welcome back welcome back welcome back to science all right in our final section no surprise we are talking about the large intestine the large intestine is just about five feet long and the distal end is going to open uh through the body's anus and so it's the main purpose of our large intestine is to absorb some of the water electrolytes and reabsorb and recycle water and digestive secretions and ultimately it's going to form and store the feces until ready for defecation so let's talk about the structure of the large intestine there's going to be pouches that are going to form at the beginning at the large intestine right as it's moving from ilium and to like the large intestine itself this area is going to be called the cecum so the appendix is going to be attached to the cecum and it's going to be lymphatically active whenever it is um when you have a immune response and I'll tell you this from medical school when I was we were in our cadaver lab and we had been working on things for months and months and months now and we are filing into the abdominal cavity and every day there's a set of orders of the exact thing we have to do so we don't just kind of explore and poke things instead it's very regimented that you're going through you're noticing these things you're documenting charting um as you're seeing and one of those things you know at this day was the appendix I've taught about the appendix um before that point as I was a TA back in college and I had never seen one in real life and I thought somebody was playing a prank and by this point it was probably October um and so once again we have been with a cadaver for a long time and I thought somebody had and people don't do this but I thought somebody had it looked just like this it looks like a pinky finger and it's smooth and has the ridges and it's that long and that wide I mean it doesn't have the fingernail part but it looked just like uh the little finger and I was like oh my gosh and I was looking at it and I was like you know I was waiting for Kutcher to come out and if you don't understand that reference it's um it's because you're young so enjoy that um I was kind of looking around for people like to be laughing or something and once again people don't do that it has never happened I like a good prank um this would have been kind of out of line but I thought that's what was going on I knew that the appendix would be there and I thought somebody had surgically removed the appendix and put in the little finger and I was like oh my gosh do I tell my professor uh what's going on here and so the first time I'd ever seen an appendix um I was dumbstruck on how much it looks like the smooth side of your pinky so here is the appendix here's the cecum and this is just at the beginning so as categorically we talk about parts of the large intestine the part once again we went through the small intestine uh it's 22 to 27 feet long and now we've empty it into this area this is going to be ace and then colon the one that is transfer first yeah that's the transverse colon then when it turns and descends it's called the descending colon and when it's kind of an S shape at the end that's a sigmoid colon and then towards the very end you're going to have an area that's called the rectum and then anal canal and anus all right a few other structures that we can point out along the way we can see the momentum that's there but the mesentery that's wrapping around it notice that there's four layers here the outermost excuse me the inside of that tube the innermost layer is going to be the mucosa just outside of the mucosa is going to be the submucosa go another layer out and you're going to get to the muscularis and I don't know about you but I feel like they just gave up on naming things like this is the muscle in Latin Musk muscularis yeah it's it's the muscular component it's going to be a smooth muscle and then the outermost layer it's a serious layer and we see that in like so many things and like seriously yeah seriously all right as we move descending we have the tinea coli these are three different bands of smooth muscle that are going to help hold things together and then we see these like pouchings that are here these are the Hofstra and Hofstra are going to be pretty involved in helping shape the overall shape that we get for for fecal material so PCS has those shapes due to Hopsters helps form the feces all right so the colon has the ascending transverse descending and final terminates into the sigmoid portions there's also going to be different areas that are the hepatic and the splenic flexor so these are going to be the left um because the colic so your spleen is going to be in this region so this is going to be the left colic this is the right colic colic is referring to the colon and so this is the paddock flexure this is the splink flexure the rectum extends from the sigmoid colon to the anal canal and it lies next to the sacrum so if you're trying to figure where that would be on the skeleton and the anal Canal itself is going to be about inch inch and a half and length of the last inch inch and a half of the large intestine and this is going to open to the outside as the anus in this area you're going to have the internal and external anal sphincters once again a sphincter is a circular