continuing on with digestion fun so remember the small intestine we do the whole DJI thing duodenum jejunum ileum this extends from the pyloric sphincter which is the little exit door from your stomach all the way to the large intestine and so the opening to the large intestine is this little pocket called the cecum so remember the function of the small intestine is all about beating your entire body so here's where the chemical digestion the actual breaking down of your food occurs and all of your sucking it up so that's the most important step is getting these nutrients into your bloodstream so they can be delivered to all the other cells an anatomical structure that's important for the digestive system is the greater omentum so this is actually just part of that peritoneum and so you have this stuff called mesentery which I have kind of pictured here the models in lab do such a lame job trying to show this so it's like this kind of saran wrap material that's there between the intestine folds to just kind of keep everything in place cuz you have 30 feet of this stuff crammed in there so it like has to fit a certain way so the mesentery kind of helps with that so additional part of the mesentery or peritoneum is this what they call the greater omentum which has a lot more fat content so you can kind of see it's this yellowish structure and so that's there to just kind of make sure all your innards stay in so it's all about sucking up these nutrients ok so we've got to make sure that we've broken things down into their basic parts so nutrients have to be simplified that's the whole point of chewing mastication remember sounds dirty it's the whole point of adding saliva which has the amylase to start breaking down the starch it's the whole point of the Mixy Mixy journey journey of the stomach we want to make sure that by the time we hit the small intestine everything is broken down into its simple forms so just to review those four macromolecules nucleic acids have to be broken into nucleotides I can't remember in some old notes I have this wrong so just fix it if I screwed it up so if I think it says new nucleic acids and some of the notes so nucleic acids are broken into nucleotides carbohydrates broken into monosaccharides fats and lipids are broken down into glycerol and fatty acids and then proteins are broken down into their amino acids and so otherwise if we don't break these things down they're just simply too big so it goes back to that example from the previous lecture where if I'm trying to suck up some chunky cat vomit that ain't gonna work with a paper towel it has to be liquefied right so you just picture your intestine as paper towels well we've got to make sure that molecules are really really tiny otherwise they won't get absorbed into the blood and it kind of defeats the purpose of this whole thing it's all about absorption so this is the major site where you're gonna suck up all those carbs proteins and fats you're gonna finish your chemical digestion so almost all of your chemical digestion of fat is beginning and ending in the small intestine because remember if fat is really hard for us to process so the small intestine is so crucial and so it's all about making sure we're feeding all of our cells and so this is the last opportunity if it does not get absorbed by the small intestine once it hits the large intestine it's destined to be duty and exit your body if we think about that the fact that it's all about absorbing everything we possibly can this slide makes sense so we can't have our small intestine just be a hollow tube it has to have a lot of like fancy structures to make sure we're grabbing as many things as possible so it kind of goes back again to paper towels if you buy cheap all-day paper towels which I love my I love me some Aldi so I'm not insulting my Aldi I don't know what I would do without their wine and chocolate but if we think about Aldi paper towels a lot of them are cheap and so when you use them it's like the paper towel itself is really really flat whereas if you use like a brawny paper towel a more expensive paper towel there the quilted quicker picker-upper is what they say and so they have more like folds they have more invaginations because that's a good word to use and so they can grab more right they can absorb more so the more expensive paper towels tend to do a better job than the cheap paper towels just because of their structure so it's the same thing here inside the small intestine there are lots of structures whose sole goal is to just grab onto stuff so the first thing you have tons and tons of these finger-like projections that are called villi so villi in latin just means finger like projection just like papillae means finger like projection so these are large creepy little fingers so just picture your intestine kind of lined with these creepy little fingers that's there to absorb everything so this increases surface area it's just like fingers that grab stuff without all these little villi a lot of stuff would just float right through your small intestine so this increases surface area it helps with mixing because the little fingers are kind of like the rugae inside the stomach and helps with absorption because there's