hi everybody and welcome back to miss Angler's biology class I am Miss angler in today's video we are going to be looking at the digestive system we're going to start with the mouth to the stomach it's quite a complex system with lots of different processes so we've had to put this into bite-sized chunks for you to understand and so I've made it super simple now there is some videos already out on absorption and I've linked it above now if you want to go and watch that that specifically focuses on how we absorb different nutrients but for now I'm going to do an introduction and an overview of the digestive system starting with the first few organs their functions and the processes that occur there now first things first we need to look at the different processes that happen throughout the digestive system and we're going to start off with the mouth now the mouth is associated with the process of ingestion which is to take food in and it includes the teeth the tongue the saliva all of it mixing together now once food has entered into our digestive system digestion can happen now the main site of digestion is going to take place inside of our stomach but something I need to clarify for you I want you to know that there are two kinds of digestion we've got mechanical digestion and we have got chemical digestion now mechanical digestion takes place inside the mouth and in the stomach chemical digestion however takes place inside the mouth the stomach and it finishes uh off in the duodenum which is the beginning part here of the small intestine that's the last little bit of chemical digestion so there's three places for chemical digestion and two for mechanical now the next process that is associated with the digestive system once the food has moved through the stomach and the intestines is we need to absorb and that takes place in our intestines particularly our small intestines that is where absorption takes place and it's a very specific process every nutrient follows its own pathway into the blood now associated with absorption is going to be the process of what we call assimilation and assimilation means to become a part of and what it means is when nutrients becomes a part of your tissues now a very very separate video will be on that so I'm not going to label it on this picture because you can't see it happening in this picture but the final thing that we can see in this picture has to do with the very end of our digestive system which is egestion and egestion is when your body takes um undigested food and it removes it through defecation or feces and we do this because it's all food that we were unable to digest it's important that you don't confuse this waste with metabolic wastes urine is a metabolic waste whereas when you ingest Solid Waste it's just undigested Foods now grade 11s if any of this is really difficult to understand don't forget that I also have a study guide called the cheat sheet it is available in a grade 11 English and Afrikaans Life Sciences Edition so go and check that out on my website it makes studying so easy I've simplified everything I can put so many notes onto one page easy to study so go and check that out now moving on to the structures that are associated with ingestion which is going to be our teeth now we don't need to know a huge amount of content on teeth um maybe your school or your teacher wants you to know a little bit more that I'm going to say here but I'm going to do the basics and the key parts now in total you have 32 adult teeth and you add an extra four to your total so maybe right now you have 28 but you will eventually have 32 it's because you grow some wisdom teeth now starting off with the types of teeth you have your first four teeth which are these teeth over here are going to be our incisors and they sit at the front of our mouth those are our cutting teeth right they're the ones that we usually bite into things then we have four of these teeth over here two at the top and we also have two at the bottom down here that is going to be our canines and canine teeth are used for tearing particularly things that are pretty fibrous and tough we do have reduced canines and that is because we don't eat a lot of raw meat and we don't use our teeth for fighting so our canines are quite small as humans then moving on to our Monas now you get premolars which are these little teeth over here and we've got two up here so in total we have four at the bottom and four at the top and we call those our pre-molars they're smaller grinding teeth um and we don't use them for as difficult grinding in other words they're not far at the back of the mouth where we have a lot of grinding and biting power there's less biting power but the pre-motors are there to assist us in grinding the main grind teeth are going to be these guys here at the bottom and so they are the molars and the molars common sets as well you have a set at the top of your mouth and a set at the bottom of your mouth and some of you are still growing this very last molar at the back here which is your wisdom teeth and you'll have four wisdoms in total and these molars are for heavy grinding these are the things that you are really chewing with and it's your strongest bite power and you know that because every time you want to bite something that's really tough what do you do you move it to the corner of your mouth and you bite down with your back molars so that you can pull and tug on the thing that you want to chew now it's also important to note what is the purpose of the teeth the teeth has really two important functions one we need to break it down into smaller pieces and that's actually an overall function of our digestive system is we want food to be smaller in smaller pieces because it assists Us in digestion if it's in smaller pieces it's easier to digest another thing about chewing food and making it smaller is it also increases the surface area and so if we ever ask you this in an exam why do we chew we chew because we want to increase the surface area and in doing so it means that the enzymes can work faster now what we're going to do is move into the mouth we're going to move past the teeth I'm going to look at all the accessory structures that are assisting us with chewing and swallowing starting off with the salivary glands now you have three pairs of salivary glands we're going to start off by looking at the biggest one which is this one here located at the back of your mouth underneath your ear and this one is called the parotid gland you have one on the other side of your mouth too but we can only see one here then the second pair of glands sit just under your tongue that one no guess is what it's called is sublingular and it makes sense because like linguistic language speaking you know use your mouth to speak that's the one under your tongue and then the last one we have underneath here which is in your lower jaw is called the submandible and that is because the submandibular is in your mandible in the lower jaw now those all secrete saliva and remember saliva contains an enzyme which assists with digestion gym now we're busy chewing right and we're using our teeth but we need something else to help us move all of our food around so we're going to bring our attention to the other diagram now we're going to pay attention to this big structure here which is your tongue and your tongue is there to like Swish and mix and move your food and eventually form it into what we call a bolus which is a ball of food that we're now going to swallow now speaking of swallowing we need to talk about what happens when the food is moving down your