Digestion, Absorption, and Transport

Chapter three is going to be about what happens with the food once it enters our body which includes food being digested absorbed and then transported now before we get started let&#39;s go ahead and take a look at what digestion and absorption actually mean the digestion is the breaking down of food so anytime you hear me say that this food is broken down this nutrient is broken down it&#39;s the same thing as me saying that it is being digested now we break down food or digest food so that it is small enough to be absorbed into our body so absorption is when your body actually takes in the nutrients so that it can then use them but before we can absorb the nutrients they need to be small enough and that&#39;s the purpose of digestion a few other new terms that I want you to know are what we call the food in different parts of the digestive pathway so before the food actually enters your digestive system before it enters your body at all that&#39;s when we call it food but once it enters your body once it enters your mouth we have other terms for it the first term is bolus bolus is what we call the mixture of food after it enters your mouth now it will continue to be called bolus until it leaves your stomach in your stomach we have digestive acid that we&#39;ll talk a little bit about a little bit more about later on and once the bolus enters the stomach it&#39;s gonna mix with this acid so when it leaves the stomach it will be a mixture of food along with the acid now so we then call it kind so again food is before it enters your mouth when it enters your mouth its bolus after it leads your stomach it&#39;s kind we also have a few new terms for how our food moves along the digestive system and that is using peristalsis and segmentation we have muscles that go in all different types of directions in our digestive system so for example your stomach as muscles that line its walls same thing with your intestines you have muscles along the walls that contract and release to help move things along and depending on the direction that gait muscle is going in is going to determine the outcome so for example we have horizontal circular longitudinal muscles along your stomach and along your intestines and as they contract and release they help to move the food along so as this continues to happen the time or the mixture of food is being moved down your digestive system and as these circular muscles contract on their own basically we are crimping that digestive system the small intestine so that we are squeezing apart the food so that it is broken up into smaller segments so both of these peristalsis and segmentation are a result of the contraction and the release of the muscles of your digestive system but peristalsis is when the contraction and the release moves food along segmentation is when it basically breaks apart the chyme into smaller pieces or smaller segments all right now we&#39;re going to go ahead and go onto the digestive system itself first thing that we want to know are what are the organs that make up the digestive system and that&#39;s what I have for you here so we have a little key that shows you in color coding what each of the items on the diagram are so everything that is in black is going to be a digestive organ so you have the pathway going down the middle mouth to esophagus to stomach to small intestine and then to your large intestine that is your main digestive pathway or the path that food is gonna take once it enters your stomach but then we have other organs that also help help us with digestion even though they&#39;re not necessarily part of the pathway and that includes our liver or gallbladder and the pancreas so now that we have down the different digestive organs we&#39;re gonna go ahead and take a look at some other things that make up our digestive system first thing is going to be our sphincters sphincters i&#39;m going to go ahead and list in blue and basically what a sphincter is is kind of like a little doorway or a little flap that closes and opens to control the movement of food throughout the digestive system so let me show you an example the very first one is between the mouth and the esophagus and we call it the upper esophageal sphincter now the purpose of this Viktor is to prevent food from blackback splashing into your mouth after you&#39;ve already swallowed it the esophagus is the tube that goes down your throat so once the food has entered your mouth you chew and swallow it it has now moved into your esophagus we don&#39;t want it to move back up from the esophagus into your mouth you don&#39;t want that spit up that regurgitation and so what we have in place is that little flap in between the mouth and the esophagus which we call sphincter and what this does is it opens up to allow food to downwards but then once the food passes it closes back up to prevent it from moving backwards into your mouth so that is what sphincters do in general and the upper esophageal sphincter controls the passage between the mouth and the esophagus it&#39;s at the very top of your esophagus the next one we have at the bottom of the esophagus to control the passage of food between the end of the esophagus and the stomach so basically we want food to continue through the esophagus and enter the stomach but once it&#39;s entered the stomach we don&#39;t want it to splash back up into the esophagus and so we want to make sure that we have a sphincter that is going to control that and that is your lower esophageal sphincter now that is especially important for the stomach because the stomach actually has a bunch of acid in it now the stomach has this thick mucous lining around it that makes it so that the acid doesn&#39;t irritate the stomach wall that thick mucous lining protects it but the rest of the digestive system isn&#39;t made to withstand acid it doesn&#39;t have that thick mucous lining so the only part of the digestive system that can really handle acid is the stomach and so we want to make sure that once the food enters the stomach it&#39;s not splashing back up into the esophagus because if it does it&#39;s very likely that some of the acid in the stomach is also splashing back up and that&#39;s what we call acid reflux or heartburn if you&#39;ve ever experienced acid reflux or heartburn it&#39;s that burning feeling that you get sometimes after eating and it is because the acid is splashing from your stomach up into your esophagus and your esophagus can&#39;t handle it because it doesn&#39;t have that protection acid isn&#39;t meant to go there and so that&#39;s why you have that burning sensation it&#39;s from the back splash of acid from your stomach up into your esophagus so if you do have acid reflux or heartburn that would be a sign that your lower esophageal sphincter is malfunctioning because the lower esophageal sphincter is in between the esophagus and stomach and should be controlling that password&#39; passageway sometimes this can be from things like release right foods chocolate those are things that can weaken the sphincter for some people sometimes it happens with age or sometimes it&#39;s just that you&#39;ve eaten so much that your stomach is so full it&#39;s pushing up against the sphincter and forcing things to splash back up so lower esophageal sphincter very important for preventing heartburn the next one we have is between the stomach and the small intestine and this one we call our pyloric sphincter so it is going to prevent food from going back from the small intestine and back into the stomach last one we have is called the ileocecal valve this one is a little bit different because it doesn&#39;t actually have the word sphincter in it but it is considered a sphincter and it controls the passageway between your small and large intestine all right next we&#39;re going to go ahead and look at our red and green which are going to signify the nutrients that are being digested at that specific location as well as the digestive enzymes or digestive juices that are helping that nutrient be digested so basically we&#39;re going to be looking at our carbohydrates or proteins and our lipids those are the three main nutrients that we&#39;re going to discuss the digestion and then absorption of so these different nutrients can begin their digestion in different places and can also complete their digestion in different places and the first example that we see is in the mouth in the mouth the only real nutrient that is being digested there is carbohydrates so anything that you see in green is the nutrient that is being digested in that location what you see in red is the enzyme or the digestive juice that is being used to digest it so carbohydrates begin their digestion in the mouth using salivary amylase salivary amylase is an enzyme that&#39;s released from your salivary glands and it begins the breakdown of carbohydrates now anytime you see the word amylase that is going to refer to carbohydrates amylase is always going to be an enzyme related to carbohydrates so just keep that in mind to make it a little bit easier for you to learn the upcoming ones now nothing else is going to be digested in the mouth so we&#39;re going to go ahead and move on to our next place of digestion which is our stomach and our stomach we have protein digestion so here we have two things happening you&#39;ll notice that even though carbohydrates began their digestion in the mouth I don&#39;t have carbohydrates listed next to the stomach and that&#39;s because there is actually a pause of carbohydrate digestion when we reach the stomach and the reason for that is because the enzyme salivary amylase is not able to function when there is acid in the environment and remember the stomach has a lot of acid so basically when we reach the stomach the acid is going to deactivate or what we call denature the enzyme salivary amylase and carbohydrates are going to have to take a pause they&#39;re not going to be able to be digested so that&#39;s the first thing that&#39;s happening is taking a pause of our carbohydrate digestion the next thing that&#39;s happening in the stomach is now we can begin protein digestion protein wasn&#39;t digested in the mouth it only begins its digestion in the stomach and that is for one main reason which is that proteins need to be denatured before they can be digested now what I mean by denatured the word DNA sure is when a protein basically is uncoiled or loosened up in a sense so that the enzymes can have better contact with it we&#39;re gonna take a closer look at the structure of protein later on but basically protein is this big jumbled up knotted mess and because of that it&#39;s really hard for the enzymes to get into all those little nooks and crannies and break down the protein and so what we want to happen is we want to loosen that protein up we want to uncoil it unknot it and that way it&#39;s more of a linear simple structure and enzymes can reach all the different sides of the protein easily and the way that we do that is primarily by using acid or we can also do it by heat in this situation we don&#39;t have acid until we reach the stomach so that protein that you