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Chapter 19: Respiratory System

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Diagram The Respiratory Passege
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Chapter Summary

Introduction (page 7 79)

The respiratory system includes the passages that transport air to and from the lungs and the air sacs in which gas exchanges occur. Respiration is the entire process by which gases are exchanged between the atmosphere and the body cells. Respiration is necessary because of cellular respiration. Cells require oxygen to extract maximal energy from nutrient molecules and to rid themselves of carbon dioxide, a metabolic waste.

Organs of the Respiratory System (page 780)

The respiratory system includes the nose, nasal cavity, sinuses, pharynx, larynx, trachea, bronchial tree, and lungs. The upper respiratory tract includes the nose, nasal cavity, sinuses, and pharynx; the lower respiratory tract includes the larynx, trachea, bronchial tree, and lungs.

1. Nose a. Bone and cartilage support the nose.

b. Nostrils provide entrances for air.

2. Nasal cavity a. The nasal cavity is a space posterior to the nose.

b. The nasal septum divides it medially.

c. Nasal conchae divide the cavity into passageways and help increase the surface area of the mucous membrane.

d. Mucous membrane filters, warms, and moistens incoming air.

e. Particles trapped in the mucus are carried to the pharynx by ciliary action and are swallowed.

3. Sinuses a. Sinuses are spaces in the bones of the skull that open into the nasal cavity.

b. They are lined with mucous membrane that is continuous with the lining of the nasal cavity.

4. Pharynx a. The pharynx is located posterior to the mouth and between the nasal cavity and the larynx.

b. It provides a common passage for air and food.

c. It aids in creating vocal sounds.

5. Larynx a. The larynx is an enlargement at the top of the trachea.

b. It is a passageway for air and helps prevent foreign objects from entering the trachea.

c. It is composed of muscles and cartilages; some of these cartilages are single whereas others are paired.

d. It contains the vocal cords, which produce sounds by vibrating as air passes over them.

(1) The pitch of a sound is related to the tension on the cords.

(2) The intensity of a sound is related to the force of the air passing over the cords.

e. The glottis and epiglottis help prevent food and liquid from entering the trachea.

6. Trachea a. The trachea extends into the thoracic cavity in front of the esophagus.

b. It divides into the right and left bronchi.

c. The mucous lining continues to filter incoming air.

d. Incomplete cartilaginous rings support the wall.

7. Bronchial tree a. The bronchial tree consists of branched air passages that connect the trachea to the air sacs.

b. The branches of the bronchial tree include primary bronchi, lobar bronchi, segmental bronchi, intralobular bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

c. Structure of the respiratory tubes

(1) As tubes branch, the amount of cartilage in the walls decreases, and the muscular layer becomes more prominent.

(2) Elastic fibers in the walls aid breathing.

(3) The epithelial lining changes from pseudostratified and ciliated to cuboidal and simple squamous as the tubes become progressively smaller.

d. Functions of the respiratory tubes include distribution of air and exchange of gases between the alveolar air and the blood.

8. Lungs a. The left and right lungs are separated by the mediastinum and are enclosed by the diaphragm and the thoracic cage.

b. The visceral pleura is attached to the surface of the lungs; parietal pleura lines the thoracic cavity.

c. The right lung has three lobes, and the left lung has two.

d. Each lobe is composed of lobules that contain alveolar ducts, alveolar sacs, alveoli, nerves, blood vessels, lymphatic vessels, and connective tissues.

Breathing Mechanism (page 792)

Inspiration and expiration movements are accompanied by changes in the size of the thoracic cavity.

1. Inspiration a. Atmospheric pressure forces air into the lungs.

b. Inspiration occurs when the intra-alveolar pressure is reduced.

c. The intra-alveolar pressure is reduced when the diaphragm moves downward and the thoracic cage moves upward and outward.

d. Surface tension holding the pleural membranes together aids lung expansion.

e. Surfactant reduces surface tension within the alveoli.

2. Expiration a. The forces of expiration come from the elastic recoil of tissues and from surface tension within the alveoli.

b. Expiration can be aided by thoracic and abdominal wall muscles that pull the thoracic cage downward and inward and compress the abdominal organs inward and upward.

