Gas Laws - Gas Exchange Summary Body cells must obtain...

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G a s E x c h a n g e Summary: Body cells must obtain oxygen and eliminate carbon dioxide. Gas exchange occurs at the alveoli of the lungs. The functions of the respiratory system include (1) providing an area for gas exchange between air and circulating blood; (2) moving air to and from exchange surfaces; (3) protecting respiratory surfaces from environmental variations and defending the respiratory system and other tissues from invasion by pathogens; (4) permitting vocal communication; and (5) providing olfactory sensations to the CNS. The respiratory system includes the nose, nasal cavity, paranasal sinuses, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli of the lungs. The respiratory tract consists of the conducting passageways that carry air to and from the alveoli. The passageways of the upper respiratory system filter and humidify incoming air. The lower respiratory system includes delicate conduction passages and the alveolar exchange surfaces. The respiratory mucosa (respiratory epithelium and underlying connective tissue) lines the respiratory tract. The respiratory epithelium changes in structure along the respiratory tract. It is supported by the lamina propria , a layer of areolar tissue. The components of the upper respiratory system consist of the nose, nasal cavity, paranasal sinuses, and pharynx. Air normally enters the respiratory system through the external nares , which open into the nasal cavity . The vestibule (entryway) is guarded by hairs that screen out large particles. Incoming air flows through the superior , middle , and inferior meatuses (narrow grooves) and bounces off the conchal surfaces. The hard palate separates the oral and nasal cavities. The soft palate separates the superior nasopharynx from the rest of the pharynx. The connections between the nasal cavity and nasopharynx are the internal nares . The nasal mucosa traps particles, warms and humidifies incoming air, and cools and dehumidifies outgoing air. The pharynx is a chamber shared by the digestive and respiratory systems. The nasopharynx is the superior part of the pharynx. The oropharynx is continuous with the oral cavity. The laryngopharynx includes the narrow zone between the hyoid bone and the entrance to the esophagus. Inhaled air passes through the glottis en route to the lungs; the larynx surrounds and protects the glottis.
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The cylindrical larynx is composed of three large cartilages (the thyroid cartilage , cricoid cartilage , and epiglottis ) and three smaller pairs of cartilages (the arytenoid , corniculate , and
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