throat now this back area of your throat over here is called the pharynx and the pharynx is where food passes down into the esophagus now there is a little flap that is located here and this little flap prevents any food from going down into your Air passages so while you are breathing it sits open but as soon as you swallow it is going to close and this little bit that closes is called the epiglottis and so what happens is right now as I speak to you my epiglottis is open but the moment I stop and swallow it will flap closed and it's flapping closed into the larynx or the voice box and that's what prevents food from passing into your Airways so now that we've chewed the food we've made it smaller easier to swallow we now need to move down the esophagus now this is the esophagus in front of us and we need to know what the esophagus is made out of so this esophagus here is made out of smooth muscle and smooth muscle remember moves involuntarily it doesn't need to be told to do that and what it's doing is it's moving the bolus of food which is this thing over here that is the bolus which is a ball of digesting food it is moving down the esophagus and it's doing this in a wave-like contraction called peristalsis now peristalsis as I just mentioned is wave-like contractions and you can see the wave because here if we go around the edges of the esophagus you see how it bulges and squeezes around the food that is not just because the bonus is there it is because this top portion over here is Contracting and the lower portion is relaxing which is this bit down here and this whole motion of Contracting and then relaxing is what squeezes the food down and many of you probably know the analogy of like squeezing toothpaste from the bottom of the tube up that's exactly how it is working with your food now it's important to note that in order for this to all also happen your food needs to have moisture in it now it does have some moisture from your saliva and maybe the water content in your food but it's also important to know that lining the esophagus are specialized cells and you may or may not recognize these specialized cells but these are goblet cells and so this is a goblet cell sitting here and a goblet cell secretes mucus and mucus is what keeps our food softened and so it's easier for the bonus to continue traveling down and so that doesn't give caught along the way now we are at our final destination organ for this particular video and that is going to be the stomach now the food has now moved down the esophagus and we are approaching the stomach in order to keep the food or the bonus in the stomach we don't want it to go back up again and so we have a sphincter muscle at the opening of the stomach and this one is called the cardiac sphincter it simply gets its name because it's closer to the heart and it's a ring of muscle that closes and opens to allow food to pass through you have another sphincter muscle lower down in the stomach over here and this opens and closes between the stomach and the small intestine and we call this the pyloric sphincter this makes sure that the food doesn't leave too soon student before digestion has taken place now speaking of digestion let's not forget that the stomach's major role is digestion but it has two types of digestion it has mechanical digestion which is simply the churning and mixing of the stomach and it's the contraction and relaxation of the stomach walls that are doing all the mechanical digestion and then we get the chemical digestion now chemical digestion is where the majority of the nutrients is broken down and accessed and made into their monomers or their building blocks getting them down really really small so that they can be absorbed into the bloodstream now to do this as food or the bolus moves down into the stomach it stimulates the cells lining the stomach now this is a stomach cell now when this cell is stimulated with food like the food is pushing up against it it produces a hormone called gastrin and gastrin then goes on to stimulate the glands lining the walls of the stomach to produce gastric juices now what exactly are gastric juices so there are technically three that fall under this category the first gastric juice that we are going to talk about is going to be hydrochloric acid now hydrochloric acid or HCL is a acid that is used mostly to break down proteins it also is protective in that it kills pathogens that may be on and in your food now the second thing that we find in our gastric juice is going to be enzymes now these particular enzymes are used to a very acidic a pH so again these are mostly protein enzymes that we will find in the stomach and they like in acidic environment and the final substance that is secreted is actually a protective one as well as to Aid and ease digestion it's going to be mucus now mucus is there to make sure that number one the hydrochloric acid doesn't eat a hole through your stomach um and into your organs but two it also adds more moisture to the food so that it starts to become a liquid now once you have added all of these substances together along with the food bolus and it mixed and churned together they produce a substance called Khan and that is what we can see now inside of the stomach is this liquid substance inside the stomach it's now ready to be absorbed in the small intestine now as always I like to finish off my lessons with a terminology recap remember you can use all of these words on flash cards to make studying so much quicker and faster remember the terminology is the most important part of biology when you also want to explain yourself now there are a lot of words in nutrition and so I suggest you go this route of flashcards starting off with our teeth we looked at the incisors the canines the premolars and the molars please also know their functions and how they do their job we then spoke about the salivary glands in the mouth which was the parotid the sublingual and the submandibular now we moved on to the organs that are passing the food from the mouth down to the stomach which is the esophagus remember that contracts and relaxes with peristalsis which is this word over here the waves of contraction and once we get down to the stomach we have the cardiac sphincter which keeps the food in the stomach so it doesn't go back up the esophagus but we also have the pyloric sphincter which keeps the food in the stomach long enough so it can digest so that it doesn't move on to the small intestine too quickly speaking of which we have the muscular bag which can stretch and move which is the stomach we have gastrin which is the hormone stimulated by food once it's inside the stomach so that we produce gastric juice what is gastric juice well it's made out of hydrochloric acid mucus and enzymes and that's food that moved down into our stomach is called a bolus but once you combine the bolus with the gastric juices you produce kind which is like a liquid now also at the beginning of the video we spoke about some of the anatomy in the back of the throat which was the pharynx which is where food passes down into the esophagus in the pharynx is the epiglottis which is that little flap of skin that ensures no food moves into your Airways and last but not least goblet cells they were the ones lining the esophagus secreting mucus and these goblet cells can also be found in the stomach as well because they also secrete mucus there too now if you like this video make sure to give it a thumbs up and make sure you are also subscribed with your notifications turned on because I post every Tuesday and Thursday and I will see you all again soon bye