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Respiratory System Respiratory surfaces must be moist for gas exchange Larynx=voice box Trachea=windpipe Air sacs for gas exchange=alveoli Right lung: Three lobes lobes Left lung: Two How do you breathe? • Your diaphragm contracts, moving downward. This increases the volume in your lungs, therefore decreasing the pressure. • Air moves from high pressure to low pressure, so air flows into your lungs. You inhale. This is called NEGATIVE PRESSURE BREATHING • Your diaphragm then relaxes, moving back up and decreasing lung volume. This increases lung air pressure, causing the air to flow out of your lungs.You exhale. Inhaling and exhaling • Vital capacity is the maximum amount of air that we can inhale or exhale-See model Cilia help to clean air as it passes They constantly beat upward. Vocal Folds •Functions –Epiglottis prevent swallowed material from moving into larynx –Vocal folds are primary source of sound production Where does gas exchange happen? • In the alveoli • They are moist air sacs in the lungs • Oxygen goes from the air space in the alveoli to the capillaries to the blood stream, while carbon dioxide goes from the blood stream cappillaries to the alveoli air space to be expelled as a waste So what happens to your lungs when you smoke? • You can get emphysema, where the alveoli walls become brittle and less “springy” • This reduces vital capacity • They can even rupture, reducing the amount of area for gas exchange. Blood flow • Major route brings deoxygenated blood to the lungs via the pulmonary artery (artery=AWAY from heart), to pulmonary capillaries, is oxygenated and returns to the heart through the pulmonary veins (to heart).