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Chapter 21
The Respiratory System
I. Functional Anatomy of the Respiratory System (pp. 614–630, Figs. 21.1–21.14, and Table 21.1)
A. The function of the respiratory system is to supply the body with oxygen and dispose of carbon dioxide. (p.
B. Respiration involves the following processes: pulmonary ventilation, external respiration, transport of
respiratory gases, and internal respiration. (p. 614)
C. The nose and paranasal sinuses are functional organs of the respiratory system. (pp. 614–618, Figs. 21.1–21.4,
and Fig. 7.10)
1. The nose and nasal cavity provide an airway for respiration and house olfactory receptors.
2. Respiratory mucosa lines the nasal cavity and paranasal sinuses.
3. Nasal conchae increase turbulence as air passes through the nasal cavity.
4. Paranasal sinuses drain into the nasal cavity.
D. The funnel-shaped pharynx connects the nasal cavity and the oral cavity to the larynx and esophagus; three
parts of the pharynx are the nasopharynx, the oropharynx, and the laryngopharynx. (pp. 618–619, Figs. 21.1
and 21.3)
E. The larynx is the voice box and entryway into the trachea. (pp. 619–621, Figs. 21.5–21.6)
1. The larynx contributes significantly to voice production.
2. The vocal folds of the larynx may act as a sphincter to prevent the passage of air.
3. Innervation of the larynx is served by recurrent laryngeal nerves that are branches of the vagus.
F. The trachea is the “windpipe” connecting the larynx to the primary bronchi. (pp. 621–622, Fig. 21.7)
G. The right and left primary bronchi are the largest conduits for air in the conducting zone of the bronchial tree.
(pp. 622–624, Fig. 21.8, Table 21.1)
1. Secondary bronchi (lobar bronchi) enter each lobe of the right and left lung.
2. Segmental bronchi branch from the secondary bronchi to serve each lung segment.
H. Important changes in connective tissues, epithelium, and smooth muscle occur along the length of the
conducting zone of the bronchial tree. (pp. 623–624)
I. The respiratory zone is the distal end of the respiratory tree and contains respiratory bronchioles, alveolar
ducts, alveolar sacs, and alveoli. Additionally, alveoli contain type II cells, which secrete surfactant and
alveolar macrophages, trap and remove inhaled particles. (pp. 624–637, Figs. 21.19–21.10, and Table 21.1)
J. Lungs, the primary organs of respiration, are covered by pleurae. (pp. 627–628, Fig. 21.11)
1. Parietal pleura lines the thoracic cavity and visceral pleura is in direct contact with the surface of the lung.
K. Gross anatomical features of the lung include the base and apex, lobes and fissures, hilus and root, and cardiac
notch of the left lung. (pp. 629–630, Figs. 21.12–21.14)
L. Pulmonary arteries and pulmonary veins serve the lungs; lungs are innervated by sympathetic and
parasympathetic fibers through the pulmonary plexus. (p. 630, Fig. 21.13)
II. Ventilation (pp. 630–634, Figs. 21.15–21.17)
A. The mechanism of breathing (pulmonary ventilation) consists of two phases: inspiration and expiration. (pp.
630–633, Figs. 21.16–21.17)
1. Inspiration is the active process by which the diaphragm and intercostal muscles contract, increasing
thoracic volume and decreasing pressure within the lungs. Deep inspiration additionally involves the actions
of the scalenes and sternocleidomastoid muscles, the pectoralis minor, the quadratus lumborum, and the
erector spinae muscles.
2. Quiet expiration is chiefly a passive process involving the relaxation of intercostal muscles and the
diaphragm, decreasing thoracic volume and increasing pressure within the lungs. Forced expiration is an
active process that involves the actions of the oblique and transverse abdominis muscles.
III. Disorders of the Respiratory System (pp. 634–637, Fig. 21.19)
A. Examples of disorders of the lower respiratory structures are bronchial asthma, chronic obstructive pulmonary
disease (COPD), and cystic fibrosis. (pp. 634–636, Fig. 21.19)
B. Disorders of the upper respiratory structures include epistaxis and epiglottitis. (pp. 636–637)
IV. The Respiratory System Throughout Life (pp. 637–638, Fig. 21.20)
A. Embryologically, the nasal cavity develops from the olfactory placodes; the pharynx forms as part of the
foregut; and the lower respiratory tubes grow from an outpocketing of the embryonic pharynx. (p. 637, Fig.
