This lecture we'll be going over the anatomy of the digestive system. So in the organs of the digestive system, uh they consist of a group of organs that work together to break down the food you eat into lots of smaller molecules because your body can't handle like a big hamburger. It has to break it down into its individual components in order to then absorb it into the bloodstream for your body to use it. Um the whole of the organs of the digestive tract um consist of a tube that runs from the mouth to the anus. This is commonly called the gastrointestinal tract or sometimes it's called the elementary canal. And all along that way from the mouth to the anus, there is various um constrictions. There's various dilations. Um it's going to be just a continuous tube that's going to allow your body to process whatever it is you bring in for nutrition in order to extract the nutrients that it needs from it. Additionally, there are going to be some organs that are considered to be um accessory. And the accessory ones, you can see are labeled here in this image in red. The accessory ones essentially are places that there is going to be no food passing through them, but they contribute to the process of breaking down by either producing or storing secretions that get into the GI tract. And then that's going to help further with the breakdown of food. So the GI tract or the gastrointestinal tract consists of these particular organs that goes from the mouth to the anus. So it goes from the esophagus, the stomach, um the small intestine parts, large intestine parts and then through the rectum. The accessory organs that are considered to be a part of the digestive tract but again no food passes through them. So they don't come in contact direct contact with the food but they contribute to the processing are going to be your teeth, your tongue, salivary glands, liver, gallbladder and pancreas. Overall there are six basic processes that are involved in the act of digestion. And you can see the picture down here is just showing you a tube to go from the mouth basically to the anus and a flattened out um tube to show you those six processes. So they include ingestion, secretion, motility, digestion, absorption, and defecation. Let's talk more about that on the next slide. So the six main functions again of your digestive system involve these six items. So ingestion, that's a process by taking food into the mouth. And by the way, food also encompasses liquid in this case. So anything that you bring into your mouth, ingestion. Motility is the act of moving and mixing um materials through the GI tract through alternating contractions and relaxations of the smooth muscle in the walls of the GI tract. And so it's moving it from your mouth to your anus. The third activity then is going to be secretion. Secretion is going to um come from the cells within the walls of the GI tract and the accessory organs. In total, in a day, they secrete about seven liters total of water, acid buffers, and enzymes into that tract. And then that's going to help with the chemical breakdown of the food. The fourth is the actual act of digestion. And digestion is the process of breaking down food into smaller components. And those smaller components then is how your body can absorb them. There are two divisions of digestion. There is mechanical digestion and chemical digestion. Mechanical digestion means that you are physically grinding the food. So like your teeth are grinding it, the smooth muscles are going to be churning it. You are physically making a broken down component of a food. The chemical digestion means that you are splitting all of your foods into the four categories of carbohydrates, lipids, proteins, and nucleic acids. So what's helping with the chemical digestion are enzymes and um chemicals to further break it down at a microscopic level that you cannot see. And then the fifth function is absorption. Absorption is when you are moving whatever it is that you've brought into the GI tract into your blood or your lymphatic system. And after it gets into your blood or lymphatic system, this means that the body is going to process those items and move them into the body if it needs to store them or utilize them. And then the final act is defecation. Defcation is going to be basically undigested materials that your body doesn't need or were not absorbed during the journey. And so it's going to leave the body via feces or stool getting rid of things that your body can't use or um was not able to break down. When it comes to the digestive system, there are four layers that make up the GI tract. And again the GI tract goes from the mouth to the anus. So the four layers from deep to superficial or innermost to outermost begin with the mucosa followed by the sub mucosa followed by the muscularis layer and then followed by the adventicial layer which is commonly called the sarosa. Sometimes a way that students can remember this is just ms. And so deepest is mucosa followed by sub mucosa followed by your muscularis layer followed by the sorosa layer. The mucosa is the innermost and mucosa we also call the epithelium. This layer is in direct contact with the GI tract food. And so the space that the food is passing through is called the lumen. And that's what the mucosa is going to be in contact with. This tissue then has to uh withstand abrasions of the food basically scraping along the walls as it passes through the GI tract. So it's known to having a very he uh very fast cell turnover in the fact that roughly every 5 to seven days the cells sllo off. And so some of those cells become part of your feces when you defecate because you need to get rid of anything that has been used outside of the mucosa layer. then is going to be the sub mucosal layer. And the sub mucosal layer is where you find some blood vessels, lymphatic vessels. Those are what's going to be used to absorb the nutrients that come in from your food and the food molecules. Also, there's going to be a very expansive um network of neurons known as the sub mucosal plexus. That's going to help with intervating the smooth muscle in the glands that are found in the sub mucosa as well as the mucosal layer. Then there is the muscularis layer. And the muscularis layer is going to be a third layer that consists of basically two layers of muscle, an inner circular and an outer longitudinal layer. And so those run the entire length of the GI tract. It begins as being skeletal muscle when you go to swallow. So that means that that is muscle that you control. But after that the muscle that's in the GI tract is involuntary, meaning you do not think of it. So it's smooth muscle. Inner circular means it's wrapped circumferently around the GI tract and it will contract the lumen. And then the outer longitudinal means that it's going to be more of like an accordion type contraction that's going to be able to shorten the tube as it's going to push food along. So both of those work together to move the food the motility part from the mouth to the anus. Additionally this is also going to have its own nerve plexusy called the mayanteric nerve plexi and the meantic nerve plexi is going to help with that um the motor neurons or the movement neurons for these particular uh for this layer of muscle. Additionally, with the muscularis layer, there's going to be several points throughout the GI tract that it thickens and forms what is called a sphincter. A sphincter, if you think of a hollow tube and you tie a rubber band around it to narrow that tube, that's exactly what this is going to be like. A sphincter commonly is between organs or divisions of the GI tract. So, there'll be a sphincter from your esophagus to your stomach. There'll be a sphincter from your stomach to your small intestine. And then there's a sphincter from your small intestine to your large intestine. And then you have a sphincter that you open when you go to defecate. So sphincter help to kind of control the movements of the GI tract throughout um the various organs that are utilized. Additionally, the processing of the muscularis layers, the inner circular and the outer longitudinal contracting together. We call this the fancy name of paristalsis. Paristalsis means that you were pushing the food kind of like you squeeze a toothpaste tube to um get the toothpaste out forward. And then there's also going to be some mixing that takes place as well with that paristalsis to help with a back and forth movement while paristalsis is pushing it forward. The final layer is known as the adventicia or the sorosa. So either name is commonly used for it. It just means that it's a superficial um piece of tissue that's along the outside and it's going to also then outside of this be covered by the layer of tissue called the visceral paritonyium. So adventure sorosa work to be able to name it as this layer. So again those four layers we have the mucosa layer that's what's in direct contact. So here is the lumen where the food is going to be found. Then we have the sub mucosa layer. And the sub mucosa is where you're going to find here's your blood vessels and veins. You're also going to find your nerve plexi that's found here. Outside of this we have the two layers of the muscularis. So the inner circular which wraps circumferently around outer longitudinal which goes long ways and then the fourth layer is going to be the sarosa also known as the adventicia. Um and so those four layers are found throughout the GI tract in various um thicknesses, components, divisions, things like that. So in the abdomen there is going to be a piece of tissue known as the paritonyium. Perry means around andium basically means to stretch. This is the largest um cirrus membrane layer which basically means it's like saran wrap and it's going to help to compartmentalize the walls of the abdominal cavity. and then the organs itself. So there's a small piece of fluid that's in between these layers that allows for a little bit of movement of them. Um but but this tissue was talked about in P1 for you again to uh hopefully remember that. But the series of cirrus membranes that are found in your body. So we have the parietal paritinium. Again the word parietal means it's along the outside. If you removed all of the organs from the abdominal cavity, you would see this thin layer of saran wrap tissue that we call the parietal paritinium. Then on the organs directly itself, we have the visceral paritinium. So every organ in the abdominal cavity has a piece of saran wrap surrounding it called the visceral paritinium. So these three again parietal paritinium lining the inside surface of the body wall visceral paritinium directly on the organs itself and then the space in between them is called the paritinal cavity and that's where you find a small amount of fluid that allows those two tissues to slide over each other. Inside the abdominal cavity, there's also going to be five important large folds that are going to weave their way between the visca or the organs of the abdominal cavity. These folds are important to help bind the organs to one another as well as to the walls of the abdominal cavity. They also contain blood vessels, lymphatics, and nerves that are going to be supplying those abdominal organs. So the five folds begin with what's a piece of tissue called the greater momentum. The greater um means fatty apron. It's called that because that's what it looks like when you open up the abdomen. It's going to extend off of the greater curvature of the stomach, which is why it's called greater curvature with a greater momentum. And it's also going to cover superficially your abdominal organs. So the greater um is going to basically be a piece of fat tissue. It's usually yellow in its contents. When people have a beer belly, it's this tissue is going to greatly expand with the weight gain and that's the tissue that's going to contribute to that beer belly. It also has the capacity to have lymphatic parts to it, meaning it can move around your abdominal space to provide extra lymph to your organs. Second fold is called the lesser momentum and this is a piece of tissue that's going to connect the stomach to the liver. So it's a very thin piece of tissue that connects it but it acts as protection as a pathway for any blood vessels entering the liver um and any lymphatic vessels as well. Third fold is called the falsoform ligament. Falsoform means or this ligament I should say is going to attach the liver to the anterior abdominal wall and the liver is the only organ that attaches to the anterior abdominal wall. So the three again. So here we have the greater um you can see why it looks like an apron. It's going to extend off your greater curvature of your stomach and that's where then you're going to find it. Then here's the falsoform ligament. Falsifform ligament again is going to attach your liver to your anterior abdominal wall. To find your lesser um you have to kind of flip up the greater or the liver and then you see this piece of saran wrap- like tissue connecting the stomach to the liver. So here's what it would look like in real life in the picture on the far right. You can see the greater um hanging off right here. Again, this yellow fatty substance on superficially on top of the organs. And then there's the falsoform ligament right here connecting the liver to the anterior abdominal wall. And there you can see the greater momentum on the left side has been flipped up to show you tissues underneath. The fourth fold of the paritinium is called the mezzent. The mezzent is kind of this fanshaped piece of paritonyium and it's going to attach to the small intestines. So mezzent oftentimes refers to like middle or intestines in this case. This piece of tissue helps fold all of those small intestines into the abdominal space and not allow them basically to fall out. So on the right side you can see that the intestines have been kind of pulled out to show you this tissue which is the saran wrap- like tissue here of the mezzent and then it contains neurovvascular bundles which are the vein looking like structures that you see traversing through that. That's what the mezzent does for the small intestine. Then for the large intestine it is called the messylon. So meo again meaning middle colon referring to your large intestine. It specifically is going to attach to your sigmoid colon and your transverse colon in humans, but we can just say that it's going to attach to the large intestine. It does the same thing with the mezzent in the fact that it's going to help hold your large intestine in its spot as well as deliver the nerve, artery, and vein to those places. So again the five folds of paritinium greater momentum lesser momentum balsform ligament mezentary messylon. So now we're going to work our way through um each of the digestive organs. Um so beginning with the oral cavity. So the oral cavity also known as the mouth. Sometimes this is called the buckle cavity as well. This is going to be the opening of the GI tract. And so whenever you're ingesting food, this is where you um bring it in. Inside the mouth of the oral cavity, there is a space called the vestibule. The vestibule is the space between your gums and your lips and your cheeks. So when your teeth are clenched and you can puff open your cheeks, that is the vestibule. What's known as the oral cavity proper then is where your tongue is essentially going to be. So the central um space inside your teeth and that's what's going to be where your food is going to be chewed at and then eventually swallowed into the oral fairings. On either side of your mouth or your oral cavity, you are going to have the um cheeks. Cheeks are actually going to be a skin that is going to consist of stratified squamus. So tissue that's allowed to be able to be constantly turned over. But they are going to be made up of a muscle called the bucinator muscle. And the bucinator muscle is utilized to hold your food inside your mouth as you chew it. Uh imagine a world in which you didn't have those muscles. What would we all look like when we are chewing our food? Kind of bizarre, right? And then we have the lips or the labia. Um, those are going to be the openings surrounding of the mouth and they are going to be this external piece of tissue that contains just a little bit of um keratinized uh skin uh to make it clear. So that's why the lips have color to them. In light of listing the organs that you need to know or the structures, I have in this image a picture from your textbook and the top left to know all of the parts that are found here. So, let's kind of walk through them that are mentioned. The hard pallet, of course, is going to be the hard or the bony part that separates your mouth from your nose. Soft pallet is more posterior and it's going to be the muscular portion that is still separating your mouth from your nose. Posterior, then there's going to be the structure called the uvula. Uvula's role is that when you swallow, it's going to swing superiorly, closing off the passageway to your nose, helping to prevent swallowed foods and liquids from getting to your nasal passageway. Um, and so it does serve a purpose even though it just kind of dangles there in the back of the throat. Cheeks of course form the lateral walls with muscles. And then you have your four different divisions of the teeth, mers, preolars, canines, and insizers that are talked about coming up. the oral vestibule which is the space between your teeth and um gums and your lips. Then we're going to have the superior label fernulum. So frenulum is a piece of tissue that's going to attach your um lips. So you have a top one to attach your top lip right there and the bottom one to attach your bottom lip. You also have one underneath your tongue called the lingual frenulum and that's going to attach your tongue to the floor of your mouth. The tongue then is found central to your teeth. The tongue is used not only for talking but also for manipulating your food when you are chewing it. And then in the back of the mouth, the opening for you to swallow is called the faucets. And that's going to be the opening to allow food to pass from the mouth to the oral fairings. There are two folds of the tissue back here that we call the arches. The platog glossal arch and the plataringial arch. And those two arches are going to be protecting one of your tonsils called the palentine tonsils that are between that. The tonsils were talked about lymphatic system because they contain lymphatic tissue to help fight off anything that doesn't belong. And then the last bold one is the gingiva which is a fancy name for your gums. Contributing to your oral cavity are going to be the salivary glands. Um the salivary glands lie outside the mouth but they empty their contents into the mouth. There's a total of six of them. There are three individual ones but then they paired together. Um when they when food enters the mouth the secretion of saliva increases which is going to help to lubricate, dissolve and begin the chemical process of the breakdown of the food. So the three major pairs of salivary glands include the parotta glands, submandibular glands, and sublingual. Parata then is going to be the largest. This is situated right in front of the ear. Um and it's going to secrete its substance into roughly where your second molar is going to be found at. So there's a tiny little hole there. Um the parotted gland then secretes a lot of the saliva. Underneath the mandible is the submandibular gland. This is found in the floor of the mouth. And the submandibular gland is going to be secretreting their um product underneath the tongue. In addition, there's going to be the sublingual, which is a gland that's found underneath the tongue as well. And they're going to be secretreting their product with the submandibular underneath the tongue. So here in this image, you can see the location of the glands. Parotate gland found right in front of the ear secretreting this product to about the second mer. Submandibular below the mandible or your jaw. Sublingual below the tongue. Both of them secretreting their product into the floor of the mouth. What exactly is saliva? So chemically saliva is mainly water about 99.5% water. The remaining.5% are solutes which include things like sodium, potassium, chloride, bicarbonate, phosphus. basically things that are going to help to break down anything that comes inside your mouth. There's also going to be bacteria that's normal there. Um, not necessarily coming from the saliva, but mixing with the saliva inside your mouth in order to help further break down the food. You produce roughly about a liter to a liter and a half daily. Most of it increases when you are eating to help um moisten the food. And as you chew the food, it becomes a structure that we call the bolus. And the bolus is actually what you swallow when saliva has wrapped around it. Additionally, saliva contains a enzyme called a salivary amaase. And the salivary amaase is what's going to be begin the breakdown of starch. And starch is a carbohydrate. So that's where starch or the beginning of carbohydrates can be broken down into. As the food is churned throughout the the mouth, what's also happening is that your um taste receptors are going to be stimulated here. The chemicals in the food stimulate the receptors in your taste buds on your tongue and then those impulses are going to be conveyed from the taste buds to your two salivary nuclei in the brain stem. Additionally, before we brushed our teeth, we had to have a way to kind of clean off the teeth. And saliva, believe it or not, does contain enzymes and bacteria to help clean off your teeth. Not as effective, of course, um, as brushing your teeth, but they are present in large amounts in order to help um, fight off microbes inside your teeth to help clean it. So, a clinical view is mumps. Mumps happens when the mumps virus attacks your parotted gland, which is the gland again in front of your ear. Mumps causes an inflammation or enlargement of those parotted glands and commonly it's accompanied by fever, general discomfort, pain in the throat. Swelling can occur on one or both sides of the face. You can see in this picture there that it's on just one side. Fortunately, because there's a vaccination, this presence of this disease has dramatically um declined. Therefore, we don't see it as often. But that swollen parotic gland would be indicative of mumps. Next organ is the tongue and the tongue is going to be in that oral cavity proper. It