literally more to grab right well then if you look at the villi picture if you look there's micro villi so the little fingers have fingers so these tiny little micro villi that kind of look like cilia so on this diagram they're labeling them brush border of micro villi if you don't notice them it's like the third thing down so your intestine has all of these finger-like projections these big villi and then microscopically the villi are covered with these little tiny micro villi like little tiny fingers so I think of it like if you ever saw the moody movie spider-man like before he goes to like climb on the wall like these creepy little hairs like come out of his fingers so it's like his fingers have fingers so these villi have micro villi the whole goal again increasing surface area and grabbing things as much as possible and then we have these little intestinal crypts or intestinal glands that are between the villi and then lacteals lacteals are the green so we've already done the lymphatic system and so we've already kind of seen this remember that that the lymphatic system has those blind ends those little dead ends so if you look at this picture inside that villi is a capillary bed because that's where we're gonna absorb all these nutrients right is in this capillary bed so this lacteal is this little green lymphatic vessel that's running right next to the capillary beds because that's what lymphatic vessels do so remember for when we did blood and when we did the immune system we talked about kind of the function of this to absorb excess water so we want to make sure that we're not you know losing a ton of water we want to absorb it remember we're sending out in the car do we send out more water than we can reabsorb because we have this guys are backed up but if you remember the additional function that I just kind of like casually mentioned that I said would be more important when we got to digestion fat even when we break fat down fat is still fat and sassy these big ol molecules like trying to absorb jello with a paper towel fat is really hard for us to absorb and so the capillary beds although they have their holes they have their little fenestrations if you remember it's still not big enough to easily grab fat and so these lacteals they have the holes as well and there's hole there holes are bigger and remember also lymphatic fluid is traveling three liters a day versus five liters a minute so there's just like a lot more time for the fat to get into the lacteals and if you remember anything that we bring into the lymphatic system is going to up into your cardio anyway under the subclavian veins and so it's just that kind of fat middleman is what I called it in an earlier lecture it's like yeah it's the way that we absorb the fat into our bloodstream and it gets there anyway it's like it's not really going directly into the bloodstream but the lacteals the lymphatic system will we'll get it there eventually our body is designed for so many tricks just to make sure we increase this absorption so another structure that's in there is the ply case circulars which is shown in that third picture so these are circular folds that are increasing surface area so it's like you have these these circular folds inside the walls in the intestine and then those are covered with the tissue that has the villi and the micro villi so it just gives you more and more folds more and more imagination which is there to just make sure we are doing all we can to grab every single nutrient we only have 21 feet to feed the entire body the small intestine is our last opportunity to break down our food so that means more enzymes so this is helping again just break things down right so these digestive enzymes are gonna finish digestion because if it doesn't get done in the small intestine it's gonna be duty so the good news is we don't have hardly any enzymes after this because if we have if we haven't done the job it's not going to get done so for the proteins we have pepcid ASE's so if you remember peptide bonds is what bonds proteins that's why this is named this so remember enzymes usually end in ASE and they're often named for the job they do so these are enzymes in our small intestine that break proteins carbohydrates we have disaccharide ASIS so saccharide means sugar dye means two so this is all you need to know is just the red but some examples of disaccharides table sugar sucrose so table sugar is very easy for us to digest because all we have to do is break one bond because all sucrose is is two sugars that are stuck together so because of this enzyme dye side a curt dice i decorate ace we're able to just pop it lipids we have intestinal lipase just like we had gastric lipase that just helps us break down fat and then nucleic acids we have nucleases which help us break down DNA and RNA because every meal we consume has DNA RNA in it because everything you eat used to be alive like even if you're eating like mushrooms I mean they obviously used to be alive and they have DNA as well so I don't know if I've thrown this at you but it's worth repeating that the average meal has 24,000 miles of DNA in it so I mean that's enough to go around the earth once and so you definitely need the new clay the