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BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 22 Respiration: The Exchange of Gases Modules 22.1 – 22.4 From PowerPoint® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings MECHANISMS OF GAS EXCHANGE • Gas exchange / respiration - interchange of O2 and CO2 between organism and environment • Gas exchange essential because energy metabolism requires O2 and produces CO2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings O2 Lung CO2 1 Breathing Circulatory system 2 Transport of gases by the circulatory system Mitochondria 3 Servicing of O2 cells within the body tissues CO2 Capillary Cell Figure 22.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Some animals use entire skin as gas-exchange organ – Example: earthworms Cut Cross section of respiratory surface (the skin covering the body) CO2 O2 Capillaries Figure 22.2A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • In most animals, specialized body parts carry out gas exchange – Gills in fish Body surface Respiratory surface (gill) CO2 Capillaries O2 Figure 22.2B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings – Lungs in land vertebrates – Tracheae in insects Body surface Body surface Respiratory surface (tracheae) O2 Body cells (no capillaries) Respiratory surface (within lung) CO2 O2 Capillary CO2 Figure 22.2C, D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 22.3 Gills are adapted for gas exchange in aquatic environments • Gills: extensions of body that absorb O2 dissolved in water • In fish, gill filaments have numerous platelike lamellae – Lamellae: packed with blood vessels – Are respiratory surfaces Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The structure of fish gills Gill arch Direction of water flow Gill arch Blood vessels Oxygen-poor blood Gill filaments Oxygen-rich blood Lamella Water flow Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 22.3 22.4 Countercurrent flow in the gills enhances O2 transfer • Blood flows through the lamellae in opposite direction to water flow – Countercurrent maintains diffusion gradient that maximizes uptake of O2 Water flow over lamellae Blood flow through lamellae Figure 22.4 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 22.5 The tracheal system of insects provides direct exchange between the air and body cells • Land animals exchange gases by breathing air – Air contains more O2 - easier to move than water – But water loss from respiratory surfaces can be problem Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Insects: network of tracheal tubes carries out gas exchange – O2 diffuses from finely branched tubes directly into cells Figure 22.5B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Air sacs Tracheae Opening for air Body cell Tracheole Air sac Trachea Air Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Body wall Figure 22.5A, C 22.6 Terrestrial vertebrates have lungs • In humans and other mammals, air enters through nasal cavity – Passes through pharynx -> larynx -> trachea – Trachea -> two bronchi – Each bronchus -> numerous bronchioles Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Gas exchange in the body Figure 22.10A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The human respiratory system Nasal cavity Pharynx (Esophagus) Left lung Larynx Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Figure 22.6A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Brionchioles end in clusters of tiny sacs - alveoli – Alveoli: respiratory surface of lungs – Oxygen diffuses through thin walls of alveoli into blood Figure 22.6C Oxygen-rich blood Oxygen-poor blood Bronchiole Alveoli Blood capillaries Figure 22.6B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 22.8 Breathing ventilates the lungs • Breathing: alternation of inhalation and exhalation Rib cage expands as rib muscles contract Air inhaled Rib cage gets smaller as rib muscles relax Air exhaled Lung Diaphragm INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) Figure 22.8A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Bird: air sacs – keep air flowing through lungs but not function directly in gas exchange Air Air Anterior air sacs Trachea Posterior air sacs Lungs Lungs Air tubes in lung INHALATION: Air sacs fill Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings EXHALATION: Air sacs empty; lungs fill 1 mn Figure 22.8B 22.9 Breathing is automatically controlled • Breathing control centers: pons and medulla of the brain – Automatic controls based on need Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • When CO2 level in the blood rises, lowering the blood pH – This triggers a cascade of events Brain Cerebrospinal fluid BREATHING CONTROL CENTERS—stimulated by: Pons Medulla CO2 increase / pH decrease in blood Nerve signal indicating low O2 level Nerve signals trigger contraction of muscles O2 sensor in artery Diaphragm Figure 22.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Rib muscles • Hemoglobin: protein in red blood cells – Carrie most of the oxygen in blood Heme group Iron atom O2 loaded in lungs O2 unloaded in tissues O2 O2 Polypeptide chain Figure 22.10B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 22.11 Hemoglobin helps transport CO2 and buffer the blood • Hemoglobin helps buffer pH of blood and carries some CO2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Most CO2 in the blood + water carbonic acid (H2CO3) – Carbonic acid breaks down to form H+ ions and bicarbonate ions TISSUE CELL CO2 produced INTERSTITIAL CO 2 FLUID BLOOD PLASMA WITHIN CAPILLARY CO2 Capillary wall CO2 H2O – Help buffer blood RED BLOOD CELL H2CO3 Carbonic acid HCO3– + Bicarbonate HCO3– Figure 22.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings H+ Hemoglobin picks up CO2 and H+ • Most CO2 transported to lungs as bicarbonate ions ALVEOLAR SPACE IN LUNG CO2 CO2 CO2 CO2 H2O Hemoglobin releases CO2 and H+ H2CO3 HCO3– HCO3– Figure 22.11B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings + H+ 22.12 Connection: The human fetus exchanges gases with the mother’s bloodstream • Human fetus depends on placenta for gas exchange Placenta, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus Figure 22.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Network of capillaries exchanges O2 and CO2 with maternal blood that carries gases to and from mother’s lungs • At birth, increasing CO2 in the fetal blood stimulates the fetus’s breathing control centers to initiate breathing Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings