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Chapter 16 The Respiratory System UPPER RESPIRATORY TRACT Nose • Nasal septum • Nares • Frontal, maxillary, sphenoidal, and ethmoidal sinuses drain into nose • Warms and moistens inhaled air • Contains sense organs of smell Pharynx • • • • • aka throat 3 sections Plays a role with respiration and digestion Passageway for food and liquids Passageway for air Larynx • Cartilage forms framework • Thyroid cartilage (Adam’s apple) is largest • Epiglottis partially covers opening into larynx • Vocal cords stretch across interior of larynx • Passageway for air to move to and from lungs • Voice production LOWER RESPIRATORY TRACT Trachea (Windpipe) • Extends from larynx to thoracic cavity • C-shaped rings of cartilage hold trachea open • Provides passageway for air to move to and from lungs Right and Left Bronchi Bronchioles Alveoli • Microscopic sacs • Surrounded by capillaries • Exchange gases between blood and lungs Respiratory Mucosa • Specialized membrane that lines respiratory tree • Serves as a filter by trapping inspired irritants such as dust and pollen • Upward movement of cilia helps remove trapped irritants Lungs • • • • Apex—narrow upper part Base—broad lower part Right larger than left Divided into lobes – Right upper, middle, lower – Left upper, lower • Function: pulmonary ventilation Pleura • Moist membrane that lines chest cavity and covers outer surface of lungs • Reduces friction MECHANICS OF BREATHING Respiration • Two phases – inspiration – expiration (movement of air out of lungs) • Changes in air pressure cause air to move into and out of the lungs Inspiration • Active process • Diaphragm and external intercostals contract • Thoracic cavity enlarges • Pressure in thoracic cavity is less than that of the atmosphere • Air rushes in Expiration • Ordinarily a passive process • Diaphragm and external intercostals relax • Pressure in thoracic cavity greater than that of the atmosphere • Air is “pushed” out of lungs by pressure Gas Exchange • Carbon dioxide moves out blood into alveoli and out of body in expired air • Oxygen moves from alveoli into blood Volumes • • • • Measured with a spirometer Tidal volume (TV)— normally breath Vital capacity (VC)—forced expiration Expiratory reserve volume (ERV)— what is left after forced expiration • Inspiratory reserve volume (IRV)— forcibly inhaled after a normal inspiration • Residual volume (RV)— air that remains in the lungs after the most forceful expiration Respiratory Rate Usually about 12 to 18 breaths/minute Regulation of Respiration Located in respiratory center of the medulla oblongata