hi so uh I wanted to continue my lecture talking to you about the um so let's get right there because there's nothing like digesting and we have to digest this material so um so just to recap where we were here is the digestive system um a 30ft tube extending extending all the way from the mouth the anus here I said it's all external we talk about the mouth we talk about the esophagus and I was just about to talk about the stomach can you see where the stomach is here it's up in the um vest and it is just below the diaphragm and the liver and so the heart is located just slightly above that so often stomach pains make an individual think they're having a heart attack um and sometimes it's just indigestion actually drive somebody to the e but we would prer that but we need to rule out that they are having a heart attack so last time I said the stomach food that gets there um you now has been this Bess it's been semit tude uh it goes in that way but when it is finished being processed there it ends up being a soupy mixture called C so the process is going on in the stomach then on mechanical digestion as well as chemical stomach secretes um a variety of products um that are going to break down the so the stomach is a muscular sack uh its volume ranges from 50 milliliters four liters huge that's for those giant bottles of Coke versus a very small you know um of um so 50 m small 4 L long muscle so it's stretchy we recognize it is being a j-shaped spru um it has the cardiac orifice which is I was telling you about last time is where the food enters from the esophagus upper dorm D portion uh is called the fundus the body is the main region in the pyic um area is the area close to the small intestine the first portion of that being the Jenum and it is actually innovated by parasympathetic and sympathetic fibers um and all blood leaving the stomach and in fact any of your digestive um structures any of those um blood and things that are absorbed into the blood travel Direct ly to the liver so here we have there a lot of noise outside today guys I'm very very sorry about that so here we have this j-shaped structure here's the fundus um so this is the diaphragm on top of it food has come in through the sphincter here so we have the fundus we have the body and this connects to the pylorus here and that is the first portion this area here the duodenum connected VI the pyloric sphincter um which is the small intestine so esophagus small intestine here we have the sphincter either end and if you take a look at the structure of the stomach here it is made up of longitudinal muscle circular muscle and oblique these referring to the directions that the muscular cells are organized in so longitudinal circular and oblique um and the lining the stomach has gastric rug rug are kind of these um Ripple like structures we also have these on the um in the pet of the mouth and that has the effect of kind of gripping and acting like a washer board and good is kind of Tears it up a bit and sometimes if you get the opportunity when you're in somewhere like Whole Foods if you go to some of the meat counters you can see that there is um uh material that you can purchase that we actually call Trip in England that has the rug present on it so stomach has those typical layers that I was mentioning to you about last time the mucosa sub mucosa and then we have muscle and these layers again as I said already found throughout the um digestive system but in the in the stomach the muscle lay is the most pronounced of all okay so the surface area of the stomach and everywhere along the digestive system is composed of simple columia epithelium okay simple columna epithelial tissue and those cells then are readily shed shred off through the digestive process so the sub mucosa is replacing these a lot of wearing there um this is a wonderful um his IAL section that um shows you what the lining of the stomach looks like so we have layers of cells here making up what are called gastric right and there are several different types of cells that are present here you can see there's these cells that look like very clear in the center and then you can see um there are other cell types that are present so below that in the sub mucosa you can gland here's another one so as this lining is worn down through the digestive process these cells get and this is a layer of muscle um you can just about see so the whole things um move up there are regenerative cells throughout and these closer to the surface so looking at the gastric glands then we have cells that are producing mucus compose the the glass then we have these ones here called peral cells these peral cells um these are the ones that look like those empty cells on my histology slide these are cells that are producing hydrochloric acid um and for this reason it is very important the cells above the gland that once on the layers of the gland the outer layers produce mucus stomach has to be lined with a great deal of mucus otherwise the hydrochloric acid that these cells produce um is going to break down the stomach lining if you look at the cells also further down in the gland you can see there are some here that have little dots on them that are facing towards the Lumen of the gland these are chief cells their job is to secrete pepsinogen pinen is an inactive