respiratory system Respiratory system 02 19 2014 Gas exchange oxygen in and Carbon dioxide out Secondary functions o Cleans air humidifies air so that mucous membranes within lungs aren t dried out o Speech o Regulating body temperature more for animals packing evaporating moisture from the respiratory system o Ventilation movement of air b t inside and outside worlds Gas exchange happens in alveoli Conducting zone conducts air b t outside world and lungs Only 150 ml volume o Where air is humidified o By the time air reaches alveoli its body temp o Cleans the air o Mucociliary 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 Ventilation movement of air inside and outside the lungs o Air is a gas gases are fluids fluids flow downhill a pressure bed of capillaries gradient atmospheric 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 VOLUME during inspiration and expiration we increase and decrease the volume of the thoracic cavity lungs are elastic natural tendency of lungs is to collapse what prevents them from collapsing is that the box thoracic cavity is closed we have muscles that act to change volume of thoracic cavity o diaphragm lower section of thoracic cavity Innervated by o people with spinal cord injuries are still able to breathe b c phrenic nerve phrenic nerve o when the diaphragm contracts the volume in thoracic cavity goes up pressure goes down lungs contract o external intercostal when you contract these your ribs are pulled up and away from spinal column and therefore increase the volume in your thorax o with normal breathing at rest all you do every 5 seconds is contract your diaphragm and external intercostal muscle push out more o expiration is passive doesn t take any energy to do it relaxation of muscles o when engaged in more strenuous activity increase 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 chest o you can increases how much air you bring in by contracting your abdominal muscles Your abs push up on diaphragm and the more forcibly these muscles are use the more air will get taken increase volume in and taken out poiseuille s law resistance increase as pipes get longer and decreases as diameter gets bigger Bronchioles smooth muscle on their walls so their diameters can be changed to bigger or smaller doing so changes the airway resistance o 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 o to relieve asthma you have to use sympathetic stimulation inhaler that dilates bronchioles so air can pass o airway is obstructed called an obstructive disorder o Pneumonia fluid leaks into alveoli so you cant get air into them Airway resistance is normal but lung volume is less This is a restrictive disorder o smooth muscle relaxes when oxygen concentration is low and contracts when oxygen concentration is high when oxygen levels fall bronchiole levels fall Elasticity of Lungs 2 things makes your lung elastic o capsule of lungs includes elastic fibers resists being stretched contributes small of lung elasticity o fluid lined sacs major part of elasticity layer of fluid covering epithelium surface 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 collapse o pressure decreases as volume increases balloon example o alveoli are tiny spheres and will want to collapse o pulmonary surfactant without this we cant breathe b c it reduces surface tension so it can overcome pressure in alveoli 02 19 2014 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 move LUNG VOLUME total 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 lungs tidal volume Normal breath you take in and out 500 ml can increase by increasing expiration expiratory reserve when you exhale as hard as you can 1000 ml inspiratory reserve when you inhale as hard as you can 3000 ml pulmonary 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 space If you want to increase alveoli respiration rate o Increase breathing rate o Increase tidal volume If 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 breathe Gas exchange Metabolically you need oxygen and take out CO2 Everything happens by diffusion down their concentration gradient o CO2 diffuses out because its at a higher conc in body than o O2 diffuses in because its at a higher concentration outside Room air 1ATM 760 mm Hg 80 nitrogen 20 oxygen outside than body 150mmHg Each molecule of each gas