hi everybody and welcome back to miss Angler's biology class I am Miss angler in today's video we are going to be doing a follow-on from the mouth to the stomach we are now moving into the intestines now it's at this point that if you haven't watched that video I've linked it up above now for you to go and watch that one first and then the video following this is going to focus on digestion and then following that is absorption so make sure to watch these videos in the correct order now if you are new here make sure you have subscribed with your notifications turned on because I post every Tuesday and Thursday for grades 10 to 12 Life Sciences so let's get into the video around the intestines and we're going to be focusing in on the lower portion now of your digestive system or your Elementary canal and we're going to focus in on the structure of the intestines in a later video we are going to look at the process of digestion and then absorption we're also going to talk about these accessory organs like the liver the gallbladder as well as the pancreas here hiding behind the stomach and we're going to see how those accessory organs along with the intestines facilitate digestion and how their structures and their secretions allow for absorption to take place now the first thing that we need to start looking at is the small intestine now what we have here is a piece of your small intestine we've cut it open so we can see it on the inside now the small intestine is structured for its function in a couple of ways and in the exam we are going to need these lists of adaptations and we need to be able to elaborate and explain them now the first adaptation the small intestine has is going to be the presence of villi and microvilli now what these structures are is if we were to zoom in on one of these folds that we see over here on the inside of our intestine Villi and microvilli essentially are these long finger-like projections so that is the Villi and then on the outside of the Villi you have even smaller little hair like projections covering the entire surface of the valley and those are our microvilli the purpose of these is always of course to increase the surface area because the main point of our small intestine is for absorption so it makes sense to have as much surface area as possible seeing of which another reason or another structure that we have that allows surface area to be increased is transverse folds now what they're talking about here and we can actually see it in this diagram here is you will notice that the intestines are not smooth you see they have these folds all the way through and these folds again are increasing surface area now another thing that small intestines have which make them really good at their job is their thin walls now when we're talking about thin walls we are referring to this outer layer over here and what happens is if food is moving through the small intestine it's going to move through three layers and it's going to move outwards into the bloodstream and that is a pretty thin layer in actual fact the small intestine is only one cell layer thick on the Villi which means if we go back to my little Villi drawing earlier it means that there is only one cell layer thickness all the way around it and the blood vessel that runs in the middle of it so let's say there's a blood vessel over here there's only one cell layer thick that you have to pass through which means diffusion is really fast and so that's why we have thin walls because diffusion is going to be really quick and it makes it more efficient now the next thing about the small intestine which makes it really great at its job is it is long now how long is the small intestine uh it's plus minus about seven meters it depends on the person as well um and so it can be a little bit longer if you are a taller bigger person and it can be shorter if you're slightly smaller but the length of it means that your food spends quite a lot of time inside the small intestine once it has been chemically digested and again that means we have even more time for diffusion to take place so the longer the better the more diffusion now the final uh adaptation that our small intestine has is it is filled with a capillary Network now we can't see it in this particular diagram over here but as I spoke to you earlier there is a capillary which I just drew in blue over here inside the Villi and what that means is running through the full length and weaving all the way through all of these folds all of the Villi are going to be capillaries and the capillaries provide a Transportation Route and so that Transportation means that we are more efficient and we can absorb faster and it can go straight into the bloodstream now what we need to do is focus in on the regions of the small intestine so we've looked at its adaptations that are throughout but there are actually three regions to the small intestine starting with the duodenum this is the small intestine that is linked to the stomach so it is the small section just outside of the stomach and the duodenum has a really important function because ultimately what happens is this the food you have just eaten enters into the duodenum and this particular food is very low in PH right now in other words it is acidic and the problem with the acidic pH is that the enzymes that exist in the small intestine are all alkaline and or neutral and they need to be higher so we need to raise that pH and also the small intestine is not the stomach it's not structured the same way so it doesn't have the same protective layers um and so we don't want to we don't want to eat a hole through our small intestine with the hydrochloric acid that's now mixed in with your food so what we do is in the lining of the duodenum we find something called the crypts of libucin now these Crypts of libikin they are stimulated by the acidic chyme that has arrived from your stomach and we secrete a hormone called secretin now this hormone is going to stimulate the pancreas now the pancreas is really important because it has exocrine and endocrine functions and in this instance what it's going to do is it's going to secrete pancreatic juice now pancreatic juice is going to and we're going to change color for this it's going to come out of our pancreas and it's going to go