Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Dee Unglaub Silverthorn, Ph.D. H UMAN P HYSIOLOGY PowerPoint ® Lecture Slide Presentation by Dr. Howard D. Booth, Professor of Biology, Eastern Michigan University AN INTEGRATED APPROACH T H I R D E D I T I O N Chapter 17 Mechanics of Breathing

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings About this Chapter Structure and function of the respiratory pumps How gasses are exchanged with blood The role of pressures and surfactants in rate of exchange How respiration is regulated

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Respiratory System: Overview Lungs: exchange surface 75 m 2 Thin walled Moist Ribs & skin protect Diaphragm & ribs pump air

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Interesting Facts about the Lungs Each lung contains approximately 150 million alveoli We lose half a liter of fluid a day from breathing Normal breathing rate is between breaths per minute, but women and children breathe faster than men Breathing rate may to increase to 60 after exercise The capillaries in the lung would extend approximately 1000 miles is laid end to end Approximately 1500 miles of airways are found in the lungs A typical sneeze travels at a velocity of 100 miles per hour The right lung is larger than the left lung and has three lobes as compared to 2 for the left Every minute we breathe 13 pints of air or 6.15 Liters/min We inhale and exhale approximately 22,000 times/day

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Respiratory System: Overview Figure 17-2 b: Anatomy Summary

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Respiratory System Structure 1.Conduction zone: pathway for pulmonary ventilation 2.Respiratory zone: membrane for gas exchange  external respiration Clinically, two parts: Upper respiratory tract Lower respiratory tract

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cross Section Through Lung

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Smoker’s Lungs Non-smoker 

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Small Bronchiole

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lung Tissue slide Respirato ry Bronchiol e Alveolar Duct Alveo li Alveol ar Sac

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the Respiratory System: Overview Figure 17-1: Overview of external and cellular respiration Exchange O 2 Air to blood Blood to cells Exchange CO 2 Cells to blood Blood to air Regulate blood pH Vocalizations Protect alveoli

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Filter, warm & moisten air Nose, (mouth), trachea, bronchi & bronchioles Huge increase in cross sectional area The Airways: Conduction of Air from Outside to Alveoli Figure 17-4: Branching of the airways

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Key Gas Laws Reviewed Gas is compressible & flow  with  resistance Air is a mix of gasses, each diffuses independently

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Key Gas Laws Reviewed Solubility of a gas depends on: Partial pressure of that gas (example: O 2 =156 mmHg) Temperature Solubility in a particular solvent Water: solvent for life O 2 into water: 0.1 m moles/L (poor) CO 2 into water: 3.0 m mole/L (good)

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Ventilation: The Pumps Inspiration Expiration Diaphragm Low energy pump Concavity – flattens Thorax: ribs & muscles Pleura: double membrane Vacuum seal Fluid-lubrication

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Ventilation: The Pumps Figure a: Surfactant reduces surface tension

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Respiratory Damage & Diseases Pneumothorax ("collapsed lung") Fibrotic Lung Disease Emphysema Chronic Bronchitis Asthma NRDS

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pink Puffer-Emphysema is Primary Problem A "pink puffer" is a person where emphysema is the primary underlying pathology. As you recall, emphysema results from destruction of the airways distal to the terminal bronchiole--which also includes the gradual destruction of the pulmonary capillary bed and thus decreased inability to oxygenate the blood. So, not only is there less surface area for gas exchange, there is also less vascular bed for gas exchange--but less ventilation-perfusion mismatch than blue bloaters. The body then has to compensate by hyperventilation (the "puffer" part). Their arterial blood gases (ABGs) actually are relatively normal because of this compensatory hyperventilation. Eventually, because of the low cardiac output, people afflicted with this disease develop muscle wasting and weight loss. They actually have less hypoxemia (compared to blue bloaters) and appear to have a "pink" complexion and hence "pink puffer". Some of the pink appearance may also be due to the work (use of neck and chest muscles) these folks put into just drawing a breath.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Blue Bloater-Chronic Bronchitis is Primary Problem A "blue bloater" is a person where the primary underlying lung pathology is chronic bronchitis. Just a reminder, chronic bronchitis is caused by excessive mucus production with airway obstruction resulting from hyperplasia of mucus-producing glands, goblet cell metaplasia, and chronic inflammation around bronchi. Unlike emphysema, the pulmonary capillary bed is undamaged. Instead, the body responds to the increased obstruction by decreasing ventilation and increasing cardiac output. There is a dreadful ventilation to perfusion mismatch leading to hypoxemia and polycythemia. In addition, they also have increased carbon dioxide retention (hypercapnia). Because of increasing obstruction, their residual lung volume gradually increases (the "bloating" part). They are hypoxemic/cyanotic because they actually have worse hypoxemia than pink puffers and this manifests as bluish lips and faces--the "blue" part.

