the hardest part of this chapter is this idea of pulmonary ventilation which is basically what I referred to in the last PowerPoint as having to trick the air into coming in and out of your body by changing pressure so breathing is of course a two-phase process we're involving inspiration for inhalation and expiration or exhalation so this picture here really demonstrates that you can see the diaphragm moving so if you kind of feel yourself breathing right now it's not like your chest cavity is dramatically moving up and down right it's not like you're panting like a dog so basically what's happening is the diaphragm is doing all the work so remember that diaphragm is that really skinny muscle that goes across your chest cavity and separates the thoracic cavity from the abdominal pelvic and so you can see this diaphragm in this picture is contracting up and down remember that's controlled by the phrenic nerve which is pH not F even though it sounds like it that goes across the chest of our cadavers so this is an extremely important muscle without the diaphragm we cannot breathe so starting with inspiration if you inspire if you take a deep breath in this is what we call an active process because you're using muscles right it takes effort to breathe in whereas to let your breath out is kind of relaxing right so drawing air into the lungs occurs because of a pressure change so you do not have to memorize this number but this is normal atmospheric pressure for Danville about 760 millimeters of mercury well inside your lungs when your lungs are at rest so take a breath in and a breath out so once you've taken your normal expiration your lungs are at rest so at rest after a normal exhalation the pressure outside is pretty much the same as the pressure inside so when you take a normal exhale like at that moment no air is coming in no air is going out right well that's because from the airs perspective if I'm 760 outside and it's 760 inside why would you move that's like God forbid being 760 at lines at Walmart and lying next to us 760 why would you go anywhere so again we have to give the air an incentive to want to come inside so we call this Boyle's law and again it sounds really complicated and I'm gonna have a couple of slides where I try to simplify it so if the volume which is the space to be filled increases pressure decreases so I think of this like our classroom if we were in a room that only fit 24 people or four in a room that only fits 48 people it can get kind of tight in there right but if I take us all to the gym whether we have 24 or 48 in a class if we have class in the gym we're gonna have a huge space to fill right but the number of students doesn't change so pressures gonna go down whereas if I crammed you all into a small classroom pressure would go up right nobody likes to share their space so especially if I put us in a really tiny classroom we would just feel like we were kind of constricted so if volume increases if the space gets bigger pressure goes down so what do we do in our body we're not switching classrooms in our body in our body we expand our thoracic cage so when you take a deep breath you kind of feel that okay your lungs expand because those pleural membranes especially the parietal pleura is attached to your ribs so as the lungs expand we're increasing our volume in our space so therefore the pressure inside our lungs goes down just like I fight just like if I give you a bigger classroom you guys have more room to stretch out in Rome right so the air all of a sudden goes man I'd rather rush in there right I'd rather go from where I'm crowded to inside the body which is less crowded so air rushes in to balance this pressure out otherwise check out Boyle with his hair that is an attractive dude right there it's a sad thing we've abandoned that look right because I am NOT great at visualizing pressure laws I drew this which is kind of lame but it's just showing you that as volume increases so see the square I've just made it bigger but we have the same amount of molecules or Reese's peanut butter cups or glasses of wine however you want to think about these five dots but as soon as you take a deep breath you're giving those five dots a much bigger space which means pressure goes down so as soon as pressure drops in your lungs the outside air is like well damn I'd rather be in there where it's better just like when a new line opens up at Walmart and we all rush into it so how do we do this in our body well it's all about this diaphragm so you've most likely seen the diaphragm on cadaver by this point if you haven't it's such a sin muscle and it is shaped like a parachute or an umbrella and so this is how this muscle can like go up and down so that way it can squeeze your lungs so we have multiple ways of expanding our chest so our thorax is our chest region so the biggest way we do it is superior inferior that's the diaphragm diaphragms job so especially when you're just sitting there taking normal breaths you're not exercising you're just hanging out the diaphragm is doing all the work so he's gonna flatten out which increases the thoracic height so superior inferior you can change the shape of your chest cavity lateral which is out to the sides well now we use our rib muscles so if you take a really deep breath you could kind of feel how your ribs are lifting up so when they lift up you're expanding the width of your chest cavity now it's not doing it a lot but we don't need it to do it a lot and then anterior posterior front and back again we have the intercostal muscles that will kind of push your sternum up so if you put your hands on your sternum and take a deep breath you can kind of feel how that opens up your chest so it's not like a car door I mean it's not going woo or anything like that but our whole goal is just to make our throat thorax a little bit bigger and if