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Chapter 8: Respiratory System
Structure and Function
The most basic human need is the need to breathe. We take our first breaths as soon as we are born and continue this vital function through the last moments of our lives. The complex and amazing structures of the respiratory system sup- port this life-sustaining process. The respiratory system helps to provide oxygen to the cells and tissues and remove carbon dioxide. When studying the respiratory system, we often divide it into the upper and lower airways. The upper airway consists of the mouth, nose, sinuses, and pharynx. The pharynx is further divided into the nasopharynx (back of the nose) and oropharynx (back of the mouth). The nose begins with the nares (nostrils) and extends back to the nasopharynx. The nasal passages are divided into right and left sides by the nasal septum . The hard palate divides the nasal cavity from the mouth, which sits beneath it. The sinus cavities are air-filled spaces named for the facial bones within which they are located; they include the maxillary, frontal, ethmoidal, and sphenoidal sinuses. Refer to Figure 8-1, which illustrates the structures of the respiratory system, as we discuss the path that air takes into and out of the body.
Sphenoidal sinus
Nasopharynx
Frontal sinus
Oropharynx
Pharynx
Nasal cavity
Upper respiratory tract
Laryngopharynx
Oral cavity
Esophagus
Epiglottis Tongue
Trachea
Left bronchus Bronchi
Larynx
Right bronchus
Lower respiratory tract
Left lung
Right lung
Pleurae
Diaphragm
Artery
Capillary
Alveolar sac
Vein
Alveoli
FIGURE 8-1 The respiratory system is divided into the upper and lower respiratory tracts.
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