B Fruitfull

Acid Reflux causes and Treatment



– [Voiceover] This slide
is from the esophagus. The current magnification is 40X total magnification. Now what we’re looking for are the four different layers or four tunics that are found in the esophagus. So before we zoom in, you can actually see the four different layers from this view. This very, very thin line right out here, that would be the adventitia. It’s the most external of the layers. Moving inside, from about here to here, you notice it looks like
it’s two different tissues. Well, it’s the same tissue, smooth muscle, but these two layers together make up your muscularis externa. Now the muscularis externa
has this portion of it, which is going to be
the longitudinal layer, and this portion over
here, this is going to be your circular layer. Now you’re saying well,
how do you know that? We’re in a cross section right now. If you look at these fibers right here, so if we zoom in a little bit, you can see how it looks like they’re poking out of the screen at you, they’re going into and out of the screen. That means they’re running down the length of the esophagus, hence longitudinal. But these over here, you can notice they’re going in bands going around the esophagus. That’s why those are the circular layers. Now moving inwards from the adventitia to the muscularis externa
to this area right here. This area is known as your submucosa. And then the most internal
layer is comprised of actually three different regions here. You can see this portion of muscle, this portion of connective tissue, and this portion of epithelium. Together, all three of these are gonna make up the mucosa. Now this layering right here, this portion of mucosa, is going to be the muscularis mucosae. This is your smooth muscle. This area right here, this is going to be the lamina propria. The lamina propria is mostly made of connective tissue. Well, this area right here that you can see tracing around, this is going to be epithelium. Now in this case, in the esophagus, it’s gonna be stratified squamous. In the very center here, this is where the chewed up food or the
bolus will be moving through. This is the lumen. You can see how it looks
like it’s very thin. That’s because the esophagus
is usually collapsed unless something is being pushed through. So our layers or tunics go from the outside, the adventitia, to this layer, which is gonna be your muscularis externa, to this layer which is the submucosa, to this layer which is the mucosa. So this is going to be your esophagus with the four tunics of the GI tract.

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