consumed was in that jumbled up mess that enzymes couldn&#39;t really penetrate up until it reached the stomach once the protein hits the stomach there we have acid that can help uncoil it so that the enzymes can have better access to it and can break it down easily so that&#39;s why we didn&#39;t have any kind of protein digestion until we reached the stomach is because we were waiting for the acid to help us uncoil that protein now the acid that I&#39;m referring to is what you&#39;ll see listed as HCl or hydrochloric acid that is the acid that is in the stomach another one you see listed in red is pet sin&#39; pepsin is an enzyme that is there to digest protein but unless protein is denatured first pepsin can&#39;t break it down so HCl is going to prepare the protein for digestion by naturing it which is uncoiling it and then pepsin can come around and begin the breakdown now moving on to our last place of digestion which is our small intestine you&#39;ll see that for the small intestine we have all of the nutrients listed we have our carbohydrates our protein and our lipids and this is because all of those nutrients can actually be digested in the small intestine and this is actually where the nutrients are going to finalize their digestion so everything is going to be completely digested in the small intestine now we have a few different things that are going to help us with this and here is where the different organs deliver the gallbladder and the pancreas are going to start helping out the first thing that we have is something called vital now bile is something that is both hydrophobic and hydrophilic and what that means is that when something is hydrophobic its afraid of water when something is hydrophilic it wants to attach to water and so when we have something that is part hydrophobic and the other end is hydrophilic it&#39;s basically allowed to associate with both water and other hydrophobic substances now our lipids or fats are always hydrophobic hydrophobic remember means that it&#39;s afraid of water now the problem here is that our digestive enzymes that are ready to break down our lipids are in the digestive juices which are hydrophilic so basically the digestive enzymes for lipids are hydrophilic meaning they&#39;re in this mixture of water but the is hydrophobic meaning it doesn&#39;t want to associate with water and that&#39;s a problem because that means that the enzymes aren&#39;t going to be able to reach the lipids in order to break them down or digest them because the lipids are afraid of water so they&#39;re gonna stay as far away from those enzymes as they can but since bile is both hydrophobic and hydrophilic it&#39;s basically going to act like a peacemaker it&#39;s gonna take hand of the lipids using its hydrophobic end and then it&#39;s gonna take hand of the hydrophilic enzymes using its hydrophilic end and bring them to both together and that is a process that we call emulsification emulsification is when in a hydrophobic and hydrophilic substance are able to come together and that is the role of bile bile performs emulsification on the lipids so that they can mix with the digestive juices so to summarize that we need bile to allow the lipids to make contact with the digestive enzymes so that they can be broken down and the bile is something that is made by the liver and then sent to the gallbladder for storage and once our small intestine senses that there is fat coming into the small intestine it tells the gallbladder hey need some bile sent over and the gallbladder will go ahead and send whatever it has stored into the small intestine so that we can help the lipids make contact with the digestive enzymes so what that tells us is that anytime that the lipids were trying to be digested beforehand they were unable to because they couldn&#39;t make contact with the hydrophilic enzyme we have to wait until they can be emulsified by bile in order for them to make contact with the enzymes and become digested and bile is only available in the small intestine that&#39;s why we didn&#39;t have any lipid digestion any fat digestion beforehand because we had to wait for the bile now that tells us how we are preparing the lipids for being digested but where did those enzymes actually come from to digest our lipids as well as the carbs and the protein that are going to complete their digestion in the small intestine that is where the pancreas comes in so we have first the pancreas releasing what we call pancreatic enzymes and these pancreatic enzymes include enzymes that are specific for digesting carbs another one that&#39;s specific for digesting protein and lastly a specific one for digesting lipids we aren&#39;t going to learn the names of them right now we&#39;ll learn them in the upcoming chapters for now we&#39;re just going to refer to them as pancreatic enzymes now those pancreatic enzymes are going to allow us to finalize the digestion of all of those different nutrients now one other thing that the pancreas is going to do is release something called bicarbonate now bicarbonate is a substance that is on the basic end of the pH scale so it&#39;s a base and the reason that this is important if we look back at the stomach remember we said the stomach has HCl it has that acid and we said that the digestive system is not made to withstand acid with the exception of the stomach now we had the lower esophageal sphincter there to prevent the it from going up into the esophagus but we don&#39;t have anything protecting the small intestine from the acid that&#39;s gonna come down from the stomach into the small intestine we have the pyloric sphincter with the pyloric sphincter opens to allow things to move downwards so that the food can continue and that food is going to be mixed with acid and so either way no matter what the acid is going to enter the small intestine even though the small intestine does not have a thick mucous lining to protect it against the acid so what we have instead is the pancreas making this substance called bicarbonate that is on the complete opposite end of the spectrum when it comes to the pH scale it&#39;s very basic it&#39;s a base so when it is combined with an acid it is going to neutralize it so we have HCl the acid coming in to from the stomach into the small intestine but because we already have bicarbonate being released into the small intestine the small intestine is not going to get burned by the acid so the bicarbonate is first released into a small intestine which makes the pH of the small intestine basic and that way when the HCL is making its way into the small intestine along with the food it is going to automatically be neutralized by the bicarbonate before it gets a chance to cause any damage to a small intestine so bicarbonates main role is to neutralize the acid in these that is going to be entering the small intestine to prevent any damage from the acids before we will digestion I just want to touch on the new terms that we learned in the diagram that we drew up we mentioned denaturation and emulsification I know these can be a little bit difficult to grasp so I want to just go over them one more time and then after you get a better understanding of denaturation and emulsification maybe you can go back to the previous slide and get a better grasp of what we were discussing so starting off with denaturation we said that denaturation happens in our stomach and it is what is required for our proteins to be able to be digested so again we said that proteins need to be denatured before they can be digested denaturation is when the protein is deactivated and as a result of that it untangles this is important because normally the protein is in this tangled mess like you see over here and when it&#39;s in this shape the enzymes can&#39;t get into all of those folds and bends and because of this they can&#39;t access all parts of the protein to break it down so in order for the enzymes to successfully break down the protein a protein it needs to be more accessible so we need to untangle it like the structure that we see at the bottom so that the enzyme can access all parts of that protein and break it down now remember that proteins can&#39;t be denatured until we reach the stomach and the reason for this is because we need either heat or acid for denaturation to occur up until the stomach we didn&#39;t have that the stomach contains hydrochloric acid HCL and because of that we can go ahead and denature the protein using the acid in the stomach and that allows the protein to become untangled and accessible for the enzymes so again just to recap the reason that we weren&#39;t able to begin digestion until we reach the stomach is because up until now we didn&#39;t have acid to denature it and until it&#39;s denatured the enzymes not gonna have full access to it and they&#39;re not going to be able to break it down the other new term that we mentioned was emulsification we said our facts needed to go through the mullah fication before they could be digested and we said that the bile would allow us to emulsify our facts in our small intestine and so that&#39;s where our digestion would begin remember emulsification is when we allow a hydrophobic and hydrophilic substance to mix now just to recap on what we learned we learned that bile allows allows us to emulsify our fats so it allows hydrophobic and hydrophilic substances to mix and the reason it can perform that emulsification is because it has a hydrophilic end and a hydrophobic end so since it has both it can kind of act like a peacemaker and bring the two together now remember we said hydrophobic means afraid of water it doesn&#39;t want to mix with water or any fluids hydrophilic means it likes water it wants to mix with water and other fluids we also said that fats are usually hydrophobic and that&#39;s why if you were to ever drop some oil into a cup of water that oil would just stay there on top and it wouldn&#39;t mix with the water and the reason for this again is because oil is a type of fat and fats are hydrophobic they do not want to mix with water which is why oil and water will always remain separate they will just sit on top of each other and not mix and join together now the same kind of concept happens in the body with the fact that we want to digest it from our diet so let&#39;s go ahead and apply this to the fact that we&#39;re trying to digest so instead of this being a drop of oil let&#39;s go ahead and say that this is the hydrophobic fact that we just got got from the food that we ate and we want to digest and instead of this being a cup of water let&#39;s say that this is our digestive fluid digestive fluid is basically what carries enzymes to different parts of the body wherever the enzymes are needed so this digestive fluid will be carrying some enzymes so let&#39;s go ahead and drop some enzymes in here as well since the enzymes are in the fluid that would have to mean that they are hydrophilic because remember hydrophilic are fine mixing with water or other fluids hydrophobic would refuse to mix so since the enzymes are in the fluid that would mean that they are hydrophilic now this is actually how things look in our