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Current time:0:00Total duration:7:46

Video transcript

before we talk about what asthma looks like let's take a look at a normal airway so we've taken a cross-section of somewhere along the airway as was a small airway disease so this is not the trachea or the stuff in your throat but your chest and one of the important players in the caliber or the structure of the airway that I want to start with is the smooth muscle layer so we'll use red for muscle and this layer controls the diameter of the opening diameter of the lumen of course outside the muscle there's other things too there's connective tissue and cartilage depending on where if you're higher high up enough on the airway those things are not really as affected by asthma so we'll just leave it kind of like this alright so we got our smooth muscle which smooth also remember you can't control cautiously it reacts to the environment and usually it keeps our airway nice and open like this label that here smooth muscle the inside that we have a layer of the mucosa so we call it the mucosal layer let me just label that the mucosa that basically coats the inside opening of the airway and within this layer that's very important that we have these glands that can secrete mucus into the lungs they're there for lubricating the opening and keeping our lungs moist and also when there is inflammation or their foreign bodies we have to get rid of the mucus that they secrete is important in clearing out the area so when we call on a cup of the phlegm the phlegm comes from these glands that secrete the mucosa so they're kind of everywhere in the mucosal layer and of course here we have the lumen this is where the air actually moves in and out it is dry but nice and lubricated by the mucus so this is a quick look at what the normal lung the normal cross-section of the airway looks like now let's look at what happens when this person is having asthma as you know as becomes and so most of the changes happens during an attack depending on the severity this person might get it more often than the next patient so first we still have our muscular layer but now the lung is in spasm the muscles are spasming which means it's constricting and the opening is going to be much smaller the connective tissue like the card illusion other things are still out there so I'll still draw it like this but the important thing to focus on right now is the fact that the muscular layer has thickened and it's clamping down in this opening in addition the mucous layer which is nice and round here that I've drawn has swelled up in reaction to the inflammation so instead of a nice round opening like this now we have this amorphous shape the further clamps down on the opening so now look at what has happened to our lumen it's much smaller and to make matters worse don't forget the glans so the glans are still here but this time they are also reacting to the immune response as a result they're filling up with mucus and they're secreting it into the lumen that's already narrow and blocked off so now we've got the swirling mucus in here that only makes matters worse so look at the difference between air going through this nice big opening and the air trying to get through this so between the constriction and they'll the fluid in there we're going to have little bubbles that's why you hear the popping and the wheezing we'll listen to a person having an asthma attack the wheezing comes from the obstruction both from mechanically narrowing this area and the extra fluid in there from these glands going crazy so that's how it happens but why does this whole thing take place what triggers asthma but that is sort of the million-dollar question because there are so many things in the environment I'm drawing here are it could be pollution it could be smoke it could be food or dander anything that this particular person reacts to these are the allergens in the air and when they get into the body our body has an immune response that reacts to anything that's foreign so people react more than others and we have these antibodies that kind of look like a y-shaped molecule so these in the immune reaction tend to be IgE that's just the name of these antibodies now the body has a tricky memory system if it's the first time that is seeing these allergens you might only get two oh geez because they're working hard to make new ones to recognize them but this third or fourth time every time you get exposed because the memory is still there is easier to make the IgE each time it's like fighting an enemy that you've already fought before so the IgE actually increases in number so the size of this IgE response is proportional to the size of this immune response or to this allergic response I should say because when the immune response goes haywire responding to something that's foreign and trying to fight it off that's called an allergy okay so we've got these foreign allergens whatever the trigger is with these IgE the job of that GE is to recognize and pick up these foreign particles the idea is in the same family of antibodies that help us fight off infections but in this case it goes to search for a cell we call it the mast cell it's spelled mast like the mast on a ship and inside the mast cell it's just floating around our body carrying little pockets of a molecule we call histamine this amine is the main player in any allergic reaction if you remember if you ever taken anything to fight off an allergy there's a class of drugs called the antihistamines right so histamine is just usually walled off in the mast cell not in our system with IgE antibodies we just talked about they are friends with the mast cells and only when they're carrying a foreign body like this do they find the mass L and attach to it so every pair of the IgE that is picked up an allergen will go then look for a mast cell to attach to it like this this attachment right here kind of wakes up the mast cell so all these little pockets inside it open up histamine then flows out of them SL like this and kind of floods into our system into our bloodstream causing allergic reactions everywhere this is why you sneeze your eyes water you can get hives the whole cascade of that allergic reaction is thanks to these little histamine molecules and in the lungs if this person has asthma this is exactly what happens as a result of the histamine we just draw a few more particles here to show you and voila we get this constriction we get the mucosal swelling and we get the wheezing so asthma is really an immune response going overboard as all allergies are it's a part of our body's natural response to a foreign body that then causes us harm by reacting too strongly and releasing things that cause us discomfort so to sum up the pathophysiology of asthma remember first we've got the muscular layer thickening and constricting then we've got the mucosal layer swelling up and third we have the glands over producing the mucus that then floods the already constricted opening