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CHAPTER
22
The Respiratory System
Objectives
Functional Anatomy of the Respiratory System
1. Identify the organs forming the respiratory passageway(s) in descending order until you
reach the alveoli.
2. Describe the location, structure, and function of each of the following: nose, paranasal
sinuses, pharynx, and larynx.
Mechanics of Breathing
7. Explain the functional importance of the partial vacuum that exists in the intrapleural
space.
8. Relate Boyle’s law to the events of inspiration and expiration.
Gas Exchanges Between the Blood, Lungs, and Tissues
14. State Dalton’s law of partial pressures and Henry’s law.
Transport of Respiratory Gases by Blood
17. Describe how oxygen is transported in blood, and explain how temperature, pH, BPG,
and 2
CO
Paffect oxygen loading and unloading.
Control of Respiration
19. Describe the neural controls of respiration.
Respiratory Adjustments
21. Compare and contrast the hyperpnea of exercise with hyperventilation.
22. Describe the process and effects of acclimatization to high altitude.
Homeostatic Imbalances of the Respiratory System
Developmental Aspects of the Respiratory System
24. Trace the embryonic development of the respiratory system.
Suggested Lecture Outline
I. Functional Anatomy of the Respiratory System (pp. 802–816; Figs. 22.1–22.11;
Table 22.1)
A. The respiratory system includes the nose, nasal cavity, and paranasal sinuses; pharynx,
larynx, trachea, and bronchi; and the lungs, which contain tiny air sacs, the alveoli
(p. 803; Fig. 22.1).
B. The Nose and Paranasal Sinuses (pp. 803–806; Figs. 22.2–22.3; Table 22.1)
1. The nose provides an airway for respiration; moistens, warms, filters, and cleans incom-
ing air; provides a resonance chamber for speech; and houses olfactory receptors.
2. The nose is divided into two divisions: the external nose, which is formed by hyaline
cartilage and bones of the skull; and the nasal cavity, which is entirely within the skull.
a. The external nose includes the root between the eyebrows, bridge and dorsum nasi
anteriorly, ending at the apex, or tip: two exterior openings exist, the external nares.
C. The Pharynx (p. 806; Fig. 22.3; Table 22.1)
1. The pharynx connects the nasal cavity and mouth superiorly to the larynx and
esophagus inferiorly.
D. The Larynx (pp. 807–809; Figs. 22.3–22.5; Table 22.1)
1. The larynx attaches superiorly to the hyoid bone, opening into the laryngopharynx,
and attaches inferiorly to the trachea.
2. The larynx provides an open airway, routes food and air into the proper passageways,
and produces sound through the vocal cords.
3. The larynx consists of hyaline cartilages: thyroid, cricoid, paired arytenoid, cornicu-
late, and cuneiform; and the epiglottis, which is elastic cartilage.
4. Voice production involves the intermittent release of expired air and the opening and
closing of the glottis.
5. The larynx can act as a sphincter preventing air passage; Valsalva’s maneuver is a
behavior in which the glottis closes to prevent exhalation and the abdominal muscles
contract, causing intra-abdominal pressure to rise.
E. The trachea, or windpipe, descends from the larynx through the neck into the mediasti-
num, where it terminates at the primary bronchi (p. 809; Fig. 22.6; Table 22.1).
1. The tracheal wall is similar to other tubular body structures, consisting of a mucosa,
submucosa, and adventitia.
F. The Bronchi and Subdivisions (pp. 809–812; Figs. 22.7–22.9; Table 22.1)
1. The conducting zone consists of right and left primary bronchi that enter each lung
and diverge into secondary bronchi that serve each lobe of the lungs.
2. Secondary bronchi branch into several orders of tertiary bronchi, which ultimately
branch into bronchioles.
3. As the conducting airways become smaller, structural changes occur:
a. The supportive cartilage changes in character until it is no longer present in the
4. The respiratory zone begins as the terminal bronchioles feed into respiratory bron-
chioles that terminate in alveolar ducts within clusters of alveolar sacs, which consist
of alveoli.
a. The respiratory membrane consists of a single layer of squamous epithelium, type
I alveolar cells, surrounded by a basal lamina.
alveolar macrophages.