body we have the fat that is trying to be digested just kind of sitting there separate from the digestive fluid refusing to mix in there but we need this fat to come down here into the fluid because that&#39;s where the enzymes are the enzymes are hydrophilic so they are in the fluid but the fat is hydrophobic so it doesn&#39;t want to enter the fluid so we have a situation here where the fact is not able to make contact with the enzymes and because of that it can&#39;t be digested so we need to find a way to make this fact enter into this fluid so that the enzymes can make contact with it and start digesting it or breaking it down and this is where bile is going to come in remember we said bile can allow hydrophobic substances to mix with hydrophilic and it&#39;s able to do this because it has both hydrophilic and hydrophobic ends so what&#39;s gonna happen is the bile is actually going to latch onto fat using its hydrophobic end it will not be able to attach to fat with its hydrophilic end because the fat would just run away from something that&#39;s hydrophilic it wants nothing to do with things that are hydrophilic but since this tail over here is hydrophobic the fat doesn&#39;t my mind attached into it since they&#39;re both the same they&#39;re both hydrophobic so they&#39;re fine attaching to each other and that&#39;s what we see happening here so now we have our bile that has latched onto the fat with the hydrophobic end and when we attach to bile with our hydrophobic end the end that is left hanging down will be be hydrophilic that&#39;s what we see here we have the hydrophilic part of bile hanging down now what&#39;s actually going to happen is the bile is going to continue surrounding the fat we&#39;re gonna have more bile come in and completely surround the fat until the fact is completely covered with bile or a structure like you see over here so again we have fat on the inside and we have all of these parts of bile that are latching on to the fat again they will latch on with the hydrophobic end and that leaves the hydrophilic end on the outside when fat is completely surrounded by bile like this what we have is a fact that actually has a hydrophilic outer layer remember these blue ends are hydrophilic so now the fat is completely surrounded with an outer layer that is actually hydrophilic and when it&#39;s in this state it can actually mix with the hydrophilic fluid because it now has a hydrophilic outer layer so it&#39;s not afraid to enter into a hydrophilic area anymore so again this structure that we see over here where the fat has been completely surrounded with file and now has a hydrophilic outer layer this is what we call emulsified fats so the fat has now been emulsified by bile which means it has this hydrophilic outer layer that makes the fat to feel safe and drink into the hydrophilic fluid now that it can enter the hydrophilic fluid it&#39;s going to be able to make contact with these enzymes and begin its digestion so just to recap the fats cannot become digested until it has become emulsified emulsified fats would look like this meaning that it now has a hydrophilic layer the bile that is required for this emulsification to occur is not found until we reach the small intestine and because of this the fact was not able to begin its digestion until we reach the small intestine because again fat cannot digest until it has been emulsified because emulsification is what allows it to make contact with the enzymes bile is not available to emulsify our fat until we reach the small intestine so we have to wait until the small intestine where bile is available in order to emulsify our fat like this and allow it to enter into this fluid and make contact with the enzymes and beginnings digestion now here we have a little summary slide of basically everything that we just talked about so here it lists the different organs or glands what they release and basically what those different secretions do in terms of either emulsifying fact breaking down nutrients neutralizing acid it is all listed here for you so if you missed something you didn&#39;t get to jot down something from the previous slide you can always look at this as a good review slide another thing that we want to know is how does the body know when to release these digestive enzymes and digestive juices usually this is through the use of hormones hormones are the directors of our body their role is to tell our body what to do now there is an exception which is the salivary amylase that is released in your mouth to begin carbohydrate digestion it&#39;s not listed on this slide because it is not regulated by hormones once your mouth recognizes the presence of food it automatically starts stimulating salivary amylase so that&#39;s something that&#39;s not controlled by hormones it&#39;s controlled by the presence of food the rest of them are controlled by hormones starting off with gastrin gastrin is what tells your stomach to release hydrochloric acid or the HCL secretin is another hormone and secretin tells your pancreas to release bicarbonate anytime it senses that something is coming from the stomach we have acid that&#39;s about to hit the small intestine secretin is released and tells your body to hurry up and send bicarbonate from the pancreas to the small intestine to make sure that we can utilize that acid lastly we have cholecystokinin or what we call C CK C CK is what tells your gallbladder to go ahead and release bile into the small intestine so it is going to be what recognizes that fat is on its way into the small intestine we need to make sure we have bile or the fat to be emulsified and so once we sense that fat is on its way cholecystokinin or C CK will tell the gallbladder to release bile it also lets the pancreas know that it&#39;s time to start sending those digestive enzymes into the small intestine as well another new have been digested we can go ahead and absorb them remember the reason we digest is so that nutrients are small enough to be absorbed we completed our nutrient digestion in our small intestine so that means the small intestine is the first organ that is going to have access to absorbable nutrients because again that&#39;s the first place where the nutrients have completed their digestion so the nutrients are finally small enough to be absorbed now that being said the small intestine is the first organ that absorbs the nutrients but it&#39;s actually where the majority of nutrient absorption occurs altogether and the reason for this is because the small intestine is actually very long it can be about 20 feet long but the reason it&#39;s able to fit inside of us is because it&#39;s really compacted so if you can think of for example slinky a slinky doesn&#39;t take up much space but if you were to stretch it out it&#39;s actually very long and it has a lot of surface area your small intestine is the same way so when the digestible nutrients are in your small intestine there is a lot of surface area that those nutrients can get absorbed into so because of this again the small intestine is the first place where our nutrients get absorbed but it&#39;s also where the majority of nutrients are going to be completing their absorption as well now another thing that I want to mention is that the nutrients are going to be absorbed into these cells that line the intestinal wall so our small intestine has cells all along its walls and that&#39;s actually where our nutrients are being stored they&#39;re entering into those cells and are being stored in there and waiting to be picked up and delivered tor ever they are needed in the body so this here is showing us an illustration of what&#39;s going on in the small intestine so we have a picture here for us that shows us the actual small intestine and here we&#39;re zooming in and seeing that the folds of the slow intestine actually have these hair like structures on them these hair like structures are what we call villi and they add a little bit more surface area and they also help us to latch on to our nutrients but if we were to zoom in even further we would see that there&#39;s even more things on top of the villi themselves so I&#39;ve gone ahead and drawn up this picture here for you kind of like a little cross-section of our small intestine and we&#39;re gonna look at the other components that aren&#39;t shown in this picture so here we have the walls of the small intestine and along the walls of the small intestine we actually have cells so these circles that you see along the walls these are all cells and that&#39;s actually where the nutrients are going to be absorbed when we say that the majority of nutrient absorption happens in the small intestine where they&#39;re actually being absorbed are into these cells on the walls of the small intestine so those nutrients are all hanging around in the walls of the small intestine in those cells that are lining the walls now to take a look at some of the other components that weren&#39;t shown in the first picture the first picture showed us the hair like structures which were the villi we&#39;ve drawn them here in red but if you were to look in a little closer you would see that on top of the villi we actually have even more hair like structures ones that are smaller that we call micro villi so the micro villi will serve the same purpose a little more surface area and helpless latch onto our nutrients but they also have enzymes on top of them the enzymes on top of our micro villi are gonna help us complete our digestion in particular they will help us complete carbohydrate digestion but we don&#39;t need to know the names of them now learn a little bit more about those in the carbohydrates chapter so once we get there we will reference these again but what I want you to know for the absorption is that the nutrients are going to be absorbed into the cells of the small intestine these cells are lining the walls of the intestine so technically the nutrients are being absorbed into the walls into the cells that are on the walls of the small intestine the other components I want you to know is that along the walls of the small intestine we have hair like structures called villi and smaller hair like structures called micro villi on top of them both of them give us a little more surface area and help us latch on to our nutrients and on top of the micro villi we have enzymes that will help us complete digestion so that is the gist of the small intestine components that I want you to be aware of or absorption one other thing that I want to point out is here we have an arrow pointing to this cell over here this is supposed to show us that each one of these cells that is on the wall of the intestine actually has a barrier around it or what we call a cell membrane and so even though we said the nutrients are being absorbed into these cells those nutrients need to first find a way to pass the cell membrane in order to enter into the cell and actually be absorbed into the cell itself so again we have a bunch of cells on the wall of the small intestine if we zoom in we&#39;ll see that each of these cells has a cell membrane surrounding it our nutrients need to find a way to