we do that it will cause the pressure of our lungs to go down therefore the air outside the atmospheric air is going to be desperate to rush inside we also have forced inspiration so if you take a normal breath in that's not very much right forced inspiration is like you keep sucking in like all the air you possibly can so if you do that you see how your chest is really rising up so your external intercostals your rib muscles and the diaphragm are gonna construct kontrick construct oh my goodness contract a lot more strongly but other up muscles if your panting like a dog you're gonna use your pecs you're also gonna use that sternocleidomastoid and your neck you ever notice people that are working out like their neck muscles pop out because they're trying to force all that extra air in another chemical that we have to really help us out in this process is called surfactant so every breath you take if you picture these like microscopic little balloons every breath you take you don't have to reinflates or balloons so as soon as you scream when you're shooting out of your mom like you're coming off a log ride that first screen that you take inflates your alveoli and ideally they stay open but the reason they stay open if you think of the alveoli like little balloons is because of surfactant so for surfactant is a chemical that has a lot of lipids in it so it's almost like dishwashing soap and you know how when you wash something with dishwashing soap it's almost like your fingers feel kind of slick like they don't stick together so lining the inside of our lungs we have this this chemical called surfactant which basically keeps the alveoli from collapsing like a rubber balloon a latex balloon would kind of like collapse and stick together right well we don't want this to happen with our alveoli because otherwise every breath that we take we not only would be exchanging oxygen and carbon dioxide but we'd be like puffing our alveoli up and so that would take a lot of work right like right now you're probably breathing very shallow just hoping this lecture and soon you're not putting a lot of effort into it but if you've ever seen preemies one of the biggest issues that premature babies have is their lungs are always underdeveloped because if we think about it your lungs would be logically the last organs to mature right because you don't really need them you're using your mom's lungs until you shoot out of her right and so if I'm focusing all my efforts I'm gonna be developing the intestines and the liver and the heart and all of those other organs saving the lungs for last so if you have a child that is born a month premature their lungs are nowhere near ready to go so if you've ever seen a preemie inside an incubator their little chest is just moving up and down so dramatically right because they're sitting there trying to pump that air so the good news is respiratory distress syndrome we at least have a treatment for because now we actually have artificial surfactant before then kids sadly baby's little preemies would die because they met a ball we couldn't make enough ATP to keep up with how fast their chest cavity and how hard their chest cavity had to work so luckily we do at least have artificial surfactant so how do we control all of this so nerves and their effects the phrenic nerve so that's that little nerve that in-lab the only place we can see it is on cadaver so it's a little string that goes across the chest because on cadaver we can take the lungs and the heart out whereas on our models we can't do that so the phrenic nerve is one of the most important nerves in our body this guy is going to signal the diaphragm to contract so by doing that it increases our thoracic volume and so all of a sudden the there's more space in your lungs so all of a sudden the air that's in there has a lot more room to roam so pressure goes down so this is going to cause the air from the outside of our body to want to rush in we also have the intercostal nerves which is going to cause your intercostal muscles to contract and if you take a deep breath you can feel your chest cavity opening up because your rib muscles are participating expiration this is what we call a passive process so where inspiration or inhalation you kind of have to work for it you're using muscles you're using a lot of ATP an expiration is passive it doesn't require any ATP and so if you take a deep breath huh and then you let it all out that's kind of relaxing right like I don't take yoga cuz there's no way I could shut my mouth up long enough but when you take a deep breath it is kind of this like satisfying thing to let it go right that's because everything's going back to its original position the lung tissue is snapping back because there's a lot of elastic tissue in there everything's kind of going back to normal so my little picture here is because I needed a visual of this so when I take a box whether it's a box of M&Ms or a box of you know rats or a box of kittens and I shrink the size those kittens are gonna start fighting in that second box right so all I've done when I exhale is I've changed the shape of my thoracic cavity therefore the air that's in my lungs is starting to get really crowded right so now just like my little box picture there so now the air inside my body is looking for every opportunity to get the hell out of there right because it's so crowded so this forces the air out after the end of a normal breath you can still squeeze more out right so if you just take a normal exhale huh I can still have like there's still a lot in there right but I have to like work it so that is an active process so I can use muscles especially my internal intercostals so I can pull my ribs down but also my abdominal muscles if you really put your abdominal muscles into this you can squeeze tons of air out of your lungs that you don't