B. As humans age, the nose becomes dryer and the thorax becomes more rigid; lungs become less elastic. (pp.
Fifth Edition
Chapter 21: The Respiratory System
To the Student
The respiratory system is responsible for delivery of air to your lungs where gas exchange occurs that ensures your
survival. Within lung tissue, oxygen is picked up by the bloodstream and the waste product, carbon dioxide, is removed
from the bloodstream for disposal via the same air tubes. This life-sustaining interaction between the cardiovascular
system and the respiratory system provides the oxygen needed by every cell for its survival. If your cells die, tissues
die, and ultimately you “suffocate” in a matter of minutes if cells are deprived of oxygen. The use of oxygen by cells
for obtaining energy from food molecules such as glucose is termed cellular respiration, and this is a completely
different topic from systemic respiration covered in this chapter. Do not confuse the two concepts. This chapter has
several key concepts and focal points explaining how the respiratory system interacts with other organ systems in your
body, not just the cardiovascular system. Additionally, the mucosal lining of the respiratory system provides an
excellent avenue for disease organisms to travel along, and the many openings and passageways of the nasal cavity to
other parts of the body provide disease organisms with a ready-made entry to those regions.
Step 1: Describe the functional anatomy of the principal organs of the
respiratory system.
- For each of the following principal organs of the respiratory system, provide a general anatomical description and
note any distinctive features: nose, pharynx, larynx, trachea, bronchial tree, alveoli, lungs, and pleurae.
- Describe the function of each of the listed principal organs of the respiratory system.
- Distinguish between the structures of the conducting zone and the structures of the respiratory zone.
Step 2: Describe the mucosa of the respiratory tract.
- Identify the lining of the respiratory tract, name the major type of epithelium associated with the tract, discuss its
functions, and define goblet cells.
- Distinguish between respiratory mucosa and olfactory mucosa.
Step 3: Describe the nose and nasal cavity.
- Describe the bony framework of the nasal cavity, including functions of conchae.
- Discuss locations and functions of the paranasal sinuses.
- Define and distinguish between choanae and fauces.
Step 4: Describe the pharynx, larynx, and trachea.
- Describe the structure and function of the pharynx, including regions, openings, tonsils, and location.
- Describe the structure and function of the larynx, including cartilages, sound (voice) production, sphincter
functions, and innervation.
- Explain the mechanics of swallowing and how entry of food into the nasopharynx and larynx is prevented.
- Relate the sphincter functions of the larynx, i.e., closing of the glottis and abdominal muscle contractions
(Valsalva’s maneuver), to functions of the urinary, digestive, and reproductive systems.
- Describe the structure and function of the trachea, including its anatomical relationship to the esophagus and
vertebral column, trachealis muscle, and wall tunics.
- Define carina (and be careful not to confuse it with concha or choana).
Step 5: Describe the bronchial tree.
- Discuss the structure and function of the bronchial tree, beginning with primary bronchi and ending with terminal
bronchioles, distinguishing between bronchi in the conducting zone and bronchi in the respiratory zone.
- Describe the anatomy of the alveoli, and discuss gas exchange, the blood-air barrier, and other significant features.
- List tissue changes that occur in the bronchial wall as air tubes progressively become smaller and smaller.
Step 6: Describe the lungs and pleurae.
- Review the difference between serous membrane and mucous membrane.
- Distinguish between visceral pleura and parietal pleura, pleural cavity, and pleural fluid and draw and label a
diagram of these structures in the thoracic cavity.
- Draw a right lung and a left lung, labeling gross anatomical features.
- Define mediastinum and explain the anatomical relationships of organs in the thoracic cavity.
- Review pulmonary circulation, and describe blood supply to the lung tissue itself.
- Name the plexus of innervation to the lungs.
Step 7: Explain the mechanism of ventilation (breathing).
- Describe the mechanical aspects of inspiration and expiration, summarizing changes in the thoracic volume, the
action of the diaphragm, and the action of intercostal muscles.
- Explain why surface tension of the alveolar fluid does not collapse the microscopic alveoli after each breath.
(Hint: Do you remember the role of surfactant?)
- Explain the neural control of ventilation, including the location of the respiratory center in the brain and the types
of monitoring chemoreceptors.
Step 8: Read about the major disorders of the respiratory system covered in
your textbook, study in detail disorders assigned by your instructor, and
consider changes in the respiratory system throughout life.
- Read this chapter’s A Closer Look: Lung Cancer: The Facts Behind the Smoke Screen.
- Describe the symptoms and causes of bronchial asthma.
- Describe the symptoms and causes of cystic fibrosis.
- Explain the significance of a nosebleed from the posterior nasal cavity as opposed to a nosebleed from the anterior
part of the nasal cavity.
- Summarize prenatal, postnatal, and aging changes that occur in the respiratory system.