protein digesting made in these cells and they secrete it into the Lumen of the Cogen made throughout life when you're an infant um those CH cells secrete kimin and lipas and these are um enzymes that are important IND digesting proteins so as you get an you become an adult they startop making kimin and like this just to not actually be living on a fat diet um a milk diet when you are um an adult just when you're a baby which is also why the teeth speak you deal with your know your more um consistent for the rest of your life cinogen is made by the che cells hydrochloric acid made by the peral cells and deep down at the bottom of the gland here I have got some cells in my cartoon that have these red granules that are pointing not into the Lumen of the land but pointing away from it and these are cells that we call enta Endocrine cells endocrine because they are going to be secreting chemical Messengers some of those are secreted into the blood scam and act as a hormone and some of those act locally a baracine messenger is one that acts locally so there's quite a few different cell types that are present in the gastric glands by the way the cells at the bottom are called intera endocrine because often things that are related to the gut are referred to as inter so the eneric system related to anything to do my next slide shows you a fantastic um scanning electron micrograph where um you know the microscope scans the surface of the cells and this is a gastric pit so the stomach contains these pits these are all the mucous secreting cells you can see here some of them actually have some mucus on them but you can imagine this is a very very deep and in there there are the cells there are the peral cells right down at the bottom we have our Intero ocins um I've said already that we make um uh hydrochloric acid in the uh Lumen of the gastric now that happens because the peral cells actually contain one enzyme that we've already talked about and that enzyme is carbonic and hydrates so the hydrochloric acid is made uh in a similar process so not only do red blood cells contain Carbonic and hydrates so also you the peral so in this case instead of making um you know um bicarbonate and um transporting carbon dioxide carbon dioxide diffuses into the peral cells where it interacts with Hydro chloric a with water form carbonic acid and this time when it's broken down to hydro to bicarbonate and hydrogen ions the bicarbonate um is switched out for chloride which exactly happens in red blood cells however in red blood cells these are compartmentalized um but in the peral cells this chloride is actually combined with the hydrogen ions to form hydrochloric acid um and this happens in an active process so it's pumping mechanism pumps that chloride to form hydrochloric acid and as a consequence there's a lot of bicarbonate that is released directly into the bloodstream around the stomach so we would to measure your pH there um we would see an increase in PH because of the this alkaline typ so that just happens briefly around the stomach it's very interesting how the peral and the red blood cells exploit the same chemical reaction have the same enzyme to do so Carbonic and hydrates very important um so hydrochloric acid then is just one of the components of gas here's our statistic we make about 2 to three liters of gastric juice a day mixture of water hydrochloric acid and pepsinogen which gets converted to pepsin reactive so hydrochloric acid important then for activating pepsin pepsin was produced in the form of pepsinogen it's activated by hydrochloric acid um there's a small amount of lingual lipase um that is made in the mouth that actually does nothing that gets temporarily activated in the stomach but this really is not uh significant to our digestive process only significant in an infant um so I don't need you guys to worry about that too much you should know again that Hydrochloric a acid important for activating pepsin the active form of pepsinogen hydrochloric acid is important for breaking up some of those tougher components of our diet uh you know the connective tissues in um meat uh breaking down the cellulose in plant cell walls we don't have an enzyme for that so it's very very important uh in digestion it also helps to convert feric ions to feris ions which is the form we need for incorporation into our red blood cells in making hemoglobin and that hydrochloric acid also acts as part of our innate digestive system and destroy bacteria and pathogens we ingest so that's a very important function in addition to the um pepsin that is secreted as pepsinogen um as I said already it's important in activating some of the um enzymes in infants um so we're not going to worry about that uh and also produced in the stomach is intrinsic factor so intrinsic factor is something that the peral cells produse um which is key in the absorption of vitamin B12 vitamin B12 is something that's very difficult for us to absorb it's a very you know out of all the vitamins they usually small molecules this is a complex molecule um camine it's only going to be absorbed in the presence of intrinsic factor uh and we need that uh again for making up um red blood cells so it's of interest to note that as you get older and the intrinsic cells and the peral cells lose some of their function