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Chapter 26: Anatomy of the Respiratory System

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1 Chapter 26: Anatomy of the Respiratory System
Anatomy & Physiology Chapter 26: Anatomy of the Respiratory System

2 Structural Plan of the Respiratory System
Structure determined by respiratory system functions of air distributor and gas exchanger— supplying oxygen and removing carbon dioxide from cells (Figure 26-1) Alveoli—sacs that serve as gas exchangers; all other parts of respiratory system serve as air distributors The respiratory system also warms, filters, and humidifies air Respiratory organs involved in speech, homeostasis of body pH, and olfaction 2

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4 Structural Plan of the Respiratory System
The respiratory system is divided into two structural divisions Upper respiratory tract—the organs are located outside the thorax and consist of the nose, nasopharynx, oropharynx, laryngopharynx, and larynx Lower respiratory tract—the organs are located within the thorax and consist of the trachea, the bronchial tree, and the lungs Accessory structures include the oral cavity, rib cage, and diaphragm 4

5 Upper Respiratory Tract
Nose Structure of the nose—external portion consists of a bony and cartilaginous frame covered by skin containing sebaceous glands The two nasal bones meet and are surrounded by the frontal bone to form the root The nose is surrounded by the maxilla (Figure 26-2) 5

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7 Upper Respiratory Tract
Nose (cont) Internal portion of the nose (nasal cavity) lies over the roof of the mouth, separated by the palatine bones Cleft palate—condition in which the palatine bones fail to unite completely and only partially separate the nose and the mouth, thereby producing difficulty swallowing Cribriform plate—separates the roof of the nose from the cranial cavity Septum—separates the nasal cavity into right and left cavities; it consists of four structures: the perpendicular plate of the ethmoid bone, the vomer bone, the vomeronasal cartilages, and the septal nasal cartilage 7

8 Upper Respiratory Tract
Nose (cont) Each nasal cavity is divided into three passageways: superior, middle, and inferior meatuses (Figure 26-3) Anterior (external) nares—external openings to the nasal cavities; open into the vestibule Sequence of airflow through the nose into the pharynx—anterior nares to the vestibule to all three meatuses simultaneously and then to the posterior (internal) nares 8

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10 Upper Respiratory Tract
Nose (cont) Nasal mucosa Air passes over respiratory mucosa, which contains a rich blood supply (Figure 26-4) Olfactory epithelium—special sensory membrane containing many olfactory nerve cells and a rich lymphatic plexus 10

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12 Upper Respiratory Tract
Nose (cont) Paranasal sinuses Four pairs of air-containing spaces that open or drain into the nasal cavity Each is lined with respiratory mucosa (Figure 26-5) 12

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14 Upper Respiratory Tract
Nose (cont) Functions of the nose Provides a passageway for air traveling to and from the lungs Filters the air, aids speech, and makes possible the sense of smell 14

15 Upper Respiratory Tract
Pharynx (throat) Structure of pharynx Tubelike structure extending from the base of the skull to the esophagus Made of muscle and divided into three parts (Figure 26-3)— nasopharynx, oropharynx, and laryngopharynx 15

16 Upper Respiratory Tract
Pharynx (cont) Pharyngeal tonsils Located in the nasopharynx Called adenoids when they become enlarged Oropharynx contains two pair of organs—the palatine tonsils (most commonly removed in tonsillectomy) and the lingual tonsils (rarely removed) Functions of the pharynx—pathway for the respiratory and digestive tracts 16

17 Upper Respiratory Tract
Larynx (Figures 26-6 and 26-7) Location of larynx—positioned between the root of the tongue and the upper end of the trachea Structure of larynx Consists of cartilages attached to each other by muscle Lined by a ciliated mucous membrane, which forms two pairs of folds (Figure 26-8)— vestibular folds (false vocal folds) and vocal folds 17

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21 Upper Respiratory Tract
Larynx (cont) Cartilages (framework) of the larynx— formed by nine cartilages Single laryngeal cartilages—the three largest cartilages: the thyroid cartilage, the epiglottis, and the cricoid cartilages Paired laryngeal cartilages—three pairs of smaller cartilages: the arytenoid, the corniculate, and the cuneiform cartilages 21

22 Upper Respiratory Tract
Larynx (cont) Muscles of the larynx Intrinsic muscles both insert and originate within the larynx Extrinsic muscles insert in the larynx but originate on some other structure Functions of the larynx—forms part of the airway to the lungs and produces the voice 22

23 Lower Respiratory Tract
Trachea—often called “windpipe” (Figure 26-10) Structure of trachea Extends from the larynx to the primary bronchi Wall composed of (outer) adventitia, (middle) smooth muscle and C-shaped cartilage rings, (inner) respiratory mucosa; posterior wall is very elastic (Figure 26-11) Incomplete rings and posterior elasticity allows esophagus to expand into trachea during swallowing Functions of trachea—furnishes part of the open airway to the lungs; obstruction causes death 23

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26 Lower Respiratory Tract
Bronchi and alveoli Structure of bronchi Lower end of the trachea divides into two primary bronchi, one on the right and one on the left Primary bronchi enter the lung and divide into secondary bronchi, which branch into bronchioles and eventually divide into alveolar ducts and alveoli 23 levels of branching (Figure 26-12) 26

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28 Lower Respiratory Tract
Bronchi and alveoli (cont) Structure of alveoli—the primary gas exchange structures Respiratory membrane—the barrier between which gases are exchanged by alveolar air and blood (Figure 26-15) Respiratory membrane consists of the alveolar epithelium, the capillary endothelium, and their joined basement membranes Surfactant—a component of the fluid coating the respiratory membrane that reduces surface tension; produced by type II cells 28

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30 Lower Respiratory Tract
Bronchi and alveoli (cont) Functions of bronchi and alveoli Distribute air to the lung’s interior; 23 levels of branching are optimal for oxygen transfer to the blood Mucus blanket cleans the airways as it is moved upward by the ciliary escalator 30

31 Lower Respiratory Tract
Lungs Structure of the lungs—cone-shaped organs extending from the diaphragm to above the clavicles (Figure 26-17) Hilum—slit on the lung’s medial surface where the primary bronchi and pulmonary blood vessels enter Base—the inferior surface of the lung that rests on the diaphragm Costal surface—lies against the ribs 31

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33 Lower Respiratory Tract
Structure of the lungs (cont) Left lung is divided into two lobes—superior and inferior Right lung is divided into three lobes—superior, middle, and inferior Lobes are further divided into functional units— bronchopulmonary segments Ten segments in the right lung Eight segments in the left lung Functions of the lungs—air distribution and gas exchange 33

34 Lower Respiratory Tract
Thorax (Figure 26-18) Structure of the thoracic cavity—three divisions divided by the pleura Pleural divisions—the part occupied by the lungs Mediastinum—part occupied by the esophagus, trachea, large blood vessels, and heart Functions of the thorax—brings about inspiration and expiration 34

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36 Cycle of Life: Respiratory System
Respiration may be affected by developmental defects, age-related structural changes, or loss of function throughout the life cycle Age-related changes affect lung capacity, make ventilation difficult, or reduce the oxygen- or carbon dioxide–carrying capacity of blood Respiratory efficiency is reduced in old age as a result of changes in ribs, respiratory muscles, and hemoglobin levels 36

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