food I'm telling you the stomach is a very important thing so this guy's gonna store digestion which remembered I just digest you is just a stupid word that's basically like any food right but the point with the stomach is there's minimal absorption so absorption is actually bringing the nutrients into your bloodstream the stuff like really doesn't do that so the stomach is more like a washing machine where its whole goal is to Mixy Mixy journey journey grindy grindy to give plenty of time to pulverize that food which remember was in the form of a bolus which is the ball of food to move it into a liquid that we call kine we are going to get a little bit of protein digestion done here in the sense that we are gonna start to break down proteins a little bit but that's because proteins are these huge molecules and so that kind of has to start in the stomach but otherwise the goal really is just mixing and churning and pulverizing and giving plenty of time for the gastric juices to kind of get in there and do their work so if you kind of think of gastric juices like tide or any kind of detergent that you use it's like it's just giving time you know it's not like you turn on your washing machine and throw in a tide pod and immediately take your clothes out right you got to give plenty of time for the tide pod to go to work and so we got to give plenty of time for this time to mix with all these juicy juices and then we're going to send it to the small intestine stomach has a lot of components and so if you look at this picture we have the esophagus which is the tube that sends things from your mouth to your stomach we have this kind of dome part of the stomach which is called your fundus the kardea which is named because it's closer to your heart so that's the cardia or cardiac region of your stomach if you don't have to know these muscle layers for lab but just appreciate like all of the directions of the muscle in your stomach so again if you kind of go back to that washing machine example it's like a lot of washing machines kind of churn in all different directions right so all these muscles are contracting and you've kind of felt this when your stomach growls when it's empty when those muscles are contracted acting even though they don't have anything to work with you're really just churning that food up on the inside of the stomach look at all those groovy grooves so those guys have two names you can call them rugae which is what the term we use in lab but you can also call them just gastric folds so the inside of your stomach is not smooth it has all these intense groovy Bruce and so I always think of it like if you've ever seen a washboard which some of you probably never have but like my grandma used to have him hanging on the wall and she would talk about how that's how they had to do laundry it's like you would take these these metal wash boards that kind of had this texture to them and you had to take like a bar of soap and like kind of hand scrub your clothes I definitely would not have survived in those times and I also wouldn't survive lucky if I was Amish like there's just no way I need a washing machine but those have a very intense texture because again the whole goal is to like bump and grind this food right and like really break it down we have the grater and sir curvature to the stomach which are labeled there and they're obvious it's like the lesser is like the C shaped curve on the inner part of your stomach and the greater curve is they like C shaped curve on the outer part but it's all about making sure that we control the food it's just like your washing machine you control your washing machine right there tight Merson you have certain settings so heavy heavy clothes you wash a lot longer than light clothes that are really light and don't aren't very dirty so it's the same thing of food food that's really intense stays in the stomach a little longer if it's hard to break down whereas some foods move through the stomach really easy but the point is we want to control it if you think of your gastro intestinal tract is a huge tube you don't want things going from your mouth to your anus just like flying through their like they're on waterslide I mean that would be a bad day right we want to control it so we have all these sphincters so at the top of the stomach where it says cardia underneath that is the cardiac sphincter and so inside the stuff like is the sphincter and it's like a door that's gonna let things go from your esophagus to your stomach and then at the end of the stomach we have the pyloric sphincter that's allowing things to go from the stomach to the small intestine so the pyloric sphincter is really really important it's like we want to make sure we leave stuff in the stomach long enough to get completely pulverized is into crime so when things go into the small intestine they have to be liquefied because the small intestine is where we quote-unquote feed ourselves the stomach's not really feeding us it's the absorption that's what's feeding us it's the fact that we're getting these nutrients into the bloodstream and that happens in the small intestine makes these gastric secretions like I said it's kind of like the type odds in your washing machine so the mucosa of your stomach is very very thick we have to protect our stomach right because most of us know our stomach has stomach acid in it we've kind of talked about that with the immune system already and so we have to protect our own tissues from the acid that they're making and so there are three types of cells in our stomach lining we have the goblet cells with a mucous cells which we've seen in other chapters like respiratory and then we have these new types of cells we haven't talked about yet the parietal cells and the cheap cells you so starting with the goblet cells or the mucus cells these guys are secreting an alkaline mucus to provide protection so it's all about balancing it's all about balancing out the intense acidity of your stomach so if you look at this little picture here it's like you have the lumen of the stomach which is just the space Insider's stomach where all the food would be and that can be a pH ranging from one to three so that's pretty acidic so in the lining of your stomach you have these mucous cells sending out a base kind of like a roulade so if you've ever had an acid