Digestive Tract Anatomy and Physiology

my stomach hurts oh hey you know that's not your stomach right what are you talking about i know what my stomach is and it hurts really bad that's definitely not your stomach that's where your intestines are wait you don't know your digestive anatomy how would i know my digestive anatomy you haven't taught us that yet oh i'm excited because i made a whole video about it and i really like talking about it oh i should probably go to the bathroom first but all right let's do the lesson i guess let's jump to the whiteboard so let's start at the beginning we eat food we put that food into our mouth or our oral cavity now connected to the oral cavity i've got these three glands in yellow these are called the salivary glands and they're going to produce enzymes which help us break down the food that we start chewing in our mouth there's three salivary glands in total we have the parotid gland right here we have the submandibular gland because it's sort of under your mandible or under your jaw bone and then the sublingual gland which is under your tongue hence the term sublingual under the tongue but all three of those glands produce our saliva so we call them the salivary glands now connected to the oral cavity we have our throat and our throat connects to our esophagus and that's where food is going to travel after we swallow our food it's going to take that food from our oral cavity or our mouth all the way down to our stomach which as you saw in the intro is not in your belly if you want to find your stomach on your body just put your hand underneath your ribs on the left side and that's kind of where your stomach is up in there so just inferior to the esophagus then is the stomach food will travel down the esophagus into the stomach where it's going to undergo a bunch more digestion because the stomach's got muscle that's going to squeeze on the food as well as a bunch of acid to help break down some of the food as well but we also want to be able to control where food goes and where it doesn't and where that stomach acid goes and doesn't and so one of the things that we have in order to prevent things from going where they're not supposed to are these little tiny muscles called sphincters sphincters are circular muscles and they work to close off parts of the digestive system whenever we don't want something to pass back and forth we've got two and the esophagus one on the top and one on the bottom the one on the top is called the upper esophageal sphincter and the one on the bottom of the esophagus is called the lower esophageal sphincter these two sphincters are really important because they prevent acid from your stomach from going up into your esophagus and then up into your oral cavity if that acid gets up into your esophagus oral cavity it'll start to burn we call that acid reflux or heartburn which has nothing to do with your heart but those sphincters prevent that acid from traveling up the wrong way then on the other end of the stomach we have something called the pyloric sphincter and the reason we need this is because we want food to stay in the stomach for long enough to undergo proper digestion before it goes into the intestines so that pyloric sphincter will be closed off until we're ready for that food to go from the stomach into the intestine in which case that muscle will relax open up and the food can pass through and from the stomach it's going to travel into the first part of the small intestine which we call the duodenum or sometimes called duodenum i've heard it pronounced both ways so that duodenum is that little curved section that's the beginning of our small intestine and actually a lot more digestion happens in the duodenum of the small intestine and we'll come back to that in a minute once we see some other organs that food doesn't pass through we'll come back to it next up we're going to go through the rest of the small intestine and if you notice the rest of the small intestine is going to wrap around it's going to like a bunch of squiggles there's a reason that we're trying to maximize the time that the food is in the small intestine that's because we're going to be absorbing nutrients out of the small intestine into the bloodstream and we want to have plenty of opportunity we don't want to waste any nutrients so we have this long curvy small intestine so that food stays in the small intestine a long time so we can absorb every nutrient that we can from our food so at this point we've traveled through the small intestine we've reached the end of it and we're ready to move into the large intestine the large intestine isn't called large intestine because it's longer it's actually shorter than the small intestine but it's bigger around it's larger and so we call it the large intestine but it also has another name and that other name is the colon so anytime you hear colon or large intestine it's exactly the same thing they're synonyms of each other you can call it whichever one you want they both mean the same thing colon large intestine one in the same so at this point we've absorbed all those nutrients out of the food we've entered into the large intestine but you'll notice this little dangly thing hanging off the bottom of the large intestine and that's called the appendix the appendix for a long time we thought was just a pointless organ left over from our evolution but we think now it probably acts as a as a reservoir for our gut bacteria so that whenever we have like diarrhea and stuff and we gotta flush out the contents of our large intestine we keep some of that good gut bacteria in our appendix to repopulate our large intestine after that's happened now the colon has a bunch of different