is going to be attached to the base of the oral cavity by that piece of tissue known as the lingual frenulum. The tongue is composed of skeletal muscle which means this is muscle that you control because you need your tongue to be able to do chewing, swallowing, talking. You manipulate your tongue for that purpose. The top of your tongue is covered in what's called pilla. Pella are projections um that contain taste buds. And there's various types of taste buds that are important for various aspects in the surface of the tongue. Not all of the pella contain taste buds. A lot of them do. Um but they're the taste buds are going to help with your tasting sensation and texture. Next organ is going to be the teeth. And teeth collectively um we known we call them the dentistician which is where the word dentist comes from. Your teeth overall are responsible for mastication which mastication is the fancy name for breaking down the food. What you see of your teeth is the visible portion called the crown. Embedded within the socket is the roots and that's what's going to help anchor your tooth to your jaw. Within the root you have the very tightly fitted dental avioli and the dental avioli are going to be um where the the basically the root is taken up inside of the jawbones. So either your maxul or your mandible. Then your teeth are also anchored in that place by what's known as the perodontal ligament. So perry means around dant referring teeth. The whole structure together is known as the gyosis, which is that tooth joint. And your tooth joint is not all that movable. You can do that by um using braces, which acts on your cells of your bones, but for the most part, it's not a very movable joint. What you use your teeth for is to do mechanical digestion. So the breakdown, the churning of the food, that's what you're using it for. So in the picture on the right here, you need to know these structures. So you have the enamel which is going to be the outer white tissue that you see there. Underneath the enamel is going to be um the dentin and the dentin is harder than bone tissue and this is going to make up the majority of the weight of your um tooth and provide the hardness of it. Enamel is also hard. It is considered to be the hardest substance in the body because it will help protect your teeth from wear and tear from the chewing. Then there's also going to be the cementum which is going to help attach your um root to the periodontal ligament. Here is your periodontal ligament, the ligament that's going to be wrapping around your root. Inside the dentin, we have the pulp cavity. And the pulp cavity is where each of the tooth gets supplied a bundle of blood vessels, nerves, and lymphatics. It enters into this space through what's known as the root canal. And that's the extension of that through the bottom of the tooth then into the jaw. So when people have a root canal, that's what's happening is that that's getting cleaned out or repaired. The opening then into the root canal is called the apical fammen. You can see that's allowing your nerve, artery, and vein to pass through there. Teeth again. So enamel are going to be the is the hardest surface on the outside of the dentin. The pulp cavity is going to be the center of the tooth and that contains what we call the pulp which is your blood vessels, nerves and lymphatics. The root canal is going to be the continuous part of the pulp cavity that contains the entrance for blood vessels, nerves as they pass through there. We have humans are considered to be um we have two dentitions because we have two sets of teeth. We have deciduous teeth and then permanent teeth. Deciduous teeth are known as your primary teeth, milk teeth, baby teeth. They begin commonly to get inside the mouth roughly around 6 months of age and then a baby will continue to expose them until they're about 30 months or more. It kind of varies from person to person. Once those are lost, then what happens is that they are replaced by the permanent teeth. Permanent teeth set in usually around age six and can take up to age 12 for them to kind of finish coming in. Sometimes beyond that if you get your wisdom teeth which comes usually in your mid to late teens or sometimes early 20s. So if you happen to have all of your teeth including your third mers known as your wisdom teeth then you have a total of 32 permanent teeth. If you don't have your wisdom teeth, then most likely you're going to have 28 because all four of those commonly have been taken out. So, the four divisions or the four types of teeth present are going to be the insizers, which are going to be closest to the midline. These are chisel shaped for the slicing of the food. Canines, which have that pointed surface. They're used to tear and shred food. Then you have the preolars which are going to be for grinding and then you have the molers which are fully used for grinding. Your mouth is divided into quadrants. So that means four divisions and within each quadrant you should have an insizer, a canine, a preolar and one to two mers depending upon the presence of them sometimes up to three. So the process down here is a 2123. two incizers, one canine, two preolars up to three mers in each of your um quadrants of your mouth. This image from your textbook shows you roughly when these teeth will appear. Everybody is slightly different when it comes to this. So, it's not necessarily how everyone will develop these teeth, but you can see that they are numbered and you can see when they're supposed to come in deciduous first, followed then by your permanent. After the mouth, the food is going to pass into the ferinx. And the fairings is a structure that was talked about in the respiratory system as well because this is known as the throat. The fairings is going to pass um air into your trachea or the food into the esophagus. The esophagus is posterior to the trachea. So the bolus of food that you swallow will move posteriorly posteriorly into the esophagus because that um epiglatus covers the trachea. Connected to the fairings is the muscular tube known as the esophagus. The esophagus is a whole bunch of muscles um that are banded together and it will connect from basically right behind the trachea where the fairings ends to the stomach. It will pass through the entire thoracic cavity and then it's going to pierce through the diaphragm into the abdominal space. The you purpose of the esophagus is to basically just push the food from your mouth to your stomach. So no absorption happens here. no um further breaking down of digestive enzymes. It's simply for transporting the food from your mouth to your uh stomach. So you can see it has those four layers that we've talked about muscularis, mucosa, sub mucosa, adventicia, and it is relatively collapsed. And then here you can see lots of muscle along the outside there. And that's going to help to squeeze the food as it passes through there. Your esophagus is normally collapsed unless you are actively eating. And so therefore, it stays relatively flat. Um, as it pierces through the diaphragm, it goes through the diaphragm through an opening called the esophageal hiatus. And that's where it's going to connect to the superior portion of the stomach. When someone has a, for example, hiatal hernia, it means that like the stomach has protruded up with the esophagus into thoracic cavity. There are two sphincters on each end of the esophagus. Uh you have the upper esophageal sphincter which is skeletal muscle. That's one that you control