth CO 2 in fetal blood increases Breathing control centers initiate breathing
Placenta, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus
Lamella Water flow Blood flow
Gas exchange requires moist, thin often relies on (a) (b) for exchange of to transport gases between red blood cells contain O 2 needed for CO 2 waste product of (c) (d) (e) mammals ventilate by and binds and transports helps to (f) tissue cells (g) regulated by breathing control centers transport CO 2 and buffer the blood
a. b. c. d. e. f. g. h.
100 80 Llama Human 60 40 20 0 0 20 40 60 PO (mm Hg) 2 80 100
You should now be able to 1. Explain how geese can fly at altitudes higher than Mount Everest 2. Describe the three main phases of gas exchange in a human 3. Describe four types of respiratory surfaces and the types of animals that use them 4. Explain how breathing air compares to using water for gas exchange
You should now be able to 5. Describe the parts and functions of the human respiratory system 6. Describe the impact of smoking on human health 7. Explain how blood transports gases between the lungs and tissues of the body 8. Describe the functions of hemoglobin 9. Explain how a fetus obtains oxygen before and after birth