parts this bottom part right here that connects to the small intestine we call the cecum from there the remnants of our food are going to travel upward so we call this part the ascending colon then the food is going to travel across the body and so we call that the transverse colon and then to bring the food back down we're going to have the descending colon so again the cecum ascending colon transverse colon and descending colon now towards the end of the colon it makes a sort of s shape if you use your imagination a little bit um right here kind of curves one way and it curves back the other way and so that part where it makes that sort of s curve we call that the sigmoid colon sigmoid just means s-shaped so one more time cecum ascending colon transverse colon descending colon and then sigmoid colon and the purpose of the colon is to absorb water out of our food we absorb all the nutrients out through the small intestine into the bloodstream and then from the large intestine we're absorbing all the water out into the bloodstream so both of these intestines are going to have lots of blood vessels going to them because we're getting all these nutrients and water from our food that's going to go directly into the bloodstream so there'd be a lot of blood vessels all throughout these intestines so we've kind of reached the end of our digestive tract now we've got a couple more structures the first of which is the rectum the rectum is going to be where our feces is stored before it's ready to exit the body and finally the anus which is the hole through which our feces will travel whenever we poop now we really want to be able to control when we poop so we've got two more sphincters which are going to help with that we've got the internal anal sphincter and the external anal sphincter now why have two of those you might ask well one is going to be voluntarily controlled and one will be involuntarily controlled the one that's voluntarily controlled that's the one that you can consciously sort of think about and tell it to stay closed that one's really important whenever you like feel like you need to go to the bathroom but you you're not in a place where you're able to go to the bathroom at the moment so you're going to actively work to keep that feces in you're using your external anal sphincter but then at other times there might be feces in your rectum but you don't feel like you have to go use the restroom that's going to be your internal anal sphincter just holding it there but that one you don't have to consciously think about to keep it closed so the internal anal sphincter that one's involuntarily controlled you don't have to think about it and the external anal sphincter that one's voluntarily controlled you can consciously control it to prevent yourself from going to the bathroom when you're not ready to so all of this we've covered so far is the digestive tract it includes all the structures that food actually passes through from the time you eat it till the time that you get rid of it out the other end all of this is connected together sort of like a maze so one thing i like to do is to trace the path through the body and see that it's just all connected and i can follow along with it so let's do that real quick food's going to come in through the oral cavity it's going to travel past those salivary glands down into the esophagus it'll travel through the upper esophageal sphincter through the lower esophageal sphincter it'll be in the stomach and it's going to stay in the stomach and get sloshed around in the acid and stuff it'll pass through the pyloric sphincter down through the duodenum where it's finishing digestion or breaking the food down down into our small intestine and it's going to be a long small intestine so that we can maximize the absorption of nutrients from our food then it'll enter into the cecum of the large intestine it'll travel up through the ascending colon the transverse colon the descending colon during all that time it's going to be removing water absorbing that water into the bloodstream then that's going to travel through the sigmoid colon into the rectum it'll travel through the internal sphincter and the external anal sphincter and then out the anus at the other end so everything there is connected and these are all of the structures that the food passes through but we have a few other organs that we need to talk about that are part of the digestive system but they're not part of the digestive tract itself in other words food doesn't pass through these but they're important for the digestion or breaking down of food the first of those digestive organs is the liver the liver is one of the biggest organs in the body and it's going to make this digestive substance called bile that's really going to help us to break down fats that we eat just inferior to the liver is the gallbladder the gallbladder is this little sac that's going to hold the bile which is that substance that the liver makes so that whenever we eat a fatty meal we've got a bunch of bile ready to eject into it to help break down that fat so that's the gallbladder right there but they're connected to each other and they're connected to each other through something called the bile duct which makes sense bile will travel from the liver into the gallbladder through that bile duct here it's connected to the liver and the bile can travel down and be stored in the gallbladder right there and then whenever we're ready for that bile to enter into our digestive tract to help us break down fat that bile will be ejected out through this tube the bile duct down and then into the duodenum where it's going to mix with the foods that we've eaten so again we have the liver we have