nucleic acids being broken down by the nucleases so the lacteals again those are those little green extensions of your lymphatic system next to the capillary beds help you absorb fat we also are going to absorb electrolytes like sodium and chlorine and then water is going to follow that so the more nutrients we absorb the more calcium and other electrolytes that we absorb that's going to help us absorb water because if you remember water follow solute so things always go water always goes from where it's crowded to where it's not so water always goes from hypotonic to hypertonic if you don't remember those fantastic tonicity terms I know you've missed two them we will be doing them again when we get to the urinary system so now it is time to move on to the large intestine so this picture here is showing the large intestine and we're starting with what's called the ileocecal valve you can also call it a sphincter because that's basically what it is so we've said this before that it's all about control if you have a tube that moves from the mouth to the anus you want to make sure you're controlling how fast things go through that tube we don't want things shooting out of our body that's a bad day but we need to push things through our body as well so the ileocecal valve is the little doorway if you look at this picture between the ileum which is the end of your small intestine and the cecum which is the beginning of the large intestine so that's why they named it the ileocecal valve it's just the little sphincter because once we put things in the large intestine whatever nutrients are still in there are just going to be wasted so we want to control this so this sphincter or valve is usually closed but after you eat we have what's called the gastro ileal reflux gastro being stomach ileum being small intestine causing it to open because as foods moving into the small intestine you need to make sure that whatever's in the small intestine is moving on down the road right kind of like an assembly line so some structures we've seen in lab the hofstra those are those puffy things so that's because you have all the the circular muscle in there kind of like kinking the hose and so it creates this kind of puffy texture the tanea coli that guy is the ribbon-like longitudinal muscle that's pushing things along the large intestine the epiploic appendices or appendages remember you can call those just fatty appendices because that's what your lab manual does that kind of cushions the large intestine as things are moving through we have the a sending colon going up the transverse going across the descending going down and remember the Shoup the sigmoid colon coming out and then we have two additional sinkers because it's all about controlling this right so this is just a different viewpoint of that ileocecal valve sitting in there you can also see the appendix it's kind of hanging off there like a weird little rat tail we have the anal canals which is just the groove that the fecal matter eventually travels through and those anal columns which are like the little ridges that are kind of in inside the rectum so it's it's a thrilling time to be alive I know you're very excited for the end of this chapter there are a lot of functions of the large intestine but the biggest function I highlighted there in red so that is the key point absorbing water but some other things that it does okay the alimentary canal or the gastrointestinal tract the tube from the mouth to your anus uses a lot of things for storage but usually it's storing and breaking things down so we're gonna store things here but we're not actually digesting because digestion means we are absorbing things into the blood well we're not doing that we're basically this is the waste that's gonna exit your body so the good news is there aren't any enzymes which is good because we had plenty of those right but there is no point in breaking anything down if it's just gonna exit your body like why would your body waste the effort we are gonna see the goblet cells again cuz it's all about making mucus and so these guys are sticky to bind the feces together has no-one wants like squirty feces lubricates feces movement because you don't want stuck feces and helps control pH so mucus is a little is slightly alkaline slightly more basic which is good because a lot of the stuff coming out of your digestive system is slightly acidic so it kind of counteracts that absorption of water minerals and vitamins so water is the key here okay it's all about absorbing water because you do not want squirty duties okay so one of your biggest issues is dehydration you can die in just a few hours from dehydration so water balance is crucial water balance is over half of our body weight and everything that we eat and drink has a certain amount of water in it right so we want to make sure that we're absorbing all of that we don't want shooty squirty duties okay but also we need that water so sodium is going to be a key player here so na plus if you remember sodium we're gonna absorb by active transport so what that means is it's gonna take us some ATP so if you remember aldosterone that was a hormone from the endocrine system that that was part of its job was to help