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Respiratory systemGas exchange, oxygen in and Carbon dioxide outSecondary functions:Cleans air, humidifies air so that mucous membranes within lungs aren’t dried out,SpeechRegulating body temperature  more for animals (packing – evaporating moisture from the respiratory system)Ventilation: movement of air b/t inside and outside worldsGas exchange happens in alveoliConducting zone: conducts air b/t outside world and lungs. Only 150 ml volume.Where air is humidified.By the time air reaches alveoli its body tempCleans the airMucociliary system: cells that line it are ciliated. Their surface in embedded in mucus. So cilia are embedded in mucus. As air passes particulate matter, stuff gets stuck on mucus. Prevents alveoli from getting bad material in it.Respiratory zone: alveoli and bronchioles, volume = 4500 ml. little air sacs that are lined with thin membranes behind which there is a bed of capillariesVentilation: movement of air inside and outside the lungsAir is a gas, gases are fluids, fluids flow downhill a pressure gradientatmospheric pressure is 760 mm Hg.**if you are going to take air into alveoli the alveoli pressure has to be below atmospheric (inspiration) and to get air out the pressure has to be higher than atmospheric (expiration)boyle’s law: pressure will increase as # of molecules of gas increase, pressure will decrease when volume goes up PRESSURE = # OF MOLECULES/VOLUMEduring inspiration and expiration we increase and decrease the volume of the thoracic cavitylungs are elastic, natural tendency of lungs is to collapse, what prevents them from collapsing is that the box (thoracic cavity) is closedwe have muscles that act to change volume of thoracic cavitydiaphragm: lower section of thoracic cavity. Innervated by phrenic nervepeople with spinal cord injuries are still able to breathe b/c phrenic nerve……when the diaphragm contracts, the volume in thoracic cavity goes up, pressure goes down, lungs contractexternal intercostal: when you contract these your ribs are pulled up and away from spinal column and therefore increase the volume in your thoraxwith normal breathing at rest, all you do every 5 seconds is contract your diaphragm and external intercostal muscle (push out more)?,expiration is passive, doesn’t take any energy to do it, relaxation of muscleswhen engaged in more strenuous activityincrease the volume when you exhale so you use internal intercostal muscles (push in more)with even more strenuous activity you use your abdominal neck and chestyou can increases how much air you bring in by contracting your abdominal muscles. Your abs push up on diaphragm and increase volume the more forcibly these muscles are use, the more air will get taken in and taken outpoiseuille’s law: resistance increase as pipes get longer, and decreases as diameter gets biggerBronchioles: smooth muscle on their walls so their diameters can be changed to bigger or smaller, doing so changes the airway resistance.In arterioles sympathetic stimulation makes them contract and sympathetic makes them relax; and in bronchioles parasympathetic stimulation makes them smaller in diameter, sympathetic makes them dilate to allow more oxygen.in an asthmatic episode, you have to use muscles to exhale (normally we don’t use muscles to exhale); wheezing with asthma occurs with expiration b/c they’re forcing air out with high velocity through narrow tubes.to relieve asthma, you have to use sympathetic stimulation (inhaler) that dilates bronchioles so air can passairway is obstructed, called an obstructive disorderPneumonia: fluid leaks into alveoli so you cant get air into them. Airway resistance is normal, but lung volume is less. This is a restrictive disordersmooth muscle relaxes when oxygen concentration is low and contracts when oxygen concentration is highwhen oxygen levels fall, bronchiole levels fallElasticity of Lungs2 things makes your lung elasticcapsule of lungs, includes elastic fibers, resists being stretched, contributes small % of lung elasticityfluid lined sacs: major part of elasticity, layer of fluid covering epitheliumsurface tension: surface of water has different properties than water in the bulk of it. Water molecule on surface has different forces acting on it (all directions but up) than water molecule in the middle of water (all directions)la Place’s law: pressure inside a sphere that has surface tension, gets greater as the diameter of the sphere decreases. Surface tension increases as diameter decreases. So small spheres will tend to collapsepressure decreases as volume increases – balloon examplealveoli are tiny spheres and will want to collapsepulmonary surfactant: without this we cant breathe b/c it reduces surface tension so it can overcome pressure in alveoli*Lungs are surrounded by sac, pleural membrane, and thin layer of fluid comes b/t lung and thoracic cage  allows less friction in lungs when they moveLUNG VOLUMEtotal volume of lungs is 5700 ml.residual volume : even if you exhale as hard as you can there will still be 1200 ml of volume left in lungstidal volume: Normal breath you take in and out; 500 ml, can increase by increasing expirationexpiratory reserve: when you exhale as hard as you can; 1000 mlinspiratory reserve: when you inhale as hard as you can; 3000 mlpulmonary ventilation = tidal volume X Rate of Respiration. 500 X 12 = 600L/min.Anatomical dead space: 150 ml; volume of air inhaled that doesn’t take part in gas exchange either because it remains in conducting airways or reaches alveoli that are not perfused or poorly perfused.Alveolar vent: (Tidal Volume – Dead Space) X respiration rate. The amount of fresh air getting to alveoli per minute.The only fresh air you bring is volume in excess of dead spaceIf you want to increase alveoli respiration rateIncrease breathing rateIncrease tidal volumeIf we breathe through hose, we are making dead space bigger. If you make hose big enough, you will get to point where you aren’t getting any fresh air at all.Airway resistance: (resistance increases with length) if you breathe thru hose that has a bigger length, you will need a larger force to breatheGas exchangeMetabolically you need oxygen and take out CO2Everything happens by diffusion down their concentration gradient.CO2 diffuses out because its at a higher conc. in body than outsideO2 diffuses in because its at a


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VCU PHIS 206 - Respiratory system

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