Gastrointestinal | GI Motility of the Esophagus & Stomach

I know engineers in this video we are gonna talk about GI motility but we're primarily going to focus on the motility of the esophagus and the motility of the stomach and will have a very very brief intro on the fundamentals of GI motility but again that is gonna be the primary focus of this video it's going to be again the motility specifically occurring within the esophagus and in the stomach okay so let's go ahead and get started here's the thing when we talk about GI motility for pretty much all of them the esophagus the stomach

the small intestine large intestine they all have different types of motile functions so what do I mean so when we talk about motility they're gonna come in three different flavors okay one is it can come in what's called segmentation okay and we'll go into all these in detail for each individual organ but segmentation is this type of activity that causes a lot of mixing and churning so here let's say the 2-bit let's at least get the big functions out of this segmentation has two big functions one is it loves to mix and mix the time

with digestive juices let's just put it like that okay so its design is whenever the actual this is more common in the small intestine time even the large intestine for example let me take my hands here okay my hands are going to be representing the intestines what happens is a large area of the intestines will actually their circular smooth muscle will contract and it'll create these rings the circular smooth muscle contract and produce rings at multiple different points of the intestines but when it does that it contracts at another point and it just keeps mixing

and mixing the kind contents it helps to with the digestive process so one thing is it's really really good at being able to mix the con with the digestive juices and by doing that it helps to increase the absorption of nutrients okay so it really helps to aid in this digestion and the absorption of nutrients this is again more common within the small intestine and in the large intestine but again this is more for the mixing trying to mix the food with the digestive juices to help to break that substance down and the segmentation also

allows for the mucosa we'll talk about that in the astrology of the GI tract the mucosa the inner lining of the GI tract to come into close contact with that substances to aid in the absorption of the nutrients the second motile function is going to be propulsion okay so it's going to be called propulsion and this propulsion we can also kind of use another term and that is called para stall sious now peristalsis is defined as the alternating wave of contraction and then relaxation where a segmentation was you're moving the com a few centimeters forward

and backward and forward and backward it's helped to aid in that digestion absorption peristalsis is trying to move the actual substances along throughout the GI tract so that it can be moved into a certain point of the GI tract to be absorbed or it can be eliminated from the body so the purpose of the propulsion is to move v let's just say GI content along GI tract okay whether it be for elimination or pushing it to the next segment of the GI tract so that it can be absorbed alright so that is really really important

with this the last one that I want to mention here is the reservoir okay the reservoir function or we can kind of say a storage function here this is going to be where certain organs like the large intestine and the stomach they can actually hold food substances in them for a long period time the large intestine can hold a lot of the feces in it for a long period of time and the stomach can hold a lot of the food contents in it for a decent amount of time maybe four to six hours and stuff

so it can actually act as a reservoir function now the significance with this is that this is carried out and we'll talk about a couple of these along the way this journey of geometry that we're gonna go on its carried out by sphincters now there's a bunch of different sphincters that we'll talk about we'll talk about the upper esophageal sphincter the lower esophageal sphincter the pyloric sphincter gastro I'm sorry the ileocecal sphincter lot of them that are gonna be really really important internal anal external anal sphincter but they're basically acting as reservoirs are storage they

can help to play a role within the reservoir function of storage of certain contents GI contents within these different organs okay and you'll see that whenever we go through each individual one of them now one more thing about smooth muscle when we talk about smooth muscle there is two different types of contractions okay there's rhythmic contractions the rhythmic is more carried out by a lot of this segmentation and then this propulsion so this is more of your rhythmic okay so in other words it's going for that alternating attraction relaxation type of activity the sphincters they

play more of a toning contraction role in other words they have sustained contractions so that's important remember rhythmic is kind of like alternating contraction relaxation whereas tonic is more of a sustained contraction now again I'm not gonna go into a lot of depth here we're gonna keep this super super simple let's say that we take a smooth muscle cell and this smooth muscle cell has the ability to depolarize okay and let's say that it also has the ability to contract now in this smooth muscle cell you'll notice we're gonna kind of go back and forth

between the smooth muscle cell in this graph so we can get a good understanding here so if we come down to the graph here we're gonna assume that this smooth muscle cell is that it's you know usually smooth muscle cells have a resting membrane potential you know somewhere we can say you know around let's just say for this one it's negative eighty that's what we used for the other smooth muscle video right so let's assume that it's like negative 80 okay and then let's say that there is another point which is the threshold potential and