you absorb sodium and then water follows like a puppy so it's the same way you kill slugs cute little garden slugs with their cute little end Tenace just trying to live their lives and have a good day and people pour salt on them well it forces the water out of the slugs body and dehydrates them and kills them so water chases solute if you've heard that before or water follows salt this is how we're gonna reabsorb all this water so at the end of the day there's very little sodium or water in the fecal matter because our goal was to to keep that in the bloodstream keep that in the body the large intestine also have lots and lots of bacteria so bacteria as some of you have already taken micro bacteria is a crucial part of our body so even though we're very anti bacterial freaked out most of the time there are certain bacteria that we can't live without and so the especially in the intestine the intestinal bacteria is so crucial so we call this our bacterial flora because this is our normal flora this is the stuff that should be there the stuff that you know bacteria that should be living in our large intestine and so they do a lot of things for us okay so this is a beautiful relationship we get vitamin K from them vitamin b12 thiamine and riboflavin which are some B vitamins so basically we're getting tons of vitamins from them so that's a huge benefit they're also helping us to break down our food they're helping us do our digestion so we can't live without them they get a nice place to live plenty of water and plenty of food so it's a win-win relationship so these guys though are what break down the fiber in our body so you've probably heard you need fiber in your diet so fiber from like the skins of plants and like the you know crust on a bread fiber is basically what we call cellulose which is just a chemical but it's basically just a like a starch it's like a polysaccharide but our body can't digest fiber so I know it sounds weird that they say oh you need fiber in your diet but you're not actually getting nutrition from the fiber in our diet with the fiber in our diet does is it cleans your intestines so again kind of gross to think about right but it's like if you picture like little scrubbers scrubbing your large intestine so that's what the.oh fiber is doing it keeps your large intestine scraped out and very healthy well these bacteria feed on that produce gas so this gas is flatus isn't that a fun word flatus so if you've heard of flatulence that's a nice word for farts okay flatulence so flatus that sounds a lot better so 99% of flatus is nitrogen and oxygen which is the air that surround us all the time so 99% of flatus doesn't smell but you gotta watch out for that other 1% right so I grew up with my uncle and he was 13 when I was born so he was more like a big brother so he used to like you know torture me and he would always like you know flatus on the couch and then he'd start giggling and he would always call them silent but deadly I'm like okay you're disgusting so though you gotta watch out for that 1% because sometimes they'll be methane gas and ammonia sulfide which smells like rotten eggs which is a very aggressive smell but we have to have these bacteria to the point where if something happens to them you'll have to have a fecal transplant and that does not sound like a good time can you imagine the pressure of trying to do tea for someone you love to give them your feces no thank you but we've got to have this balance otherwise we can't make these vitamins and we can't break down our food so we'll die so our our bacteria are very important so the amount of e.coli for example in your body the basically almost the entire weight of your feces is dead e-coli so that gives you a nice visual of how much of this bacteria is inside our body but it needs to be there methane is a very very dangerous greenhouse gas so climate change is the thing whether you want to quote believe it or not in quote I mean science is one of those things that no one cares if you really believe it it's happening but climate change is caused from too much carbon dioxide because basically we have paved paradise and put up a parking lot right so we don't have as many plants as we used to absorbing carbon dioxide plus we start burning fossil fuels we screwed up the planet but carbon dioxide stays in the environment and traps sunlight methane though is worse so methane is actually a greenhouse gas as well there's not as much of it in the atmosphere but it stays in the atmosphere for times as long as carbon dioxide so it's a really dangerous gas well one of the largest producers of methane is cows so cows have four chambered stomachs which means they've got tons and tons of bacteria in their body that is sitting there trying to digest all that cellulose from like the grass and hay and everything that cows are eating and so when they get gas they belch so in this case which I know is ridiculous and so that's why I like this picture it's like I'm just really visualizing all these belching cows I've never heard a cow belch but I imagine I would laughs so these guys are out there belching living their lives the the company that owns the most cows in the United States is McDonald's so the McDonald's