when you go to swallow. You open it. And you have the lower esophageal sphincter which is the one that you don't control because that's going to move from the esophagus into the stomach. This is a fairly infamous sphincter because this is one that if it's not closing properly can cause heartburn. And heartburn is when the contents of your stomach are regurgitating back up in the esophagus, which makes it feel like you have a burning sensation every time you swallow. And so that is what's happening here. The next organ in the digestive system is the stomach. Uh the stomach is considered to be a J-shaped kind of sack that's found in the upper left um abdominal quadrant. Sometimes it can be towards the middle, but most commonly it's in the upper left. It is found right below the diaphragm. And so that connection of the esophagus as it pierces through the diaphragm is why we have the esophageal hiatus um in the diaphragm to ensure it can connect to the stomach. Once the food in your mouth forms a bolus, it is then going to be swallowed through the esophagus and it enters the stomach. In the stomach, what happens is that food is going to have or the bolus portion is going to have a lot of of fluid added to it which eventually will turn into a liquid substance that we call kim. Kime you are familiar with because you have all vomited it up before. It is the soupy liquid that comes out when your stomach is upset. Food can spend anywhere from 2 to six hours inside your stomach. A lot of it depends upon what you have eaten as to why it will stay in your stomach, but also what's ahead of it. Your digestive system works in the fact that when food, for example, is in your large intestine, it's going to back up the food that's in your small intestine, backing up the food that's in your stomach. So, they they don't move forward until things have continued to pass through. So, that's why it can spend a little bit of time there. What's significant about the stomach? um in addition to the fact that a lot of fluid and um enzymes are added to the stomach is that it's going to also begin the process of breaking down protein and fat. Um remember from the mouth there is the salivary amalayise that's going to be breaking down the initial carbohydrates and then the mouth is also going to add the lingual lipase which is a fat enzyme but it's not activated until it gets to the stomach and then protein digestion also is going to begin in the stomach because of the enzymes that are added in. One key misconception about the stomach is that the stomach actually does very little absorption. The only really absorption that it does is if the stomach is relatively empty, you can absorb a small amount of aspirin as well as alcohol. Um, outside of that, the stomach does no absorption. Remember, absorption means it goes from the lumen into the bloodstream. So parts of the stomach that are important for you to know again on the upper left I have written know parts of the stomach. So these are parts that we will also be covering in lab. Um in the bold are the important structures that you need to know. So we have the initial part and when food enters the stomach known as the cardia. It's called cardia because it's positioned right behind the heart and this is right after the lower esophageal sphincter. So this is why commonly when people have heartburn, it feels like it's the heart and not the stomach because of the position of a stomach right behind the heart. Then the dome-shaped portion at the top called the fundus. Then there's going to be the main part called the body. And then the end of the stomach is the area that we call the pyloric antrum which will then transition to the pyloric canal. And then it's going to terminate at the end of the stomach with another sphincter that we call the pyloric sphincter. The stomach then has a sphincter at the proximal end and the distal end and that helps to churn all of the substances inside the stomach before it then moves to the small intestine. Additionally, the boundaries of the stomach are the fact that you're going to have a curve called the lesser curvature. I talked about this with the lesser momentum. That's why it's called the lesser curvature because a lesser momentum is attached here. And then there's the greater curvature. That's the bigger curve. And this is going to be where your greater momentum is going to attach. The inside of the stomach then looks really rippled and we call it the rug. The rug provide more of a surface area for the surface of the stomach which provides the ability to include more fluid into the stomach because it's more than one um flat layer. It's just a whole bunch. And then additionally, the stomach is mainly going to be muscle that's contracting together still identifying those four layers of the GI tract. Mucosa, sub mucosa, muscularis, sarosa. And so that's what's also going to be found in the stomach. Here's what a real stomach looks like in real life. So you again can identify those parts of the stomach. Uh this picture shows a really good uh image of the rug. Um and the rug, this is spelled wrong over there. The rug is that rippled um again additional kind of look of the stomach but that provides more surface area for the stomach as a whole. The main functions of the stomach is that the stomach is going to be used to mix the saliva that came from your mouth, mix the food that we call the bolus as it enters your stomach and add gastric juices to form what is called kime. Um the gastric juices, gastric means stomach, are going to help to liquefy the bolus of the food that you eat. It's also going to serve as a food reservoir, meaning that it's going to hold on to the food that you have eaten before it passes in the small intestine and passes in the large intestine because again, it's sequential. It can't move forward until those other items have passed out. The gastric juices that it's going to secrete include chemicals such as HCL, which stands for hydrochloric acid, uh, pepsin, intrinsic factor, and gastric lipase. We'll talk a little bit more about all of those in upcoming slides, but those are part of the gastric juices. And then additionally, there's a hormone called gastrin that's going to be secreted from the stomach into the bloodstream. So gastrin is a hormone versus the other ones are gastric juices. A clinical view here is of vomiting, also known as emmesis. Vomiting or emmesis is when you forcibly um expel the stuff from your stomach through the mouth. Uh what happens is that there's a strong nerve impulse connection between the vomiting center found in the medulla oblangatada and causing the stomach to squeeze as well as the abdominal muscles to squeeze because you have to squeeze to force enough um pressure to push things back up from the stomach through the esophagus. Too much vomiting or emmesis can lead to alkalossis because your acidic gastric juices are necessary to maintain that pH of the stomach and so without them you can definitely swing to more of an alkyoic state. On to the next organ which is the pancreas. So the pancreas is one of the three main accessory organs to the digestive system in the abdominal cavity. Um the pancreas sits behind the stomach. So it's often times considered to be retroparitinal. 99% of the function of the pancreas is actually as the in exocrine part to the um digestive system. 