into the duodenum and the purpose of this pancreatic juice is to neutralize the pH all right it's to rise the ph and so we are trying to make it a more alkaline environment and when we do this we are now making it more suited to the enzymes of the small intestine because remember it's very acidic we want to raise it so the pancreatic juice is released now we're not done yet because right now the chyme that is inside of your small intestine in the duodenum needs a couple of other extra additives to it before we can start absorption and and completing the rest of digestion so now that we've neutralized the pH we need to deal with the fat that is in the kind because fat is non-soluble in water so we need to introduce another player to the story and that is going to be the liver now the liver produces a substance called bile and essentially bile is made up of um broken down red blood cells that we no longer need and it then stores that bile inside of the gallbladder which is this little structure over here and so what happens is the bile is stored in our gallbladder until we need it the bile is then sent from the gallbladder into the small intestine and its main function is for emulsification now what is emulsification emulsification is taking fat and making the fat like globuts which means like the the droplets or the chunks or the molecules we are taking them from really big and we want to make them really small because when they are really small they are easier to absorb and get into the bloodstream and in another video I'll explain why that is so complicated when we do absorption but emulsification is taking fat and emulsifying it into the water that is found in your digestive system so you can absorb these nutrients now the whole time also by the way I've been speaking about these like substances that are neutralizing the pH the duodenum also has its own way of maintaining the pH as well so there's actually a third substance that the walls of the duodenum can secrete and that is of course mucus but specifically bicarbonate mucus and so this mucus is going to be secreted from the walls of the duodenum and it again neutralizes and protects because remember mucus is thick it's got a protein base to it so it's going to prevent any of the gastric acids from eating away now all of these three things put together create a substance we want to refer to so if we take the pancreatic juice the bile and the bicarbonate mucus and we put them together we make a substance collectively known as the suckus entricus and essentially what that is is all of the secretions that are put into the duodenum to ensure that absorption and digestion can be completed now one last little last little bit about the duodenum is it is the final place where chemical digestion can take place um after this point in the small intestine chemical digestion is done for and we go into absorption but it's important to note that we are doing all of this pH correction for one very important enzyme which is amylase and so I'm going to put amylase at the bottom over here just so we can remember it on the side but amylase is the enzyme that is responsible for breaking down carbohydrates so it's a very important enzyme because carbohydrates are of course the food of the body the fuel of the body so we need amylase to be working at an Optimum now we're moving on to the longest part of the small intestine which is called the jujinum now it is the majority of the small intestine it's roughly five ish meters and the jujinum's main responsibility is absorption and so absorption is quite a complicated process it does get its very own video and so I will link that up above now and for you to go and watch but absorption is quite complex depending on the molecule you're trying to absorb and but we need to talk about what's on the inside of the jujinum that allows it to do such a good job at absorbing substances so if we move the jujinum over to the side here and we take a look at what is inside the duodenum and we spoke about these structures earlier it is the Villi and in this picture here my Villi have two slightly different structures it's just to make it easier to see but I want you to know that actually they they overlap you you find both in one Villi but in this picture we've made it simpler now what you're looking at in this picture over here is Villi and microvilli and Villi if we remember from earlier on are these finger-like structures these bigger finger-like structures as opposed to microvilli which are these teeny tiny little finger hair like structures on the outside and that is what gives us our absorption surface and gives us a large surface area now what we find though on the inside of our Villi are important so first of all we have this structure here in green and often in textbooks it is drawn in green it's called a lacteal that is where fat is going to be absorbed exclusively then we have our capillary bed which we have over here and that of course is for absorption into the bloodstream this is where proteins and carbohydrates will be absorbed now again I want you to know that these two things the lactal and capillary they go together they actually overlap in photographs but here we've made them separate now one other thing that I want to bring your attention to is the cells that line the um small intestine and these are found throughout the whole small intestine but we're going to focus them on the jujinum and that is these epithelial cells over here now I just mentioned to you earlier that the Villi R1 cell layer thick which they are and remember epithelium is a thin tissue um and what it can do is facilitate diffusion now what is also found in the duodenum and we actually spoke about mucus earlier and and someone needs to be making this mucus someone needs to be secreting it is these cells over here which are different in color and they're different in function those are our goblet cells goblet cells are cells that secrete substances that can secrete hormones they can secrete mucus and most importantly in the jujinum they are responsible for maintaining the mucous layer and the water balance and because water is really important to facilitate absorption which of course is the main point of the duodenum Now we move into the final section of the small intestine this is the shortest