G. The Lungs and Pleurae (pp. 812–816; Figs. 22.10–22.11; Table 22.1)
1. The lungs occupy all of the thoracic cavity except for the mediastinum; each lung is
suspended within its own pleural cavity and connected to the mediastinum by vascular
and bronchial attachments called the lung root.
2. The left lung is smaller than the right because the position of the heart is shifted
slightly to the left; each lung is divided into lobes, separated from each other by
fissures.
6. The lungs are innervated by parasympathetic and sympathetic motor fibers that
constrict or dilate the airways, as well as visceral sensory fibers.
7. The pleurae form a thin, double-layered serosa.
a. The parietal pleura covers the thoracic wall, superior face of the diaphragm, and
continues around the heart between the lungs.
d. The pleurae divide the thoracic cavity into three discrete chambers, preventing one
organ’s movement from interfering with another’s, as well as limiting the spread
of infection.
II. Mechanics of Breathing (pp. 816–824; Figs. 22.12–22.16; Tables 22.2–22.3)
A. Respiratory pressures are described relative to atmospheric pressures: a negative pressure
indicates that the respiratory pressure is lower than atmospheric pressure (pp. 816–817;
Fig. 22.12).
1. Intrapulmonary pressure is the pressure in the alveoli, which rises and falls during
respiration, but always eventually equalizes with atmospheric pressure.
2. Intrapleural pressure is the pressure in the pleural cavity. It also rises and falls during
respiration, but is always about 4 mm Hg less than intrapulmonary pressure.
B. Pulmonary Ventilation (pp. 817–820; Figs. 22.13–22.14)
1. Pulmonary ventilation is a mechanical process causing gas flow into and out of the
lungs according to volume changes in the thoracic cavity.
a. Boyle’s law states that at a constant temperature, the pressure of a gas varies
inversely with its volume.
2. During quiet inspiration, the diaphragm and intercostals contract, resulting in an
increase in thoracic volume, which causes intrapulmonary pressure to drop below
atmospheric pressure, and air flows into the lungs.
C. Physical Factors Influencing Pulmonary Ventilation (pp. 820–821; Fig. 22.15)
1. Airway resistance is the friction encountered by air in the airways; gas flow is reduced
as airway resistance increases.
a. Airway resistance is greatest in the medium-sized airways due to two factors:
upper airways are very large diameter, and lower airways, while smaller, are very
numerous.
D. Respiratory Volumes and Pulmonary Function Tests (pp. 821–823; Fig. 22.16;
Table 22.2)
1. Respiratory volumes and specific combinations of volumes, called respiratory capaci-
ties, are used to gain information about a person’s respiratory status.
a. Tidal volume (TV) is the amount of air that moves in and out of the lungs with each
2. Respiratory capacities are sums of multiple respiratory volumes.
a. Inspiratory capacity (IC) is the sum of tidal volume and inspiratory reserve volume
and represents the total amount of air that can be inspired after a tidal expiration.
3. The anatomical dead space is the volume of the conducting zone conduits, roughly
150 ml, which is a volume that never contributes to gas exchange in the lungs.
4. Pulmonary function tests evaluate losses in respiratory function using a spirometer to
distinguish between obstructive and restrictive pulmonary disorders.
1. Nonrespiratory air movements cause movement of air into or out of the lungs, but are
not related to breathing (coughing, sneezing, crying, laughing, hiccups, and yawning).
III. Gas Exchanges Between the Blood, Lungs, and Tissues (pp. 824–828;
Figs. 22.17–22.19; Table 22.4)
A. Gases have basic properties, as defined by Dalton’s law of partial pressures and Henry’s
law (pp. 824–825; Table 22.4).
1. Dalton’s law of partial pressures states that the total pressure exerted by a mixture of
gases is the sum of the pressures exerted by each gas in the mixture.
C. External Respiration (pp. 825–827; Figs. 22.17–22.19)
1. External respiration involves O2 uptake and CO2 unloading from hemoglobin in red
blood cells.
a. A steep partial pressure gradient exists between blood in the pulmonary arteries and
2. The respiratory membrane is normally very thin and presents a huge surface area for
efficient gas exchange.