3. Respiratory volumes and capacities a. One inspiration followed by one expiration is called a respiratory cycle.

b. The amount of air that moves in and out during a respiratory cycle is the tidal volume.

c. Additional air that can be inhaled is the inspiratory reserve volume; additional air that can be exhaled is the expiratory reserve volume.

d. Residual air remains in the lungs and is mixed with newly inhaled air.

e. The inspiratory capacity is the maximum volume of air a person can inhale following exhalation of the tidal volume.

f. The functional residual capacity is the volume of air that remains in the lungs following the exhalation of the tidal volume.

g. The vital capacity is the maximum amount of air a person can exhale after taking the deepest breath possible.

h. The total lung capacity is equal to the vital capacity plus the residual air volume.

i. Air in the anatomic and alveolar dead spaces is not available for gas exchange.

4. Alveolar ventilation a. Minute ventilation is calculated by multiplying the tidal volume by the breathing rate.

b. Alveolar ventilation rate is calculated by subtracting the physiologic dead space from the tidal volume and multiplying the result by the breathing rate.

c. The alveolar ventilation rate is a major factor affecting the exchange of gases between the alveolar air and the blood.

5. Nonrespiratory air movements a. Nonrespiratory air movements are air movements other than breathing.

b. They include coughing, sneezing, laughing, crying, hiccuping, and yawning.

Control of Breathing (page 800)

Normal breathing is rhythmic and involuntary, although the respiratory muscles can be controlled voluntarily.

1. Respiratory center a. The respiratory center is located in the brain stem and includes parts of the medulla oblongata and pons.

b. The medullary rhythmicity area includes two groups of neurons.

(1) The dorsal respiratory group is responsible for the basic rhythm of breathing.

(2) The ventral respiratory group increases inspiratory and expiratory movements during forceful breathing.

c. The pneumotaxic area regulates the rate of breathing.

2. Factors affecting breathing a. The partial pressure of a gas is determined by the concentration of that gas in a mixture of gases or the concentration of gas dissolved in a liquid.

b. Chemicals, lung tissue stretching, and emotional state affect breathing.

c. Chemosensitive areas (central chemoreceptors) are associated with the respiratory center.

(1) Carbon dioxide combines with water to form carbonic acid, which, in turn, releases hydrogen ions in the CSF.

(2) Stimulation of these areas increases alveolar ventilation.

d. Peripheral chemoreceptors are in the carotid bodies and aortic bodies of certain arteries.

(1) These chemoreceptors sense low oxygen concentration.

(2) When oxygen concentration is low, alveolar ventilation increases.

e. Stretching the lung tissues triggers an inflation reflex.

(1) This reflex reduces the duration of inspiratory movements.

(2) This prevents overinflation of the lungs during forceful breathing.

f. Hyperventilation decreases carbon dioxide concentration, but this is very dangerous when associated with breath holding during underwater swimming.

Alveolar Gas Exchanges (page 804)

Gas exchanges between the air and the blood occur within the alveoli.

1. Alveoli a. The alveoli are tiny sacs clustered at the distal ends of the alveolar ducts.

b. Some alveoli open into adjacent air sacs that provide alternate pathways for air when passages are obstructed.

2. Respiratory membrane a. The respiratory membrane consists of the alveolar and capillary walls.

b. Gas exchanges take place through these walls.

3. Diffusion through the respiratory membrane a. Gases diffuse from regions of higher partial pressure toward regions of lower partial pressure.

b. Oxygen diffuses from the alveolar air into the blood; carbon dioxide diffuses from the blood into the alveolar air.

Gas Transport (page 807)

Blood transports gases between the lungs and the body cells.

1. Oxygen transport a. Oxygen is mainly transported in combination with hemoglobin molecules.

b. The resulting oxyhemoglobin is relatively unstable and releases its oxygen in regions where the PO2 is low.

c. More oxygen is released as the blood concentration of carbon dioxide increases, as the blood becomes more acidic, and as the blood temperature increases.

2. Carbon dioxide transport a. Carbon dioxide may be carried in solution, either as dissolved CO2, CO2 bound to hemoglobin, or as a bicarbonate ion.

b. Most carbon dioxide is transported in the form of bicarbonate ions.

c. Carbonic anhydrase, an enzyme, speeds the reaction between carbon dioxide and water to form carbonic acid.

d. Carbonic acid dissociates to release hydrogen ions and bicarbonate ions.