stomach and you take a roulade or heartburn and you take a roulade to kind of counteract that that's what the stomach is doing protect itself you what I want you to know about parietal cells so if you're highlighting I would highlight they secrete hydrochloric acid so that these guys are the acid producers in your stomach so we're gonna see in another slide that this activates pepsinogen so pepsinogen it's going to help us absorb vitamin b12 so without the stuff i'ma Cassidy we can't activate pepsinogen and then we can't absorb vitamin b12 so if you remember when we talked about blood like all the things that can go wrong with your blood one of them was pernicious anemia which was the red blood cells were really large and fragile and it was because you're not absorbing b12 so it wasn't it's a situation where you could just take more vitamin b-12 people that have pernicious anemia had issues with their stomach lining and these are the cells they have issues with they're not making enough hydrochloric acid to activate the pepsinogen to absorb the vitamin b12 so right now though like I said all I need to know from this slide is the parietal cells secrete hydrochloric acid you so these guys they're secreting digestive enzymes than the two enzymes pepsinogen which we just mentioned on the other slide and gastric lipase so pepsinogen pepsin is coming from proteins like peptide bonds right whereas lipase is obviously coming from lipids so protein Dean's and lipids proteins and fats are these really big molecules and so these are important molecules you obviously have to have protein and fat in your diet or you're gonna die but they're a lot harder for us to break down than say sugar so we need to help so pepsinogen helps us break down proteins so we secrete pepsinogen and in active form so when the cells are making pepsinogen it's not actually doing any work but once it comes in contact with the hydrochloric acid from the parietal cells it gets converted into pepsin so then we start breaking down proteins so it is really crucial really crucial that we secrete pepsinogen in an inactive form and that's because think about what your stomach is made of think about what your body is made of almost all of your body is made of what out of the four macromolecules fat protein carbs and DNA and RNA which one of those is like your hair your nails your skin so I said a zillion times right it's protein so almost all of your body is protein so if your stomach is secreting a protein splitter think how dangerous that is it's not like pepsin knows the difference between a protein and chicken nuggets versus the protein in your stomach lining and so if we're just secreting pepsin all the time we would digest our own body like eventually you'd have gaping holes in your body where all of your innards would be spilling all of this Lord so it's too dangerous right so we only want pepsin when there's protein from our food in our stomach otherwise if we add pepsin in an empty stomach we'd be screwed so we secrete pepsinogen and so it's ready to start breaking down protein if our stomach starts producing acid so you only start really cranking out a lot of acid when it's time to eat it's kind of like your washing machine you don't just walk by your washing machine and throw in a tide pod you don't put detergent in a washing machine just be because the washing machine is there you do it because you're doing laundry right so when there's laundry in the washing machine you put your tide pop pot when there's protein in your meal you want pepsin otherwise pepsinogen is what keeps it from like going crazy and digesting your body so pepsinogen becomes pepsin when it's Bo's to acid otherwise we would not want pepsin because pepsin would digest our body this is an enzyme that works on milk fat because as gross as it is to think about now you were probably breastfed and so breast milk has a lot of fat in it it has a lot of butter fat in it has a lot of milk fat and so we can digest that because we were fed by our moms but fat in and of itself lipids in and of themselves these huge molecules and our body is not really great waking down fat anyway as some of us know because the only thing we can really do to kind of break tell kills is is hydrolysis adding water to break down bonds is hydrolysis we'll remember fat hates water so if all I can do to a fat molecule is say hey here's some water why don't you like share with me the fat says hell no h2o I don't like you so because these molecules are so big we kind of have to start breaking down fat in the stomach as well however most begins and ends in the small intestine the stomach really is just like that washing machine with the Mixy Mixy journey journey but because of the size of proteins and fats we do get a little jumpstart on breaking down fat and protein in the stomach but most of this happening in the small intestine all of these juicy juices have to be regulated it's just like those Tide Pods you know it's like you don't waste them you don't just walk by your washing machine and throw in a tide pot Tide Pods are expensive right if you use bleach or a fabric softener all of that stuff costs a lot of money you don't want to waste it so we want to regulate this like why would I have a Tide pod in an empty washing machine why would you have all these gastric secretions in an empty stomach so it's back to nerves so parasympathetic impulses remember parasympathetic is rest and digest and relax so this obviously controls the stomach because if you're being chased by a lion tiger bear oh my you do not have time for a sandwich so your sympathetic nervous system wouldn't do this we also have a new hormone that we didn't do when we did the endocrinologist Ric secretions cause your juicy juices to start flowing in the stomach so gastrin is secreted by the cells that are in your pyloric region which remember is the region towards the end of the stomach so that kind of makes sense if we think of gravity right when you eat food would hit the pyloric region first and so that's gonna cause lots and lots of gastric juices from all of these glands just like throwing in a tide pod when you put laundry in the machine sorry a neighbor just walked by and I thought he was in my yard and I thought I was gonna have to kick some ass but it's all good there are three phases of gastric secretion and