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Normal colon tissue

Dr. Andy Connolly from Stanford Medical School introduces Sal to what normal colon tissue looks like. Created by Sal Khan.

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  • aqualine ultimate style avatar for user Hazle
    How do doctors take out bits of the colon?
    (17 votes)
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  • leaf green style avatar for user Paul Kïttson
    So do they remove whole sections of your colon tubing? What do they do with the ends, fuse them together?
    (11 votes)
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  • male robot hal style avatar for user I give up
    How do the goblet cells that Sal mentions at help the colon?
    (3 votes)
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  • marcimus pink style avatar for user Triona
    So does that mean that ibs and crohn's disease are a form of cancer? As the treatment often leads to removing part of the colon?
    (4 votes)
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    • piceratops seed style avatar for user M.Z.Strickland
      Nope, neither of those are forms of cancer. Crohn's disease, ulcerative colitis and inflammatory bowel diseases (IBD) generally are diseases where the body attacks the colon or other parts of your digestive system. Sometimes the inflammation gets so bad that we have to remove parts of the colon (or other parts of the bowel for Crohn's) because the intestine gets scarred down, gets a perforation, or you becomes so sick that it starts dragging the rest of your body down.

      The second disease you asked about, irritable bowel syndrome (IBS), is what we call a functional disorder and isn't cancer either. This is a problem where people can have abdominal pain and fluctuating bowel habits that can really interfere with their lives. We're still not sure of the cause and the diagnosis is based more on the person's symptoms matching a certain list. We don't usually do surgery for IBS.

      A lot of people get IBS (irritable bowel syndrome) and IBD (inflammatory bowel disease) confused--and, based on their similar acronyms, it's easy to see why! :)
      (5 votes)
  • leaf orange style avatar for user Savanna Amber Williams
    How can you get colon cancer? And also is it contagious?
    (4 votes)
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    • sneak peak green style avatar for user Valeria Zuluaga-Sanchez
      Hi Savanna,
      There isn't an exact reason why you get colon cancer, but it may either be inherited (meaning that your genes have mutations in them that promote the risk of developing cancer cells in your colon), the most common of which are Hereditary nonpolyposis colorectal cancer (HNPCC) and Familial adenomatous polyposis (FAP), both of which increase your risk of colon cancer by at least 50%. However, people may get colon cancer even if they don't have mutations in their genes, and there are risk factors that increase the risk of colon cancer. These are:
      -old age
      -minority races
      -personal history of polyps or colon cancer
      There are more than that, but these are the most common risk factors. To answer your second question, no, colon cancer is not contagious, but it can be hereditary.
      Hope this helped, and sorry for the late response!
      (1 vote)
  • blobby green style avatar for user Lina Abu-Ghosh
    Do colon-patients always have cancer!
    I mean many members of my family say that there's something wrong with their colon , but Is it always cancer!
    (2 votes)
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    • orange juice squid orange style avatar for user Joshua Dietz
      This one is a bit difficult to answer, but problems with colons don't "always" transmit into colon cancer. Also some colon cancers are less severe then others. you may want to look up "Diseases of the intestinal tract" to narrow down your question! There are literally dozens of different problems associated with the colon, of which many can be serious.
      (2 votes)
  • piceratops seedling style avatar for user Emily
    What are the "tall cells" called at ?
    (2 votes)
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  • blobby green style avatar for user Melquiades     Velez
    what is the difference between a flex exam vs. a colonoscopy?
    (2 votes)
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    • leaf green style avatar for user Nahn
      A flexible sigmoidoscopy is like a "Mini-colonoscopy". It allows for visualization of the rectum and the sigmoid colon. There are some diseases which are so likely to cause problems in this area, that using a flexible sigmoidoscopy to screen for them is all that needs to be done. However, for most people a colonoscopy needs to be done so that the entire colon can be visualized and any abnormal structures beyond the reach of a flex sig can be removed and biopsied. A flex-sig could potentially be used as a screening tool for cancer, but it is less sensitive than a colonoscopy. This means that you will probably be recommended to do a prep and flex-sig once every 5 years, vs doing a prep and full colonoscopy once every 10 years (barring any abnormal findings). http://www.cancer.org/healthy/findcancerearly/examandtestdescriptions/faq-colonoscopy-and-sigmoidoscopy
      (1 vote)
  • starky ultimate style avatar for user Greacus
    The lighter pinkish part in the middle of the microscopy has some white tears and area's in it. What are those tears/area's? (I suspect the slice of tussue literally teared up a bit?)
    (1 vote)
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  • duskpin ultimate style avatar for user Sudha
    is there any way to fix colon cancer or any cancer for that matter?
    (1 vote)
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    • piceratops ultimate style avatar for user Courteney
      There are different kinds of cancer treatments, including chemotherapy; removing the tumor if possible; radiation; and various medications. There is no guarantee that these treatments will work, and treatment depends on the kind and stage of cancer. Some cancers are more easily 'fixed' than others.
      (2 votes)