pass the cell membrane in order to be absorbed and stored into the cells and that&#39;s what this picture is showing us here it&#39;s showing us the different methods that we can take to allow nutrients to pass the cell membrane so that nutrients can actually absorb into the cells of the small intestine so the method that we choose is going to depend on the size and the complexity of the nutrient so starting off on the far left side you&#39;re gonna have the easiest and most simple way for nutrients to pass which is basically slipping right on through the cell membrane this is going to be primarily your really tiny nutrients and very simple nutrients like water now going on to the nutrients that might be a little bit bigger or more complex they&#39;re actually going to need a helper a carrier to help move them through the membrane and then spit them out inside of the cell now since they need a helper we&#39;re gonna call this facilitated diffusion the word facilitate means to help so we&#39;re using a helper or a carrier to help move us along so we&#39;re going to call it facilitated diffusion now some other nutrients are going to need even more help meaning they don&#39;t just need a carrier to help move them through they also need additional energy to move this carrier along and this is when we call it active transport active is referring to the to the point that there is energy required in this transport it is the only one of the three that requires energy now that digestion and absorption are done our next step is going to be transport so first we break down the nutrients so that they&#39;re small enough to be absorbed then they&#39;re absorbed into the cells of the small intestine and they&#39;re basically gonna hang around in those cells of the small intestine until the body picks them up and transport them to our ever they need to go and we have two main systems that we can use for this transport and that is our vascular system and then our lymphatic system and before we take a look at these two different systems I just want you all to know the differences between them the main difference is what each one is responsible for transporting the vascular system is going to be what transports are water soluble nutrients and some small fats but the main one that&#39;s going to be responsible for fat transport is going to be the lymphatic system it&#39;s going to take our fat soluble nutrients and our large fats there&#39;s also a difference in what they are composed up which is blood or our red blood cells for our vascular system so the vascular system is your bloodstream and the lymphatic system is made of a substance called the limb which is primarily composed of white blood cells another difference is the way that they are handled by the liver the vascular system any nutrients that pass through the system are going to be detoxified by the liver from their very first round around the body the nutrients that go through the lymphatic system are actually going to bypass the liver on the first round now this will make a little bit more sense in a minute when we go ahead and look at the diagram so let&#39;s go ahead and look at that now we&#39;re gonna go ahead and take a look at the different transport systems starting with the vascular system the vascular system is your blood stream and remember blood can be pumped to all different parts of your body but for the purpose of this class we&#39;re just gonna focus on how the blood picks up nutrients from your small intestine and then transports it elsewhere so for that we&#39;re just going to focus on these few organs that I have listed for you here now before we get into all of the different steps I want to mention a few tips that can help you memorize all of the different arteries and veins that make up this system and the first thing is to remember that the blood will usually lead your heart through arteries and then enter your heart through veins so if something is leaving your heart it will usually lead in an artery if it&#39;s entering your heart it will usually be entering as a vein another thing to remember is any time you hear the word hip addict it&#39;s referring to your liver any time you hear the word pulmonary it&#39;s referring to your lungs so now that we have those tips down let&#39;s go ahead and take a look at the different steps of the vascular system and how we could put these tips to use so the very first thing that we have is the heart and the heart is the pump of the vascular system it&#39;s what&#39;s going to help move the light along so we&#39;re gonna start off pumping blood from the right side into your lungs here we are going to be picking up oxygen and dropping off carbon dioxide now if we want to know what to name this arrow here first thing we know is that it is going to your lungs remember anything related to the lungs is called pulmonary so we already know pulmonary should be part of the name the next thing that we know is that it is leaving the heart we know when something leaves the heart it leaves in an artery so now we have two words down pulmonary and artery and that&#39;s exactly what this is called this is our pulmonary artery because it&#39;s going to the lungs and it&#39;s can even be parts so this is going to be how you&#39;re going to be able to use those tips to help you memorize things now after we&#39;ve picked up oxygen in the lungs we can go ahead and send that oxygenated blood back into the heart and this one is still again related to the lungs since it&#39;s leaving the lungs so it will also be pulmonary but since it&#39;s entering your heart remember blood enters the heart through veins so this will be pulmonary vein now after that the we can go ahead and pump that oxygenated blood back out and blood leads your heart primarily through one really large artery called the aorta so this one has its own special name and the aorta can send blood straight to the liver or it can branch off and send blood to the intestines instead now if it were to go straight to the liver it&#39;s going to be detoxified there that&#39;s what the livers role is the livers role is to detoxify anything that comes its way so the blood is going to go through the liver to make sure there&#39;s nothing toxic and then the liver can go ahead and pump that blood back to the heart now since this relates to the liver we&#39;re going to call it hepatic and since it is entering the heart it will be a vein so our hepatic Vinni now if the aorta instead sent the blood to the small intestine what&#39;s gonna happen is we&#39;re gonna pick up all of those nutrients that we absorbed so if you remember we had a bunch of nutrients that were absorbed into the cells of the small intestine and now they&#39;re just hanging around in those cells waiting to be picked up so when the blood goes from the aorta to the small intestine it&#39;s gonna pick up all those nutrients that were sitting in the cells of the small intestine and send them to the liver now this is something that relates to the liver so you&#39;ll see we called it hepatic again since it&#39;s going to the liver it&#39;s also on its way to enter the heart and remember things that enter the heart are called vein but in order to differentiate it from the one that&#39;s going directly into the heart we put the word portal in there so this is called our high product portal vein now that we&#39;ve covered the vascular system let&#39;s go ahead and take a look at the lymphatic system the lymphatic system isn&#39;t its own system really it&#39;s more so an added step onto the vascular system remember the vascular system is our blood stream and the lymphatic system was there to take nutrients that the blood stream couldn&#39;t take on initially on its own so things like our larger facts and the fat soluble nutrients needed to go through the lymphatic system instead and the reason for this is remember the facts are gonna be hydrophobic meaning they don&#39;t want to mix with a fluid technically your blood is a fluid so the facts don&#39;t necessarily feel comfortable mixing in their entering straight into your bloodstream so what they&#39;re gonna want to do is basically create that outer layer the hydrophilic outer layer around them like we saw earlier with bile because that will allow them to feel safe entering into the bloodstream so again for those larger facts we want to surround them with a hydrophilic layer repackage them that way so that they can enter the bloodstream now the problem is that if those bats are already large and then we add a hydrophilic layer around them sometimes they can be too large to enter straight into the bloodstream the entry way from the small intestine into the bloodstream is more narrow than that and so the lymphatic system is there to allow the facts to enter in a different place where the entryway is not as narrow and those larger facts can enter into the bloodstream there where we have a less narrow entryway so that&#39;s the gist of the lymphatic system so let&#39;s go ahead and take a look at how that would work so for the nutrients that couldn&#39;t be picked up by the bloodstream directly instead they&#39;re gonna filter into what we call the lymph and through there they have access to the subclavian vein which is actually a vein that empties out into the hepatic vein so it opens up to the hepatic vein which is actually a larger entry way for those larger fats so the larger facts actually get a chance enter and become part of the vascular system when they enter at the hepatic vein because that is a larger entryway so if they couldn&#39;t fit before straight from the small intestine they can enter into the lymph into the subclavian vein and then the subclavian vein will empty into the hepatic vein which is a larger entryway that can allow the larger facts to become part of the blood stream so as you can see the lymphatic system isn&#39;t its own system it&#39;s just this added step that we have to add on to allow the larger facts to make way to an entry point where they can actually fit and enter into the bloodstream after that they become part of the vascular system just like the other nutrients and they will continue going around the body now remember the lymphatic system we said the nutrients will bypass the liver on the first round you can see why that is the nutrients that enter through the lymphatic system are entering into the hepatic vein the hepatic vein has already left the liver so they basically missed their chance to come by the liver on their first time around just because they enter too late but again they&#39;re part of the vascular system now so they will get a chance to come around again and at that point they will be able to come by the liver and be detoxified

