Current time:0:00Total duration:5:27
0 energy points
Studying for a test? Prepare with these 4 lessons on Gastrointestinal system diseases.
See 4 lessons
Video transcript
SAL KHAN: This is Sal here. And I'm at Stanford Medical School with Dr. Andy Connolly, who's a pathologist here. And this is the second in our series on looking at some of these slides. ANDY CONNOLLY: Yeah. So we left off last time, Sal, looking at this piece here, which is normal colon. We had said this is an example of what you'd see at the edge of a specimen released for colon cancer. Now I'm going to click to the next one, which is a slightly more worrisome area if you're a pathologist looking through the colon. And so I'm going to zoom in just a little bit here to take a look at these. SAL KHAN: Looks very worrisome compared to the last one. ANDY CONNOLLY: And so what we don't like about it is we saw before this is what the normal gland looks like. It's a test tube shape and down, and it has these cells which are normal. Now all of a sudden it looks a little thicker here, and what catches our eye also is these aren't just straight test tubes anymore. They divide. They kind of go in and out like that. SAL KHAN: But they still are test tubes. Following up what we said in the last video is that they just look like circles as opposed to test tubes because we're taking a cross-section, because they're kind of popping out of the two dimensions. ANDY CONNOLLY: That's right. But although, when you come from the surface here and you go down, they normally should never branch. SAL KHAN: I see. ANDY CONNOLLY: And so these ones are branching, and that's always bad. And then you can see the way-- when you're putting a cross-section, there's normally just a little hole in the middle. And that's where the mucin-- you can even see it spilling out there. SAL KHAN: Wow. You can. ANDY CONNOLLY: So you can see it just kind of coming right out of there. This one here looks different. And what it is, it's piled up. And so it's a little bit bigger around. And in order for these cells, more cells-- they're going to be all piled up and going like this, and they even branch. And so what this is, is that we look a little more closely at this piece. And we say, hmm, I wonder if that's cancer. Could it be pre-cancer, or is this just an area of irritation? And a common response of the body to irritation is some sort of change. And like we were saying before, epithelium is the top layer. SAL KHAN: Right, right. The stuff that's facing the outside world. ANDY CONNOLLY: Facing the outside world. So if it's irritated, often the epithelium will change. And in this case, it's changing by undergoing more growth. SAL KHAN: Is it always-- even if it's non-cancerous, is it going to be a higher likelihood that it's going to become cancerous in the future? ANDY CONNOLLY: A lot of cancers, it appears, in the body come from parts of the body that are either irritated or have some sort of environmental challenges that are constantly at them. And part of that is because there's a lot of cell division. SAL KHAN: I see. ANDY CONNOLLY: If you keep dividing a cell, you might have errors in the DNA. SAL KHAN: So that's why skin cells, bowel cells-- ANDY CONNOLLY: That's right. And even things like liver. If you keep damaging your liver, you might have ongoing things and liver cancer. So when you're looking here, the pathologist would look at this area and say, well, it's a dividing gland that's kind of thrown up in these areas. But largely, they're still making mucin or they're this type here, which looks like it's tall and probably absorbing water. SAL KHAN: I see. So even within these test tubes-- well, they're not really test tubes. But inside of these vessels, there are also still the absorptive cells as well. ANDY CONNOLLY: That's right. So here, we would sign this off as hyperplasia. SAL KHAN: Hyperplasia. So hyper, like too much of something. ANDY CONNOLLY: Yes. SAL KHAN: And plasia? ANDY CONNOLLY: Growth. SAL KHAN: See. ANDY CONNOLLY: And so plasia just means growth. And so hyperplasia means too much growth. But the important thing is if you took away the irritant, it wouldn't do this. SAL KHAN: I see. ANDY CONNOLLY: So if you took away whatever the irritant is for the hyperplasia, it would go back to being normal. SAL KHAN: I see. I see. And that's just something we know. ANDY CONNOLLY: That's right. SAL KHAN: There's some stimulus that was causing these cells to do that. It might have been diet, might have been some chemical. It could have been just-- ANDY CONNOLLY: We're never really sure what, because so much of it is things that just float on through. So it's really hard to know. But, yeah, this is probably too much growth in response to an irritant. SAL KHAN: So it's possible that it just happened to be when this section of the colon was taken out. If this was done a day later maybe, then maybe this might have not been there? ANDY CONNOLLY: Yeah, probably take longer than that. A couple weeks. SAL KHAN: A couple weeks, but it's-- ANDY CONNOLLY: Because what happens is that the cells come from the bottom, and they work their way up towards the top. And so eventually the top would behave-- SAL KHAN: And so the way the body works here-- and it's kind of like the skin-- is this as constant. These cells are being used up, because things are kind of scraping by them. And they get a lot of use. ANDY CONNOLLY: They do. And in fact, there's a lot known now about stem cells. And the stem cells for the intestine are these guys. SAL KHAN: Oh, wow. So how do you differentiate the stem cell versus-- ANDY CONNOLLY: At the very bottom, the bottom hemisphere, there are going to be cells there that do not have the open chromatin and kind of elongated. SAL KHAN: I see. ANDY CONNOLLY: There may be ones which are endocrine cells, meaning they release hormones. And so they may have hormone-releasing cells. But in this bottom hemisphere, that turns out to be where the intestine keeps them. And these guys are probably the stem cells. SAL KHAN: And stem cells are cells that haven't picked their jobs yet. ANDY CONNOLLY: They haven't, and so there's all kinds of stem cells. There's the stem cell that can make a whole body, being. But then there's also the kind that can make the rest of the colon. SAL KHAN: I see. ANDY CONNOLLY: And so this one is probably the stem cell they can make the rest of the epithelium, but these two different kinds. SAL KHAN: The two different types, right. ANDY CONNOLLY: So they're down here at the bottom. That's about where you'd want them. SAL KHAN: Exactly. Right. ANDY CONNOLLY: So that makes sense. So down there are your stem cells, and it grows like that. So this is a hyperplasia. So I'd like to show you next the next step, which is a pre-cancer legion. Should we do that in another videos? SAL KHAN: Yeah. Let's do that in another video.