normally do so we call this a forced expiration and this would take ATP so what events are involved in ventilation you're going to contract your inspiratory or inhalation muscles your your thorax which is your chest is going to get bigger therefore the pressure inside your lungs is going to drop the air vent is going to go from outside your body which is a lot higher pressure to inside your body which now has lower pressure the lungs inflate this stops when your stretch receptors kick in because obviously you don't want your lungs to explode and then inspiration stops expiration is passive you decrease your chest cavity by kind of relaxing everything right everything goes back to a normal size so this is going to increase the pressure inside your lungs because all of a sudden a smaller chest cavity means the air is going to be very crowded and it's going to want to leave we measure the activity of your lungs and the health of your lungs by using what's called respiratory volume so you do not have to memorize these numbers or these equations but what I basically need you to do for the exam is just match the definition to the description and this shouldn't be too bad it looks very scary so tidal volume that's what you're doing right now so just breathing in and out very gently like the tide like the ocean waves going in and out this is the amount of air that's moving in and out of your lungs with each normal breath so we call it resting tidal volume so it's about 500 milliliters cubic cubic centimeters or milliliters so like if you think about a wine bottle being 750 milliliters this isn't very much air but it makes sense right you're not using that much air right now you're just trying to make ATP and trying to stay awake but think about all of the air that you could use so inspiratory reserve is the amount that you could inhale after a normal inspiration to take a normal breath in this is all the that you could keep sucking in and it's like 3,000 so it's like six times the amount of a normal breath that you could inhale let's say a lion Tiger barrel Maya's chasing you you might need that air expert or e-reserve if something's on reserve it's extra right so this is the amount that you can forcibly exhale so after you take a normal breath in and out this is all the air that you could like shoot out of there and it's about 1100 residual volume this is one that we have to kind of estimate we can never measure this the other three we can measure but this one we cannot this is what is in your bronchial tree even after you exhale everything you physically can so this is the air that's inside your bronchi it's the air that's inside your bronchioles it's the air that's inside your alveoli and so the only way we can count residual volume if there's residue on something it's like the leftover stuff right the only way we can count residual volume is if you were dead well if I was trying to measure your lung health being dead isn't exactly good right so it's just something that we estimate vital capacity if we're really talking about lung health vital capacity is the number that really important because this is the maximum amount of air that you can exhale after you've taken the deepest breath ever so you take the deepest inhale you possibly can and then you squeeze out all of the air you physically can so when they're really talking about lung health vital capacity is all of the air that you have to make a teepee whereas title or total lung capacity is adding that residual volume and so yeah residual volume something to count for but it's like that's not air that you're really using that's just air that's trapped inside your body so this picture here is just kind of showing it so if you look at the little yellow that's a very small part right that tidal volume like you're barely using it whereas the purple is inspiratory reserve which you have quite a bit the dark blue is expert ory reserve which you have quite a bit the light blue at the bottom is that residual volume that remember that is stuck in your body no matter what and so if you look at vital capacity which is like about halfway over it's showing everything you can inhale and everything you can exhale the comparison between vital capacity and total lung capacity is remember with total lung capacity we're just adding that residual volume which isn't really that crucial anyway so if you look the average person has 6,000 milliliters of average total lung capacity when really with every breath you're just using about 500 so you're not memorizing these numbers the whole point of this picture is just to appreciate that wow we have a lot of lung capacity that we don't use but on a day-to-day basis when you're just a normal homeostasis you're just sitting there breathing whereas I could inhale and exhale a lot more if I was in the sympathetic nervous system like the lions tigers bears oh my were chasing me I would have access to that air if I needed it but no matter how perfect your lungs are they're still dead space some of the alveoli in your lungs collapse some of them don't have a good capillary bed laying on top of them which means they can't exchange air so I think of this like if you have a doubles tennis court space for your lungs what you do if we were to take your alveoli and flatten them all out you would have a doubles tennis court of absorption space but if you think of a tennis court there's very few tennis courts that are perfect some would have like a little piece of gum on them or would have a little crack in them like there's always a part that wouldn't be usable right so you know a lot about vo lie in your lungs but some of them just aren't functioning so we just call this dead space as bad as it seems it's it's normal when we think about the movement of our lungs were of course thinking about exchanging oxygen and carbon dioxide but there's a lot