muscle and so this is going to help in defecation process we'll get to that in just a moment all right so this is a cross section of the end here you have the anus you have the internal anal sphincter you have the external anal sphincter that are there these muscles here and you're going to have the levator Ani which shows here this is a muscle it's a great name for a muscle levator Ani you're right whenever um somebody scares you it's the levator Ani that really goes into play it's going to be also used in defecation yeah I think you guys can figure out how right so the structures there's four different layers of this of this tubular organ of the elementary Canal this does not have the Villi it doesn't have the plique circularis so it doesn't have those segments to work things back and forth like a plique circular layers the rings that are within and it doesn't have the Villi which are going to increase the amount of surface area instead there's going to be the longitudinal muscle that we talked about the three different bands the 10 I coli which are going to go down the entire length of the colon as we see the 10A coli here here and it's that band in the middle there all right muscle bands create pouches a hostra and the Hofstra are going to be there there that's all over it um and the Hofstra is going to help form the feces into the structure that we look at and see those lifter different pieces not to be graphic but you know it's not typically slick and smooth instead it's going to be lumpy and Hofstra are the reason one all right so the large intestine has no digestive function like it's not breaking down carbohydrates here it's not breaking down lipids here you're going to have goblet cells that are going to be secreting mucus this is going to help things move through but most of the water that has moved through will be absorbed so roughly 90 percent of the water is going to be removed here this is going to house your intestinal Flora so bacteria are going to break down a few things like cellulose and produce vitamin K and b12 thymine all are going to be key for your diet now at the end once you have formed feces it's going to carry out defecation the gas itself like if you're going to flatulate this is going to be a mixture of several different gases now you've probably heard that there's methane yeah there's methane there but nitrogen oxygen as well carbon dioxide hydrogen ammonia and the hydrogen sulfide is usually the bad smell that you get from flatulence so when people pass gas the gas that's stinky is the hydrogen sulfide there's a few others that are going to be in there as well But ultimately it's going to cause a lot of the odor is the hydrogen sulfide so the movements of the large intestine similar to the small intestine it's going to be slower and less frequent so types of movement we're going to have mass movement and we're going to have the defecation reflex so mass movement is going to have peristaltic waves so it's going to be the arithmetic contraction as it's moving things through these happen two to three times a day usually after meal specifically if you want to set a clock about 45 minutes after you eat a meal you probably have to go to the bathroom and that's why and if you don't eat a lot maybe it's less often than that because input has a direct correlation on output so if you eat a lot you'll probably defecate a lot if you eat very little you'll probably defecate a little if you're a healthy individual without any secondary conditions all right the defecation reflects as you guessed this is how feces is going to relieve the body so this is going to involve holding a deep breath Contracting abdominal muscles then your VC will move into the rectum peristaltic waves are then going to be triggered in the descending colon you're going to relax the internal sphincter then the external sphincter and then the feces will leave the body so what is feces feces is the stuff that's not digested or absorbed and so that includes you know water 75 percent of feces is water and you're like it doesn't look very watery if you wanted to like be scientific about it if this was put into a biological oven and heated until there was no more water in it it would be about 25 percent of its original Mass because most of it is water all right it's going to have some electrolytes mucous bacteria bile pigments that's going to be why it's that color is because of that so this is after you have bacterial alterations some of the punching odors that are released from bacteria include phenols the hydrogen sulfide that we already talked about it's indole scuttles and ammonia now if let's say you take an antibiotic um let's say you go to the doctor and you have a viral infection they say you get an antibiotic you get an antibiotic and so they give out that antibiotic and you take the antibiotic and you're taking it religiously and you kill off your normal microbial Flora that's not a good thing now what you'll actually kill off usually would be the E coli that's there I know they're gram negative and now that but with the removal of the E coli you have another bacteria that's there in your colon a really common one when it's kept in small numbers like within reason it's not a problem it's called Clostridium difficile so clostridium the facil and E coli these are a