Chapter three is going to be about what happens with the food once it enters our body which includes food being digested absorbed and then transported now before we get started let&amp;#39;s go ahead and take a look at what digestion and absorption actually mean the digestion is the breaking down of food so anytime you hear me say that this food is broken down this nutrient is broken down it&amp;#39;s the same thing as me saying that it is being digested now we break down food or digest food so that it is small enough to be absorbed into our body so absorption is when your body actually takes in the nutrients so that it can then use them but before we can absorb the nutrients they need to be small enough and that&amp;#39;s the purpose of digestion a few other new terms that I want you to know are what we call the food in different parts of the digestive pathway so before the food actually enters your digestive system before it enters your body at all that&amp;#39;s when we call it food but once it enters your body once it enters your mouth we have other terms for it the first term is bolus bolus is what we call the mixture of food after it enters your mouth now it will continue to be called bolus until it leaves your stomach in your stomach we have digestive acid that we&amp;#39;ll talk a little bit about a little bit more about later on and once the bolus enters the stomach it&amp;#39;s gonna mix with this acid so when it leaves the stomach it will be a mixture of food along with the acid now so we then call it kind so again food is before it enters your mouth when it enters your mouth its bolus after it leads your stomach it&amp;#39;s kind we also have a few new terms for how our food moves along the digestive system and that is using peristalsis and segmentation we have muscles that go in all different types of directions in our digestive system so for example your stomach as muscles that line its walls same thing with your intestines you have muscles along the walls that contract and release to help move things along and depending on the direction that gait muscle is going in is going to determine the outcome so for example we have horizontal circular longitudinal muscles along your stomach and along your intestines and as they contract and release they help to move the food along so as this continues to happen the time or the mixture of food is being moved down your digestive system and as these circular muscles contract on their own basically we are crimping that digestive system the small intestine so that we are squeezing apart the food so that it is broken up into smaller segments so both of these peristalsis and segmentation are a result of the contraction and the release of the muscles of your digestive system but peristalsis is when the contraction and the release moves food along segmentation is when it basically breaks apart the chyme into smaller pieces or smaller segments all right now we&amp;#39;re going to go ahead and go onto the digestive system itself first thing that we want to know are what are the organs that make up the digestive system and that&amp;#39;s what I have for you here so we have a little key that shows you in color coding what each of the items on the diagram are so everything that is in black is going to be a digestive organ so you have the pathway going down the middle mouth to esophagus to stomach to small intestine and then to your large intestine that is your main digestive pathway or the path that food is gonna take once it enters your stomach but then we have other organs that also help help us with digestion even though they&amp;#39;re not necessarily part of the pathway and that includes our liver or gallbladder and the pancreas so now that we have down the different digestive organs we&amp;#39;re gonna go ahead and take a look at some other things that make up our digestive system first thing is going to be our sphincters sphincters i&amp;#39;m going to go ahead and list in blue and basically what a sphincter is is kind of like a little doorway or a little flap that closes and opens to control the movement of food throughout the digestive system so let me show you an example the very first one is between the mouth and the esophagus and we call it the upper esophageal sphincter now the purpose of this Viktor is to prevent food from blackback splashing into your mouth after you&amp;#39;ve already swallowed it the esophagus is the tube that goes down your throat so once the food has entered your mouth you chew and swallow it it has now moved into your esophagus we don&amp;#39;t want it to move back up from the esophagus into your mouth you don&amp;#39;t want that spit up that regurgitation and so what we have in place is that little flap in between the mouth and the esophagus which we call sphincter and what this does is it opens up to allow food to downwards but then once the food passes it closes back up to prevent it from moving backwards into your mouth so that is what sphincters do in general and the upper esophageal sphincter controls the passage between the mouth and the esophagus it&amp;#39;s at the very top of your esophagus the next one we have at the bottom of the esophagus to control the passage of food between the end of the esophagus and the stomach so basically we want food to continue through the esophagus and enter the stomach but once it&amp;#39;s entered the stomach we don&amp;#39;t want it to splash back up into the esophagus and so we want to make sure that we have a sphincter that is going to control that and that is your lower esophageal sphincter now that is especially important for the stomach because the stomach actually has a bunch of acid in it now the stomach has this thick mucous lining around it that makes it so that the acid doesn&amp;#39;t irritate the stomach wall that thick mucous lining protects it but the rest of the digestive system isn&amp;#39;t made to withstand acid it doesn&amp;#39;t have that thick mucous lining so the only part of the digestive system that can really handle acid is the stomach and so we want to make sure that once the food enters the stomach it&amp;#39;s not splashing back up into the esophagus because if it does it&amp;#39;s very likely that some of the acid in the stomach is also splashing back up and that&amp;#39;s what we call acid reflux or heartburn if you&amp;#39;ve ever experienced acid reflux or heartburn it&amp;#39;s that burning feeling that you get sometimes after eating and it is because the acid is splashing from your stomach up into your esophagus and your esophagus can&amp;#39;t handle it because it doesn&amp;#39;t have that protection acid isn&amp;#39;t meant to go there and so that&amp;#39;s why you have that burning sensation it&amp;#39;s from the back splash of acid from your stomach up into your esophagus so if you do have acid reflux or heartburn that would be a sign that your lower esophageal sphincter is malfunctioning because the lower esophageal sphincter is in between the esophagus and stomach and should be controlling that password&amp;#39; passageway sometimes this can be from things like release right foods chocolate those are things that can weaken the sphincter for some people sometimes it happens with age or sometimes it&amp;#39;s just that you&amp;#39;ve eaten so much that your stomach is so full it&amp;#39;s pushing up against the sphincter and forcing things to splash back up so lower esophageal sphincter very important for preventing heartburn the next one we have is between the stomach and the small intestine and this one we call our pyloric sphincter so it is going to prevent food from going back from the small intestine and back into the stomach last one we have is called the ileocecal valve this one is a little bit different because it doesn&amp;#39;t actually have the word sphincter in it but it is considered a sphincter and it controls the passageway between your small and large intestine all right next we&amp;#39;re going to go ahead and look at our red and green which are going to signify the nutrients that are being digested at that specific location as well as the digestive enzymes or digestive juices that are helping that nutrient be digested so basically we&amp;#39;re going to be looking at our carbohydrates or proteins and our lipids those are the three main nutrients that we&amp;#39;re going to discuss the digestion and then absorption of so these different nutrients can begin their digestion in different places and can also complete their digestion in different places and the first example that we see is in the mouth in the mouth the only real nutrient that is being digested there is carbohydrates so anything that you see in green is the nutrient that is being digested in that location what you see in red is the enzyme or the digestive juice that is being used to digest it so carbohydrates begin their digestion in the mouth using salivary amylase salivary amylase is an enzyme that&amp;#39;s released from your salivary glands and it begins the breakdown of carbohydrates now anytime you see the word amylase that is going to refer to carbohydrates amylase is always going to be an enzyme related to carbohydrates so just keep that in mind to make it a little bit easier for you to learn the upcoming ones now nothing else is going to be digested in the mouth so we&amp;#39;re going to go ahead and move on to our next place of digestion which is our stomach and our stomach we have protein digestion so here we have two things happening you&amp;#39;ll notice that even though carbohydrates began their digestion in the mouth I don&amp;#39;t have carbohydrates listed next to the stomach and that&amp;#39;s because there is actually a pause of carbohydrate digestion when we reach the stomach and the reason for that is because the enzyme salivary amylase is not able to function when there is acid in the environment and remember the stomach has a lot of acid so basically when we reach the stomach the acid is going to deactivate or what we call denature the enzyme salivary amylase and carbohydrates are going to have to take a pause they&amp;#39;re not going to be able to be digested so that&amp;#39;s the first thing that&amp;#39;s happening is taking a pause of our carbohydrate digestion the next thing that&amp;#39;s happening in the stomach is now we can begin protein digestion protein wasn&amp;#39;t digested in the mouth it only begins its digestion in the stomach and that is for one main reason which is that proteins need to be denatured before they can be digested now what I mean by denatured the word DNA sure is when a protein basically is uncoiled or loosened up in a sense so that the enzymes can have better contact with it we&amp;#39;re gonna take a closer look at the structure of protein later on but basically protein is this big jumbled up knotted mess and because of that it&amp;#39;s really hard for the enzymes to get into all those little nooks and crannies and break down the protein and so what we want to happen is we want to loosen that protein up we want to uncoil it unknot it and that way it&amp;#39;s more of a linear simple structure and enzymes can reach all the different sides of the protein easily and the way that we do that is primarily by using acid or we can also do it by heat in this situation we don&amp;#39;t have acid until we reach the stomach so that protein that you consumed was in that jumbled up mess that enzymes couldn&amp;#39;t really penetrate up until it reached the stomach once the protein hits the stomach there we have acid that can help uncoil it so that the enzymes can have better access to it and can break it down easily