let's assume that that's you know pretty constant and let's assume that that's negative 55 millivolts okay what happens is is our smooth muscle cells particular smooth muscle cells let's assume that this is what's called a inter Stickle cells of Kajal these are pacemaker cells in other words they have the ability to spontaneously depolarize and generate action potentials that can cause a lot of the smooth muscle the GI tract to contract okay now how do they do that they generate these things here called slow waves okay if you guys again we've all talked about this in

the smooth muscle video go check that out if you haven't already I'm gonna go through it pretty quick but it produces these sub-threshold waves and these sub-threshold waves here are called slow waves now these slow waves what causes them to be formed okay well if you look here in this smooth muscle cell it has these leaky calcium channels so here's a leaky calcium channel and what it allows for is it's kind of always open and it allows for a little bit of calcium to trickle into the cell and this little bit of calcium trickling into

the cell helps to kind of depolarize the cell you know slightly depolarize it bring the inside of the cell be coming from resting to a threshold right that's its goal now here's the thing these threshold these sub threshold waves they're obviously not enough to be able to trigger an action potential so sometimes and the reason why is is as this cell starts kind of depolarizing and getting ready to approach threshold there's special channels that open up in the cell membrane when we get close to that threshold portion and that is if we don't actually hit

threshold there's potassium channels that open and the potassium actually leaves the cell if potassium leaves the cell what happens to the inside of the cell it becomes negative so what are you going to see here this rise will be due to calcium if it doesn't hit threshold potassium channels open potassium leaks out and starts to repolarize here's the thing we should understand what are the things that can cause the cell to become to get to the level of threshold and that is going to be things like for example a seal choline acetylcholine which is released

by your parasympathetic nervous system by like the vagus nerve or the sacral the actual s2 s3 s4 nerves or it could be hormones for example gastrin okay there might be other ones like cholecystokinin C Cretan maybe even another one called mote Ilyn the whole point here is that these guys have the ability to load cations into the cell so let's say that they have a way to be able to somehow stimulate a lot of cations to flow into the cell making the cell super positive if that's possible what this can do is is it can

stimulate this sarcoplasmic reticulum which is inside of these actual smooth muscle cells it might be doing it through certain signaling processes again that we talked about in that video but let's just assume that it was enough that this was trying to cause the sub-threshold if it didn't hit threshold potassium channels open potassium leaks out repolarizes let's say that it produces again tries to produce another slow sub-threshold wave here it doesn't get to the point but then we have this extra stimulus from acetylcholine gastrin mote Ilyn all those things that load cations into the cell and

then guess what it does it brings it up just enough to break the threshold value there okay what brought it from this point to this point it was the extra assistance from acetylcholine gastrin Motel and there could be other factors as well stretching of the end of the GI tract organ certain types of humoral chemicals but it's just enough to break the threshold value once it breaks the threshold value what that does is it stimulates the sarcoplasmic reticulum so let's say that this is our Sarco plasmic reticulum in the sarcoplasmic reticulum there is tons and

tons of calcium ions that are stored here or sequester here by cows equestrian and calreticulin and stuff like that but it's stimulated by this depolarization enough to push a lot of this calcium out here into the sarcoplasm if the calcium is pushed out to the sarcoplasm what can it then eventually do depending upon if the enzymes are present it can help to initiate the cross bridge formation and let's say that this is a smooth muscle cell that I actually can contract it will generate a contraction okay that's important okay it's super important that we understand

this okay so again let's say that we have the sub threshold not enough then you hit a point where it's trying to generate a sub threshold but we get this extra assistance from neurotransmitters maybe hormones maybe stretch it brings it above threshold when it brings it above threshold it's enough to stimulate the sarcoplasmic reticulum to push out calcium on its calcium ions along with the you know different myosin light-chain kinase enzymes will play a role in initiating the contractile response so what you see when you look on this actual graph here's the point at which

it actually passes this threshold it produces what's called spike potentials so in other words let's say that you have a really large release of acetylcholine a lot of gastro and a lot of different hormones and what they do is they bring this depolarizing R wave really really high above the threshold the higher above threshold the more spike potentials you produce and the more spike potentials you produce the more intense the contraction so in other words the force of contraction will be high on this one but it'll be super high on this one okay so that's

important that we understand that okay and again just remember the interstitial cells of kajol they're the ones that are basically generating the action potentials so really what they're doing is this calcium is being released and they could be connected but imagine here like imagine like this imagine here is a smooth muscle cell and here's another one here's another one let's say this one right here is an interstitial this is the interstitial cells of Kajal okay they have little gap junctions that connect to them between the cells okay and let's say that this guy was the