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Respiratory Damage & Diseases Figure 17-11b: Surfactant reduces surface tension

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Factors Affecting Ventilation Figure 17-2e: Anatomy Summary Airway Resistance Diameter Mucous blockage Bronchoconstriction Bronchodilation Alveolar compliance Surfactants Surface tension Alveolar elasticity

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lung Volumes: Spirometer Measurements Tidal volume: Inspiratory reserve Expiratory reserve Residual Vital capacity

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lung Volumes: Spirometer Measurements Figure 17-12: The recording spirometer

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Spirometry

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Efficiency of Breathing: Normal & High Demand Total Pulmonary Ventilation (rate X tidal vol about 6 L/min) Alveolar ventilation (– dead air space – 4.5 L/min) Little variation [O 2 ] & [CO 2 ] Exercise- High Demand  Depth of breathing Use inspiratory reserve

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Efficiency of Breathing: Normal & High Demand Figure 17-14: Total pulmonary and alveolar ventilation

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Mucociliary Escalator Figure 17-6: Ciliated respiratory epithelium

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gas Exchange in the Alveoli Thin cells: exchange Surfactant cells Elastic fibers Recoil Push air out Thin basement membrane Capillaries cover 90% of surface

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gas Exchange in the Alveoli Figure 17-2 h : Anatomy Summary

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The exchange membrane components and organization Gas Exchange External Respiration

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Capillaries in Alveolar Wall

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Gas Exchange External Respiration alveolus pulmonary capillary arteriole end venule end P O 2 = 40 mm Hg P CO 2 = 46 mm Hg P O 2 = 100 mm Hg P CO 2 = 40 mm Hg P O 2 = 100 mm Hg P CO 2 = 40 mm Hg P O 2 = 40 mm Hg P CO 2 = 46 mm Hg O2O2O2O2 CO 2 inspired air expired air

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Gas Exchange Internal Respiration systemic cell systemic capillary arteriole end venule end P O 2 = 100 mm Hg P CO 2 = 40 mm Hg P O 2 = 40 mm Hg P CO 2 = 46 mm Hg P O 2 = 40 mm Hg P CO 2 = 46 mm Hg P O 2 = 100 mm Hg P CO 2 = 40 mm Hg O2O2O2O2 CO 2

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Gas Exchange What happens when alveolar P O 2 drops? Solubility rules indicate that If P O 2 drops, then the amount dissolved in blood also drops! Creating a hypoxic condition Factors that may cause low arterial P O 2 1.Not enough O 2 reaching alveoli 2.Exchange between alveoli and pulmonary capillaries has a problem 3.Not enough O 2 transported in blood

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Matching Ventilation with Alveolar Blood Flow (Perfusion) Mostly local regulation Low [O 2 ] in alveoli  vasoconstriction of arteriole Reduced blood flow at rest (lung apex ) saves energy High blood [CO 2 ]  bronchodilation

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Matching Ventilation with Alveolar Blood Flow (Perfusion)

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Ventilation & Gas Exchange Relationship Net effect of ventilation is to exchange air within the alveoli to Maintain a partial pressure gradient which is required for gas exchange in the tissues and in the lungs! Blood flow and ventilation rate are optimized to ensure a usable gradient remains despite changing conditions, this is mainly controlled at the local (lung) level by the pulmonary capillaries collapse at low bp, diverting blood to areas of the lung with higher bp (away from the apex, towards the base) Bronchiole diameter is affected by CO 2 levels  P CO 2 in expired air =  in bronchiole diameter (and vice versa) Arteriole diameter in the lungs, controlled by blood gas levels With a  P CO 2 and a  P O 2, the pulmonary arterioles constrict With a  P CO 2 and a  P O 2, the pulmonary arterioles dilate weakly

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Summary Diaphragm & rib cage are pumps for inspiration Alveolar surface exchanges O 2 & CO 2 with blood The gasses in air act independently & move down a pressure gradient Airway resistance can limit ventilation efficiency Typically ventilation matches blood perfusion via local regulators of vasodilation & bronchodilation