the gallbladder and then we have the bile duct which connects all of those structures to the duodenum now there's another branch off the bile duct which is going to connect to our pancreas now our pancreas you might remember is part of the endocrine system so it's going to make hormones to help us regulate our blood sugar but it has a second really important function in the digestive tract which is making digestive enzymes and those enzymes are going to get dumped out into the duodenum just like that bile is so here's our pancreas that's going to make a bunch of enzymes to break down food here is the pancreatic duct it'll connect to the bile duct and then connect to the duodenum so all of those enzymes will get dumped into the duodenum of the small intestine all right now we're going to jump to terry and take a look at the three-dimensional positioning of a lot of these things and then at the end you'll have a chance to see if you can label all of these from memory before we go all right so we've got two of the torso model here let's take a look we've got the oral cavity right there and we're gonna have these three salivary glands we've got the sublingual gland right here if we turn terry and look under here we've got the sub mandibular gland of course because this is the mandel of the jaw bone submandibular is right under that and then over here we have the parotid gland and of course this is on both sides we just see on this side because of the cutout here and all three of those are going to connect to the oral cavity so that we can produce saliva all right so whenever terry swallows food that food is going to travel down the esophagus which we can't see until we get down in here this of course is the trachea but if i remove the trachea we can see the esophagus that's going to travel down through the diaphragm which we can see right there this is the liver of course that liver is a pretty big organ also take note of where the ribs are the ribs kind of go down to here so your liver is kind of up under the ribs your lungs are above that here's your diaphragm your stomach is also just underneath your ribs on the left side if you'll notice there's that green sack right there that's the gallbladder so the gallbladder is kind of tucked up underneath the liver right there so let's remove the liver and then back in there that's going to be connected to the esophagus right there so that's the end of the esophagus that's where that lower esophageal sphincter will be and then we've got the stomach here which is very muscular we're going to take that stomach out but you'll notice here is the other end of the stomach which is going to connect to the duodenum of the small intestine so here's the beginning of the duodenum and then right down in here you can see this little hole right there that's where the bile duct is going to connect we also have the pancreatic duct that's going through the pancreas so this is all the pancreas right here we didn't draw this in our diagram but this is the spleen in purple over here and then here's part of that bile duct you can see in green right there that's going to connect up to the gallbladder which i just removed now that duodenum of the small intestine is going to go down it's going to wrap around here and it'll connect right there and then it'll travel through all throughout the small intestine right here and then once we get down over here here's the cecum or the beginning of the large intestine you can see where that small intestine connects to the cecum down right there will be the entrance to the appendix and here we have the ascending colon transverse colon descending colon so you can see kind of the sigmoid colon where it makes the s shape right there and then feces will travel out through the bottom there and then out through the anus which will be at the end of that tube let's do a quick recap of all these structures food is going to travel in through the mouth or the oral cavity we'll swallow that food it'll pass by the salivary glands it's going to pass through the upper esophageal sphincter into the esophagus down through the lower esophageal sphincter into the stomach from the stomach it'll pass through the pyloric sphincter down into the duodenum of the small intestine the liver and the gallbladder are both going to be connected to the duodenum via the bile duct which also connects to the pancreatic duct and into the pancreas all of that will connect to the duodenum right here and of course the liver is making bile the gallbladder storing bile the pancreas is making a bunch of digestive enzymes all of that gets dumped in the duodenum to help us continue breaking down food the food's going to pass through the small intestine we're going to absorb nutrients from that food once it gets to the end of the small intestine it'll join into the colon or the large intestine where water is going to get absorbed the food will travel up through the ascending and then through the transverse and then the descending and the sigmoid colon it'll pass into the rectum and then through the internal and external anal sphincters to the outside of the body all right take a moment pause the video see if you can identify all of the structures of the digestive tract in this diagram and here are all those structures again so you can check your answers where's your stomach where's your stomach what about your mouth where's your mouth yeah very good where's your esophagus where are your intestines at

Channel: Siebert Science

Views: 515,411

Keywords: science, anatomy, physiology, education, flipped classroom, high school, Cecum, Caecum, Sphincter, Pancreas, Digestion

Id: MgVaBwniceU

Length: 14min 37sec (877 seconds)

Published: Sun Apr 18 2021