hello hello hello it's meticosus perfixinitis where medicine makes perfect sense let's continue our biology playlist in the last video we had a discussion on the anatomy of the respiratory system today we'll talk about the physiology part the mechanics of breathing get the air in and get it out oxygen in carbon dioxide out which one is more important getting the carbon dioxide out is more important than getting the oxygen in to know why please refer to the last video getting the air in is known as inhalation or inspiration getting the air out is known as exhalation or expiration fun fact from physics positive pressure pushes stuff while negative pressure pulls example if a freaking meteorologist told you that a big gust of wind is blowing from california to arizona what does that mean well it means that the air pressure in california is higher than air pressure in arizona that's why air is moving from high pressure to low pressure this is true for liquids and gases because these are the fluids according to physics this pressure difference is known as pressure differentials no duh if the air is blowing from california to arizona it's as if california has a positive pressure relatively speaking whereas arizona has a negative pressure relative to california why because positive pressure pushes but a negative pressure poles let's give a hypothetical example suppose that the pressure in california was about 20 torr but the pressure in arizona was just five torr okay now what's the driving pressure or the pressure differentials 28 minus 5 equals 15. let me take you back to the good old days which were not so good when you were it's cool science class and there was this device that is a vacuum basically there is a lovely pump or small device here that sucks the air out of this container so let's talk about before sucking versus after sucking before removing air out of the system the pressure here inside this vessel was atmospheric if it's atmospheric we call it zero zero here does not mean absolute zero it just means that we have the same pressure here as in the atmosphere that's it nothing more nothing less now when you suck the air out of the device what's going to happen to the air pressure here well if air is moving the pressure is going to decrease and this will be a negative pressure which means the pressure inside is lower than the atmospheric pressure outside here comes the question when the pressure becomes negative what's going to happen to the balloon that's hanged freely here the balloon is going to expand why because negative pressure pulls this is exactly how your lungs work during inspiration now this is not a vessel this is your chest wall or thoracic cavity nice who's the balloon the balloon is your lung who's the device that's creating the negative pressure well there are two devices number one the diaphragm number two the external intercostal muscles why do you call them intercostal the word inter means between costal means ribs the muscles between the ribs during inspiration the diaphragm is gonna descend and go down the external intercostal muscles are gonna expand the chest wall this will increase the volume of the chest wall but decrease the pressure when you lower the pressure you create a negative pressure which means a pressure that's lower than the atmosphere negative pressure pulls so the air is going to leave the atmosphere and will enter into your lungs this is what we call inspiration this video will discuss the basics if you want to dig deeper check out my pulmonology playlist here on youtube a video titled normal quiet breathing when air comes in this is called inspiration or inhalation when air goes out it's called expiration or exhalation from here you can deduce that the pressure in the atmosphere is higher than the pressure in your chest wall relatively speaking of course the pressure in the atmosphere is like atmosphere we call it zero and therefore the chest cavity has to have a negative pressure that's why air moves from the atmosphere to your lungs during inspiration conversely during expiration the pressure in your thoracic cavity is higher than the outside world that's why air moves from here to here since the atmosphere is always atmosphere or zero your thoracic cavity pressure has to be positive in order for air to leave your lungs and go to the outside during expiration here's the question can your body control the pressure in the outside world the answer is no therefore you have to take control of that which you can control your own body you can only tweak your chest wall and therefore during inhalation i have to create a negative pressure in my chest wall but during exploration i have to create a positive pressure in my chest wall but how do i do that let me say it one more time for the kids in the back during inspiration you shall create a negative pressure however during expiration thou shall produce a positive pressure remember boyle's law mr boyle said that when the temperature is constant the relationship between gas pressure and gas volume is inverse if the volume goes up pressure goes down volume goes down pressure goes up during inspiration your chest wall gets a negative pressure and the volume expands and it fills up with air during expiration the pressure of the chest wall increases but the air is leaving so the volume decreases during inspiration diaphragm goes down external intercostals contract to expand the chest wall cavity and therefore what's going to happen to the volume increase pressure decrease but during expiration the exact opposite habits diaphragm moves upwards and the chest cavity decreases in volume pressure increases air leaves now this slide is super duper sophisticated please refer to my video titled normal quiet breathing in my pulmonology playlist but as a very quick review inspiration versus expiration what happens to the lung volume during inspiration well i'm breathing in therefore it has to increase okay during expiration i'm breathing out therefore the lung volume has to decrease easy peasy now who pulled the air in the decrease in the pressure oh i get it so pressure goes down volume goes up this is boyle's law here during expiration you have the exact opposite pressure increasing volume is decreasing please note that the intra plural pressure which is the pressure inside the pleural cavity is always negative whether you're talking about inspiration or expiration doesn't matter it's always negative but why is that medicosis the negative intrapolar pressure is due to the dynamic harmonious antagonism between the chest wall which wants to expand and the lungs which want to recoil imagine that this is your right lung lung is here chest wall is here the chest wall of course is bones muscles joints etc we're talking about the ribcage the lung is on one side the chest wall is on the other side what's in between the pleural cavity the chest wall wants to expand the lungs want to recoil creating a negative pressure between them which prevents them from being separated if you cannot grasp this imagine two slides two glass slides like the ones they use under the microscope get two of them add a teeny tiny drop of water between them okay then push them toward each other until they hug each other okay then i will try to pull this one this way and pull the