this sounds way more complicated than it is so we have the cephalic phase which if I remember cephalic means head we have the gastric phase which means stomach and we have the intestinal phase which obviously is your intestine so the cephalic phase is happening while you're just thinking about food which is what I do all the time the gastric phase is when the foods actually in the stomach and then the intestinal phase is when it you can see in this picture where it's starting to move on from the stomach where the stomach is starting to drink so I have individual slides addressing each one of these phases the cephalic face so this is before food even is eaten okay so before food has even reached your stomach it could just be laying on your plate so your vagus nerve which is cranial nerve number 10 is parasympathetic so again rest and digest relaxed homeostasis that's what this nerves all about so this nerve is stimulated by sight sound smell and taste of food so this is the whole you're preparing to eat thing like how glorious is it to smell food like especially like Thanksgiving or the covered bridge festival you just smell like the all these amazing food smells so then you start salivating right it's like you start thinking about eating when you smell all these amazing things or like if you look at a picture of a pizza in a magazine or a picture of a shamrock shake because those are very important to me or a sound like my cats oh my god I've never given them tuna in their entire lives but if I open a tuna can just the sound of the can being opened on the can opener like they all fly into the kitchen so like just that sound makes them think oh it's time to eat or like for me if you ever hear like the sounds of microwave popcorn like that always makes me want to eat popcorn right or of course the taste so all of these things are happening before the food has even gotten to your stomach right before it even entered your body maybe so it's the anticipation of the food which is part of the fun right like I mean I like to eat don't get me wrong foods amazing but sometimes it's nice just to think about food and like when they first bring you the food from a restaurant and they put it in front of you it's like oh my god this is so exciting because it's so good so 30 to 50 percent of the secretions in your body the juicy juices in your body for digestion happen during the cephalic phase so this is an important phase and most of us know that Americans we eat too fast or we eat on the run like a lot of us are just eating in the car on the way home we don't really take the time to enjoy our meals but if you like really do take your time to sit there and be excited about the meal and smell your food you'll have better digestion because 30 to 50 percent of these juices are produced in this stage the bigger the appetite the more this kind of goes back to the laundry thing again it's like sometimes if your load is really really big you'll throw in to Tide Pods right but like if I'm washing like one shirt I'll barely put in any detergent at all so if you're really really hungry your body is going to produce more of these juicy juices because the juices are gonna help break down your food well if you're really really hungry obviously every bit of nutrition you're putting in your body is probably really important so we want to make sure like we do digestion like really well then we have the gastric phase so now the food is in the stomach so the stomach is distended which just means stretched out if you've heard the term distend abour Gonzaga store genstat stretch like your stomach and the uterus if you have one in the bladder we say distend so stretch receptors so as your stomach gets more and more full the lining of the stomach has stretch receptors in it that say oh wow this is a lot of food so that triggers the release of gastrin the hormone which causes you to make more juice so just like the laundry the more laundry you have the more bleach you need the more soap that you need proteins begin to be broken down in the stomach because we have pepsin so remember pepsin is turned on by the acid otherwise it's secreted in the form of pepsinogen so the more peptides you have in your stomach the more proteins you have in your stomach we're gonna release even more gastrin releasing then even more juicy juices and so especially proteins and fats you're gonna need lots of chemicals in your stomach to help you break down these really big molecules so this is an additional forty to fifty percent of your juices so you don't have to know those numbers but the first two phases we've almost hit 100% right meaning the first two phases are where almost all of your juicy juices occur so there's very little absorption in the stomach remember absorption is going from your stomach to the blood so we're not really absorbing a lot of nutrients in the stomach we're basically just Mixy Mixy journey journey we're basically just pulverizing that food and getting ready to absorb it but there are some things we absorb in the stomach alcohol oh yes God love it I don't know about you but at the end of a workday especially on a Friday even though I miss work days I feel like we haven't had work dates in a while this working from home thing is very strange but when on a Friday after a really long work day one of my favorite things to do is to have a glass of wine like especially like if I'm cooking dinner or something and that glass of wine on a Friday if I haven't eaten especially in like six hours is like whoa party time okay if you don't drink good for you but I drink okay and that first glass of alcohol like instantly goes to my head because alcohol absorbs in the stomach aspirin aspirin absorbs in the stomach as well so if you've ever had a really nasty headache aspirin really does help very quickly because it does start to absorb in the stomach and so especially they make this weird stuff called Goody's headache powder and it's terrible it's so nasty tasting but it's basically they've taken aspirin and pulverized it and made it into a powder and so if you have nasty headaches this headache powder you get like almost instant relief because like the pulverizing is already done so that stuff just hits your stomach and gets absorbed really quickly water gets absorbed in the stomach glucose and salts can be and those of course keep