chapter 022

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 22:Respiratory System

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


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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


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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


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Gas Exchange and the Alveoli• O2 moves from

alveoli into pulmonary capillaries.

• CO2 moves from pulmonary capillaries into alveoli.


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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.

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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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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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chapter 022

Health & Medicine

imprint of elsevier

alveoli alveoli

right lung

blood copyright

lungs alveoli

alveoli o2

elastic recoil lung

respiratory muscles