so that&amp;#39;s why we didn&amp;#39;t have any kind of protein digestion until we reached the stomach is because we were waiting for the acid to help us uncoil that protein now the acid that I&amp;#39;m referring to is what you&amp;#39;ll see listed as HCl or hydrochloric acid that is the acid that is in the stomach another one you see listed in red is pet sin&amp;#39; pepsin is an enzyme that is there to digest protein but unless protein is denatured first pepsin can&amp;#39;t break it down so HCl is going to prepare the protein for digestion by naturing it which is uncoiling it and then pepsin can come around and begin the breakdown now moving on to our last place of digestion which is our small intestine you&amp;#39;ll see that for the small intestine we have all of the nutrients listed we have our carbohydrates our protein and our lipids and this is because all of those nutrients can actually be digested in the small intestine and this is actually where the nutrients are going to finalize their digestion so everything is going to be completely digested in the small intestine now we have a few different things that are going to help us with this and here is where the different organs deliver the gallbladder and the pancreas are going to start helping out the first thing that we have is something called vital now bile is something that is both hydrophobic and hydrophilic and what that means is that when something is hydrophobic its afraid of water when something is hydrophilic it wants to attach to water and so when we have something that is part hydrophobic and the other end is hydrophilic it&amp;#39;s basically allowed to associate with both water and other hydrophobic substances now our lipids or fats are always hydrophobic hydrophobic remember means that it&amp;#39;s afraid of water now the problem here is that our digestive enzymes that are ready to break down our lipids are in the digestive juices which are hydrophilic so basically the digestive enzymes for lipids are hydrophilic meaning they&amp;#39;re in this mixture of water but the is hydrophobic meaning it doesn&amp;#39;t want to associate with water and that&amp;#39;s a problem because that means that the enzymes aren&amp;#39;t going to be able to reach the lipids in order to break them down or digest them because the lipids are afraid of water so they&amp;#39;re gonna stay as far away from those enzymes as they can but since bile is both hydrophobic and hydrophilic it&amp;#39;s basically going to act like a peacemaker it&amp;#39;s gonna take hand of the lipids using its hydrophobic end and then it&amp;#39;s gonna take hand of the hydrophilic enzymes using its hydrophilic end and bring them to both together and that is a process that we call emulsification emulsification is when in a hydrophobic and hydrophilic substance are able to come together and that is the role of bile bile performs emulsification on the lipids so that they can mix with the digestive juices so to summarize that we need bile to allow the lipids to make contact with the digestive enzymes so that they can be broken down and the bile is something that is made by the liver and then sent to the gallbladder for storage and once our small intestine senses that there is fat coming into the small intestine it tells the gallbladder hey need some bile sent over and the gallbladder will go ahead and send whatever it has stored into the small intestine so that we can help the lipids make contact with the digestive enzymes so what that tells us is that anytime that the lipids were trying to be digested beforehand they were unable to because they couldn&amp;#39;t make contact with the hydrophilic enzyme we have to wait until they can be emulsified by bile in order for them to make contact with the enzymes and become digested and bile is only available in the small intestine that&amp;#39;s why we didn&amp;#39;t have any lipid digestion any fat digestion beforehand because we had to wait for the bile now that tells us how we are preparing the lipids for being digested but where did those enzymes actually come from to digest our lipids as well as the carbs and the protein that are going to complete their digestion in the small intestine that is where the pancreas comes in so we have first the pancreas releasing what we call pancreatic enzymes and these pancreatic enzymes include enzymes that are specific for digesting carbs another one that&amp;#39;s specific for digesting protein and lastly a specific one for digesting lipids we aren&amp;#39;t going to learn the names of them right now we&amp;#39;ll learn them in the upcoming chapters for now we&amp;#39;re just going to refer to them as pancreatic enzymes now those pancreatic enzymes are going to allow us to finalize the digestion of all of those different nutrients now one other thing that the pancreas is going to do is release something called bicarbonate now bicarbonate is a substance that is on the basic end of the pH scale so it&amp;#39;s a base and the reason that this is important if we look back at the stomach remember we said the stomach has HCl it has that acid and we said that the digestive system is not made to withstand acid with the exception of the stomach now we had the lower esophageal sphincter there to prevent the it from going up into the esophagus but we don&amp;#39;t have anything protecting the small intestine from the acid that&amp;#39;s gonna come down from the stomach into the small intestine we have the pyloric sphincter with the pyloric sphincter opens to allow things to move downwards so that the food can continue and that food is going to be mixed with acid and so either way no matter what the acid is going to enter the small intestine even though the small intestine does not have a thick mucous lining to protect it against the acid so what we have instead is the pancreas making this substance called bicarbonate that is on the complete opposite end of the spectrum when it comes to the pH scale it&amp;#39;s very basic it&amp;#39;s a base so when it is combined with an acid it is going to neutralize it so we have HCl the acid coming in to from the stomach into the small intestine but because we already have bicarbonate being released into the small intestine the small intestine is not going to get burned by the acid so the bicarbonate is first released into a small intestine which makes the pH of the small intestine basic and that way when the HCL is making its way into the small intestine along with the food it is going to automatically be neutralized by the bicarbonate before it gets a chance to cause any damage to a small intestine so bicarbonates main role is to neutralize the acid in these that is going to be entering the small intestine to prevent any damage from the acids before we will digestion I just want to touch on the new terms that we learned in the diagram that we drew up we mentioned denaturation and emulsification I know these can be a little bit difficult to grasp so I want to just go over them one more time and then after you get a better understanding of denaturation and emulsification maybe you can go back to the previous slide and get a better grasp of what we were discussing so starting off with denaturation we said that denaturation happens in our stomach and it is what is required for our proteins to be able to be digested so again we said that proteins need to be denatured before they can be digested denaturation is when the protein is deactivated and as a result of that it untangles this is important because normally the protein is in this tangled mess like you see over here and when it&amp;#39;s in this shape the enzymes can&amp;#39;t get into all of those folds and bends and because of this they can&amp;#39;t access all parts of the protein to break it down so in order for the enzymes to successfully break down the protein a protein it needs to be more accessible so we need to untangle it like the structure that we see at the bottom so that the enzyme can access all parts of that protein and break it down now remember that proteins can&amp;#39;t be denatured until we reach the stomach and the reason for this is because we need either heat or acid for denaturation to occur up until the stomach we didn&amp;#39;t have that the stomach contains hydrochloric acid HCL and because of that we can go ahead and denature the protein using the acid in the stomach and that allows the protein to become untangled and accessible for the enzymes so again just to recap the reason that we weren&amp;#39;t able to begin digestion until we reach the stomach is because up until now we didn&amp;#39;t have acid to denature it and until it&amp;#39;s denatured the enzymes not gonna have full access to it and they&amp;#39;re not going to be able to break it down the other new term that we mentioned was emulsification we said our facts needed to go through the mullah fication before they could be digested and we said that the bile would allow us to emulsify our facts in our small intestine and so that&amp;#39;s where our digestion would begin remember emulsification is when we allow a hydrophobic and hydrophilic substance to mix now just to recap on what we learned we learned that bile allows allows us to emulsify our fats so it allows hydrophobic and hydrophilic substances to mix and the reason it can perform that emulsification is because it has a hydrophilic end and a hydrophobic end so since it has both it can kind of act like a peacemaker and bring the two together now remember we said hydrophobic means afraid of water it doesn&amp;#39;t want to mix with water or any fluids hydrophilic means it likes water it wants to mix with water and other fluids we also said that fats are usually hydrophobic and that&amp;#39;s why if you were to ever drop some oil into a cup of water that oil would just stay there on top and it wouldn&amp;#39;t mix with the water and the reason for this again is because oil is a type of fat and fats are hydrophobic they do not want to mix with water which is why oil and water will always remain separate they will just sit on top of each other and not mix and join together now the same kind of concept happens in the body with the fact that we want to digest it from our diet so let&amp;#39;s go ahead and apply this to the fact that we&amp;#39;re trying to digest so instead of this being a drop of oil let&amp;#39;s go ahead and say that this is the hydrophobic fact that we just got got from the food that we ate and we want to digest and instead of this being a cup of water let&amp;#39;s say that this is our digestive fluid digestive fluid is basically what carries enzymes to different parts of the body wherever the enzymes are needed so this digestive fluid will be carrying some enzymes so let&amp;#39;s go ahead and drop some enzymes in here as well since the enzymes are in the fluid that would have to mean that they are hydrophilic because remember hydrophilic are fine mixing with water or other fluids hydrophobic would refuse to mix so since the enzymes are in the fluid that would mean that they are hydrophilic now this is actually how things look in our body we have the fat that is trying to be digested just kind of sitting there