hi and welcome to pulmonary ventilation this is the second video in on the respiratory system so we're going to talk about how do we ventilate so we're gonna be okay all right so again the function of the respiratory system is gas exchange so we need to be able to bring that material into the lungs and send it back out of the lungs and how is this going to take place so first of all we need to take a look at how do the lungs remain inflated so we have some things we have two things called intrapleural pressure and I'm going to diagram this out in a minute um let's do that color so intrapleural pressure between the membranes between the parietal and visceral pleura is very low in fact it is about 756 millimeters of mercury I'll talk more about that in a minute or minus four millimeters of mercury if we use atmospheric pressure at zero it's going in atmospheric pressure is 760 millimeters of mercury at sea level all right so um our chest wall is configured to expand outward thus increasing the volume of floral cavity and according to Boyle's Law anytime you increase volume or pressure decreases so there isn't much pressure and we'll talk more about it in just a minute um your lungs will move with your chest wall due to the um uh let's see I guess it would be cohesive cohesion of water at the two pluries um interfaces so between so the water that's on the parietal side and the water the serous fluid that's on the visceral site that's going to attract and again I'll show you the picture and then also to increase the volume of the thoracic cavity elastic tissues of the lungs pulls Inward and and I'll show that in just a minute I showed that to you I showed the fact that you do have elastic fibers around your alveoli in the respiratory anatomy video so um you can go back and review that so because intrapulmonary pressure is greater than intrapleural pressure so I just um posted your notes so I hope that so this needs to be intrapleural pressure the lungs remain inflated and experiences and lungs experience an outward pull from the chest wall I like to think of it more as a push so that the air in lungs pushes out into the cavity all right so I'm going to draw a picture I'm just going to go to this picture first and then I'm going to go to the Whiteboard and show you everything that's going on all right so here is the the parietal pleura it's white on the outside here's the visceral pleura touching the lungs and then we have the pleural cavity in between and this is where we get intrapleural pressure so in that cavity and it's going to be a negative pressure it's almost like a suction but we know there's no such thing as a section it's just decreased pressure um in an area and the air wants to flow towards it all right so then Bridal plural thorough cavity visceral again all right so let's go to the Whiteboard and let me show you what I'm talking about so um sorry I'm just trying to find a different color um all right so here are here's your trachea and your primary bronchi and your lungs and we're just gonna just do really basic and then around the outside in pink we're gonna put the parietal pleura and of course you would have a heart in the middle okay so then there's one parietal pleura and here is the other so each lung is in its own pleural cavity so this is going to be parietal pleura and then in blue is going to be visceral plural Okay so all right so then if we take I'm going to do it even a different color feet this way okay so here's our bronchial tubes okay and so they're going to branch and branch and branch and branch and branch and branch and branch and Branch Branch branch and they're going to have air inside of them and that air is always trying to be 760 millimeters of mercury or um zero so in other words no difference from the outside atmosphere and so this is known as p-a-l-v or alveolar pressure enter a pulmonary pressure let's put that intrapulmonary pressure is p-a-l-v and so that's due to the presence of air within the alveoli and then out here we have atmospheric pressure and that's always going to be 760. millimeters of mercury or instead of dealing with big numbers all the time we just say it's zero this is my Baseline pressure is zero millimeters of mercury all right now um what's going to happen to create this pressure inside of here also is that the alveoli we get down to our little alveolar sacks don't look like a nose okay around all of the alveoli we have little yellow like three or four rubber bands around and that is going to cause the alveoli to shrink okay so this decreases those elastic fibers elastic fibers decrease volume of alveoli and any time you decrease volume and so then the pressure goes up now it's not going to be as great as outside or air would always be leaving your brain your lungs but it's greater than what's going to be here in the pleural cavity okay so more than in oral cavity okay then we also have now I'm going to open up dang it I'm going to open up the alveoli I guess it doesn't look any different than when they were closed we're going to have those type 1 alveolar cells we'll just make them a little thicker in here so these are type one alveolar cells and they make alveolar fluid make alveolar fluid and so what we saw um in the last video is that if you are going to put a lot of fluid into um let me just draw a little water molecules inside of here in these little small tubes they're going to draw the alveoli together towards the center now not all the way to collapsed because we have surfactant but it is going to draw the alveoli together okay again decrease volume increase pressure so another reason why the pressure in your lungs is greater than outside okay greater than the in the pleural cavity and then one other thing is that your chest wall oh go ahead and do that is that the muscles in your chest wall are always pulling outwards okay so chest wall muscles move outward all right so now I'm pulling out this way and the other ones are pulling in this way oops not your parietal pleura let's see let's erase that okay um okay so that's pulling these guys in so if the chest wall is pulling out and the lungs themselves are pulling inward that is going to give you right here in your pleural cavity greater volume and less pressure and therefore intrapleural pressure pip is always going to be at least minus four millimeters of mercury or less okay you get even more negative and we'll talk about how that's possible all right so that is um what all of this before me so this back here intrapleural pressure intrapulmonary pressure and what's going on with the pressure in the lungs now let's say that you got a you got some air in your pleural cavity oh dang it sorry you guys air in your pleural cavity um penetrating wound to the chest rib lacerates lung or alveolus ruptures or visceral also the visceral oops visceral pleura can rupture so air is either coming in from outside or air is coming in to the