Video transcript

This is Sal here and I'm at Stanford Medical School with Dr. Andy Connelly. Hi there Sal, I'm here to discuss with you histology today. Histology! And, and forgive me, for what is probably a simple question, but what is histology? So it will be the -ology, the study of, in this case the histo-, means tissues. We're going to be looking up the cellular components of organs. Cool... yeah. So what we're going to be looking at today is the histology of the colon. And so for the colon we often have colon specimens coming in from pathology. And so the colon, like you were saying before, is the large intestine. So if you have this piece of large intestine, and its removed from the patient because there is an area of cancer. It might be cancer, they're actually pretty good now about doing colonoscopy. Looking from the inside-- They'll often have looked inside think it looks like cancer take a little piece and send it to us before hand, and then they remove it. And the reason why they want to send it to you is even if they know its cancer how severe is this cancer? How severe is the cancer? They also want to get a really good tissue diagnosis to make sure if they're going to go remove a piece of your colon, that they really know that its cancer rather than it just looks like cancer. So its the definitive proof before they remove it. So then if this is the cancer that's removed they clearly want to be able to check the margins to make sure its removed in its entirety. But often inside of there, they'll find other pieces of tissues, like here's a polyp And when we say check the margins, this is literally, just making sure you've covered enough material so that you've gotten all the cancer in it that you're not kind of cutting through the cancer and that you've missed something. That's right, because this is actually one of the traditional surgical cures of cut it out to cure. Colon cancer, that tends to still be the case. Because you cut it out to make sure you cure it. There are many other kinds of cancers that which spread so widely early on that you don't usually cut out. So then the polyp can be found in a piece of colon removed a polyp is something that just sticks up. Any tissue that sticks up. It's not necessarily cancer. No, so for instance another common place you hear about is some people in the sinuses might have sinus trouble and they'll have a sinus polyp those are almost always just inflamed. And then we'll find areas in which it's just the lining that's been roughened, and we'll take sections of those. And that can happen from just someone being allergic to food Yeah, irritations of such. Yes, irritations of certain sites. So we're going to have the areas where its kind of irritated some in which there's a polyp sticking out and we'll look at it under a microscope and then that's the thing that we're mainly worried about So that's what we're going to cover in the slides that we look at today. So this first one we're looking at is an example of a normal margin And so it's from a little piece from the edge So they actually call the tissue margin? Yeah, tissue margin Normal tissue. So this is the edge of the specimen, and [the surgeons will] say, "Is the margin clear?" Dr: In this case this is an example where the margin IS clear. This is normal-looking colon. S: This is a cross-section, crossing the boundary of the colon, this area at the top right here, would be the inside of the colon, where the poop is... Dr: Doctors say stool. That's the stool in the middle, and the supportive tissue is underneath. S: Part of the structural tissue of the tube? Dr: Right. Now let's drive around the slide. This is a virtual slide where we took the typical glass microscope slide, and put it in a special machine which took lots and lots of photographs at high power, then stitched them all together as one massive image. So that allows you to zoom in and look around. S: To let me get my own bearings, this polyp... Dr: No, this is just regular tissue--a little bit of a fold, not a polyp. S: So how large is this, about a centimeter? Dr: About like that. If I had to guess, about 5-6mm. So, now to drive around, these are the controls for zooming in and out. So I can look at something more closely, and this is the mucosa. S: Mucosa. Sounds very similar to mucus. Dr: Right. The mucosa is the lining that makes the mucus, it's the slimy part. S: This white stuff up here? Dr: This suff is the slimy mucus. So, it keeps the insides from drying out-- because it's a very hydrated gel. It also means that things can glide along without abrading the surface. When you look at it, it has architecture in which these glands, they're like test-tubes sticking