1% is what was covered in the endocrine system. So the main role really of the pancreas inside the body is to produce a large amount of the pancreatic juices which contains enzymes to break down the food contents. It's going to empty its contents into the first part of the small intestine called the dadum. One of the aspects of the contents that's important also from the pancreas is a substance called the sodium bicarbonate. Inside the stomach, remember it's kept at a very low pH. So this sodium bicarbonate ensures that when that um kim moves from the stomach to the dadum, the pancreas's role is to help neutralize that really acidic kim so that way it's not going to burn through the tissue of the small intestine. Pancreatic juices on a daily basis are going to be producing anywhere from 1,200 to,500 millilit which is about 1.2 to 1.5 quarts. This is a clear colorless liquid. It's mainly water uh but it's going to contain all kinds of enzymes in order to help again buffer the acidic gastric juice that comes in the kim the enzyme the pancreatic juice include all of those components that you see listed there. So the names are on the left side of the list and then the item that it's dissolving is on the right side. So an amalayase asse again means enzyme. The pancreatic amaase is going to be breaking down starch which is one of the carbs. We talked about the salivary amalayise from the mouth. Trison kimotriin caroxyeptidase all three of those are going to be breaking down proteins. The pancreatic lipase. So this is going to be a um fat dissolving enzyme. So it's going to break down triglycerides. And then we have the two that are going to be working on DNA and RNA. So riboucle deoxy um ribouclease. Just a refresher DNA does not bring any energy into the body. But the foods that you eat have cells and cells have DNA. So that's where it comes from for that. In the arrangement, the anatomical arrangement of the pancreas, liver and gallbladder, it is important to know that the pancreas is very intimately involved with um the ducts coming from the liver and the gallbladder to empty into the deadum. So you can see right here in the pancreas the main structure is going to be that duct and that duct is traversing through the entire structure of the pancreas and then it's going to empty into the uh dadum there. Then from the pancre or from the pancreas from the liver and the gallbladder, they're going to have a series of ducts that we'll talk about in just a little bit that are going to be working together to push the bile that's being produced by the liver stored in the gallbladder into the um dadum as well by passing through and uniting as you can see right here in the picture with the duct from the pancreas. So that's going to open up into the deadnum. So here's what it looks like in real life. You are able to see that if uh the pancreas's duct has been dissected out and then the duct from the gallbladder and the liver unite together that is going to be opening then into the dadum first part of the small intestine. And so the liver is going to be um arranged in a series of collection of cells known as hpatocytes. Hippat means liver. Site means cells. These are the major functional cells of the liver and they perform a wide variety of activity of what's happening in the liver. Now the liver we talk about the digestive system but it plays a role in many other systems as well. What it does in the digestive system is that's going to be important to take a lot of the food that you have eaten and basically do um the role of kind of modifying it um changing it, emulsifying it, processing it, metabolizing it. That's why we talk about it in the digestive system. Throughout the liver, it's also going to have these large spaces that are called the bileiculi. Bioiniculi are going to be places where the bile that's produced in the liver is going to start congregating together. And so here you can see the bioiniculi um identified by the color green. Bile is a little green in its coloring. So that's not unusual to have that color in images. Then we have the hippatic sinosoids. So sinosoids are going to be large spaces where oxygenated and deoxxygenated blood can mix and that's a benefit in the liver because that allows the liver to do um the role of getting nutrients from the blood and producing uh getting wastes as well. So the blood can mix together and that is absolutely normal. So here you can see the vein coming and then the artery coming and they mix together in what are called the hippatic sinosoids. functions of the liver are really diverse. There's a huge list that we could go over. Um, we're going to talk about some of the main items in relations to the digestive system. So, carbohydrate, lipid, and protein metabolism. Metabolism again means taking those um substances and putting them through a series of chemical reactions. And because those are what's coming from what you eat, that's what the liver is going to be doing is putting them through all kinds of chemical reactions. any drugs or hormones that get inside your body, the liver does a good job of detoxifying those substances such as alcohol and excrete drugs such as penicellin, urethroyiain, and sulfonomides into the bile. Um, and it can also help regulate and chemically alter any hormones that are produced inside the body. It's going to get rid of Billy Rubin. So, Billy Rubin comes from uh red blood cells that have been aged. It is absorbed by the liver from the blood and then it's uh secreted into the bile. Most of the Billy Rubin in bile is metabolized in the small intestine by bacteria and eliminated in feces. And so that's what gives feces that kind of brown color to it. Production of bile. So biosynthesis um that's going to be using to do what's called emulsification. Emulsification is how we describe how fat is being broken down. Essentially, this is like your dish detergent. So, when you use dish detergent, it wraps itself around the food droplets and breaks it down into smaller droplets, which then makes it easier to break down. That's exactly what this does inside your body. The bile wraps around food droplets that are fat and breaks them down into smaller fat droplets that can then be further metabolized. It will play a significant role for storing um glycogen is the main thing but it can store vitamins A, B, D, EK, minerals, iron and copper. Um fagocytosis. So it's going to help to get rid of any sort of dead decrepit cells that need to get out of the body including bacteria. And it will also help activate vitamin D. Vitamin D is something that you can absorb in your skin from the sun, but it becomes activated um inside the body to kind of act as a hormone to help you to store calcium in your bones. So, the big thing about the liver that is commonly confused is that the liver is the organ that makes the bile. Bile then is moved from the liver into the gallbladder. So the gallbladder is what's going to be storing the bile until it is needed. Bile is used for the emulsification of fats. Now you can live of course without your gallbladder uh because the liver is going to make up for whatever the gallbladder once did. And so then that way it just goes directly into the um small intestine. So the sequence of how all of that works is these important structures on the right. So from the liver you have the right hippatic duct and the left hypatic duct because that divides the two loes of the liver. They then unite together to form the common hippatic duct which common hypatic means it's the unification of those liver of the hippatic duct. Then the cystic duct is going to join up with that to form um from the gallbladder. And then once the cystic duct