herd is just out there belching and having a good day well when they belt they're releasing 20 between 26 and 132 gallons of methane every single day so then you multiply that times 1.5 billion cows that's a lot so this is actually a huge environmental disaster you never hear about belching cows but this is like a thing and it's all because of those digestive bacteria it's just we have way too many cows because you know we eat meat and so this is a huge environmental thing so they've actually worked on engineering cows that belch less so they've created some like strains of cows some species of cows that belch less can you imagine that is contribution to science you see that cow over there I named her Daisy you see Daisy over there she doesn't belch as much as other cows but we need to be doing creative research like this to save our planet so I just think it's kind of interesting now as far as how things get out of your large intestine so yeah it's about to get good the small intestine has that peristaltic movement and so does the large intestine but instead of like kind of constantly moving the large intestine is a lot slower so you only get about 2 to 3 waves per day which is kind of moving everything like at once towards the rectum so we have another reflux here when the duodenum stretches that tells your body stuff is heading to the colon so after eating a meal you have the dog nikolic reflex that basically just says hey things are coming on down the road now we have what you've all been waiting for good times the defecation reflex I know anatomy and physiology is a really good time so this happens when the walls of your rectum stretch so there's dudas and they're trying to get out so if you remember from lab you have the internal anal sphincter and then you have the external anal sphincter and this is all written down on a slide so don't worry about writing it down the internal anal sphincter relaxes so that is smooth muscle you can't control it this tells your brain you gots to do T but then you wait until it's time a proper time to do T then you relax your external sphincter which is skeletal muscle which you do have control over because otherwise we'd all just be dude Ian whenever and I can't imagine living in a world where everybody's just walking down the street and they just do T so I'm glad that we control this so how do we get rid of fecal matter we call this defecation good times so there's this mass movement from the peristaltic movement two to three times a day this mass movement of waste stretching the rectal wall so like I just said the internal anal sphincter is smooth muscle remember smooth muscle you can't control it it's parasympathetic rest and digest right so it you have to be relaxed to do T so I know there are people that can't do T at work which like fascinates me because I'm like what if you're away from home for like two days but I had a friend that was like this she couldn't do T away from home so like when she'd go on a trip for like three days she wouldn't do T the whole time I'm like that's kind of a lot you know but it stressed her out so like if you're stressed you can't do T so a lot of people are shy in public restrooms like I have friends that can't pee in public restrooms because they they're so nervous that they're sphincters won't open and so I have one friend that I always have to like turn on the faucet in the in the bathroom to like you know kind of get her to like zone out a little bit so parasympathetic rest and digest you got to have that for this muscle to work for it to open up then the external anal sphincter is skeletal muscles so you have voluntary control over this so when you're potty training your kids you're basically teaching them how to kind of respond to the duty the duty signal come into their brain so we always have in every chapter kind of when things go wrong this chapter is one of the least pleasant to think about but when your large intestine is not working properly all kinds of things can happen so we always talk about kind of too slow or too fast the same thing here so diarrhea I love the definition of diarrhea it's due to a rapid transit time so basically things things are flying through your large intestine there's not enough time to reabsorb that water because remember that's the biggest goal of the large intestine is to reabsorb that water well if stuff's not staying in the large intestine long enough you're gonna be in some trouble this can result in electrolyte imbalance because you're not gonna pull in enough sodium and you got to have sodium for muscle contraction so it can mess that up it can cause metabolic acidosis which is basically you've got the acid kind of coming off the stomach and you're not neutralizing it with that alkaline mucus from the large intestine because again there's just not time constipation is the opposite where it stays in there too long so you want the waste to move through your body you don't want it too fast you don't want it too slow too fast it'll be all squirty and you'll lose a lot of water too slow and it's gonna be hard and dry like more like a chalky feces no one wants a chalky feces so constipation it's gonna be hard for you to get the Duty out because it's it's like a rock