3. Ventilation-perfusion coupling ensures a close match between the amount of gas
reaching the alveoli and the blood flow in the pulmonary capillaries.
a. In order to optimize perfusion and maximize oxygen uptake into the blood, arteri-
D. Internal Respiration (pp. 827–828; Fig. 22.17)
1. The diffusion gradients for oxygen and carbon dioxide are reversed from those for
external respiration and pulmonary gas exchange.
IV. Transport of Respiratory Gases by Blood (pp. 828–833; Figs. 22.20–22.22)
A. Oxygen Transport (pp. 828–829; Figs. 22.20–22.21)
1. Because molecular oxygen is poorly soluble in the blood, only 1.5% is dissolved in
plasma, while the remaining 98.5% must be carried on hemoglobin.
a. Up to four oxygen molecules can be reversibly bound to a molecule of
hemoglobin—one oxygen on each iron.
B. Carbon Dioxide Transport (pp. 829, 832–833; Fig. 22.22)
1. Carbon dioxide is transported in the blood in three ways: 7–10% is dissolved in
plasma, 20% is carried on hemoglobin bound to globins, and 70% exists as bicarbo-
nate, an important buffer of blood pH.
V. Control of Respiration (pp. 834–838; Figs. 22.23–22.26)
A. Neural Mechanisms (pp. 834–835; Fig. 22.23)
1. Two areas of the medulla oblongata are critically important to respiration: the dorsal
respiratory group near the root of cranial nerve IX and the ventral respiratory group
extending from the spinal cord to the pons-medulla junction.
3. The cyclic behavior of inspiratory and expiratory neurons produces a breathing rate
of 12–15 breaths per minute, which is called eupnea.
4. The pontine respiratory group within the pons modifies the breathing rhythm and
prevents overinflation of the lungs through an inhibitory action on the medullary
respiration centers.
B. Factors Influencing Breathing Rate and Depth (pp. 835–838; Figs. 22.24–22.26)
1. The most important factors influencing breathing rate and depth are changing levels
of CO2, O2, and H+ in arterial blood.
a. The receptors monitoring fluctuations in these parameters are the central chemore-
ceptors in the medulla oblongata and the peripheral chemoreceptors in the aortic
arch and carotid arteries.
2. Higher brain centers alter rate and depth of respiration.
a. The limbic system, strong emotions, and pain activate the hypothalamus, which
modifies respiratory rate and depth.
b. The cerebral cortex can exert voluntary control over respiration by bypassing the
medullary centers and directly stimulating the respiratory muscles.
inspiration.
VI. Respiratory Adjustments (pp. 838–839)
A. Exercise (p. 838)
1. During vigorous exercise, deeper and more vigorous respirations, called hyperpnea,
ensure that tissue demands for oxygen are met.
B. High Altitude (pp. 838–839)
1. Acute mountain sickness (AMS) may result from a rapid transition from sea level to
altitudes above 8000 feet.
VII. Homeostatic Imbalances of the Respiratory System (pp. 839–841; Fig. 22.27)
A. Chronic obstructive pulmonary diseases (COPD) are seen in patients that have a history
of smoking and result in progressive dyspnea, coughing and frequent pulmonary infec-
tions, and respiratory failure (pp. 839–840; Fig. 22.27).
1. Obstructive emphysema is characterized by permanently enlarged alveoli and deterio-
ration of alveolar walls.
D. Lung Cancer (p. 841)
1. In both sexes, lung cancer is the most common type of malignancy and is strongly
correlated with smoking.
2. Adenocarcinoma originates in peripheral lung areas as nodules that develop from
bronchial glands and alveolar cells.
VIII. Developmental Aspects of the Respiratory System (pp. 841–844; Fig. 22.28)
A. By the fourth week of development, the olfactory placodes are present and give rise to
olfactory pits that form the nasal cavities (p. 841; Fig. 22.28).
B. The nasal cavity extends posteriorly to join the foregut, which gives rise to an outpocket-
ing that becomes the pharyngeal mucosa. Mesoderm forms the walls of the respiratory
passageways and stroma of the lungs (pp. 841–842; Fig. 22.28).
Cross References
Additional information on topics covered in Chapter 22 can be found in the chapters listed below.