separate from the digestive fluid refusing to mix in there but we need this fat to come down here into the fluid because that&amp;#39;s where the enzymes are the enzymes are hydrophilic so they are in the fluid but the fat is hydrophobic so it doesn&amp;#39;t want to enter the fluid so we have a situation here where the fact is not able to make contact with the enzymes and because of that it can&amp;#39;t be digested so we need to find a way to make this fact enter into this fluid so that the enzymes can make contact with it and start digesting it or breaking it down and this is where bile is going to come in remember we said bile can allow hydrophobic substances to mix with hydrophilic and it&amp;#39;s able to do this because it has both hydrophilic and hydrophobic ends so what&amp;#39;s gonna happen is the bile is actually going to latch onto fat using its hydrophobic end it will not be able to attach to fat with its hydrophilic end because the fat would just run away from something that&amp;#39;s hydrophilic it wants nothing to do with things that are hydrophilic but since this tail over here is hydrophobic the fat doesn&amp;#39;t my mind attached into it since they&amp;#39;re both the same they&amp;#39;re both hydrophobic so they&amp;#39;re fine attaching to each other and that&amp;#39;s what we see happening here so now we have our bile that has latched onto the fat with the hydrophobic end and when we attach to bile with our hydrophobic end the end that is left hanging down will be be hydrophilic that&amp;#39;s what we see here we have the hydrophilic part of bile hanging down now what&amp;#39;s actually going to happen is the bile is going to continue surrounding the fat we&amp;#39;re gonna have more bile come in and completely surround the fat until the fact is completely covered with bile or a structure like you see over here so again we have fat on the inside and we have all of these parts of bile that are latching on to the fat again they will latch on with the hydrophobic end and that leaves the hydrophilic end on the outside when fat is completely surrounded by bile like this what we have is a fact that actually has a hydrophilic outer layer remember these blue ends are hydrophilic so now the fat is completely surrounded with an outer layer that is actually hydrophilic and when it&amp;#39;s in this state it can actually mix with the hydrophilic fluid because it now has a hydrophilic outer layer so it&amp;#39;s not afraid to enter into a hydrophilic area anymore so again this structure that we see over here where the fat has been completely surrounded with file and now has a hydrophilic outer layer this is what we call emulsified fats so the fat has now been emulsified by bile which means it has this hydrophilic outer layer that makes the fat to feel safe and drink into the hydrophilic fluid now that it can enter the hydrophilic fluid it&amp;#39;s going to be able to make contact with these enzymes and begin its digestion so just to recap the fats cannot become digested until it has become emulsified emulsified fats would look like this meaning that it now has a hydrophilic layer the bile that is required for this emulsification to occur is not found until we reach the small intestine and because of this the fact was not able to begin its digestion until we reach the small intestine because again fat cannot digest until it has been emulsified because emulsification is what allows it to make contact with the enzymes bile is not available to emulsify our fat until we reach the small intestine so we have to wait until the small intestine where bile is available in order to emulsify our fat like this and allow it to enter into this fluid and make contact with the enzymes and beginnings digestion now here we have a little summary slide of basically everything that we just talked about so here it lists the different organs or glands what they release and basically what those different secretions do in terms of either emulsifying fact breaking down nutrients neutralizing acid it is all listed here for you so if you missed something you didn&amp;#39;t get to jot down something from the previous slide you can always look at this as a good review slide another thing that we want to know is how does the body know when to release these digestive enzymes and digestive juices usually this is through the use of hormones hormones are the directors of our body their role is to tell our body what to do now there is an exception which is the salivary amylase that is released in your mouth to begin carbohydrate digestion it&amp;#39;s not listed on this slide because it is not regulated by hormones once your mouth recognizes the presence of food it automatically starts stimulating salivary amylase so that&amp;#39;s something that&amp;#39;s not controlled by hormones it&amp;#39;s controlled by the presence of food the rest of them are controlled by hormones starting off with gastrin gastrin is what tells your stomach to release hydrochloric acid or the HCL secretin is another hormone and secretin tells your pancreas to release bicarbonate anytime it senses that something is coming from the stomach we have acid that&amp;#39;s about to hit the small intestine secretin is released and tells your body to hurry up and send bicarbonate from the pancreas to the small intestine to make sure that we can utilize that acid lastly we have cholecystokinin or what we call C CK C CK is what tells your gallbladder to go ahead and release bile into the small intestine so it is going to be what recognizes that fat is on its way into the small intestine we need to make sure we have bile or the fat to be emulsified and so once we sense that fat is on its way cholecystokinin or C CK will tell the gallbladder to release bile it also lets the pancreas know that it&amp;#39;s time to start sending those digestive enzymes into the small intestine as well another new have been digested we can go ahead and absorb them remember the reason we digest is so that nutrients are small enough to be absorbed we completed our nutrient digestion in our small intestine so that means the small intestine is the first organ that is going to have access to absorbable nutrients because again that&amp;#39;s the first place where the nutrients have completed their digestion so the nutrients are finally small enough to be absorbed now that being said the small intestine is the first organ that absorbs the nutrients but it&amp;#39;s actually where the majority of nutrient absorption occurs altogether and the reason for this is because the small intestine is actually very long it can be about 20 feet long but the reason it&amp;#39;s able to fit inside of us is because it&amp;#39;s really compacted so if you can think of for example slinky a slinky doesn&amp;#39;t take up much space but if you were to stretch it out it&amp;#39;s actually very long and it has a lot of surface area your small intestine is the same way so when the digestible nutrients are in your small intestine there is a lot of surface area that those nutrients can get absorbed into so because of this again the small intestine is the first place where our nutrients get absorbed but it&amp;#39;s also where the majority of nutrients are going to be completing their absorption as well now another thing that I want to mention is that the nutrients are going to be absorbed into these cells that line the intestinal wall so our small intestine has cells all along its walls and that&amp;#39;s actually where our nutrients are being stored they&amp;#39;re entering into those cells and are being stored in there and waiting to be picked up and delivered tor ever they are needed in the body so this here is showing us an illustration of what&amp;#39;s going on in the small intestine so we have a picture here for us that shows us the actual small intestine and here we&amp;#39;re zooming in and seeing that the folds of the slow intestine actually have these hair like structures on them these hair like structures are what we call villi and they add a little bit more surface area and they also help us to latch on to our nutrients but if we were to zoom in even further we would see that there&amp;#39;s even more things on top of the villi themselves so I&amp;#39;ve gone ahead and drawn up this picture here for you kind of like a little cross-section of our small intestine and we&amp;#39;re gonna look at the other components that aren&amp;#39;t shown in this picture so here we have the walls of the small intestine and along the walls of the small intestine we actually have cells so these circles that you see along the walls these are all cells and that&amp;#39;s actually where the nutrients are going to be absorbed when we say that the majority of nutrient absorption happens in the small intestine where they&amp;#39;re actually being absorbed are into these cells on the walls of the small intestine so those nutrients are all hanging around in the walls of the small intestine in those cells that are lining the walls now to take a look at some of the other components that weren&amp;#39;t shown in the first picture the first picture showed us the hair like structures which were the villi we&amp;#39;ve drawn them here in red but if you were to look in a little closer you would see that on top of the villi we actually have even more hair like structures ones that are smaller that we call micro villi so the micro villi will serve the same purpose a little more surface area and helpless latch onto our nutrients but they also have enzymes on top of them the enzymes on top of our micro villi are gonna help us complete our digestion in particular they will help us complete carbohydrate digestion but we don&amp;#39;t need to know the names of them now learn a little bit more about those in the carbohydrates chapter so once we get there we will reference these again but what I want you to know for the absorption is that the nutrients are going to be absorbed into the cells of the small intestine these cells are lining the walls of the intestine so technically the nutrients are being absorbed into the walls into the cells that are on the walls of the small intestine the other components I want you to know is that along the walls of the small intestine we have hair like structures called villi and smaller hair like structures called micro villi on top of them both of them give us a little more surface area and help us latch on to our nutrients and on top of the micro villi we have enzymes that will help us complete digestion so that is the gist of the small intestine components that I want you to be aware of or absorption one other thing that I want to point out is here we have an arrow pointing to this cell over here this is supposed to show us that each one of these cells that is on the wall of the intestine actually has a barrier around it or what we call a cell membrane and so even though we said the nutrients are being absorbed into these cells those nutrients need to first find a way to pass the cell membrane in order to enter into the cell and actually be absorbed into the cell itself so again we have a bunch of cells on the wall of the small intestine if we zoom in we&amp;#39;ll