they lose their ability to produce intrinsic factor this is often something that we have to think about in elderly patients who often require vitamin B12 [Music] injections so my next slide then shows you the significant action of hydrochloric acid on pepsinogen so the peral cells they produce hydrochloric acid cells however make pepsinogen this is referred to as aogen so aogen is a very special term for an inactive protein digesting enzyme the only thing it refers to an inactive protein digesting enzyme and it is important that our cells make protein digesting enzymes in an inactive way um if you think about this briefly if the chi cells were to make an active enzyme or were to make pepsin directly then that pepsin would immediately start to break down the cells that secret it so that's not a good thing um so we have to package it in an inactive way so zymogens are made and they are activated in this case by hydrochloric acid so hydrochloric acid here on my picture is showing you how it breaks the um um the orange beads of these purple beads so the orange beads were holding the purple beads in a way to not be active um in my little schematic here when they are released that can enable the um the beads to take up a different structure or other words here they've made pepsin active so pepsin can now get in there and start to work on dietary proteins so pepsinogen is a zymogen the active digesting enzyme is peptin is pepsin um and that pepsin is only made because of hydrochloric acid so this is an enzyme that is made and active at low PH okay made at low ph at the base of those glands there are Interra Endocrine cells as I said already they produce hormones and paracrine secretions hormones enter the blood and travel to distant cells that's the strict definition of a hormone a paracrine secretion acts on neighboring cell so it acts locally so there's two different types of Messengers um that we see here equally uh it's of interest to know as well that some of these Messengers have different effects on your digestive system and we have only started to discover these uh in the last uh few decades um in the beginning we thought there was not a lot of activity that went on in the digestive system but in truth there are a lot of things that we now know that impact signaling and appetite and behavior um for example you know if you eat something tastes nice you made a memory that it tastes nice so you learn behaviors based on um signals so we now know there's a lot of interesting signaling molecules act what we call on the gut brain axis what um so we'll possibly come across a few of these in the next couple of lectures so it's interesting to know as well that it's swallowing the process of swallowing in immediately is sending the nervous signal to your stomach so as you swallow your stomach has to know that it needs to relax that um the sage your Sprinter has to know to relax so these things are relaxing and getting ready to receive the food in addition food actually entering the stomach enables the stomach to relax further so that you can get more food entering your stach and there some gentle Rippling actions that are controlled by pacemaker cells in the muscle layers of the stomach so you're going to get a gentle contraction about every 20 seconds to mix the food with the gastric juice these contractions get stronger at the pylorus because remember that's the region that's going to connect it the small intestine so it needs to be much more broken down there and you get you know after about four hours you get that emptying and getting that material moving along the conveyor belt into the small intestine uh when I think about the stomach I also have to think about vomiting sorry to mention this but vomiting uh is induced sometimes by excessive stretching of a stomach that's what happens sometimes in a baby they don't know therefore um sometimes by overheating you can actually throw up sometimes by psychological stimuli um and that's interesting because you know you've seen something that is upsetting maybe you've seen an accident happen a very horrible accident accident or you've seen um something very gory it's something that frightens you when it frightens you it's got your alert signal on so your stomach empties very very quickly because you know remember what we said about blood supply when you need to have blood supply to your stomach it goes there so if you're frightened threatened and scared you might vomit so that you can get blood supply going directly to your muscle so that you can run away so it's like a fear a fear response the other thing that will Calla you to cause you to vomit is a chemical irritate and that's a good thing too because if you've got bacteria down there um that could potentially impact you it's part of your innate mechanism to just vomit and get that thrown back up get get it out of your body so of course to coordinate that there is an tic Center in the mola um you know so that it's going to then because all those components normally get you to swallow food and move it along to act in the opposite direction the TIC Center enes the process of vomiting then relaxes the esophagal spinter and causes a contraction of your abdominal muscles all at once to force those contents back up the esophagus sometimes it's so forceable it can even called