of reasons that you move air so most of these are reflexes except for they say speeches and to reflex but I would argue because if a giant cockroach walked in this building right now a DAC I would probably say the f-word but some of these are voluntary so coughing coughing is a reflex so I've just I've had this cold for like five weeks and so sometimes I just have to coughs oh when you take a deep breath you're closing the glottis which is the hole where your vocal cords are and the air is forced up against that closure and so the goal of a good beastie cough is to clear the lower tract as sneeze clears the upper tract so with coughing and sneezing you can sit there and try to deny it I always love when you guys are in class and I can tell you're trying to cover up a cough so especially during exams when it's really quiet everybody cost like like a dainty little flower when really you need a like a nice beastie cough to really clear stuff out right same thing with the sneeze you try to fight it you're gonna sneeze right otherwise your eyes are gonna start watering like crazy so the goal of both the coughing a sneeze is to get stuff out of the respiratory tract if you think about the anatomy remember the whole goal is to keep stuff from those alveoli so it's better to get that cat hair dog hair chinchilla hair dust molds viruses it's better to just get them out of there before they actually get deep into your thorax laughing and crying those are short airburst right a hiccup hiccups are so obnoxious I've actually never had hiccups while I was teaching I feel like that's gonna be just a thrilling day when that happens because it's so obnoxious the reason it's so obnoxious is the diaphragm is in basically it's basically just cramping it's basically just spasming so just like any part of your body any other muscle can spasm but when the diaphragm spasm since it affects your breathing it messes everything up and so especially when your glottis is closed and the air hits your vocal cords then you get one of those obnoxious hiccups like you like one of those crazy ones and then a yawn there a lot of theories about yawning and so they think that it like kind of inflates some of the alveoli that aren't participating but a lot of people actually don't know so one of the theories with yawning cuz you ever notice yawning is contagious when young when one of you yawns in class you all yawn and then I'm staring at you and then I have to yawn and it's just terrible but one of the theories with evolutionary biologist is animals that hunt together we kind of need them like a pack of lions we kind of need that pack of lions to hunt as a unit so when it's time to sleep they all need to sleep so that we're all rested up and so that's why like if you notice your cats at least my cats when they are all together they'll all yawn and then they'll all kind of sleep which I mean let's face it cats sleep like 20 hours a day anyway but it's kind of an interesting theory because we do know yawning is contagious I mean we can see it in our daily lives but one of the theories is to make sure that we're all napping at the same time so that way we're all ready to go hunting at the same time and then speech is air movement over the vocal cords control of breathing is obviously one of our biggest homeostasis that's not a word mechanisms so we need it to be normal we need it to be rhythmic and we need it to be involuntary we don't want to sit there and hold our breath and we don't want to pant like a dog and we also don't want to have to say okay it's time to breathe in and it's time to breathe out because the brain has a lot of things to do so we think of breathing as needing oxygen but oxygen isn't really an issue for us the biggest thing is to get rid of the co2 that builds up in our body so yeah breathing in the oxygen is fine but we're always going to have more oxygen come in than we actually need the main goal of your respiratory system is really to purge the co2 because if carbon dioxide bonds with the water in your blood it's going to form an acid so if you remember the definition of an acid was having high hydrogen ion concentration so we've got to get those hydrogen ions out of our body or they will acidify acidify our blood and we will die so this buffering system this balance system to control carbon dioxide is crucial so if you have too much co2 it's gonna form carbonic acid but you don't really need to know the name carbonic acid we just need to know what makes an acid so this little equation here you can see when co2 gets with water we get that acid well then when that's in our bloodstream it splits into H pluses and a bicarbonate so the H pluses mean acid so if you get too much co2 in your blood you're gonna get too many H's and that's going to lower your pH and make your body very acidic consequently if you remove too much co2 then you're not gonna have enough HS and it's actually going to raise your pH so this system of being able to kind of suck up hydrogen's or spit out hydrogen's can neutralize two to three times more acid than if we use like Rolaids or something so this is the natural way that our body helps keep us kind of pH balanced when it comes to our blood so if you remember the blood chapter blood has to be between seven point three five and seven point four five or we're screwed so this is how we balance that getting that carbon dioxide out of there so if you hold your breath you're missing the opportunity for that carbon dioxide to exit the blood at your lungs so temporarily your blood will start to drop and so if we get below a 7.35 on the pH scale we call this acidosis respiratory alkalosis is if you're if you're getting rid of too much co2 so you should be normal breathing right if you sit there purposely hyperventilate you're actually getting rid of more co2 than normal which could make your blood too basic