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Happy Thursday! 2/24/11 Explain the need for, and the mechanism of, ventilation of the lungs in humans. (Total 8 marks) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 8 max (Plus up to [2] for quality) •Need: • draws fresh air / oxygen into the lungs; • removal / excretion of CO2; • maintains concentration gradient of O2 / CO2 / respiratory gases; • Mechanism: • diaphragm contracts; • (external) intercostal muscles contract; • increased volume (of thorax / thoracic cavity); • decreasing air pressure in lungs; • air rushes in down air pressure gradient; • converse of the above causes exhalation; • abdominal muscles contract during active exhalation; • elastic recoil of lungs helps exhalation; Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chapter 22 Gas Exchange PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Surviving in Thin Air • Himalayas – Have claimed many lives • Air at height of world’s highest peak, Mt. Everest – Is so low in O2 : most people would pass out instantly if exposed to it! Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Twice a year, flocks of geese migrate over Himalayas – able to fly at such high altitude b/c lung efficiency – have hemoglobin w/very high affinity for oxygen – (Adaptation) carry lg amts oxygen to tissues, to exchange with carbon dioxide Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • The process of gas exchange, often called respiration – interchange of O2 and CO2 between an organism and its environment Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings MECHANISMS OF GAS EXCHANGE 22.1 Overview: Gas exchange involves breathing, transport of gases, and exchange of gases with tissue cells O2 1 CO2 Breathing Lung 2 Circulatory system Transport of gases by the circulatory system Mitochondria 3 Figure 22.1 Exchange of gases with body cells Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CO2 Capillary Cell O2 • Gas exchange – Provides O2 for cellular respiration and – removes its waste product, CO2 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 & Smaller? the trachea, Smaller? and bronchioles Air tube? bronchi, Nasal cavity Pharynx (Esophagus) Larynx Left lung Trachea Right lung Bronchus Bronchiole Diaphragm Figure 22.5A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings (Heart) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Online Review Activity: Labeling Parts • bronchioles end in clusters of tiny sacs called alveoli – Oxygen-rich blood Where gasProcess? exchange occurs Oxygen-poor blood Alveoli Blood capillaries Figure 22.5B, C Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Colorized SEM 6,200 Bronchiole Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 22.6 Smoking is a deadly assault on our respiratory system • Mucus cilia in the respiratory passages Structures,and features? – Protect the lungs – Can be destroyed by smoking Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Smoking – Causes lung cancer, heart disease, and emphysema Lung Heart Figure 22.6 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.7 Breathing ventilates the lungs • alternation of inhalation and exhalation Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Namesand of muscles? • The contraction of rib muscles the diaphragm – Expands chest cavity, reduces air pressure in alveoli (negative pressure breathing) Air inhaled Rib cage expands as rib muscles contract Air exhaled Rib cage gets smaller as rib muscles relax Lung Diaphragm Diaphragm relaxes (moves up) Diaphragm contracts (moves down) Figure 22.7A Inhalation Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Exhalation read last night? is the maximum volume of air • Who Vital capacity we can inhale and exhale – But our lungs still hold a residual volume Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Air flows in one direction – Through the more efficient lungs of birds! Anterior air sacs Posterior air sacs Air Air Trachea Lungs Air tubes in lung Inhalation: Exhalation: Air sacs fill Air sacs empty; lungs fill Figure 22.7B Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1 mm 22.9 Breathing is automatically controlled • Breathing control centers in the brain – Keep breathing in tune with body needs, sensing and responding to the COWhat in the blood gas? Where? 2 level Brain Cerebrospinal fluid Pons Medulla Breathing control centers stimulated by: Nerve signals trigger contraction of muscles CO2 increase / pH decrease in blood CO2 and O2 sensors in aorta Diaphragm Figure 22.8 Rib muscles Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Nerve signals indicating CO2 and O2 levels • A drop in blood pH – Triggers an increase in rate & depth of breathing Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings TRANSPORT OF GASES IN THE BODY 22.9 Blood transports respiratory gases • heart pumps O2 - poor blood to lungs Where? – picks up O2 , drops off CO2 Where? • heart pumps O2 - rich blood to body cells – drops off O2 , picks up CO2 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Gas transport and exchange in the body Inhaled air Exhaled air Alveolar epithelial cells Air spaces CO2 O2 Alveolar capillaries of lung CO2-rich, O2-poor blood O2-rich, CO2-poor blood Heart Tissue capillaries CO2 Interstitial O2 fluid Figure 22.9 Tissue cells throughout body Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Gases diffuse down partial-pressure gradients – In the lungs and the tissues Online Animation of Gas Exchange Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Molecule? 22.10 Hemoglobin carries O2 and helps transport CO2 and buffer the blood Molecule? • Hemoglobin in red blood cells – Transports oxygen, helps buffer the blood and carries some CO2 Iron atom O2 loaded in lungs O2 unloaded in tissues Heme group Figure 22.10 Polypeptide chain Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Most CO2 in blood CO2 Carbon dioxide – transported as bicarbonate ions in plasma + H2O Water Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings H2CO3 Carbonic acid H+ Hydrogen ions + HCO3– Bicarbonate CONNECTION 22.11 The human fetus exchanges gases with the mother’s bloodstream • In the • placenta Placenta, containing maternal blood vessels and fetal capillaries Umbilical cord, containing fetal blood vessels Amniotic fluid Uterus Figure 22.11 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Fetal hemoglobin – Enhances oxygen transfer from maternal blood • At birth, increased CO2 in fetal blood – Stimulates breathing control centers to initiate breathing Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings To be continued...(Reproduction Unit!) Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 22.2 Animals exchange O2 and CO2 across moist body surfaces • Respiratory surfaces – Must be thin and moist for diffusion of O2 and CO2 to occur 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) CO2 O2 Figure 22.2A Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Capillaries • In most animals – Specialized body parts provide large respiratory surfaces for gas exchange Body surface Body surface Respiratory surface (gill) CO2 Body cells (no capillaries) O2 CO2 Figure 22.2C Capillary O2 Body surface Figure 22.2B CO2 CO2 Figure 22.2D Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings O2 Respiratory surface (air tubes) Respiratory surface (within lung) O2 Capillary 22.3 Gills are adapted for gas exchange in aquatic environments • Gills are extensions of the body – That absorb O2 dissolved in water 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 Oxygen-poor blood Direction of water flow Lamella Oxygen-rich blood Gill arch 15% Blood vessels % O2 in water flowing over lamellae % O in blood 2 flowing through capillaries Gill in lamellae filaments Figure 22.3 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Countercurrent exchange 22.4 The tracheal system of insects provides direct exchange between the air and body cells • Land animals – Exchange gases by breathing air Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings • Tracheal systems in insects – Transport O2 directly to body cells through a network of finely branched tubes Air sacs Tracheae LM 250 Opening for air Body cell Tracheole Air sac Trachea Figure 22.4A, B O2 CO2 Body wall Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings