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PT. 3 UNIT 1 LECTURE 1 OVERVIEW OF THE RESPIRATORY SYSTEM 1. WHEN YOU INHALE (INSPIRATION), AIR ENTERS THE RESPIRATORY SYSTEM THROUGH THE NOSE AND MOUTH AND PASSES DOWN THE THROAT (PHARYNX) AND THROUGH THE VOICE BOX (LARYNX) 2. THE ENTRANCE TO THE LARYNX IS COVERED BY A SMALL FLAP OF MUSCULAR TISSUE (EPIGLOTTIS) THAT CLOSES WHEN YOU SWALLOW, PREVENTING FOOD FROM ENTERING THE AIRWAYS 3. THE LARGEST AIRWAY IS THE WINDPIPE (TRACHEA), WHICH BRANCHES INTO TWO SMALLER AIRWAYS (BRONCHI) TO SUPPLY THE TWO LUNGS 4. THE BRONCHI DIVIDES MANY TIMES INTO EVEN SMALLER AIRWAYS (BRONCHIOLES) 5. AT THE END OF EACH BRONCHIOLE ARE DOZENS OF BUBBLESHAPED, AIRFILLED CAVITIES (ALVEOLI) 6. EACH LUNG CONTAINS MILLIONS OF ALVEOLI, AND EACH ALVEOLUS IS SURROUNDED BY A DENSE NETWORK OF CAPILLARIES 7. INHALED AIR, CONTAINING OXYGEN, PASSES THROUGH THE THIN WALLS OF THE ALVEOLI AND INTO THE BLOOD IN THE CAPILLARIES 8. OXYGEN IS EXCHANGED FOR CARBON DIOXIDE WHICH PASSES FROM THE BLOOD INTO THE ALVEOLI, AND IS EXHALED THROUGH THE NOSE AND MOUTH (EXPIRATION) PRIMARY RESPIRATORY FUNCTIONS: BRING OXYGEN INTO THE LUNGS 2. TRANSFER THE OXYGEN TO THE BLOOD 3. EXPEL THE WASTE PRODUCT – CARBON DIOXIDE 1. CONTROL OF BREATHING: 1. BREATHING IS USUALLY CONTROLLED BY THE BODY’S AUTONOMIC NERVOUS SYSTEM 2. THE RESPIRATORY CENTERS IN THE BRAIN THAT CONTROL YOUR RATE OF BREATHING ARE IN THE BRAINSTEM OR MEDULLA, AND MAY BE INFLUENCED BY SEVERAL FACTORS: A. OXYGEN – SPECIALIZED NERVE CELLS WITHIN THE AORTA CALLED PERIPHERAL CHEMORECEPTORS MONITOR THE OXYGEN CONCENTRATION OF THE BLOOD IF THE OXYGEN CONCENTRATION IN THE BLOOD DECREASES, THEY TELL THE RESPIRATORY CENTERS TO INCREASE THE RATE AND DEPTH OF BREATHING B. CARBON DIOXIDE – PERIPHERAL CHEMORECEPTORS ALSO MONITOR THE CARBON DIOXIDE CONCENTRATION IN THE BLOOD IF THE CARBON DIOXIDE CONCENTRATION GETS TOO HIGH, THE CHEMORECEPTORS SIGNAL THE RESPIRATORY CENTERS TO INCREASE THE RATE AND DEPTH OF BREATHING THE INCREASED RATE OF BREATHING RETURNS THE CARBON DIOXIDE CONCENTRATION TO NORMAL AND THE BREATHING RATE THEN SLOWS DOWN CHEMICAL IRRITANTS – NERVE CELLS IN THE AIRWAYS SENSE THE PRESENCE OF UNWANTED SUBSTANCES IN THE AIRWAYS SUCH AS POLLEN, DUST, NOXIOUS FUMES, WATER, OR CIGARETTE SMOKE C. THESE CELLS THEN SIGNAL THE RESPIRATORY CENTERS TO CONTRACT THE RESPIRATORY MUSCLES, CAUSING YOU TO SNEEZE OR COUGH 3. IN QUIET BREATHING, THE AVERAGE ADULT INHALES AND EXHALES ABOUT 15-18 TIMES A MINUTE 4. THE LUNGS HAVE NO MUSCLES OF THEIR OWN, SO THE WORK OF BREATHING IS DONE PRIMARILY BY THE DIAPHRAGM AND INTERCOSTAL MUSCLES (THE MUSCLES BETWEEN YOUR RIBS) A. WHEN YOU INHALE, THE DIAPHRAGM AND INTERCOSTAL MUSCLES CONTRACT AND EXPAND THE CHEST CAVITY THIS EXPANDS THE LUNGS AND ALLOWS AIR TO ENTER THE LUNGS B. WHEN YOU EXHALE, THE DIAPHRAGM AND INTERCOSTAL MUSCLES RELAX AND THE CHEST CAVITY GETS SMALLER THIS PUSHES AIR OUT OF THE LUNGS C. THIS CYCLE REPEATS WITH EACH BREATH 5. THE LUNGS ARE COVERED BY A SLIPPERY MEMBRANE (PLEURA) WHICH ALLOWS THE LUNGS TO EXPAND AND CONTRACT PARIETAL PLEURA: ATTACHED TO THE WALL OF THE THORACIC CAVITY VISCERAL PLEURA: COVERS THE LUNGS THEMSELVES RESPIRATORY DISORDERS 1. DISEASES OR CONDITIONS THAT INFLUENCE THE MECHANICS OF BREATHING (THOSE THAT MAKE BREATHING HARDER): A. ASTHMA: THE BRONCHIOLES CONSTRICT, REDUCING THE SIZE OF THE AIRWAYS, CUTTING DOWN ON THE FLOW OF AIR AND MAKES THE RESPIRATORY MUSCLES WORK HARDER B. EMPHYSEMA: THE LUNGS BECOME STIFF WITH FIBERS AND BECOME LESS ELASTIC, WHICH INCREASES THE WORK OF THE RESPIRATORY MUSCLES C. BRONCHITIS: THE AIRWAYS BECOME INFLAMED AND NARROWER, WHICH RESTRICTS THE FLOW OF AIR AND INCREASES THE WORK OF THE RESPIRATORY MUSCLES D. CHRONIC OBSTRUCTIVE PULMONARY DISEASE (COPD): CAUSED BY EMPHYSEMA AND CHRONIC BRONCHITIS 2. DISEASES OR CONDITIONS THAT MINIMIZE OR PREVENT GAS EXCHANGE (THOSE THAT DAMAGE THE LUNGS' ABILITY TO EXCHANGE CARBON DIOXIDE FOR OXYGEN): A. PULMONARY EDEMA: FLUID BETWEEN THE ALVEOLUS AND PULMONARY CAPILLARY BUILDS UP, WHICH INCREASES THE DISTANCE OVER WHICH GASES MUST EXCHANGE AND SLOWS DOWN THE EXCHANGE B. SMOKE INHALATION: SMOKE PARTICLES COAT THE ALVEOLI AND PREVENT THE EXCHANGE OF GASES C. CARBON MONOXIDE POISONING: CARBON MONOXIDE BINDS TO HEMOGLOBIN MORE TIGHTLY THAN EITHER OXYGEN OR CARBON DIOXIDE, WHICH MINIMIZES THE DELIVERY OF OXYGEN TO ALL THE TISSUES OF THE BODY, INCLUDING THE BRAIN, HEART, AND MUSCLES THE END THAT’S MY STORY AND I’M STICKING TO IT!!!