you to expel some contents from your small in let's move quickly away from the slide on to on my next slide which is showing you um what a healthy um mucosa looks like so this is something that you'd see from endoscopy where you would go the doctor you'd have an anesthetic and they would um into your stomach um when the stomach lining is healthy you can see it's pink in this panel here um we have an ulca so an ulca is just an area of inflammation and see the lining is inflame and lining is inflamed um you know you've got areas of engorgement with blood cells you've got areas of macras you've got areas of irritation um and so you need to take care of that this this is just an said inflammation to begin with when it becomes an air an Elsa complete ulcer it started to erode erosion can happen because of um bacteria that's um uh getting through the lining or it can happen because other underlying causes um irritants or because the damage is now led to a loss of cells that are making mucus uh and your natural of hydrochloric acid has started to irritate the lining as well so we need to find out what the underlying causes to be able to recommend a treatment so this an area of inflammation not very nice either so away from that um and let me bring a whole concept together to you that tells you that the really acts that is a conveyor belt one area is ready to act and another area is completing its action and they're all sending signals to each so here in my first panel we have what's referred to Asic phase of gastric secretion basically when you are looking thinking tasting food your nervous signal is already sending information to your stomach we have a little plus sign here and that stomach has receive signals that are telling it to start producing mucus start producing your enzymes get ready the food is coming just like you know have a visitor the um the security guard at the desk is calling up to me to say somebody's coming at which point then if they're here for a meeting I'm already bringing up the relevant information on my computer uh and I'm calling out to other people in the department so that we can all be in the conference room you know and so on um so here we have the Vegas nerve um sending signals always guess the Vegas nerve to the stomach and once food is in the stomach here we have food in the stomach then signals are going from the stomach okay from the glands themselves one of the um enteric messenger molecules is hine it's also gastrin and is going into your bloodstream hormone histamine is acting locally sometimes these things act in both ways um to tell you speed up your secretions acting from the base of the gland as a paracine Messenger to take to the peral cells um and the chief cells make more xogen make more hydrochloric acid we have these signals from the stomach itself and interestingly the stomach not only signals to itself it signals to the brains as well and says you can stop producing saliva in the at the same time it's also signaling to the in signaling to the intes sing to the intestines to say food is coming at the same point the intestines sending signals to the stomach to say hurry up and then the sending signals to this particular M molecu here K say stop your action send the food this way know we're ready we're ready for the second phase of our meeting as it would be so gastric function is regulated phase it is regulated the stomach itself the gastric phase and it is also regulated intestinal phase so the intestines themselves are saying ready you know U to switch off we are bringing um um you know more so it's saying to the stomach and it's saying to the intestines get ready the intestines so they all suppress but at the same time there's another hormone called secretin that actually on the duum the first portion of the small intestine to get it to release more product from uh and one more thing that I wanted to add when I was thinking about the stomach was actually um in addition to ulcers um and you know acid reflux disease one of the other problems which we see with the gastrointestinal um tra and particularly on this slide it's showing you stomach stomach cancer is actually what a carcinoma looks like so what's happening here we have got um glands so here are the gatric glands with the G cells and the peral El the pital ones are the ones that look like they've got nothing in them um and so here's the Lumen of the gland and as I said before we have in the sub mucosa glands that are waiting to move up as the tissue is eroded through the vigorous process of digestion um and so as the erosion happens eely appear and become more mature in a forc up but in the case of cancer look at this we have got an overgrowth of these cells these cells have overgrown they have buried and so somebody that has stomach cancer has a long-term impact on their digestion particularly their digestion of protein which is what um sin acts on so they can no longer produce pepsinogen they can no longer um convert this to pepsin so their digestion is usually somebody that has this um has been suffering silently for a very very long um so at this point I wanted to briefly go back to um my diagram here showing you the digestive system so we have talked about what happens in the mouth in the mouth we produce primarily the hormone the enzyme amalay