1. Chapter 1: Mediastinum
2. Chapter 2: Acids and bases
6. Chapter 10: Muscles of respiration
7. Chapter 12: Medulla and pons; cortex
8. Chapter 13: Chemoreceptors; proprioceptors
9. Chapter 14: Sympathetic effects
10. Chapter 15: Auditory tube; lysozyme
Lecture Hints
1. Stress the difference between ventilation and respiration.
2. The divisions of the pharynx are often confusing to students. Be sure to clearly indicate
the boundaries between these divisions.
5. Be sure the class does not confuse the respiratory membrane with subcellular level
membrane structures (plasma membrane, etc.).
6. Remind students that pulmonary vessels are exceptions to the rule: arteries carry
oxygenated blood and veins carry deoxygenated blood.
7. Be sure that students do not confuse the bronchial artery (oxygenated blood) with the
pulmonary artery (deoxygenated blood).
10. A complete understanding of diffusion is necessary for comprehension of respiratory gas
movement at lung and body tissue levels. Refer the class in advance to the section on
diffusion in Chapter 3.
11. Mention that cellular respiration is not the same as internal or external respiration, but
that cellular respiration involves the pathways of glucose catabolism.
Activities/Demonstrations
1. Audiovisual materials are listed in the Multimedia in the Classroom and Lab section of
this Instructor Guide (p. 387).
2. Provide stethoscopes so that students can listen to respiratory (breathing) sounds over
3. Using handheld spirometers, have students measure their respiratory volumes,
particularly tidal volume and vital capacity.
4. Provide straws, beakers of water, and pH paper. Have students use the straws to blow
5. Provide tape measures so that students can measure the circumference of the rib cage
before and after inspiration.
6. Use a torso model, respiratory system model, and/or dissected animal model to exhibit
the respiratory system and related organs.
7. Use two glass slides with water between them to demonstrate the cohesive effect of the
8. Use an open-ended bell jar with balloons inside to demonstrate the changing pressures as
10. Use a freshly opened soft drink to demonstrate and explain Henry’s law.
11. Demonstrate the location of the sinuses using a complete or Beauchene’s skull.
12. Obtain a fresh lamb or calf pluck (lungs plus attached trachea and heart) from a slaugh-
13. Obtain some animal blood and bubble air through the blood via a small section of tubing
to demonstrate the color change that occurs when blood is well oxygenated.
Critical Thinking/Discussion Topics
1. Discuss the benefits of athletic training at high altitude.
2. Explore the changes in respiratory volumes with obstructive or congestive pulmonary
disorders.
5. Discuss the relationship between intrapulmonary pressure and intrapleural pressure.
What happens to intrapulmonary pressure relative to intrapleural pressure when
Library Research Topics
2. Study the incidence of cancer in smokers versus nonsmokers and in individuals working
in respiratory hazard areas versus individuals working in relatively safe respiratory areas.
4. Investigate the causes, known and supposed, of sudden infant death syndrome (SIDS).
5. Research the respiratory problems a premature infant might face.
6. Research the emergence and incidence of respiratory ailments such as Severe Acute
Respiratory Syndrome (SARS).
with that in the 1930s.
List of Figures and Tables
All of the figures in the main text are available in JPEG format, PPT, and labeled & unlabeled
format on the Instructor Resource DVD. All of the figures and tables will also be available in
Transparency Acetate format. For more information, go to www.pearsonhighered.com/educator.
Figure 22.1 The major respiratory organs in relation to surrounding
structures.
Figure 22.8 Respiratory zone structures.
Figure 22.9 Alveoli and the respiratory membrane.
Figure 22.10 Anatomical relationships of organs in the thoracic cavity.
Figure 22.11 A cast of the bronchial tree.
Figure 22.12 Intrapulmonary and intrapleural pressure relationships.
Figure 22.13 Changes in thoracic volume and sequence of events during
inspiration and expiration.
Figure 22.14 Changes in intrapulmonary and intrapleural pressures during
inspiration and expiration.
Figure 22.19 Ventilation-perfusion coupling.
Figure 22.20 The Oxygen-Hemoglobin Dissociation Curve.
Figure 22.21 Effect of temperature, 2
CO
P, and blood pH on the
oxygen-hemoglobin dissociation curve.
Figure 22.26 Location and innervation of the peripheral chemoreceptors in the
carotid and aortic bodies.
Figure 22.27 The pathogenesis of COPD.
Figure 22.28 Embryonic development of the respiratory system.
