© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 22 Gas Exchange

Gas Exchange - Function of the Respiratory System  The process of gas exchange is sometimes called respiration, the interchange of –O 2 and the waste product CO 2 –O 2 is substrate for cellular respiration (ATP generation). © 2012 Pearson Education, Inc.

1.breathing, 2.transport of oxygen and carbon dioxide in blood, and 3.exchange of gases with body cells. –Body tissues take up oxygen and –release carbon dioxide. © 2012 Pearson Education, Inc. Lung Breathing Heart O2O2 CO 2 Blood vessels 1 2 Circulatory System Transport of gases by the circulatory system Mitochondria Cell CO 2 O2O2 Capillary Exchange of gases with body cells 3 3 Stages of Gas Exchange

Universal Rules of Gas Exchange  Gas exchange is occurs by simple diffusion of gases across cell membranes  Respiratory surfaces must be moist  Respiratory surfaces must be thin –Optimize SA:volume © 2012 Pearson Education, Inc.

Gas Exchange in Air vs. Water  Aquatic: –Disadvantage: –Water holds only about 3% of the oxygen in air. –Cold water holds more oxygen than warm water. –Water move difficult to move across respiratory surfaces. –Advantage: –Respiratory surfaces remain moist - can be directly exposed to water ennvironment © 2012 Pearson Education, Inc.

Gas Exchange in Air vs. Water  Land: –Advantange: –Concentration of O2 much higher in air –Air requires less energy to move over respiratory surfaces. –Disadvantage: –Respiratory surfaces more likely to dry out  Land organisms use internal respiratory systems (lungs, trachea, etc.)  Plants regulate stomata opening using guard cells to prevent water loss by transpiration. © 2012 Pearson Education, Inc.

Gas Exchange Structures in Various Organisms  Organisms have specialized body parts for gas exchange: –Skin in earthworms –gills in fish –Lungs and skin in amphibians, –tracheal systems in arthropods –Plants use stomata –lungs in tetrapods that live on land, such as –amphibians, –reptiles including birds, and –mammals. © 2012 Pearson Education, Inc.

Cross section of the respiratory surface (the outer skin) Capillaries CO 2 O2O2 Body surface Respiratory surface (gills) Capillary CO 2 O2O2

Figure 22.3 Oxygen-poor blood Water flow between lamellae Lamella Blood flow through capillaries in a lamella Oxygen-rich blood Blood vessels Gill arch Operculum (gill cover) Gill filaments Diffusion of O 2 from water to blood Countercurrent exchange Water flow, showing % O 2 Blood flow in simplified capillary, showing % O Water flow

Air sacs Tracheoles Tracheae Opening for air Air sac Body cell Tracheole Trachea Body wall CO 2 O2O2 Body surface Respiratory surface (tips of tracheae) CO 2 O2O2 Body cells (no capillaries)

Figure 22.2D CO 2 O2O2 Body surface Capillary Respiratory surface (within lung) O2O2 CO 2

THE HUMAN RESPIRATORY SYSTEM © 2012 Pearson Education, Inc.

22.6 In mammals, 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. © 2012 Pearson Education, Inc.

Nasal cavity Pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Blood capillaries Bronchiole Alveoli CO 2 O2O2 Oxygen-poor blood From the heart To the heart Oxygen-rich blood Left lung  Alveoli are well adapted for gas exchange with high surface areas of capillaries.  In alveoli, – O 2 diffuses into the blood and – CO 2 diffuses out of the blood. Alveoli are site of gas exchange in lungs!

© 2012 Pearson Education, Inc. 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

CO 2 in exhaled air Alveolar epithelial cells O 2 in inhaled air Air spaces Alveolar capillaries of lung CO 2 O2O2 O2O2 CO 2 -rich, O 2 -poor blood O 2 -rich, CO 2 -poor blood Heart Tissue capillaries O2O2 CO 2 Interstitial fluid Tissue cells throughout the body CO 2 O2O2 Gas Exchange occurs by passive diffusion!!! Gas diffuse towards regions of lowest partial pressure. (Partial pressure = measure of concentration of gas dissolved in liquid)

Figure 22.10_1 Alveolar capillaries of lung O2O2 CO 2 CO 2 -rich, O 2 -poor blood O 2 -rich, CO 2 -poor blood Heart Tissue capillaries O2O2 CO 2 [CO2] lowest in alveoli And tissue capillaries [CO2] highest in blood arriving to lung and tissues [O2] lowest in blood arriving at lung and tissues [O2] highest in alveoli and blood arriving AT tissues

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 in 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 gases in the blood. –CO 2 moves from the tissues into the blood. –O 2 moves from the blood into the tissues. © 2012 Pearson Education, Inc.

Hemoglobin carries O 2 in the blood © 2012 Pearson Education, Inc. Iron atom Polypeptide chain Heme group O 2 loaded in lungs O 2 unloaded in tissues O2O2 O2O2

CO2 is transported as bicarbonate ion in blood!!  CO 2 forms carbonic acid in water  Carbonic acid dissociates into:  hydrogen ions and  bicarbonate ions  by a reversible reaction  Ratio of acid/base regulated by mass action and breathing rates. © 2012 Pearson Education, Inc.

1 2 Cerebrospinal fluid Brain Nerve signals trigger contraction of the rib muscles and diaphragm. Diaphragm Rib muscles Breathing control center responds to the pH of blood and cerebrospinal fluid.  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. Medulla Breathing is automatically controlled

Cerebrospinal fluid Medulla Brain Nerve signals trigger contraction of the rib muscles and diaphragm. 1 Diaphragm Rib muscles Breathing control center responds to the pH of blood and cerebrospinal fluid. 2 Heart CO 2 and O 2 sensors in the aorta Nerve signals indicate CO 2 and O 2 levels. 3 Additional sensors in aorta may monitor O2 levels