other one the other way it's impossible to separate them how come because when you're pulling this one up and pulling the other one down you're creating a negative pressure in between which prevents them from being separated from each other this is exactly the story of the pleura this single drop of fluid is the pleural cavity this is the chest wall this is the lung the lung wants to recoil on its own the chest wall just wants to expand creating a negative pressure in between which prevents them from leaving each other that's why you do not have to worry about your chest wall popping out of your body nor do you have to worry about lung collapse if you are normal the lung is like a balloon if you leave it alone it wants to recoil like the balloon leave the balloon alone in the air oh it wants to recoil chest wall wants to expand creating a negative pressure in between and that's called the intra plural pressure breathing is under autonomic control the respiratory center is in the medulla oblongata which is part of the brain it's part of the brain stem however the diaphragm is under somatic control the diaphragm is a somatic muscle and that's why in the vast vast majority of cases most of the time you are not aware that you're breathing it happens automatically because under autonomic control can i override it yes you can override for a short period of time like this i just overrode my medulla oblongata but if i breathe like crazy consciously for a long period of time the medulla will get mad at me because this can kill me from respiratory acidosis or respiratory alkalosis as we have discussed in the previous video oh by the way if you want to download these notes in pdf forms go to medicosisperfectionindust.com one is more important getting the oxygen in or taking the carbon dioxide out of course taking the carbon dioxide out is more important because of the ph carbon dioxide is a freaking acid because when you add carbon dioxide to water you get carbonic acid so let's breathe in oxygen has entered into your lungs of course like not just oxygen like oxygen nitrogen carbon dioxide water vapor etc but all the oxygen is needed here we'll take that oxygen and give it to the blood because the function of red blood cells is to carry oxygen and then take that oxygen the red blood cell is going to give it to cell the cell is gonna take that oxygen and then give you carbon dioxide carbon dioxide is gonna return to be exhaled how does oxygen go from here to here three parts number one ventilation which is to get oxygen into the alveoli next is diffusion which is from here to here through this membrane number three is to jump on the red blood cell so sending oxygen to the alveoli is called ventilation sending blood near the alveoli is called perfusion sending the oxygen from the blue to the red is called diffusion or gas exchange oxygen is going to come in carbon dioxide is going to leave the chat what are causes of hypoxia a disease that affects ventilation a disease that affects perfusion or a disease that affects um diffusion here's the atmospheric air i breathe it in okay i care about the oxygen oxygen is in my lungs and then oxygen is going to leave my lungs and go to the arterial blood and then oxygen jump on the hemoglobin hemoglobin is going to give oxygen to tissue tissue or cells will take oxygen and give you carbon dioxide carbon dioxide is going to jump onto the same hemoglobin and now we are in the venous blood we're talking here about superior vena cava and inferior vena cava go back to the heart heart will take heat to the lungs breathe that carbon dioxide out now let's call them names in a good way oxygen the atmosphere is called fio2 when oxygen enters your alveoli it's called pao2 p is for pressure a is for alveoli when it's in the arterial blood it is p small a a for arterial when it's on the hemoglobin it's called sa s because it's saturation and then this is called oxyhemoglobin because it has oxygen but this is called carb amino hemoglobin because it has carbon dioxide be careful this is carb amino hemoglobin not carboxy hemoglobin carboxy hemoglobin is carbon monoxide this is poison this can kill you we're talking about the normal carbon dioxide which is part of the atmosphere this is carb amino hemoglobin which is normal carboxy hemoglobin is not normal not in significant quantities i mean do veins have oxygen they have a teeny tiny amount of oxygen called pvo2 v is for venus if my videos helped you in the last year please consider buying me a coffee go to buy me a coffee dot com slash medicosis thank you so much in advance filling your alveoli with air is called ventilation getting blood near the alveoli is called perfusion getting oxygen in carbon dioxide out is called diffusion through this membrane this lovely membrane is made of six layers first your alveoli are wet then the endothelium which is just a epithelial tissue that lines the alveoli then we have basement membrane here epithelial basement membrane and we have fluid in the interstitial space then we have the capillary endothelium which is sitting on the basement membrane so the capillary basement membrane first and then the endothelium next when oxygen leaves the alveoli and goes to the blood this is called diffusion which is simple diffusion translation no atp needed no carrier needed this does not need energy you should be thankful for this you know how many times you breathe every day a lot imagine that you needed atp for every single time that every single drop of oxygen diffuses by well you would have needed it to eat like 15 meals a day or something to learn more please check my pulmonology playlist inspiration versus expiration inspiration is active expiration is passive inspiration is shorter expiration is longer look at this expiration is longer when you inhale you increase the three dimensions of your chest cavity when you expire you decrease them during inspiration volume increases pressure decreases during expiration it's the exact opposite let's talk about normal quiet breathing when you are just reading a book the diaphragm should go down external intercostals will contract but during expiration you don't need energy it's passive the diaphragm will go back to its normal position and the lungs will shrink because they love to recoil but what if i'm doing forced inspiration like this well you need diaphragm external intercostals plus extra muscles what if i'm doing forced expiration like this now expiration will not be passive and will start getting active you will need internal intercostals and the abdominal muscles get your six packs going hey mitochosis why is expiration longer than inspiration because expiration is passive therefore slow because i'm not exerting energy here if you want to learn about the treatment of asthma and the treatment of peptic ulcer disease check out my utakoids pharmacology course on my website medicosisperfixnetis.com if you study in january you are my friend because you are a unicorn so here is 60 discount for you just use discount code new year learning at checkout thank you for watching please subscribe hit the bell and click on the join button you can support me here or here go to my website download my courses be safe stay happy study hard this is mitochosis perfectionatus where medicine makes perfect sense