salivary amalaye which acts on carbohydrates in the stomach here so we swallowed the food we've been into the stomach in the stomach we have produced pepsinogen which gets converted it starts to digest proteins a lot of protein digestion there and then from here we're going to move into the small intestine small intestine the first area is the the jum up here then we have the Juna and we have the ilum but I wanted to briefly um uh step away because when we get into the small intestine we are faced with uh the action of some of our uh accessory organs um so I wanted to just kind of mention what they do these do not come in contact with the food but they secrete also into the so let's just think very briefly um about what's going to happen here we're going to get some secs from the liver the gallbladder and the pancreas so these all release their secretions into the small intestine they do not come in contact with the food that they continue the digestive process we've really only been digesting carbohydrates um and proteins up to n so and we haven't finished that job I mean when the material leaves the stomach it is K two material and so that Kim has to be further broken down so the liver um sitting above the stomach this is the largest organ in the human body um when you open up um body or you dissect a or something like that and I'll show you a virtual dissection um in the weeks to come you're going to see that the liver is actually the eest organ that's in there so looking at it we consider it to have a right lobe and a left lobe and there is a little green structure and it really is green in appearance that is on underneath the right lobe you can only see it if you turn it up and it over so we have the left lobe and the right lobe these are separated by this structure here the fform ligament this is actually the remnants of a blood vessel from when you were in neutro because when you were in neutro your liver was mature and you were using your mother's liver so this would divert the blood so it's got no fun whatsoever in an adult but we use it to indicate the left the left and the right lobe here so left and the right lobe turn it over there is the gallbladder um and gallbladder is attached so let's on to my next slide where I show you that the cells of the liver are made U made into blocks so they're assembled into blocks called um Triads and in those Triads we have branches of the hepatic portal vein the hepatic artery and the wild so the liver is composed ofes pretty much everything um of the liver has this prefix so we have the central vein surrounded by hepatocytes uh and so as I said area everything that comes from your digestive system go straight the liver something that comes from the stomach you drink a lot of alcohol goes straight to your liver um very little things are absorbed in the stomach um antibiotics it's going to go straight the liver liver is going to break down you're going to need to have another dose biotically medicine that are substantially broken down in the stomach and the liver you often and that's something called the first class effect but I just wanted to mention that briefly to you um the liver makes a lot of proteins liver secretes a lot of things but basically the cells of the liver um um filter a lot of material nutrients toxins biopigments by drugs I don't mean drugs of abuse I mean as well of drugs of abuse I mean things like hormons um a lot of things are cleaned so the liver is very important um in producing um these functions equally it makes bile and bile is taken to the gallbladder so this diagram shows you here um the liver the gallbladder and the pancreas but without the stomach so we have these ducts coming from the liver okay the hepatic ducts that bring um bile to the gallbladder bile is stored in the gallbladder and then it is released through this duct okay this duct actually joins coming from the pancreas so we have this duct pancreas duct that go into theum and then we have this duct here that can also go straight into the duodenum but they in fact meet together in this area here called the hepatic pancreatic ampola an ampola just means a swelling and it just means the two things are joined together and there is a spincter at the end there's a spincter that controls the secretion right so the pancreas can secrete on its own the gallbladder can secrete on its own um and these things straight into the jine so just to tell you as well very briefly then the cystic duct from the gallbladder joins the hepatic duct um the duct from the pancreas and the bile duct combine to form the hpop pancreatic andola they empty into the Jenum there is a sphincter there and sometimes that sphincter goes by the common name as the sphincter of OD um so the G bladder is located unide the liver it's a small organ but basically it stores oil and it secretes a lot of of bile a day 500 milliliters to a liter there actually quite a lot of bile um and it contains cholesterol Bop pigments and fosol lipids minerals yellow green in fluid fluid in color um and so whenever you um digest fat you actually need to secrete bile from the G BL you actually need to actually break down fat so the liver makes cholesterol um and so this is one of the reasons why if somebody has a cholesterol problem we may be giving them medication help them reduce