see that each of these cells has a cell membrane surrounding it our nutrients need to find a way to pass the cell membrane in order to be absorbed and stored into the cells and that&amp;#39;s what this picture is showing us here it&amp;#39;s showing us the different methods that we can take to allow nutrients to pass the cell membrane so that nutrients can actually absorb into the cells of the small intestine so the method that we choose is going to depend on the size and the complexity of the nutrient so starting off on the far left side you&amp;#39;re gonna have the easiest and most simple way for nutrients to pass which is basically slipping right on through the cell membrane this is going to be primarily your really tiny nutrients and very simple nutrients like water now going on to the nutrients that might be a little bit bigger or more complex they&amp;#39;re actually going to need a helper a carrier to help move them through the membrane and then spit them out inside of the cell now since they need a helper we&amp;#39;re gonna call this facilitated diffusion the word facilitate means to help so we&amp;#39;re using a helper or a carrier to help move us along so we&amp;#39;re going to call it facilitated diffusion now some other nutrients are going to need even more help meaning they don&amp;#39;t just need a carrier to help move them through they also need additional energy to move this carrier along and this is when we call it active transport active is referring to the to the point that there is energy required in this transport it is the only one of the three that requires energy now that digestion and absorption are done our next step is going to be transport so first we break down the nutrients so that they&amp;#39;re small enough to be absorbed then they&amp;#39;re absorbed into the cells of the small intestine and they&amp;#39;re basically gonna hang around in those cells of the small intestine until the body picks them up and transport them to our ever they need to go and we have two main systems that we can use for this transport and that is our vascular system and then our lymphatic system and before we take a look at these two different systems I just want you all to know the differences between them the main difference is what each one is responsible for transporting the vascular system is going to be what transports are water soluble nutrients and some small fats but the main one that&amp;#39;s going to be responsible for fat transport is going to be the lymphatic system it&amp;#39;s going to take our fat soluble nutrients and our large fats there&amp;#39;s also a difference in what they are composed up which is blood or our red blood cells for our vascular system so the vascular system is your bloodstream and the lymphatic system is made of a substance called the limb which is primarily composed of white blood cells another difference is the way that they are handled by the liver the vascular system any nutrients that pass through the system are going to be detoxified by the liver from their very first round around the body the nutrients that go through the lymphatic system are actually going to bypass the liver on the first round now this will make a little bit more sense in a minute when we go ahead and look at the diagram so let&amp;#39;s go ahead and look at that now we&amp;#39;re gonna go ahead and take a look at the different transport systems starting with the vascular system the vascular system is your blood stream and remember blood can be pumped to all different parts of your body but for the purpose of this class we&amp;#39;re just gonna focus on how the blood picks up nutrients from your small intestine and then transports it elsewhere so for that we&amp;#39;re just going to focus on these few organs that I have listed for you here now before we get into all of the different steps I want to mention a few tips that can help you memorize all of the different arteries and veins that make up this system and the first thing is to remember that the blood will usually lead your heart through arteries and then enter your heart through veins so if something is leaving your heart it will usually lead in an artery if it&amp;#39;s entering your heart it will usually be entering as a vein another thing to remember is any time you hear the word hip addict it&amp;#39;s referring to your liver any time you hear the word pulmonary it&amp;#39;s referring to your lungs so now that we have those tips down let&amp;#39;s go ahead and take a look at the different steps of the vascular system and how we could put these tips to use so the very first thing that we have is the heart and the heart is the pump of the vascular system it&amp;#39;s what&amp;#39;s going to help move the light along so we&amp;#39;re gonna start off pumping blood from the right side into your lungs here we are going to be picking up oxygen and dropping off carbon dioxide now if we want to know what to name this arrow here first thing we know is that it is going to your lungs remember anything related to the lungs is called pulmonary so we already know pulmonary should be part of the name the next thing that we know is that it is leaving the heart we know when something leaves the heart it leaves in an artery so now we have two words down pulmonary and artery and that&amp;#39;s exactly what this is called this is our pulmonary artery because it&amp;#39;s going to the lungs and it&amp;#39;s can even be parts so this is going to be how you&amp;#39;re going to be able to use those tips to help you memorize things now after we&amp;#39;ve picked up oxygen in the lungs we can go ahead and send that oxygenated blood back into the heart and this one is still again related to the lungs since it&amp;#39;s leaving the lungs so it will also be pulmonary but since it&amp;#39;s entering your heart remember blood enters the heart through veins so this will be pulmonary vein now after that the we can go ahead and pump that oxygenated blood back out and blood leads your heart primarily through one really large artery called the aorta so this one has its own special name and the aorta can send blood straight to the liver or it can branch off and send blood to the intestines instead now if it were to go straight to the liver it&amp;#39;s going to be detoxified there that&amp;#39;s what the livers role is the livers role is to detoxify anything that comes its way so the blood is going to go through the liver to make sure there&amp;#39;s nothing toxic and then the liver can go ahead and pump that blood back to the heart now since this relates to the liver we&amp;#39;re going to call it hepatic and since it is entering the heart it will be a vein so our hepatic Vinni now if the aorta instead sent the blood to the small intestine what&amp;#39;s gonna happen is we&amp;#39;re gonna pick up all of those nutrients that we absorbed so if you remember we had a bunch of nutrients that were absorbed into the cells of the small intestine and now they&amp;#39;re just hanging around in those cells waiting to be picked up so when the blood goes from the aorta to the small intestine it&amp;#39;s gonna pick up all those nutrients that were sitting in the cells of the small intestine and send them to the liver now this is something that relates to the liver so you&amp;#39;ll see we called it hepatic again since it&amp;#39;s going to the liver it&amp;#39;s also on its way to enter the heart and remember things that enter the heart are called vein but in order to differentiate it from the one that&amp;#39;s going directly into the heart we put the word portal in there so this is called our high product portal vein now that we&amp;#39;ve covered the vascular system let&amp;#39;s go ahead and take a look at the lymphatic system the lymphatic system isn&amp;#39;t its own system really it&amp;#39;s more so an added step onto the vascular system remember the vascular system is our blood stream and the lymphatic system was there to take nutrients that the blood stream couldn&amp;#39;t take on initially on its own so things like our larger facts and the fat soluble nutrients needed to go through the lymphatic system instead and the reason for this is remember the facts are gonna be hydrophobic meaning they don&amp;#39;t want to mix with a fluid technically your blood is a fluid so the facts don&amp;#39;t necessarily feel comfortable mixing in their entering straight into your bloodstream so what they&amp;#39;re gonna want to do is basically create that outer layer the hydrophilic outer layer around them like we saw earlier with bile because that will allow them to feel safe entering into the bloodstream so again for those larger facts we want to surround them with a hydrophilic layer repackage them that way so that they can enter the bloodstream now the problem is that if those bats are already large and then we add a hydrophilic layer around them sometimes they can be too large to enter straight into the bloodstream the entry way from the small intestine into the bloodstream is more narrow than that and so the lymphatic system is there to allow the facts to enter in a different place where the entryway is not as narrow and those larger facts can enter into the bloodstream there where we have a less narrow entryway so that&amp;#39;s the gist of the lymphatic system so let&amp;#39;s go ahead and take a look at how that would work so for the nutrients that couldn&amp;#39;t be picked up by the bloodstream directly instead they&amp;#39;re gonna filter into what we call the lymph and through there they have access to the subclavian vein which is actually a vein that empties out into the hepatic vein so it opens up to the hepatic vein which is actually a larger entry way for those larger fats so the larger facts actually get a chance enter and become part of the vascular system when they enter at the hepatic vein because that is a larger entryway so if they couldn&amp;#39;t fit before straight from the small intestine they can enter into the lymph into the subclavian vein and then the subclavian vein will empty into the hepatic vein which is a larger entryway that can allow the larger facts to become part of the blood stream so as you can see the lymphatic system isn&amp;#39;t its own system it&amp;#39;s just this added step that we have to add on to allow the larger facts to make way to an entry point where they can actually fit and enter into the bloodstream after that they become part of the vascular system just like the other nutrients and they will continue going around the body now remember the lymphatic system we said the nutrients will bypass the liver on the first round you can see why that is the nutrients that enter through the lymphatic system are entering into the hepatic vein the hepatic vein has already left the liver so they basically missed their chance to come by the liver on their first time around just because they enter too late but again they&amp;#39;re part of the vascular system now so they will get a chance to come around again and at that point they will be able to come by the liver and be detoxified

Transcript for:Digestion, Absorption, and Transport

Transcript for:
Digestion, Absorption, and Transport