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BIOL 100C: Introductory Biology III The Respiratory System Dr. P. Narguizian Fall 2012 Principles of Biology Education-Portal: Online Video • Gas Exchange in the Human Respiratory System http://education-portal.com/academy/lesson/gasexchange-in-the-human-respiratory-system.html MECHANISMS OF GAS EXCHANGE Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. • The three phases of gas exchange. O2 1 Breathing CO2 Lung Circulatory system 2 Transport of gases by the circulatory system Mitochondria 3 Exchange of gases with body cells O2 CO2 Capillary Cell Animals exchange O2 and CO2 across moist body surfaces Respiratory surfaces must be thin and moist for diffusion of O2 and CO2 Earthworms and other animals use their skin for gas exchange Copyright © 2009 Pearson Education, Inc. • The entire outer skin of an earthworm serves as its respiratory surface. Cut Cross section of respiratory surface (the outer skin) CO2 O2 Capillaries Animals exchange O2 and CO2 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 Copyright © 2009 Pearson Education, Inc. Body surface Respiratory surface (gill) CO2 O2 Capillary • Gills are extensions of the body surface that function in gas exchange with the surrounding water. • The tracheal system of an insect consists of tubes that extend throughout the body. Body surface Respiratory surface (air tubes) O2 CO2 Body cells (no capillaries) • Lungs are internal thin-walled sacs. Body surface CO2 CO2 O2 Respiratory surface (within lung) O2 Capillary 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 Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. Gill arch Oxygen-poor blood Lamella Oxygen-rich blood Direction of water flow Gill arch Blood vessels Operculum (gill cover) Water flow between lamellae Gill filaments Blood flow through capillaries in lamella Countercurrent exchange Water flow, showing % O2 Diffusion of O2 from water to blood 100 70 40 15 80 30 5 60 Blood flow in simplified capillary, showing % O2 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 O2 – Air is lighter and easier to move Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. • The tracheal system of an insect. Air sacs Tracheae Opening for air Body cell Tracheole Air sac Trachea O2 CO2 Body wall 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 Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. • The anatomy of the human respiratory system. Nasal cavity Pharynx (Esophagus) Larynx Trachea Left lung Right lung Bronchus Bronchiole Diaphragm (Heart) • Details of the structure of alveoli (right). Oxygen-rich blood Oxygen-poor blood Bronchiole Alveoli Blood capillaries 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 – O2 diffuses into the blood – CO2 diffuses out of the blood Copyright © 2009 Pearson Education, Inc. • Scanning electron micrographs of the air spaces in alveoli (left) and the capillaries that envelop the alveoli (right). 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 Copyright © 2009 Pearson Education, Inc. 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 Copyright © 2009 Pearson Education, Inc. Rib cage gets Rib cage expands as rib muscles contract Air inhaled smaller as rib muscles relax Air exhaled Lung Diaphragm Diaphragm contracts (moves down) Diaphragm relaxes (moves up) Inhalation Exhalation 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 Copyright © 2009 Pearson Education, Inc. Breathing is automatically controlled Breathing is usually under automatic control Breathing control centers in the brain sense and respond to CO2 levels in the blood A drop in blood pH increases the rate and depth of breathing Copyright © 2009 Pearson Education, Inc. • Control centers that regulate breathing respond to the pH of blood and nervous stimulation from sensors that detect CO2 and O2 levels. Cerebrospinal fluid Brain Pons 2 Breathing control 1 Nerve signals trigger contraction of muscles Medulla centers respond to pH of blood 3 Nerve signals indicating CO2 and O2 levels CO2 and O2 sensors in aorta Diaphragm Rib muscles TRANSPORT OF GASES IN THE HUMAN BODY Copyright © 2009 Pearson Education, Inc. 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 O2 and drops off CO2 In the body tissues, blood drops off O2 and picks up CO2 Copyright © 2009 Pearson Education, Inc. 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 O2 and less CO2 than gases the blood – O2 moves from the alveoli of the lungs into the blood – CO2 moves from the blood into the alveoli of the lungs – The tissues have more CO2 and less O2 than in the blood – CO2 moves from the tissues into the blood – O2 moves from the blood into the tissues Copyright © 2009 Pearson Education, Inc. Inhaled air • Gas transport and exchange in the body. Exhaled air Alveolar epithelial cells Air spaces CO2 O2 Alveolar capillaries CO2-rich, O2-poor blood O2-rich, CO2-poor blood Heart Tissue capillaries CO2 Tissue cells throughout body O2 Interstitial fluid Hemoglobin carries O2, helps transport CO2, and buffers the blood Most animals transport O2 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 CO2 Copyright © 2009 Pearson Education, Inc. Hemoglobin loading and unloading of O2. Iron atom O2 loaded in lungs O2 unloaded in tissues Heme group Polypeptide chain O2 O2 Hemoglobin carries O2, helps transport CO2, and buffers the blood Most CO2 in the blood is transported as bicarbonate ions in the plasma Copyright © 2009 Pearson Education, Inc. Gas exchange requires moist, thin often relies on (b) (a) for exchange of O2 to transport gases between red blood cells contain CO2 (c) (d) needed waste for product of mammals ventilate by (e) binds and transports and helps to (f) tissue cells regulated by breathing control centers transport CO2 and buffer the blood (g) a. b. c. d. e. f. g. h. 100 Llama 80 Human 60 40 20 0 0 20 40 60 PO (mm Hg) 2 80 100 You should now be able to 1. Describe the three main phases of gas exchange in a human 2. Describe four types of respiratory surfaces and the types of animals that use them 3. Explain how breathing air compares to using water for gas exchange Copyright © 2009 Pearson Education, Inc. You should now be able to 4. Describe the parts and functions of the human respiratory system 5. Explain how blood transports gases between the lungs and tissues of the body 6. Describe the functions of hemoglobin Copyright © 2009 Pearson Education, Inc.