amount of cholesterol and so um we need to have these minerals um uh and fat to break down in addition the coloration of the biopigments comes from the breakdown of hemoglobin so those yellow green fluidy materials are what give um store its color by the time it's been processed somebody that has a liver problem and can't make biome um we often see coloration changes in um so um an interesting uh uh kind of side effect of having these or diseases um in addition vitamins that you digest such as fat soluble vitamins will be um breed from the body in bile so they will end up being broken down by your liver and you know excreted um through the B which will that enter your PES things that are fats things that are water soluble end up in uine so often we might need a stool sample you know if a patient has a problem with materials and we also need a urine sample to check on material that is being processed so the pancreas then so the pancreas um just below the stomach but it's kind of behind so if you were to open the body cavity the first structure you would see underneath the stomach a smooth flippery structure would be the spleen and you would have to kind of move that out of the way you look a little bit further back to note you have to lift the stomach slowly uh to see the pancreas the granular organ uh described as being retrop peral behind the peronal membrane and being posterior to the stomach it has both endocrine and exocrine functions uh for the endocrine function um it's going to secrete hormones into the bloodstream and we're going to talk about that when I get on to the metabolic chapter so we don't need to worry about insulin and glucagon in this chapter they are hormones that control metabolism however in terms of digestion releases um juice uh through exocrine secretions it has exocrine um gland activity and the duct then is going to secrete into the duid Union pancreatic juice pancreatic juice is a mixture of water enzymes zymogens and sodium bicarbonate and if you look back what I put there I put zymogens and enzymes so I wanted to indicate to you again that aogen as is an inactive protein digesting enzyme only so the other enzymes that it produces are going to digest those other food groups carbohydrates um and fats so so that's significant in addition sodium bicarbonate is a production of concrete and that's important because material that is coming from the stomach is acid in nature it's kind and very few enzymes are function are going to function at that acidic pH so sodium bicarbonate is necessary to neutralize the pH so to summarize the zymogens the zymogens produce Cogen trogen becomes when it is active fot cinogen this becomes fot when it is active and then we have Pro carboxy Pepes when this Cogen is active it is carboxy these are three protein digesting enzymes once again they are produced as an inactive form because that is significant um if they were active they would be breaking down the pancreatic Asos cells that are making them in addition to producing zymogens um the pancreas cells are also producing amalay pancreatic amalay is very important in breaking down carbohydrates we have only had partial breakdown of carbohydrates with the secretion of salivary amalay in the mouth so there was no digestion of carbohydrates in the SK in addition there's been no digestion of lipase very very little because this requires the secretion of B and bile then is going to break down fats um so we have pancreatic lipase being produced by the pancreas and of Interest we also have ribonuclear and bioxy ribonucleases being produced these are produced by the pancreas because uh every cell that we get we eat um be it a plant cell or an animal cell contains DNA and RNA and these are macro molecules macromolecules that contain sugars macromolecules that contain um bases and macro molecules that contain phosphate groups so we need to get that material as well we're not going to waste anything so we have an enzyme um enzymes that are produced by the pancreas that are capable of doing this um and interestingly just in case you wondered those um zymogens become Act AC at only when they are secreted into theum there is an enzyme called ocin ento meaning of the gut that is produced by cells of the duodena and that enzyme activates so it breaks TR cinogen down into dsin and then dsin is going to go ahead and activate the other two asign so for this chapter I need you to know tripin um kimot tripsin and carboxy peptidase um and you don't have to worry about the OS but the name comes from the fact means of the gut so these are produced a zymogens again just like cinogen in the stomach because these things are protein digesting and they're going to break down the cells that secrete other ons uh and just a little bit again to integrate the concept of hormonal secretion and regulation I said col cystic kinon was something that you um should know cck produced by the small intestine actually speeds up initially breakdown of material in the stomach and then actually suppresses it but while it's breaking down activity in the stomach it's actually working in the small intestine it's working in the small intestine on the gallbladder on the pancreas to get while being released getting um you know pancreatic enzymes being produced um and you're going to get neutralization of