one that was depolarized okay if he's depolarized that calcium can be released and pushed into these different cells if the calcium is pushed into these other cells and let's assume that these cells are the ones that contract then again the calcium will help to initiate the contractile response again calcium plays a role with activating calmodulin which activates the myosin light-chain kinase which phosphorylates the myosin head and plays a role within the contraction okay so again understand that that gives us the basic fundamentals that we need to know for motility again the basic functions segmentation propulsion

reservoir what is the esophagus - out of all of those what is the primary function of the esophagus all right so now what I want us to be able to do throughout the process of these GL Matilda videos is to cut the combine and ask ask ourselves okay what does the esophagus do out of those three functions it doesn't do any segmentation but it does do propulsion its design is to transport the GI contents from where from the oral cavity whenever we swallowed it into the pharynx right and we're gonna take it down to the

stomach that's its function it doesn't really play a huge role in the reservoir function it does there is something that we should talk about with respect to this sphincter and this sphincter but again it's not really acting as a reservoir for very much time at all usually food is transiting through the esophagus pretty quickly okay food and fluids so it's primary function out of all of these is going to be peristalsis so please don't forget that his primary function is going to be peristalsis again how would you define peristalsis it's the alternating wave of contraction

and relaxation okay it's a rhythmic activity now we if you guys haven't already we have a video on the enteric nervous system and we also did a video on deglutition where we talked about the esophagus so we're not gonna have a super in-depth conversation here I'm gonna get the basic things across again but it's always good to repeat things it's always important to do that helps with helping us to remember these these concepts okay let's pretend here I have a nice big piece of pizza okay nice big piece of pizza there's some pepperonis here on

some cheese mmm good what happens to this piece of pizza what is it gonna do let's assume that we digest it we break it down within our mouths and stuff like that use certain enzymes to help to break it down chemically we chew it up right so it's gonna be a bolus but what it'll do is it'll start causing the stretch of the esophageal walls stretching the esophageal walls if you guys remember it activated some stretch receptors let's assume that here this is the stretch receptor and it picked up that stretch in the actual GI

wall when it does that it has the ability to activate or inhibit two different types of neurons okay now if the actual food is right here the bolus we're gonna want to pinch this edge in okay so we're gonna want this part so I'm going to kind of create like a little pinch here this part here I'm gonna want to pinch to kind of a clue the loom preventing the food from going back up right I want to pinch that edge in so I want this part to contract and then I want this part here

distal to the actual bolus I want this part to relax so that it can receive the bolus so that is important so now how does it do that we're gonna go pretty quickly for this since we've already talked about it you have this plexus here which is present in between here's your muscularis externa right of the esophagus there's a inner circular and then there's an outer longitudinal so what is this one right here called this is the outer Longy - no lair and this one right here is the inner circular layer and then again what

is this plexus right here called this plexus if you guys remember what's called the my enteric plexus or our box plexus we call it right and it consists of ascending neurons and descending neurons in this case what we want to do to the ascending neurons here we'd want to stimulate them if we want to stimulate at this point here here's what's gonna happen these neurons here are gonna come over to this smooth muscle layer there and this smooth muscle layer here alright and let's just say one more I got that level and that level okay

we want these guys to be stimulated now when that happens if you guys remember we really specific chemicals on to the circular layer to cause it to contract what are those chemicals that we released if you remember it was a cetyl choline and substance P and that stimulated this circular smooth muscle layer to contract and cause this indentation into the esophagus to push the food forward the longitudinal layer though we don't want this to contract we want this part to relax okay so if that's the case then we want to release vasoactive intestinal peptide and

nitric oxide onto that level then we want to stimulate these guys this inhibitory neurons these descending ones we can say actually the descending ones so now the descending neurons are gonna be stimulated and if their stimulates let's say that we come to this part here now we're gonna have this smooth muscle here I don't say this one here and then we'll come to this layer right here and this layer right here now this was the proximal portion we wanted the circular layer to contract because it constricts it and pushes it for we went to longitudinal

layer to relax so that this part proximal to the bolus doesn't open up okay because when the longitudinal layer contracts remember it opens the actual lumen this part down here we don't want the circular layer to control now because that'll actually produce a constriction room we don't want that we want it to relax so in this case we're gonna want to inhibit the circular layer so we're gonna want to release what's called vasoactive intestinal peptide and nitric oxide in this region but we're gonna want the longitudinal layer to contract so that it opens up that

aspect of the lumen so it'll release acetylcholine and substance P here okay so don't forget too that that is the main function it's gonna keep doing that so it'll come right here right they'll say that the bolus gets to this point now this part will contract and then this part distal to it will relax and it'll keep doing that for pushing and propulsion or moving this bolus towards the stomach that's the significance of it now what I want to do is I want to completely tie in because it just it makes so much sense to