Table 22.1 Principal Organs of the Respiratory System
Table 22.2 Effects of Breathing Rate and Depth on Alveolar Ventilation of
Three Hypothetical Patients
Answers to End-of-Chapter Questions
Multiple-Choice and Matching Question answers appear in Appendix H of the main text.
Short Answer Essay Questions
17. The route of air from the external nares to an alveolus and the organs involved are as
follows: conducting zone structures—external nares, nasal cavity, pharynx (nasopharynx,
18. See p. 809.
a.
The trachea is reinforced with cartilage rings to prevent the trachea from collapsing
19. The adult male larynx as a whole is larger and the vocal cords are longer than those of
20. a. The elastic tissue is essential both for normal inspiration and expiration; expiration is
almost totally dependent on elastic recoil of the lungs when the inspiratory muscles
relax. (p. 819)
21. The volume of gas flow to and from the alveoli is directly proportional to the difference
in pressure between the external atmosphere and the alveoli. Very small differences in
22. Pulmonary ventilation, or gas flow into and out of the lungs, relies on the pressure gra-
dient between the atmosphere and alveoli, and airway diameter. Given that gas flow in
a system is equal to the pressure gradient divided by the resistance, when resistance
23. See p. 823.
a. Minute ventilation is the total amount of gas that flows into and out of the respiratory
24. Dalton’s law of partial pressures states that the total pressure exerted by a mixture of
gases is the sum of the pressure exerted independently by each gas in the mixture.
Henry’s law states that when a mixture of gases is in contact with a liquid, each gas
will dissolve in the liquid in proportion to its partial pressure and its solubility in the
liquid. (p. 824)
25. See p. 836.
a.
Hyperventilation is rapid or deep breathing.
26. Age-related changes include a loss of elasticity in the lungs and a more rigid chest wall.
These factors result in a slowly decreasing ability to ventilate the lungs. Accompanying
Critical Thinking and Clinical Application Questions
1. Hemoglobin is almost completely (98%) saturated with oxygen in arterial blood at
normal conditions. Hence, hyperventilation will increase the oxygen saturation very little,
2. a. The lung penetrated by the knife collapsed because the intrapleural pressure became
3. Adjacent bronchopulmonary segments are separated from one another by partitions of
4. Mary Ann is suffering from decompression sickness, brought on by the rapid ascent in
the plane. During the week of diving, she accumulated nitrogen gas in her tissues that at
normal altitudes leaves her tissues slowly and unnoticed. However, on the flight, cabin
pressure decreased quickly enough to allow residual nitrogen gas to leave more rapidly,
causing her symptoms. The return to a lower altitude with a higher atmospheric pressure
upon landing alleviates her symptoms. (p. 825)
Suggested Readings
Beall, Cynthia M., et al. “Pulmonary Nitric Oxide in Mountain Dwellers.” Nature 414
(Nov. 2001): 411–412.
Christensen, Damaris. “The Persistent Problem of Cystic Fibrosis.” Science News 161 (4)
(Jan. 2002): 59–60.
Fujimoto, K., et al. “Acute Exacerbation of Idiopathic Pulmonary Fibrosis: High-Resolution
CT Scores Predict Mortality.” European Radiology 22 (1) (Jan. 2012): 83–92.
Gosens, Reinoud, et al. “Caveolae and Caveolins in the Respiratory System.” Current
Molecular Medicine 8 (8) (Dec. 2008): 741–753.
Hershcovici, T., et al. “Systematic Review: The Relationship between Interstitial Lung
Diseases and Gastro-Oesophageal Reflux Disease.” Alimentary Pharmacology &
Therapeutics 34 (11–12) (Dec. 2011): 1295–1305.
Mermigkis, C., et al. “Sleep Quality and Associated Daytime Consequences in Patients
with Idiopathic Pulmonary Fibrosis.” Medical Principles & Practice 18 (1) (Jan. 2009):
10–15.
Okada, Yasumasa, Z. Chen, and S. Kuwana. “Cytoarchitecture of Central Chemoreceptors in
the Mammalian Ventral Medulla.” Respiration Physiology 129 (Dec. 2001): 13–23.
O’Toole, George A. “A Resistance Switch.” Nature 416 (6882) (April 2002): 695–696.
