Source: Video and Images Created by Amanda Soderlind
Welcome to this lesson today on the layers of the alimentary canal.
Today we'll be talking about the various layers of the alimentary canal. The alimentary canal is basically just a fancy name for your digestive tract, and it's actually composed of four layers. And those four layers are the mucosa, submucosa, smooth muscle, and serosa.
We're going to take a look at this diagram right here. Excuse my drawings skills, not super artistic, but you'll get the idea. So this drawing. We're going to use this to take a look at these four layers of the digestive tract.
The first thing I want to label here is the lumen. The lumen is that hollow part of the digestive tract that the food would actually move through. So food would actually be moving through the lumen here. the actual first a layer of our digestive tract, the innermost layer, is the mucosa. We're going to label this here the mucosa. As I mentioned, the mucosa is the innermost layer of the digestive tract. It lines the lumen. It has contact with the lumen, and it's made up of epithelial cells. That's the type of cell that the mucosa is composed of.
Our second layer of the digestive tract is the submucosa. The submucosa we will label right here. OK, so we have the lumen, the mucosa, and then the submucosa. The sub mucosa is composed of a type of connective tissue. So it's a connective tissue, and it contains blood vessels and nerve cells. Blood vessels are actually innervating through the submucosa, and it contains some nerve cells, as well. So this is the way in which nutrients from food can move into the bloodstream, is through these different blood vessels that have contact with the alimentary canal.
Our third label, our third layer, is our smooth muscle. We'll label this as our smooth muscle. The alimentary canal is actually composed of two sublayers of smooth muscle that run perpendicular to each other. One layer will run this way, and the other layer will run this way. Basically, the purpose of these smooth muscles in the digestive tract is that they aid in paracelsus. Paracelsus are those muscle contractions that help push food through the digestive tract. As those muscles contract, it'll push food onward. And again that's called paracelsus.
Our last layer is the serosa. The serosa. It actually doesn't look like this, on this drawing, but it's actually a very, very thin layer. So it's a thin outer covering of the digestive tract, and it's kind of moist and slippery. And basically, what it does is it reduces friction, so as this digestive tract is kind of bunched up inside your abdomen, it's coming in contact with some of your other organs. The serosa helps eliminate friction as it comes in contact with other organs.
We're going to take a moment here to talk about sphincters, as well. Sphincters are basically smooth muscles that are found between the various sections of the digestive tract. And basically, they help manage or control the movement of food through the digestive tract. An example is the sphincter between our esophagus and our stomach. So we have our esophagus, and then we have our stomach, and we have a sphincter located right here. This sphincter will allow food into the esophagus and into the stomach, but it doesn't allow food to move from the stomach to the esophagus. So it's controlling the way in which food moves through. We also have another one that connects the stomach to the small intestine. So again, these sphincters are helping to control movement of food through the digestive tract.
This lesson has been an overview on the layers of alimentary canal.