Upper Gastrointestinal Tract (Nursing)

00:02 Now let's talk about the gastrointestinal system, which is very complex and very far ranging.

00:09 And it consists of both the tract, which is the long tubular structure that's running proximately, from the mouth distally to the anus, as well as many GI associated organs that help aid in digestion.

00:25 When we start proximately, we're going to start with the mouth, and then a space that's actually somewhat of a shared air and food spot called the pharynx. It's an unusual area.

00:38 But then after the pharynx, it becomes again a dedicated Food Tube called the esophagus.

00:45 And then it's going to reach the stomach, below the diaphragm when we're finally into the abdomen.

00:52 Then it's going to form the first part of the small intestine, which is short called the duodenum.

00:58 And that's going to be the end of what we will call the upper GI tract before going on to the rest of the small intestine, and then the large intestine, which is going to be in the lower GI tract.

01:12 Again, there's also a lot of accessory organs of digestion, starting right away in the mouth with things like the salivary glands and the tongue.

01:21 And then down in the abdomen, we have larger structures such as the liver, and the associated gallbladder and biliary system.

01:31 As well as the pancreas, which does digestion as well as endocrine functions.

01:37 That's a really long way to move food all the way from the mouth to the anus.

01:42 And generally what's happening is the contraction of smooth muscle in a very coordinated fashion called peristalsis.

01:52 And in a nutshell, what's happening is there are two layers of muscle throughout most of the GI tract.

01:59 And there's an inner circular portion and an outer longitudinal portion.

02:05 And it's the inner circular portion that's going to contract just behind that food mass to make sure it only moves in one direction.

02:14 And that outer longitudinal layer is going to contract ahead of the food mass to help direct it further and further distally through the GI tract, until essentially it's expelled out through the anus.

02:28 So let's start by the act of swallowing.

02:31 Swallowing is a very complicated function, because this space is actually a shared breathing and digestive space.

02:41 Here we have a bolus of food sitting on top of the tongue.

02:46 posterior to the tongue, we have two important flaps of tissue, or superiorly, we have the soft palate, and inferiorly we have this flap called the epiglottis.

02:58 And as food is swallowed, the soft palate is going to prevent any sort of passage of that bolus up into the nasal cavity.

03:08 Whereas, the epiglottis is going to flap down over the entrance to the airways and therefore protect it, forcing the food bolus posteriorly and into the esophagus.

03:22 So let's look at the esophagus.

03:24 The esophagus is a very long muscular tube that's going to connect that initial act of swallowing all the way down to the stomach in the abdomen.

03:35 So if we were to zoom in to that proximal area, we see there's a lot going on.

03:40 In the respiratory system we covered the larynx which leads into the trachea.

03:45 And sitting posterior to the larynx is the pharynx.

03:50 And right where the larynx transitions into the trachea is where we're going to find the pharynx transitions into the esophagus.

03:58 And it's going to run posterior to the trachea throughout the length of the trachea and then eventually down into the abdomen.

04:08 And this is where we're going to find the first of two sphincters of the esophagus.

04:13 This one between the pharynx and esophagus is going to be the upper esophageal sphincter.

04:21 After the esophagus has passed through the diaphragm to reach the abdominal cavity, we're finally going to see the stomach which is where the esophagus is heading.

04:33 And between the esophagus and stomach is where we're going to find the lower esophageal sphincter and this is a very important sphincter because the stomach is going to be full of acid.

04:45 And that's really what the upper GI portion is doing is really breaking down food either mechanically with teeth or via acids in the stomach.

04:55 But the esophagus isn't equipped to handle acids.

04:58 It's really for transporting a food bolus down to the stomach.

05:01 So this lower esophageal sphincter is very important in stayin closed when it's supposed to so that way stomach acid doesn't get up into the esophagus and cause something called reflux or GERD, Gastroesophageal reflux disease.

05:21 Here we see the stomach itself, after it's received its contents from the esophagus.

05:28 Now, externally with the naked eye, it's hard to tell some of these locations.

05:34 But these different regions of the stomach we're gonna talk about have different microanatomies and different functions that are important to know.

05:43 So generally speaking, the initial portion of the stomach, even though it's very tiny, and there's not a lot of well defined borders for it is the cardia.

05:53 And this small area, microscopically, is going to have a lot of neutralizing glands to help prevent any acid from seeping up into the esophagus.

06:05 Then the majority of the stomach is going to be composed of the body.

06:10 And then as you can see, superiorly, there's this little bump called the fundus.

06:16 And this little bump is usually something you can see at the very bottom part of a chest X-ray, for example.

06:23 It's usually where any gas in the stomach is going to accumulate.

06:28 So it looks like what's called a little gastric bubble up in the fundus.

06:31 But even though we call this little portion that sort of rises up above the rest of the fundus, it's important to know that microscopically, and functionally, there really is no difference between the body and fundus.

06:44 They're really the ones doing the majority of the acid and digestion breakdown in the stomach.

06:51 But once you get to this angle a little bit distally called the angular incisure, things start to change.

06:58 Again, you can't see this with the naked eye.

07:00 But this is about where you're going to see the pylorus and pylorus means gatekeeper.

07:07 And it's going to be broken up into two portions, a wide antrum and a narrow canal.

07:15 And the pylorus is going to have different types of glands than the body and fundus.

07:20 In fact, is going to be very similar in a lot of ways to the cardia.

07:23 And that it's going to produce a lot of neutralizing substances to help neutralize the acids of the stomach before going into the duodenum, which is the first part of the small intestine.

07:35 And again, not something that's really meant to handle the very strong acids that the body and fundus of the stomach have.

07:42 If we were to look inside the stomach, we again see the esophagus, which is fairly smooth walled compared to the rest of the stomach.

07:53 It has a very brief portion called the cardia.

07:56 And then most of the body and fundus, for example, is going to be thrown into these folds called rugae.

08:05 Except around this very short area, to the midline of the stomach, that's something called the lesser curvature, as opposed to the outer curvature, which is much longer that's called the greater curvature.

08:21 And this lesser curvature has more longitudinally oriented folds.

08:25 And as you can see, it's actually the shortest route between the esophagus and the small intestine to go along this area.

08:33 And sometimes it's called Magenstrasse or stomach street, because it's actually the fastest route for food and fluids to pass from a esophagus to the small intestines.

08:46 And down in the pyloric area, again, pylorus means gatekeeper.

08:50 And not only does it have these neutralizing substances that it's secreting into the lumen, but it also has a very thick prominent sphincter called the pyloric sphincter.

09:02 And that's what's going to protect the duodenum from the acids coming from the stomach.

09:10 And again, the duodenum is going to be a very short portion of the small intestine.

09:15 And then right after the duodenum, we're actually going to have the junction between our upper and our lower GI tracts.