10.03 Esophagus

In this lesson, we are going to take a look at the esophagus.

To get started the first thing you need to know is that the esophagus is a tube that connects via laryngopharynx to the stomach. It's the main tube that food travels from after you eat it and it goes into your stomach. The way it works is that it's it's back behind the trachea so posterior to it, and food is moved down through the GI tract by the process of peristalsis.

When we talk about the structure of the esophagus, what we're talking about is all of the layers of the esophagus itself. The esophagus is broken up into basically two divisions. So you have an area above the diaphragm, and you have an area below the diaphragm. The outermost layer is called the Tunica adventitia or the Tunica serosa. The Tunica adventitia is a white fibrous connective tissue and that's the area above the diaphragm. So this is from the back of the mouth all the way to the diaphragm. Below the diaphragm, the outermost membrane is the Tunica serosa, and it's a serous membrane. Just inside of that you have the muscle layer which is called the Tunica muscularis. We're going to talk about the Tunica muscularis in just a minute because it's really important in peristalsis.. Then you have the layer of submucosa which basically is areolar connective tissue and it connects the Tunica muscularis to the Tunica mucosa. The Tunica mucosa is the innermost layer and it's made of a stratified squamous epithelium.

So now we have peristalsis. Peristalsis is that movement of food along the GI tract. It's initiated by the Tunica muscularis, and there are two layers to this area of tissue. There is an outer longitudinal layer which runs the length of the esophagus, and then you have the inner circular muscle layer. Now an important thing you need to recognize is that the Tunica muscularis contains different types of muscle fibers. The upper one third, so the area closest to the head is going to be comprised of skeletal muscle. The middle one third as mixed skeletal and smooth muscle, and the lower 1/3 is smooth muscle. So that's going to be the third near the stomach. These muscles work together to move food down the GI tract.


Okay so let's recap.

Of the pathway that starts in the mouth and ends at the stomach.

It's made up of four layers, the Tunica adventitia or serosa, the Tunica muscularis, the submucosa and in the mucosa.

The Tunica muscularis is made up of a circular and longitudinal muscle layers, and it also is comprised of skeletal and smooth muscle depending on the location along the esophagus you're looking at.

And finally the Tunica muscularis, or that muscle layer is going to be the main driver of moving food down the GI tract by the process of peristalsis.
And that's it for our lesson on it the esophagus. Make sure you check out all the resources attached to this lesson. Now, go out and be your best self today, and as always, happy nursing!