piece of the small intestine which is this piece over here it is the ilium the ilium is the piece of the small intestine that's going to join under the large intestine which we're going to get to shortly and the most important thing that we need to know in the ilium is there is a tiny little valve at the very end that connects the small to large and it sits roughly over here and it is called the iliocecal valve and this is the valve that opens and closes that allows food to pass from the small intestine to the large intestine and the reason why this valve is there is because you need to regulate how much nutrition you have absorbed if this valve were to stay open food would move too quickly through you and you wouldn't absorb enough nutrients another thing is we need to make sure that if it's moving uh too fast not enough water is also absorbed back into the bloodstream and you can end up with things like diarrhea or on the opposite end of that if the food is too long inside of you then you end up with something like constipation but that's more of the large intestines job so let's have a look at the large intestine so moving into our large intestine now we're looking at the final stages of food passing through you and we're going to look at the first little area of the large intestine which is this bit down here it would have been in the previous picture joining onto the small intestine that little area over there is known as the cecum and the cecum is really important because it is where we are swapping from absorbing nutrients to absorbing water so there's like a little Gateway in between the two it's also where we find and house this very important little structure at the bottom here which many of us think have no function it's the appendix the appendix does have a function its main function is to create bacteria or should I say to populate bacteria inside of your digestive system because remember you do have interflora which live inside of you and they facilitate and help your digestion so the appendix helps you keep your back bacteria alive and lets them reproduce in an area that can be then transported to the whole of the large intestine so we put it there so as food passes through the cecum we can add bacteria to it now the the large intestine is divided into three major regions we've got the area of the large intestine that is going up and we refer to that as the ascending colon this is the most important like appropriate moment that you can use the word colon so ascending means going up so that means now the food is moving up the side it then moves along and across like this and this top portion is known as the transverse colon and finally food is going to make its way down the side here and this is referred to as very easy to remember the descending colon so we've got the up the cross and the down now the final two areas of our large intestine are broken into two pieces the first bit is this region that's a little bit bulbous over here this is known as the rectum and the rectum is the end of these small intestine and it is where feces waits to be ejested so what it means is it's sort of like a waiting room right like it's there's no water that's being absorbed not necessarily um and it's just sort of waiting for the most opportune moment to be ingested because you can't always go to the bathroom immediately so we need somewhere for food to sit and wait the final structure we need to look at is this very end region over here which is known as the anus now the anus is a muscular ring it is made out of sphincter muscles and you can control some of these sphincter muscles and others you can't and that makes sense because one of them is controlled mostly by your brain and it's an indication that you need to go to the bathroom like you need to have egestion or what we call defecation take place and the other sphincter you are responsible for you control and that's when you decide to go to the bathroom interestingly this is a function that babies can't do they cannot control their sphincter muscle and that's why they wear nappies and that's why over time you actually um gain the ability to do this and this is why eventually you you stop wearing any nappies now as always I'd like to finish off these sections with a quick terminology recap please use these for flashcards because for this kind of section where there's so much terminology you really need to be able to identify and describe these things very quickly so let's do that now quick quick there is Villi which are those um finger-like projections that increase the surface area and they are covered in microvilli and we find these throughout the small intestine we then have the regions of the small intestine which is the duodenum and the duodenum has something called a Crypts of lebakun inside of them and they secrete a hormone called secretin the secretin stimulates the pancreas to create pancreatic juice pancreatic juices alkaline so it neutralizes the acidic kind making it more easier for our enzymes to do their job we then speak about the gallbladder which stores bile please remember it's the liver that makes bile the gall battle just stores it speaking of which bile emulsifies fats remember that because fat doesn't mix into water and then we had all the other substances that were put together to make our alkaline substance remember which was the pancreatic juice the bile and our mucus and that's what makes the suckers intricus which is all of those three substances put together we then had the next two regions of the small intestine which was the Judaism where the majority of absorption takes place the ilium which is the region at the very end that allows substances to slowly pass into the large intestine and we move through something called the ileocecal valve it opens and closes we then spoke about the first region of the small intestine sorry the large intestine which is the cecum and the cecum houses the appendix which repopulates bacteria so that the bacteria can help us digest and finally food is going to move through our large intestine and then finally the undigested food is going to wait in the rectum and once we are ready to egest or defecate the food then moves through the anus now if you like this video make sure to give it a thumbs up and I will see you all again soon bye