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Current time:0:00Total duration:10:48

Video transcript

hello Emily hello David so we're here today to talk about apoptosis I was going to ask you some questions about it you were going to explain what it even is to me absolutely okay talk apoptosis so so this word apoptosis I did a little bit of etymology research I broke the word apart because it comes from Greek particles that I identified so we have here's here's the limit of what I know right now so it comes from these two pieces the oppo meaning away and ptosis which means like a falling so it's really this kind of it means like took the falling away and my understanding is that this programmed cell death because that's what it is that's what you've written is kind of analogous to leaves falling away from a tree but it's something that's supposed to happen and the cells just die in this prescribed way when they're supposed to this isn't random this is this is something that the cell embarks on for a particular purpose yeah I think that's a really good way of putting it and I think that is why it was named apoptosis by some of the first folks who studied it on is that they really wanted to underscore that this is a form of cell death that is a normal healthy part of an organism's development it's maintenance of its body even its prevention of things like viral infection or cancer um so it's very much a normal and healthy thing that your body is actually doing right now so alright right now right now oh man so okay so what what are the ways in which a cell can die well what I mean cuz we have this diagram here here's a here's a normal healthy cell and then here we've got this what looks like the aftermath of some kind of explosion what is what is this so that's sort of showing two very broad categories of ways that a cell can die and the simplest way to label them would be messy and tidy but more more formally the bursting looking cell is undergoing necrosis on which is a form of cell death where the cell basically swells up and explodes and it releases its contents which not very good because those can damage other cells in the area they can attract cells of the immune system that will cause inflammation and then on the flip side you have the the tidy approach apoptosis and here you actually see the cell shrinking down and kind of breaking up its DNA breaking out of these little these little orange things in here the chromosomes being cut apart so those are like really little fragments of chromosome and it actually be much littler even than what I've drawn there but but what the cell is going to do is it's just kind of going to come apart into little fragments encircling different cell components on so you can sort of see those starting to bud off and then cells from the immune system whose job is basically to gobble up debride they're going to come and eat those little fragments it's going to be like nothing ever happened so this is kind of the difference between disposing of your garbage in trash bags and disposing of your garbage by just dumping it out the window of your apartment yes I think that's true but maybe even taking it a step further if you dispose of your garbage in trash bags or by apoptosis you can actually reuse what was in the garbage interesting so other cells can use those components on for their own purposes and they won't suffer any damage from having nasty stuff floating around outside so what what are the circumstances under which apoptosis happens like how how common is this and how common is necrosis oh so necrosis is usually something that that your body does not want to happen that's going to happen when a cell is perhaps exposed to a chemical toxin when a cell is actually mechanically damaged on so those are circumstances where a cell has basically received an insult that has caused it to die in a not very controlled way okay odd and apoptosis is kind of something that would be going on basically from the time a human being or another vertebrate is a tiny embryo throughout its life on so when you're developing when you're developing hands your hand actually kind of starts out as this chunk of tissue that's kind of like a paddle okay and it's actually a pop ptosis that is going to whittle your fingers out of that block so so I've got I've got this hand right I've got this kind of like webby hand and you're telling me that as the hand develops the tissue gets reabsorbed into the other cells that we're going to make up the rest of my hand yeah so the cells they'll first die by apoptosis and then basically the blebs will get scavenged up I'm sorry the what I guess I never named them but these are the little protrusions that's that's a very technical term that's a web I love that you see it in scientific that's a science worries totally scientific I love that all right blebs okay you can you can also see them in the the picture absol right what is this what is this image here on so those are that's basically just the same thing that the line diagram is showing a healthy cells which is the left panel and then blobby cells undergoing apoptosis which is the right panel so they're having all of their cell components repackaged into garbage bags to be or if we want recycling bags than to be sent off to other cells where their components can be reused as stuff exactly okay now what's this what's this uh this tadpole beast here what is this about so that's kind of the same thing that we were talking about with the hand on but another place where you see a pop ptosis happening and development is when you have a tadpole metamorphosing into a frog on so tadpoles this is actually kind of part of the way they're already the tadpoles have a very long tail and frogs generally don't have much of a tail to speak of and the way that the Frog loses its tail is through apoptosis um and again it's it's said to resorb the tail so that it can make use of the cellular component cool so tail just sort of shoots up and becomes hindquarters yeah I don't actually know exactly you know if it starts from the end and eats its way inward but on somehow it gets removed developmentally and that's really cool so it's not it's not it's not really like leaves falling off a tree it's not like this is a three-toed skink or something if you grabbed a metamorphosing tadpole by the tail would just break off it's really more that it gradually gets subsumed into the the tissue of the growing frog I mean at the cellular level I guess the cells do they pull away from their neighbors so in that sense it's a falling off but it's not necessarily a falling off that you see as well at the level of a whole organ it would be more falling off of an individual cell so so far we've given examples of of apoptosis that are happening within developing creatures but you're saying that within like right now apoptosis is happening in my body and in fact so does that mean is that just to keep the number of cells in my body constant that's a big part of the role that apoptosis plays on like your your blood system in particular is continually producing new cells and if you produce cells but you never got rid of cells you would eventually end up with too many cells and too many cells in general is not a great thing to have in the human body that's the kind of thing that you might get in cancer if you're having cells accumulating too much on so part of it is just keeping a healthy balance but since we also just brought up cancer that's actually another wonderful favor that all of our cells are doing for us is if they suffer DNA damage which could predispose them to become cancerous first they'll try to fix it but if they can't fix it they will actually under normal circumstances undergo apoptosis so there's no chance of them passing that damage on and becoming cancerous and that's actually a really important protective role that that apoptosis plays in an adult human or in a human at any stage of their life so it's kind of like like a big red button that you know it's like a self-destruct button if a cell comes to appreciate that it is developing cancer symptoms then it just hits the button and begins this cascade of enzymes that cause it to undergo apoptosis yeah I mean I think that's the the general way to think of it for sure on so there are actually kind of different ways that cells that are progressing towards cancer might be stopped and some of those involve internal mechanisms so the cell doing its own surveillance and observing Wow gee my DNA does not look good and I can't fix it okay but also you could have a cell that might be observable from the outside by another cell as a potential cancer cell so like an immune cell could come by and like stick a protein on the outside that also triggers the same thing yeah yeah I don't on you I don't know exactly what the mechanism of communication there is but it would be an interaction between the two cells where one of them would tell the other you know okay I see there's something wrong with you you know time to time to wrap this up cool so apoptosis can happen in a couple of ways but in pretty much all cases it is a normal healthy part of the cell life cycle do all cells die this way um I mean there are ourselves that will will undergo necrosis on so certainly in that sense not every cell in your body is going to die by apoptosis on I would imagine that there are also other ways of recycling used cells that are not exactly considered apoptosis on like skin cells on some of them will undergo kind of a similar process but it's not technically apoptosis even though it is a regulated form of cell death Oh God so I don't think that I would go as far as to say that that all of your cells were eventually going to die this way but it's sort of a very common maintenance way for cells to die and be replaced cool thanks Emily thanks David
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