and common bile duct unite um or common bile duct common hpatic duct unite they form the common bile duct and then the common bile duct will unite with the pancreatic duct and that's what's going to open into the deadnum. So if the uh gallbladder is removed then that duct is no longer present but you can see it's a whole sequence of getting the items from the liver getting the items from the gallbladder and then uniting to form the common bile duct with the pancreatic duct to empty into the small intestine. So here again you can see the right and left hypatic ducts. They unite to form the common hippatic duct. From the gallbladder is a cystic duct. And then that's going to unite to form the common hippatic duct um with the cystic duct to form the common bile duct. And then that will unite with the main pancreatic duct to open up right here into the dadum. So a clinical view is cerosis of the liver. So this occurs when the liver cells hpatocytes are going to be replaced by fibrous scar tissue. Um this scar tissue means that the liver's uh normal tissue doesn't function as it once did and this causes a change to the tissue which then puts pressure on the various blood vessels that are found in the area. It can also be caused um by injury from um hpatocytes. Commonly it is from of course alcoholism as I'm sure you're familiar with liver disease in drugs or toxins that um somebody might be taking at length that causes damage to the liver also viral infections such as hepatitis A, B and C any of the hepatitises hepatitis means in uh inflammation of the liver those commonly can cause a change to the tissue inside the liver. And then with this oftentimes people will have weight loss, nausea, pain. Um the liver can be some of it partially removed and it has been known to regenerate itself. How long it that takes I'm not sure. Um but it is an organ that you have to have. So you can't live without your liver, but there is liver transplants available. So here you can see the differences between a normal liver, fatty liver, and cerosis. Cerosis is on the far right, and you can see that it's rippled. um it's got some parts that are irregularly shaped. Again, the liver can change to this fibrous tissue which changes the entire tissue inside the liver and that's what causes it to be funky in its functioning. Along with this is the clinical view of what's called jaundice. Jaundice comes from Billy Rubin and remember Billy Rubin is a substance from your red blood cells. Billy rubin is a major constituent found in bile but it is actually not playing a role in digestion. Essentially Billy rubin just gives color um and it gives more of a yellow pigment and that's what is jaundice is that it shows up as a yellow pigment in the skin the mucous membranes very clearly in the picture there in the wide of the eyes. Um as a result it this indicates that the liver is not functioning as well as it should. Jaundice is also not uncommon in a newborn baby because newborn baby functions for about the first week or so. They um have a difficult time processing Billy Rubin. So sometimes they are put underneath a blue light to help their body convert this um until their body as a newborn can catch up with it. So for babies with this um it's usually temporary until their body is able to process it as it should be. Uh but in cases of like liver cancer um liver issues sometimes there's nothing that can be done at that point because the liver just has to process that Billy Rubin. Next organ is the small intestine. So the small intestine is going to be this long tube that goes from the stomach to the large intestine. Now, the small intestine is called the small intestine because it's narrower in diameter, but it actually is longer than the large intestine. Um, it's kind of like an accordion inside your body in the fact that it's really squeezed in there. The main role of the small intestine is that it's going to be for absorption. This is where the absorption of your nutrients, vitamins, electrolytes, your food, all of it pretty much gets absorbed in the small intestine. So the three main divisions of the small intestine are the dadum, the jigunum and the ilium. The dadum is the shortest region. It's the very first part that comes right after the stomach. Its main role as talked about previously is that it's going to be receiving the substances that come from the liver, the gallbladder, and the pancreas. The middle division is the jigunum. And then the third division is going to be the ilium. Now uh anatomically there's not a whole lot difference that you can see between the jigunum and the ilium. It would have to be dissected out to show you the differences in between blood supply, blood vessel arrangement, the amount of fatty tissue that's present. Um so we're just going to say that it's going to be found in the body um in the in the middle for the gigunum and then towards the end of the small intestine to be the illium. The distal end terminates at what's called the ilioal valve. And the ilioal valve is a valve that's going to connect the small intestine to the large intestine. So it's kind of an open door closing door scenario that's going to help to get substances moved into the large intestine when the large intestine is ready. So for the hisystologology of the small intestine inside as I described previously it's often compared to looking like an accordion because when we look at the tissue it's folded into what are called circular folds also known as plea circularis. These are folds of that mucosa and sub mucosa tissue. And the purpose of those folds inside the small intestine is to provide more surface area. So, if it was really spread out, like an accordion um spread out, you wouldn't have a whole lot of space in your abdomen. In fact, your abdomen would probably be a lot bigger than what it was. So, the fact that it's kind of folded in here like an accordion allows the small intestine to take up less room. And so, again, those extra um folds allow for more surface area for absorption. And then additionally on top of the circular folds there's even more structures called villi which are going to be these projections into the um small intestine. And then even all right so first in the image here on the left side we can see that the circular folds have been created. And so then from the circular folds we get the projections called the villi. So the villi are what's on top of what you can see there. So each one of those cells and then on top of the villi are the microvilli. So you have three places of surface area. Microvilli villi and then the circular folds. That increases the surface area um by a lot for nutrient absorption. Additionally, what I want to point out to you here is that you can see in each one of the um villi that are projecting um in the circular folds, there's going to be arteries, veins, and lymphatics. And that is how your nutrients will immediately get into the bloodstream when they are absorbed is each one of those has that extensive blood supply to them. So, on to the large intestine. So the large intestine is the end of the GI tract. Its overall function is that it's going to um complete the process of absorption, produce certain vitamins, form feces, and get rid of the feces from the body. It is a wider tube than the small intestine, but it is shorter. So the width is wide. It's called the large intestine, but lengthwise it's much shorter than the small intestine. It does the remainder of the absorption of water and electrolytes. So I want to