Anatomy of the Respiratory System

Objectives

When you have completed this section, you should be able to

• trace the flow of air from the nose to the pulmonary alveoli; and
• relate the function of any portion of the respiratory tract to its gross and microscopic anatomy.

Think About It

In what ways do the structure and function of the pleurae resemble the structure and function of the pericardium?

Key Point Review

1. A dust particle is inhaled and gets into an alveolus without being trapped along the way. Describe the path it takes, naming all air passages from external naris to alveolus. What would happen to it after arrival in the alveolus?

2. Describe the histology of the epithelium and lamina propria of the nasal cavity and the functions of the cell types present.

3. Describe the roles of the intrinsic muscles, corniculate cartilages, and arytenoid cartilages in speech.

4. Contrast the epithelium of the bronchioles with that of the alveoli and explain how the structural difference is related to functional differences.

Mechanics of Ventilation

Objectives

When you have completed this section, you should be able to

• explain how pressure differences between the atmosphere, pulmonary alveoli, and pleural cavity account for the flow of air in and out of the lungs;
• explain how the respiratory muscles produce these pressure differences;
• explain how pulmonary compliance and elasticity contribute to ventilation;
• explain the role of pulmonary surfactant; and
• define terms used to quantify and describe pulmonary ventilation.

Key Point Review

5. Name the major muscles and nerves involved in inspiration.

6. Relate the action of the respiratory muscles to Boyle's law.

7. Explain the relevance of compliance and elasticity to pulmonary ventilation and describe some conditions that reduce compliance and elasticity.

8. Explain how pulmonary surfactant and the law of Laplace relate to compliance.

9. Define vital capacity. Express it in terms of a formula and define each of the variables.

Neural Control of Ventilation

Objectives

When you have completed this section, you should be able to

• name the brainstem centers that regulate respiration and describe their locations and functions;
• contrast the neural pathways for voluntary and automatic control of the major respiratory muscles; and
• describe the stimuli and afferent pathways to the brainstem nuclei that modify the respiratory rhythm.

Think About It

Do you think the fibers from the pneumotaxic center produce EPSPs or IPSPs at their synapses in the inspiratory center? Explain.

Key Point Review

10. Which of the brainstem respiratory nuclei is (are) indispensable to respiration? What do the other nuclei do?

11. Where do voluntary respiratory commands originate? What pathways do they take to the respiratory muscles?

Gas Exchange and Transport

Objectives

When you have completed this section, you should be able to

• explain what is meant by partial pressure and state Dalton's law;
• contrast the composition of inspired air and alveolar air;
• discuss how partial pressure affects the amount of gas that dissolves in the blood;
• explain how the blood transports O₂ and CO₂;
• describe the factors that govern gas exchange in the lungs and systemic capillaries; and
• explain how gas exchange is adjusted to the metabolic needs of different tissues.

Think About It

Expired air, considered as a whole (not just the last 10 mL), contains about 116 mmHg O₂ and 32 mmHg CO₂. Why do you think these values differ from the values for alveolar air?

Key Point Review

12. Why is the gaseous makeup of alveolar air different from that of the atmosphere?

13. What four factors affect the efficiency of alveolar gas exchange?

14. Explain how perfusion of a pulmonary lobule changes if it is inadequately ventilated. How is ventilation of a lobule affected by high ^Pco₂?

15. Describe how oxygen is transported in the blood, and explain why carbon monoxide interferes with this.

16. What are the three ways in which blood transports CO₂?

17. Describe the role of the chloride shift in CO₂ loading.

18. Give two reasons why highly active tissues can extract more oxygen from the blood than less active tissues.

Blood Gases and the Respiratory Rhythm

Objectives

When you have completed this section, you should be able to

• explain how variations in blood ^Po₂ and ^Pco₂ affect the respiratory centers of the brainstem; and
• explain how homeostatic control of blood gases and pH is achieved by the reactions of these respiratory centers.

Key Point Review

19. Describe the locations of the chemoreceptors that monitor blood pH and gas concentrations.

20. Define hypocapnia and hypercapnia. Name the pH imbalances that result from these conditions and explain the relationship between ^Pco₂ and pH.

21. Explain how variations in pulmonary ventilation can either cause or correct pH imbalances.

Respiratory Disorders

Objectives

When you have completed this section, you should be able to

• name and describe the various forms of hypoxia and discuss the dangers of oxygen excess;
• describe the chronic obstructive pulmonary diseases and their consequences;
• explain how lung cancer begins, progresses, and exerts its lethal effects; and
• contrast the common cold, pneumonia, and tuberculosis as to cause and effect.

Think About It

Explain how the length-tension relationship of skeletal muscle (see chapter 12) accounts for the weakness of the respiratory muscles in emphysema.

Key Point Review

22. Describe the four classes of hypoxia.

23. Name and compare two COPDs and describe some pathological effects they have in common.

24. In what lung tissue does lung cancer originate? How does it kill?

25. How is pneumonia different from a common cold?

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