Normal colon tissue Dr. Andy Connolly from Stanford Medical School introduces Sal to what normal colon tissue looks like
Normal colon tissue
- 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.
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