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The Human Body in Health and Illness, 4th edition
Barbara Herlihy
Chapter 22:Respiratory System
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Lesson 22-1 Objectives
• Describe the structure and functions of the organs of the respiratory system.
• Trace the movement of air from the nostrils to the alveoli.
• Describe the role of pulmonary surfactants.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
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Structure: Organs of the Respiratory System
• Upper respiratory tract: Organs located outside the chest
• Lower respiratory tract: Organs located inside the chest
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
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Upper Respiratory System• Nose and nasal cavities• Pharynx
– Nasopharynx– Oropharynx– Laryngopharynx
• Larynx– Vocal cords
• Upper trachea– Cartilaginous rings
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Functions of Upper Respiratory Structures
• Nose and nasal passages: Warm, moisturize, and conduct air
• Pharynx (throat): Conducts air to lower structures
• Larynx (voice box): Vibrates vocal cords, produces sound, and conducts air to lower structures
• Trachea (windpipe): Conducts air to right bronchus and left bronchus
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
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Lower Respiratory System
• Lower trachea• Bronchi • Bronchioles • Alveoli• Lungs• Pleural membranes• Muscles of respiration
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Bronchial Tree
• Right and left bronchi– Cartilaginous rings– Carina
• Bronchioles– Smooth muscle
• Alveoli– Single layered
membrane
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Bronchial Tree: Functions
• Bronchi: Conduct air to bronchioles• Bronchioles: Smooth muscle determines
diameter, regulates air flow to the alveoli• Alveoli: Small grapelike structures; air sacs
that exchange O2 and CO2 with blood in pulmonary circulation
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
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Gas Exchange and the Alveoli• O2 moves from
alveoli into pulmonary capillaries.
• CO2 moves from pulmonary capillaries into alveoli.
Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights
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Lungs• Large, soft, cone-shaped organs; contain
structures of lower respiratory tract• Apex (top), base (bottom) • Right lung: Three lobes
– Superior – Middle– Inferior
• Left lung: Two lobes– Superior– Inferior
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Pleural Membranes• Parietal pleura:
Outer serous membrane
• Visceral pleura: Lines outside of lungs
• Intrapleural space: Located between parietal and visceral pleurae
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Factors in Lung Expansion
• Normal lung expansion depends on opposing forces.
• Two factors oppose lung expansion.– Elastic recoil– Surface tension
• One factor promotes lung expansion.– Negative intrapleural pressure
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Elastic Recoil
• Lung and balloon want to return to unstretched shape.
• Result of arrangement of fibers.
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Surface Tension
• Water has high surface tension (attraction between polar water molecules).
• Surfactants from alveolar cells decrease surface tension.
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Normal Lung Expansion
• Negative intrapleural pressure allows the lung to expand.
• It overcomes elastic recoil and surface tension.
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Collapsed Lung
• Loss of negative intrapleural pressure collapses lung.
• Lung expands if negative pressure is restored.
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Collapsed Lung: Clinical Examples
Knife wound, chest wall Ruptured bleb
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Lesson 22-2 Objectives
• Describe the relationship of Boyle’s law to ventilation.
• Explain how respiratory muscles affect thoracic volume.
• List three conditions that make the alveoli well-suited for the exchange of oxygen and carbon dioxide.
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Lesson 22-2 Objectives (cont’d.)
• List lung volumes and capacities• Explain the neural and chemical control of
respiration.• Describe common variations and
abnormalities of breathing.
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Three Steps of Respiration• Ventilation
– Inhalation (inspiration)– Exhalation (expiration)– Respiratory cycle = one inhalation + one
exhalation
• Exchange of O2 and CO2
– At the lungs (alveoli)– At the tissue level
• Transport of O2 and CO2 by the bloodCopyright © 2011, 2007 by Saunders,
an imprint of Elsevier Inc. All rights reserved.
20
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Boyle’s Law: “As volume changes, pressure changes.”
• Large tube volume > small tube volume
• Add 1 liter of air to each tube.
• Small tube pressure > large tube pressure
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Boyle’s Law: Inhalation
• Respiratory muscles contract to increase thoracic volume.
• As volume increases, intrathoracic pressure (P2) decreases.
• Air moves in.
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Boyle’s Law: Exhalation
• Respiratory muscles relax to decrease thoracic volume.
• As volume decreases, intrathoracic pressure (P2) increases.
• Air moves out.
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Respiratory Muscles and Nerves
• Diaphragm– Innervated by phrenic nerve
• Intercostal muscles– Innervated by intercostal nerves
• Respiratory muscles are skeletal muscles.– The transmitter at the neuromuscular junction is
ACh.– Blocking the receptors (NM) impairs ventilation.
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Gas Exchange: Lungs and Tissue• Lungs
– O2 moves into blood from alveoli.
– CO2 moves into alveoli from blood.
• Tissue– O2 moves from
blood to tissue.– CO2 moves from
tissue to blood.Copyright © 2011, 2007 by Saunders,
an imprint of Elsevier Inc. All rights reserved.
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Transport of O2 and CO2 by Blood
• Amount of each gas expressed as partial pressure.– PO2 and PCO2
• O2
– Almost all transported as oxyhemoglobin.
• CO2
– 70% transported as bicarbonate or HCO3–
– 20% transported as carbaminohemoglobin – 10% dissolved in plasma and transported
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reserved.
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Pulmonary Volumes
• Tidal volume• Inspiratory reserve• Expiratory reserve• Residual
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Capacities: Calculated Volumes
• Vital capacity• Maximal
exhalation following maximal inhalation
• Functional residual capacity
• Total lung capacity
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Control of Respiration
Nervous • Medulla oblongata
– Inspiratory neurons– Expiratory neurons
• Pons– Pneumotaxic center– Apneustic center
Chemical • Pco2 and H+ are
major regulators.• Chemoreceptors
– Central (CNS)– Peripheral: Carotid
bodies, aortic bodies
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Ventilatory Rate and Rhythm: Factors
• Voluntary• Emotions
• Involuntary• Chemoreceptors
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Common Respiratory Terms
• Eupnea: Normal, quiet breathing• Apnea: Temporary cessation of breathing• Dyspnea: Difficult or labored breathing• Tachypnea: Rapid breathing• Bradypnea: Abnormally slow breathing• Orthopnea: Difficulty in breathing relieved by
sitting up
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Common Respiratory Terms (cont’d.)
• Hyperventilation: Increase in rate and depth• Hypoventilation: Decrease in rate and depth• Hypoxemia: Abnormally low concentration of
O2 in the blood
• Hypercapnia: Abnormally high concentration of CO2 in the blood
• Hypocapnia: Abnormally low concentration of CO2 in the blood
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