the acid again secretin and gastr and gastrin these are hormones gastrin produced from the stomach is going to work on the gallbladder to get acity going satin is released from the duodenum and that's going to get more bicarbonate so this continuing activity um you know to to speed up the digestive process so the um small intestine is now shown back on this diagram so here we have the stomach um not showing the liver the gallbladder or the pancreas but they are secreting into the duodenum the duodenum is the first portion of the small intestine the gunum next portion and then the ilium is the portion that connects to the large in so um so we're deep down now into the small intestine and the small intestine is going to accomplish the final stages of all chemical dig that's why there are so many enzymes being secreted in something every food group in addition we have absorption taking place so nearly all chemical digestion and nutrient absorption is going to occur in the small in um and this is accomplished by creating first of all a large surface area as we've seen before a large surface area is important for absorption and for diffusion the lungs the lungs have a large we have a large surface area created first of all the small testin has circular FS on it so those circular FS causes the kind to flow around the walls of the small intestine rather than directly it takes spiral um on the surface of the small intestine there are these finger light projections these are called Villi so these Villi then all add to the area furthermore every one of the cells here has micro Villi on them so they have their own Villi so they're are villi microvilli on the cell of the Villi then we have the Villi themselves so we often refer to that layer as a Breck and I'm just going to go back to my previous slide not that one this one and if you look here the cells here so this is showing you micr can you see they all have these little projections on them we often refer to this then as the brush border so those brush border cells are important increasing the surface area so large surface area created by having circular FES by having Villi and by having microvilli those microvilli cells are very important in accomplishing the very final stages of Di okay I mean the vli present within that V we have a very good blood supply because we're going to get absorption into blood we also have lymphatic vessels here too these are important for absorbing fat as you recall I told you there were specialized branches of the lymphatic system that are in the small intestine these are called Lacs um in the intestine we also have some CS so these CPS the bases of the Villi in here we've got goblet cells making mucus there mucus everywhere we have some cells as part as part of your innate um um mechanism are secreting antibacterial chemicals remember your digestive system is external okay it is external all the way from mouth to your anus it is cells that make up mucosa Associated lymphatic tissue that are there to uh counteract and present there are layers of big cells um that are grouped together that make up pairs patches so we have you know aggregations of lymphocytes um that are there um and what they do is they are um um fighting any pathogens that might be so here's a really great um um biology section showing you the muscle of the intestines showing you the glands of the intestine and these structures these are villi okay these are Villa so if you were to look at them scanning electron micrograph here I have a scanning electron micrograph that scanning um electron micrograph shows you that these are T stonik structures that are in fact um the Villi of the intestines the muscle layer is important for motility as we've always said motility is moving things along the conveyor belt of the um of the gastrointestinal tract as it does so again it happens by peristalsis we have this rupik action that squeezes it through and what's interesting is food that moves into the stomach then because the whole thing is compartmentalized um these structures as they then compartmentalize when one is full the layer next to it has emptied so it will refill so as food from the stomach enters so as food enters the stomach it pushes what was already in the small intesting along to the next section um and as I have here on my um my diagram um I've written food in the stomach causes the gastro ilal reflex so what that means is the seeum fills the seeum is the first portion of the large intestine so once the stomach fills what was in the small intestine moves in to the large intestine to prepare um and so I'm going to start my next section I'm going to finish here and I'm going to start my next portion of this presentation by discussing the process of digestion itself so remember the whole process is designed to digest and absorb carbohydrates lipids proteins and nucleic acids these are our macro molecules and we need to extract material that composes them to use this for primarily for energy and then secondly to repair and replace materials so this process um has been pretty much accomplished by the time material gets to the um end of this small intestin so I'm going to recap this on this next time so I'm going to um come back to that and I'm going to start that with a um summary of the process of so um I'll talk to you