so neither one of these is a good thing problems that can just happen in the GI tract ulcers so ulcers are an open sore in the lining of the stomach so it can also occur in the small intestine and large intestine as well but it's something's happening to that mucous layer so they used to think it was stress and don't you love when people say if you have something from stress people say oh don't be stressed it's like oh gee thank you you solved my problem so now we know that it's actually caused by a bacterium so hilio I can talk today hey look go back to pylori so they actually named it after the stomach and so some people have like a lot of this and so now we can actually treat a lot of bleeding ulcers with antibiotics instead of like when my grandma had a bleeding ulcer like 30 years ago they just told her not to worry about stuff my grandmother worried about everything vomiting vomiting is when time moves by reverse peristalsis so if you've ever had dry heaves that's a thrilling time you can really relate to the muscle contraction of how intense that muscle contraction can be when it's trying to project things out of your stomach gall stones we saw those before on a previous slide remember they can be made of a lot of things but like cholesterol is kind of what we focused on but the you're basically getting like those big solid rocks of crystallized cholesterol filled bile which inflames and irritates the gall bladder hemorrhoids I'm telling you this day is getting good isn't it this is when you have the rectal vein which comes down in those anal columns and it gets enlarged or inflamed so a lot of times Henry hemorrhoids can be caused by constipation because if you're like pushing too hard to get the feces out it can irritate the rectal vein pregnancy having babies often causes hemorrhoids just because of all of the pressure on the pelvic girdle and area lactose intolerance so if you kind of go back to like those enzymes disaccharide aces or all we need to know disaccharide aces break down sugar but another sugar besides sucrose is lactose so lactose is a disaccharide lactose is milk sugar well you have to have lactase in your body to break down lactose well some people don't make lactase so if you don't make lactase the lactose doesn't get digested and it will upset your stomach so the good news is we've developed lactaid which is this pill you can buy at Walgreens and right before if you are lactose intolerant right before you would eat like ice cream or cheese you would take lactate and it helps with this which is a beautiful thing right because I can't imagine not being able to eat ice cream like that would be really really depressing but this is a great example of how important enzymes are it's like you have these enzymes that break down certain things well if you don't have those enzymes you can't break those things down hepatitis is inflammation of the liver caused by a virus and there's three x types a B and C cirrhosis of the liver also mentioned on a previous slide that the liver does regenerate but if you torture your liver every single day by alcohol or other toxins it gets where scar tissue builds up so instead of having liver tissue that does the job of detoxing you now have scar tissue so this is a degenerative disease because it like breaks down the tissue in the liver a colonoscopy when you turn 50 years old this becomes a yearly thing something to look forward to it also is recommended for people that have like even in your 30s for people that have a family history of colon cancer so colon cancer right now is one of the the highest like growing cancers in the u.s. especially in young people and so they use colonoscopies to screen for it and so it's basically a direct examination of the inner surface of your colon from the rectum all the way to the cecum and so they have to the prep for this they have to basically clean out your large intestine so you drink some pretty nasty things and then you yeah go do tea heartburn heartburn is the cardiac sphincter which is that car the little sphincter the little door between your stomach and the esophagus doesn't close properly some people just have weak you know it's just part of their body some people it's their diet they eat a lot of acidic foods but the reason why heartburn happens is that acid burns the esophagus because the stomach acid shouldn't be there and so there's nothing protecting your esophagus it just gets splashed over and over with that acid causing a lot of pain but also one of the biggest problems with this is esophageal cancer because if you're constantly repairing your esophagus from that acid you're constantly doing cell division while all cancer is is mitosis or cell division that's out of control and so this is kind of a nasty side effect of people with chronic heartburn so we've got like a lot of over-the-counter stuff like prilosec my husband has horrible heartburn like I always joke that he gets heartburn from breathing oxygen but he may have to have the little they actually will put a banned that so there's a surgery that you can get that'll basically help close that sphincter to Scott to stop this regurgitation because it's so dangerous to have heartburn kind of over a long stretch of time