Copyright © 2009 Pearson Education, Inc.  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?

Copyright © 2009 Pearson Education, Inc. MECHANISMS OF GAS EXCHANGE

Copyright © 2009 Pearson Education, Inc.  Three phases of gas exchange 1. Breathing 2. Transport of oxygen and carbon dioxide in blood 3. Body tissues take up oxygen and release carbon dioxide  Cellular respiration requires a continuous supply of oxygen and the disposal of carbon dioxide

Lung Exchange of gases with body cells Cell Capillary Mitochondria Breathing Circulatory system Transport of gases by the circulatory system CO 2 O2O2 O2O

Copyright © 2009 Pearson Education, Inc.  Respiratory surfaces must be thin and moist for diffusion of O 2 and CO 2 Cut CO 2 O2O2 Cross section of respiratory surface (the outer skin) Capillaries CO 2 O2O2 Capillary Body surface Respiratory surface (gill)

CO 2 O2O2 Body surface Capillary Respiratory surface (within lung) O2O2 CO 2

Copyright © 2009 Pearson Education, Inc. – Tetrapod adaptation: 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.  From the nasal cavity, air next passes to… Left lung Pharynx Larynx Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) (Esophagus) Nasal cavity

Oxygen-rich blood Bronchiole Alveoli Oxygen-poor blood Blood capillaries Nasal cavity Left lung Pharynx Larynx Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) (Esophagus)

Oxygen-rich blood Bronchiole Alveoli Oxygen-poor blood Blood capillaries

Copyright © 2009 Pearson Education, Inc.  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 Oxygen-rich blood Bronchiole Alveoli Oxygen-poor blood Blood capillaries

Why is smoking is a serious assault on the respiratory system?

Copyright © 2009 Pearson Education, Inc. 1. Damages cilia and decreases mucus production in the respiratory passages

Copyright © 2009 Pearson Education, Inc. 1. Damages cilia and decreases mucus production in the respiratory passages 2. And also… –Increases the risk of heart attacks and strokes (increases heart disease) –Raises blood pressure –Increases harmful types of cholesterol –Causes lung cancer (90%) –Causes emphysema

Copyright © 2009 Pearson Education, Inc.  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

How is breathing controlled?

Copyright © 2009 Pearson Education, Inc.  Breathing is usually under automatic control= breathing control center in brain As CO2 increases (and pH decreases) in blood  rate of depth of breathing increases

Cerebrospinal fluid Pons Medulla Brain Nerve signals trigger contraction of muscles Diaphragm Rib muscles 1

Cerebrospinal fluid Pons Medulla Brain Nerve signals trigger contraction of muscles Diaphragm Rib muscles 1 Breathing control centers respond to pH of blood 2

Cerebrospinal fluid Pons Medulla Brain Nerve signals trigger contraction of muscles Diaphragm Rib muscles 1 Breathing control centers respond to pH of blood 2 Nerve signals indicating CO 2 and O 2 levels 3 CO 2 and O 2 sensors in aorta

Copyright © 2009 Pearson Education, Inc.

 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

Copyright © 2009 Pearson Education, Inc.  Gases move from areas of higher concentration to areas of lower concentration –Example: Gases in the alveoli of the lungs have more O 2 and less CO 2 than gases the blood –How does this happen?? –Diffusion down the pressure gradient –Each gas exerts a pressure called partial pressure

What physically carries the respiratory gasses in the blood?

Copyright © 2009 Pearson Education, Inc.  Most animals transport O 2 bound to proteins called respiratory pigments –Iron-containing hemoglobin –Is used by almost all vertebrates and many invertebrates –Transports oxygen, buffers blood, and transports CO 2 O 2 loaded in lungs O 2 unloaded in tissues Iron atom Polypeptide chain Heme group O2O2 O2O2

Copyright © 2009 Pearson Education, Inc. ◦ 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

Amniotic fluid Uterus Umbilical cord, containing fetal blood vessels Placenta, containing maternal blood vessels and fetal capillaries