our body going right like glucose is how we make ATP and salt is how like our muscles contract there's no protein there's no big carbohydrates like starch and there's no fat absorption in the stomach so the big stuff is not getting absorbed in the stomach very few things are in general it's the small intestine that feeds us the stomach is just about the churning and last we have the intestinal phase so now the time if you go back to that previous picture the chyme has now entered the duodenum so the small intestine has three sections I say DJ I so this is kind of like my BCS thing it's not really a word DJ i but it's what I use duodenum jejunum and ileum and so these are the three sections of your intestines the duodenum jejunum and ileum so the chyme is now entering the duodenum the first segment of the small intestine so we get a little bit of juices and then we stop so I think of this like if you're on the way out the door to go to work and you spray on a little bit of perfume or cologne it's like you're on your way out the door so you do a quick little spritz as the food is moving kind of out the door as it's moving from the stomach it's like the stomach squirts its last little bit of chemicals before the food moves on its way so we get a little bit of secretion it's like okay the food's moving on here's your last opportunity to keep breaking stuff down but after that gastric secretions not need it anymore if food is moving out of the stomach if the chyme is moving out of the stomach you don't need any more juicy juices if you're taking the clothes out of your washing machine and putting it into the dryer you don't add another Tide pod right you just don't need it so we're gonna get the nervous system is gonna decrease its parasympathetic signals it's like we're not connected to keep stimulating the stomach when there's nothing in it so we've got a couple more hormones there's a lot of hormones in this chapter we have secretin which increases pancreatic secretion of what's called a bicarbonate so bicarbonate ion it's the same ion that your stomach releases from those mucus and goblet cells it's basically like a roulade so we have all of that acid in the stomach that stomach has a pH of like one two three I mean it could burn you but the stomach is protected from that acid but nowhere else in your body is if you've ever experienced heartburn that's from the acid splish slashing into your esophagus which is not protected so that's why it burns I mean it's literally burning you're getting acid burn so as we send this kind which is mixed with the acid as we send that time into the small intestine we have to neutralize that acid so the pancreas release is basically the equivalent of a roulade to do that so we call this secretin then we have cholecystokinin which we're just calling CCK and this guy is due to fat and protein especially fat and it's there to slow gastric secretion so if you have a lot of fat and protein in the stomach that's like having clothes that have grass stains in your washer you want to leave it in there a little longer to get it broken down and so if CCK is released a hormone it gets released from the stomach that basically says hey we don't want the time to leave the stomach too quickly because it has these huge molecules in it we want to make sure it cycles a little longer just like setting your washing machine for a heavy load versus a light load just gives it a little bit longer for these molecules to start to break down regulating what leaves the stomach and how quickly it leaves the stomach is crucial again like the laundry thing it's like you want to leave things in your washing machine longer if they're dirtier and less if they're not because you don't want to waste your effort same thing with the stomach so a lot of factors affect how quickly things move your stuff leave your stomach and you can relate to these because you've eaten so first the fluidity of the kind so if you have solids they're gonna move a lot slower than liquids so this is why a lot of liquid diets are doomed to fail like the slim fast pledge yeah I've taken that and I quit I don't want to drink protein shakes or slim fast shakes because it's not satisfying same thing with like tomato soup is not as satisfying as like a baked potato soup Oh God like a baked potato soup with like some bacon and chives and all the yummies a nice thick soup is a lot more satisfying than a broth based soup or like tomato soup because the more solid it's gonna be in your stomach longer so you're gonna feel satisfied longer like who wants to be hungry liquids fly through your body because they're already pulverized they're already broken down that's the job of the stomach right is to mix your food and break it down and create this kind fatty foods remain about 3 to 6 hours you don't have to know the times but they remain the longest this is why a lot of fatty foods first of all tastes amazing but also they're satisfying like if you eat a big piece of cheesecake you're gonna be a lot more full than if you eat an apple or if you drink some soda so fat stays in our stomach the longest because it takes so long to break down proteins move pretty fast even though they're huge molecules but that's because we're really good at breaking down protein we have that pepsin but still it stays in your stomach a lot longer than like carbs so carbs are awesome we make ATP from carbs we love soda we love candy but if you ever noticed that stuff doesn't satisfy you for very long whereas if you eat a steak or if you eat something like cheesecake you feel full for a really really long time gasps the entero gastric reflux so this is regulating how fast time leaves the stomach so have that pyloric sphincter so as the stuff moves from the stomach to the duodenum the duodenum is gonna start to fill up so if the duodenum gets too full we're gonna kind of stop the stomach from emptying right because things have to go from the stomach to the small intestine so if your stomach is squeezing but the duodenum is full there's nowhere for that time to go we're gonna inhibit the parasympathetic stimulation of the stomach so we're going to inhibit peristalsis which remember is just muscle contraction of the stomach so if fats present especially that cholecystokinin the CCK is gonna stop gastric squeezing so that keeps food in the stomach longer