down, and the purpose is to increase the surface area. S: And the term gland, is any structure containing fluid and releases the fluid? Dr: A gland is an epithelial structure, so it's made of cells that are packed tightly, and the cells have a top and a bottom, and they're formed into some sort of enfolding or structure, so that there is a middle and an outside. S: When we say something is epithelial, it's the stuff facing the outside world? Dr: Yes. The epithelium is a special class of cells in which they are facing the outside world, again, tightly packed, and there's a top and a bottom. S: And even though to a layperson this area right here does not seem like the outside world, it seems like it's inside of you, we're kind of like big donuts. Dr: That's right. And the colonoscopist proves that it's connected to the outside world. S: MUAHAHA!! I guess they do prove that! XD Dr: So that's still the outside world. This is the architecture where you have enfoldings to increase the surface area. And it's creating this mucus. Let me look at the highest power. Look at these cells! When we look at these cells, there are two main types of cells. There's this one here, which is the goblet cell. S: Goblet cell. It's not just this white part, it goes all the way down there? Dr: Yeah...let me have that pen! It has a top like that, and you see this wine glass? S: It's literally shaped like a goblet! I was circling the wrong handle. Dr: That nucleus belonged to some other cell. What's next to it is these thin cells here, which do not have all the mucus inside of them. These guys are the tall ones. S: Where you see only the nucleus? The white part is just the mucus inside the cell. Dr: Yes. Mucus is the term for either the overall structure or the material that is elaborated up here, chemically it is called mucin, and mucin is almost like that goo runners eat, it is just a lot of sugar holding a lot of water. S: I see. I guess it would be bad branding to call it Mucus-In-A-Bag. MUAHAHA!! >:-} Dr: Exactly! So they stick with "goo". But this one has a lot of sugar, takes in lots of water, that is released and it forms this surface here. S: To let stuff flow by. Dr: What the other cell does is the other main thing in addition to letting things flow through, is to absorb water. So the idea is you do not want to release the 2L of fluid you have around every one of your meals. You want to get a lot of that back. S: That's one of the main functions of the large intestine? Dr: It is. It is a consolidation process to the stool. So you're going to absorb a lot of water and doing it through these cells. S: The mucin comes out here, and the water absorbed by parts without mucin, so right there. Dr: Yupperz. That's right. The two main functions of the colon are right there with those two cells. S: To get a perspective of where we are, the whole thing is about .5cm, what's our scale here? Dr: Our favorite scale-bar here is to look for blood vessels, for red blood cells, One right there, is 7micro- m in diameter. S: 7micro-m. A micrometer is a millionth of a meter, or 1/1000th of 1mm. Dr: That's right. Let's round off to 1/100th of 1mm. S: You put 100 of these next to each other you get 1mm. So 1mm would be bigger than our entire screen. Dr: Right. You see with these glands, 1mm would be this span, which we're saying is about like that, That's why from here to here it might be about 7mm. Dr: RBCs are found in just about every microscopic field, and they're always 7micro-m. When looking here, this is very well formed. You can see these tubular glands, just a hint over here, because they are like test-tubes, sometimes they're not going straight up and down, sometimes they look a little on an angle... S: They actually are reaching the surface, we just don't see it based on the way it's cut? So this one right here, it was cut at an angle, so it looks embedded there in 2D, but in 3D we would see a full tube. Dr: Just to go back to the microscopy, we're seeing this because it's only 4microns thick, and we're sending light through this tissue. So that's why you can get a cross-section that doesn't show you 3D. Very much 2D. S: Cool! So this is what a healthy margin tissue would look like? Dr: Yes, this is a healthy colon, so you would thankfully say on the proximal margin, which is up more towards the mouth, that's clear. You take another section like this from the distal margin, more towards the end, and you say that's clear, so that means they removed the cancer. S: When you say proximal margin is close to the mouth, you're saying the mouth of that cut of the tube, not mouth of the person. Dr: That's right. So the proximal and distal margins are clear, if they look like this.