cavity from the lung so what that's going to do is make that intrapleural pressure minus four an intrapulmonary pressure minus zero to equalize so now air pushes in into the cavity and onto the lungs Okay small pneumothorax a little bit of air in there that's okay seal up the whole um maybe the pleura will cover over itself sometimes they'll just resolve themselves we don't really worry too much about that large pneumothorax though is a medical emergency if I have a lot of air going into that pleural cavity or a lot of air in the pleural cavity and that pressure is greater than -4 that's going up to zero or even more then we need to suck it out so we'll need to put a chest tube into that pleural cavity to remove the air and then we got to leave it in there until it heals okay so some maybe it may be a few weeks before that visceral pleur are days anyway before that visceral pleura will heal itself up and the hole will be gone so if that pressure if these pressures equalize then you're going to get atelectasis or lung collapse but this is only if intrapleural and intrapulmonary pressures equalize due to air in the cavity so they are both zero then your lungs will collapse and they will remain collapsed until the air is removed from the pleural space and they will inflate um on their own we don't have to blow them back up again just as long as you get that air out of the plural space then they will they will reinflate okay so now let's take a look at um pulmonary ventilation so this is the exchange of gas between the atmosphere and the body cells well respiration is so we'll have ventilation movement of gases between the atmosphere and the alveoli so that's what we're going to take a look at then we'll be looking at these other things later but right now we're just doing ventilation so ventilation is the net movement of respiratory gases so air containing O2 goes into the alveoli during inspiration O2 diffuses into the pulmonary capillaries and then we go to the systemic cells and O2 diffuses from the systemic capillaries into systemic cells then the CO2 will go from the cells to the capillary CO2 will go back to the lungs CO2 diffuses from the capillaries into the alveoli and the air containing CO2 is exhaled okay that's it but we have to go through steps that are going to take place all right so that is all of that that we just saw all right so pulmonary ventilation movement between the atmosphere and the alveoli so we have inspiration brings air into lungs also known as inhalation and expiration is exhalation don't forces the air out of the lungs quiet breathing or what we call youpnia rhythmic breathing at rest just you know what you're sitting doing right now uh Force breathing hopefully you don't um have to forcefully breathe right now but that would accompany exercise um who is going to control this we will look at control of respiration in a separate video but um autonomic nuclei so respiratory centers in the ponds in the medulla oblongata are going to regulate breathing but who is going to do the work and that's going to be the skeletal muscles of the of respiration so um with Boyle's Law that's got to be coming up I don't know why we haven't seen Boyle's Law yet oh there it's next okay so um we'll get into Boyle's Law here in just a minute but um uh what do we need to do we need to change the volume so that we can change the pressure so as the skeletal muscles contract and relax changing the thorax volume those volume changes will result in changes in pressure gradient between the lungs and the atmosphere which we're going to look at in a minute and air is also always going to move down its pressure gradient so air so when we Inspire the air pressure is greater outside of our lungs than inside of our lungs and then when we expire then the pressure inside of our lungs is greater than the outsides because air is always moving down its pressure gradient from high to low so uh if we take a look at this really quick we'll look at them again whoops what are the the muscles of quiet breathing so these muscles will contract to increase the dimensions of the thoracic cavity that would be the diaphragm and the external intercostals then if we want to forcefully inhale we need to use the sternocleidomastoid and the scalenes in our neck we're going to use the serratus posterior in our back our pectoralis minor and our rectal spinae so like I just did I just took in a deep breath you can feel what happens to your rib cage as you take in that deep breath you are expanding that rib cage in order to increase the volume and decrease the pressure that is less than outside less than atmospheric pressure so that um the pressure goes down and the volume and the air Moves In from the outside now when we when we exhale inquired expiration we just relax our muscles so we just relax these muscles and then the air goes back out again so we don't even burn any energy and expiration the only time that we use energy is during inspiration um but what if you want to blow out a candle or you want to sing a song or you want to keep talking like I am so now I have to force the air out so I want to pull my thoracic cavity down um and so I'm going to use my transversus thoracis so that's going to be oops that's going to be up here in your back I'm going to use serratus posterior inferior to pull down my internal intercostals I used my external intercostals um in Inspiration but I'm going to use them for forceful expiration blown out a candle internal intercostals external oblique and your transverse abdomness so you know if you've if you've been a singer and or you've taken singing lessons or you've been in a choir or something and they'll say okay you need to breathe with your diaphragm your diaphragm breathe with your with your abdomen yeah I'm exhaling using my abdomen to push that air out to maintain that sound so that it doesn't waver that it's good and intense and strong and all that kind of stuff all right so the relationship between Boyle's law is that there is an inverse relationship between gas pressure and volume so you can read through this but if you look at this if I have increased volume I've decreased pressure the little water molecules don't bump against the sides and the top as much so therefore less pressure but if I decrease the volume then I have increased pressure so please remember this so as as volume goes up we get a decrease in pressure and as volume goes down we get an increase in pressure all right so if we take a look at this this is just what the muscles are doing so vertically laterally and anterior postal posteriorly is what um the rib cage is doing you can read through that on your own you can take a look at this picture you can look at lateral dimensions and anterior posterior dimensional changes I'm not going to make you know that okay so we go on to pressure gradients and whoops sorry about that I need two okay let's stop sharing for a minute