make sure you know that it's not water that's absorbed in the large intestine just excuse me the remainder excuse me after the um small intestine can't absorb it then that kim that was formed in the stomach that has now gone through the small intestine nutrients have been extracted out of it whatever is left over in the large intestine forms the compacted substance that we call feces. Additionally, hanging out in your large intestine is all kinds of wonderful bacteria. And that bacteria is used to convert any proteins to amino acids, break down any amino acids, produce some B vitamins. You need to have the protein that lives inside your large intestine. It's incredibly important. Large intestine anatomy is full of many different subdivisions of it. So, it's always going to begin by the ilium going to attach to the first part called the seeum. And hanging off a seeum is going to be a structure that we call the veraform appendix also known as appendix. Veraform just means wormshaped. Um this is going to be at one time filled with lymphatic tissue but as you know you can live without it. From the seeum it turns into the part that we call the colon and the colon is divided into the ascending, transverse, descending and sigmoid colon. We'll talk about those. They both are going to have um or this the colon is going to have two uh angles to it that we call flexures and I'll point that out in the picture. From there, the sigmoid colon is going to turn into the rectum. And then the rectum will transition into the very last couple centimeters called the anal canal. The anal canal is going to contain two sphincters, an internal anal sphincter and external. Internal is smooth muscle, which means you have no control over it. External is going to be the skeletal muscle which means you have control. Both of them are closed unless you are actively eliminating feces. So here are the parts of the colon that are important for you to know. So here's the ilium that connects to the large intestine right at the seeum. There's that ilioal valve that we talked about in the small intestine. Here's the appendix hanging off of the seeum. Then we have the ascending colon because it's going to go up, the transverse colon because it's going to go across. And then descending colon because it's going to come down and sigmoid because it forms an S. Right at where it forms that S, it will turn 90° to turn into the rectum into the anal canal and then into the anus. The two main bends of the colon you can see right here you have the right colic also known as hpatic flexure left colic also known as spleenic flexure. That means that the intestines have bent and turned. The mechanical digestion that occurs inside the colon has some unique names to it. The first one is called hostra churning. Hostas are these pouches that are brought together by bands of longitudinal muscles called tenee. So teneacle are these three bands of longitudinal muscles that are going to run the entire length of the large intestine. It's kind of like elastic. The teneacle allows the colon to bunch up and when it bunches up it forms these puffy pouches that we call hostas. And so that's what gives the large intestine its kind of puckered look to it. How the hostas then are going to churn together kind of one pouch at a time. And then from there it's also going to be passing through what's called paristalsis and specifically of what's called mass paristtoalsis. Mass paristalsis is a final strong parastolic wave that begins around the middle of the transverse colon and quickly drives the contents of the colon into the rectum. And so that's when a person knows that they usually need to go to the bathroom because food in the stomach usually initiates this. Mass peristalsis usually takes place three to four times a day during or immediately after meal because your body again is sequential to have your food in various places in the digestive tract and not put too much at once um in a specific location. So it ensures that it's going to um keep sequentially going through the colon um as opposed to building up together. So the final bit of absorption is that time can remain in the large intestine anywhere from 3 to 10 hours. By the time it gets to the large intestine and the end of the large intestine, most of the water has been absorbed. And so we call it then feces because it's relatively firm. Any electrolytes that the body needs, any vitamins that the body need, that is also absorbed. 90% of the water is absorbed in the small intestine. So the large intestine just absorbs enough to make it um basically compact. What exactly is feces made up of? So feces is made up of anything that you really didn't use. So any extra water, inorganic material, um dead epithelial cells that are sloed off as food gets through your digestive tract, bacteria, undigested portions of food such as connective tissue or muscle pieces. So that's what's coming in the feces. So important clinical view of course is appendicitis, which is the inflammation of the appendix. Uh most commonly we think that appendicitis is caused by some sort of fecal matter getting down into the appendix and the appendix can't process it. A risk of an inflamed appendix is that it can rupture and if it ruptures millions of tiny little cells get inside your abdominal cavity and there's lots of places it can hide. And so that's what can cause a very um difficult disease to treat called peritonitis. And that can lead to um additional illnesses for people with appendicitis. What often happens is that that they feel relatively pain right around their umbilicus region. It also is um isolated to the lower right quadrant. It is continuous. It can be pretty severe. It usually is intensified by moving. Sometimes nausea, um vomiting are involved, fever. Um and then in order to remove it, the process is known as an appctomy. Appectomy is going to open up the body to get to the appendix. It is done fairly often. Um so it's not too much of a dangerous surgery, but it still is a surgery. And then you remove the appendix and you heal from there. So there you can see inflamed appendixes and then what it looks like when it's cut open on the inside. So full of lymphatic tissue. Also of note, the digestive system is diarrhea and constipation. So diarrhea is defined as basically having an increase in the frequency, volume and fluid of the feces. This can happen when kim passes too quickly through the small intestine or feces passes too quickly through the large intestine. It can be caused by um bacteria, viruses causing you to um have difficulty processing what's in there. Essentially, the body is saying, "Get it out of me as fast as possible because it's harmful and so it's going to move it out quick." The issue with diarrhea is that if it's chronic, it can lead to dehydration the individual and it can also lead to acidosis and that is because you are losing your bicarbonate. Remember that vomiting led to alkyossis because you were losing acid. Diarrhea leads to acidosis because you were losing bicarbonate. On the other end of the spectrum is constipation. Constipation typically occurs when you have infrequent or difficult defecation that is caused by maybe slowing down of motility intestines. Sometimes it's caused by insufficient fiber. Sometimes it's caused by lack of exercise, drugs. the feces becomes hard and dry which makes it very painful to pass and to get out of the body. Um, and so therefore it just creates a more difficult time of of pressure on the body to get it out.