Life-Span Changes (page 812)

The lungs, respiratory passageways, and alveoli undergo aging-associated changes that are exacerbated by exposure to polluted air. However, the increased work required to breathe with age is typically not noticeable unless one engages in vigorous exercise.

1. Exposure to pollutants, smoke, and other particulates raises risk of developing diseases of the respiratory system.

2. Loss of cilia, thickening of mucus, and impaired macrophages raise the risk of infection.

3. Calcified cartilage, skeletal changes, altered posture, and replacement of smooth muscle with fibrous connective tissue in bronchioles make breathing more difficult. Vital capacity diminishes.

4. The lungs contain a greater proportion of "stale" air.

5. Alveoli coalesce and become shallower, slowing gas exchange.

Critical Thinking Questions

If the upper respiratory passages are bypassed with a 4.

tracheostomy, how might the air entering the trachea be different from air normally passing through this canal?

What problems might this cause for the patient?

Certain respiratory disorders, such as emphysema, reduce 5.

the capacity of the lungs to recoil elastically. Which respiratory air volumes will this condition affect? Why?

What changes would you expect to occur in the relative concentrations of blood oxygen and carbon dioxide in a 6.

patient who breathes rapidly and deeply for a prolonged time? Why?

If a person has stopped breathing and is receiving pulmonary resuscitation, would it be better to administer pure oxygen or a mixture of oxygen and carbon dioxide? Why?

The air pressure within the passenger compartment of a commercial aircraft may be equivalent to an altitude of 8,000 feet. What problem might this create for a person with a serious respiratory disorder?

Patients experiencing asthma attacks are often advised to breathe through pursed (puckered) lips. How might this help reduce the symptoms of the asthma?

Review Exercises

1. Describe the general functions of the respiratory system.

2. Distinguish between the upper and lower respiratory tracts.

3. Explain how the nose and nasal cavity filter incoming air.

4. Name and describe the locations of the major sinuses, and explain how a sinus headache may occur.

5. Distinguish between the pharynx and the larynx.

6. Name and describe the locations and functions of the cartilages of the larynx.

7. Distinguish between the false vocal cords and the true vocal cords.

8. Compare the structure of the trachea with the structure of the branches of the bronchial tree.

9. List the successive branches of the bronchial tree, from the primary bronchi to the alveoli.

10. Describe how the structure of the respiratory tube changes as the branches become finer.

11. Explain the functions of the respiratory tubes.

12. Distinguish between visceral pleura and parietal pleura.

13. Name and describe the locations of the lobes of the lungs.

14. Explain how normal inspiration and forced inspiration are accomplished.

15. Define surface tension, and explain how it aids the breathing mechanism.

16. Define surfactant, and explain its function.

17. Define compliance.

18. Explain how normal expiration and forced expiration are accomplished.

19. Distinguish between vital capacity and total lung capacity.

20. Distinguish among anatomic, alveolar, and physiologic dead spaces.

21. Distinguish between minute respiratory volume and alveolar ventilation rate.

22. Compare the mechanisms of coughing and sneezing, and explain the function of each.

23. Explain the function of yawning.

24. Describe the location of the respiratory center, and name its major components.

25. Describe how the basic rhythm of breathing is controlled.

26. Explain the function of the pneumotaxic area of the respiratory center.

27. Explain why increasing blood concentrations of carbon dioxide and hydrogen ions have similar effects on the respiratory center.

28. Describe the function of the peripheral chemoreceptors in the carotid and aortic bodies of certain arteries.

29. Describe the inflation reflex.

30. Discuss the effects of emotions on breathing.

31. Define hyperventilation, and explain how it affects the respiratory center.

32. Define respiratory membrane, and explain its function.

33. Explain the relationship between the partial pressure of a gas and its rate of diffusion.

34. Summarize the gas exchanges that occur through the respiratory membrane.

35. Describe how oxygen is transported in blood.

36. List three factors that increase release of oxygen from the blood.

37. Explain why carbon monoxide is toxic.

38. List three ways that carbon dioxide is transported in blood.

39. Explain the function of carbonic anhydrase.

40. Define chloride shift.

41 Describe the changes that make it harder to breathe with advancing years.

Shier-Butler-Lewis: Human Anatomy and Physiology, Ninth Edition

V. Absorption and Excretion

20. Urinary System

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