normal part of your microbial Flora of your colon you want them there they have jobs that they do and they're great to be there you don't want them gone so let's say that in order um you've taken the antibiotic and you've some reason you've messed up your microbial Flora you've removed the E coli now the most common bacteria is clostridium difficile and they have spores on the inside of them which means they can go through some kind of tragic event and the spores kind of act egg-like in nature if you want to think of it that way as it's a doomsday plan so those spores will hatch out and reconstitute their colony and then they have all these open spaces and all this nutrient and so they're going to reproduce in high number and so the amount of these bacteria are just a major major spike in that population this is causing a disorder or a temporary setback called C diff the C is for clostridium the DIA diff is for difficile and this is a really horrible horrible odor um after you've been around it once you'll never forget the smell you can walk into a hospital like I smell C diff and it doesn't have to be somebody that's just a dirty hospital that kind of set up instead you just develop a nose for it um also a long time ago I was teaching micro and we did different microbes where people would do a presentation and a paper on a different kind of microbe in the microbe that this person did her presentation on was C diff and she worked at a hospital and she brought in a specimen cup half full it was disturbing and I like what are you doing what are you doing what in the hepatitis are you doing well you know you're gonna and then in her presentation she took and was shaking it back it was definitely liquidy like this is so gross you went all out oh I was Disturbed that's all I could think about and I was like don't you open it don't you and then she opened it I didn't smell it I didn't taste it either um but then she let us in on the prop that it was butterscotch pudding that was thinning a little bit of water but that that's what it looks like it was so gross um I have yet to this day uh eaten butterscotch pudding since it's kind of ruined it for me not that I was all in on it but I just thought you guys should um be aware of that so uh disorders of the large intestine one of those is diverticulitis this is the weakening of the intestinal wall lead to protrusions of the mucous membrane those out pouches are going to become inflamed and infected and even painful irritable bowel syndrome is going to be a category of things so lots of different disorders are here but ulcerative colitis is one of those and that's going to affect the mucosa and submucous at the large intestine and you can tell that this is a very British presentation because you have bloody diarrhea cramps so also uh colitis is going to be very very painful very horrible and pretty common also Crohn's disease is more serious this is going to go instead of just the mucosa and submucosa this is going to go into and also affect the muscularis and the cirrhosis as well so it's going to affect all four layers of the small intestine this is going to cause diarrhea and pain lots lots of pain so colorectal cancer is something that we should mention here with the Western diet that we consume a lot of our Foods put us at risk for colon cancer if you eat bacon is one of those it's going to increase your chances of colon cancer I think it by eight percent maybe it's 12 percent but it's drastic in the increase for colon cancer by just eating bacon and even grilled foods so it is the fourth most common cancer in the United States screening tests include the fecal a cold blood test and colonoscopy colonoscopy they're going to put you under and they're going to use a camera and they're going to look at the different Hofstra and the different layers and levels throughout your rectum sigmoid descending transverse ascending they want to make sure that you don't have any extra gross or irritations or ulcers and the occult blood test it does a couple things one is you can check for anemia this way another is it's going to check to see if you have a bleed that is hidden in the feces because it's absorbing a lot of things if you have blood in your feces if it's really really dark then it's going to be towards the beginning of your colon if it's bright red then it's going to be towards the end of your colon and you can kind of see where the injury potentially is and that would be a big sign to like get a colonoscopy and get a colonoscopy now so lifespan changes as you age you're going to have a change in the digestive system that's going to slow down tooth enamel is going to thin teeth are going to become more sensitive the gums are going to recede gingivitis is going to be the case you're going to have tooth May loosen break or Fallout the GI tract becomes less efficient you're going to slow peristalsis which may lead to heartburn gastric secretion is going to slow so digestion is going to slow constipation may be more frequent nutrient absorption decreases in soluble fat and we have the incidence of lactose intolerance increases and the accessory organs but typically not necessarily in ways that affect Health all right guys so this is going to finish the digestive system all right so long and I look forward to seeing you