tie it in to clinical correlations associated with the esophagus like dysfunctions in there motility one is this sphincter here look at this sphincter guys this one is called the upper esophageal sphincter okay economy refer to it usually as they write it as you e/s and if you guys remember we said that the upper esophageal sphincter was primarily made up of the cricopharyngeal okay which was intubated by the vagus nerve in certain people usually as they get older okay it's more common in older individuals the walls of this part of the esophagus become weak okay and

as they become weak what can happen is just above that it can form a little outpouching or a diverticulum what is this outpouching or diverticulum called right there around that level of the cricopharyngeal or the upper esophageal sphincter this is called zinc errs diverticulum and again this is more common and older individuals but usually it is a outpouching just above upper esophageal sphincter now some of the problems with this with the zinc errs diverticulum is that if you think about it the food is gonna have a hard time being able to continue to pass through

right so sometimes and even the food can actually cause this back up so it can produce trouble with swallowing so one of the big symptoms that you see with these individuals is they have dysphagia also sometimes this food whenever they're like laying down or they're trying to go to sleep some of this food can try to go into the respiratory system so it can aggravate the respiratory system may be causing some coffee or regurgitation so you might see some coffee you might even see some regurgitation here's another sign though let's say that a food just

starts percolating in there and sitting in there and as that starts percolating and sitting in there it causes some really nasty smell and that nasty smell that we start seeing is called Halla ptosis so another sign can be halitosis usually how they diagnosed as incres diverticulum is they send the patient to do what's called a a barium esophagram they just inject them what they put some dye all right so they don't inject they give them die and if they die that they swallow collects into a little pouch behind the esophagus that could be an identifier

of zinc or diverticula so what they usually do is they go in they actually remove that diverticulum and then fuse that layer together okay so that's important to understand that now another one that's associated with the esophagus is what's called ecclesia okay so there's another one which is called ecclesia ecclesia is really important because this is usually a situation in which they lose the my enteric plexus in the distal part of the esophagus usually around this sphincter here what does this finger here called this sphincter here it's got so many names I'm gonna put le

s for lower esophageal sphincter or cardiac sphincter or gastro esophageal sphincter right so there's a bunch of names for these but in the distal part of the esophagus they don't have a my enteric plexus or arbok plexus right so there is absent my enteric plexus now think about this super simply the bowls comes here let's assume that it's here now what will happen this part will contract this part will relax then again you'll come to this point here this point will contract and then this part down here should relax but guess what it doesn't relax

because it doesn't have a my enteric plexus in that region if it can't relax can the food move into the stomach no if the food doesn't move into the stomach then the food just accumulates right here and so all the food proximal to this actual portion where there is no my enteric plexus just accumulates and starts dilating the esophagus so what she'll start seeing is you'll see what's called a mega esophagus are dilated esophagus mega esophagus usually these people will present with dysphagia trouble or difficulty swallowing they'll also have some regurgitation okay they'll have a

lot of coughing okay another thing is you'll start to see that this patient is gonna have a really hard time being able to hold down food because they're gonna have weight loss okay so they're gonna have weight loss maybe some mound nourishment so these are all some symptoms that can actually happen here now with ecclesia what they do is they actually send the patient to do what's called a esophageal manometry okay all it is is they take like a little man in me like a pressure gauge basically shove it down the dudes goalie into their

esophagus and measure the pressure if the pressure in the esophagus is usually greater than 40 millimeters of mercury that's pretty darn high and that's usually maybe an indicative sign of someone who has might have some type of situation where there's the obstruction of the food maybe ecclesia maybe some other costs but it's usually an identifier there as other tests that they can go with for that but again obviously they would have to maybe treat it with surgery or they can give certain chemicals there's a you know they can get the botulinum toxin they can actually

treat patients with ecclesia with the botulinum toxin they can give them nitrates they can give them calcium channel blockers different things okay but that is something that we should truly understand with respect to the esophagus okay so that covers the esophagus now let's move on to the stomach all right so now we covered the esophagus now we're gonna go ahead and start about the stomach all right so let's go ahead and get started all right so now when we talk about the stomach this guy is super important because we have to compare him with these

functions that we had okay so we had segmentation we had peristalsis we had the reservoir or the storage function of it out of those which does it actually play a role in okay so here's the thing and we talk about the stomach it kind of does like a segmentation but we don't really call it segmentation instead we call it mixing so when we talk about the stomach there's going to be three significant functions that we should know about one is source as it serves as a storage okay or a reservoir okay so a reservoir another

thing is it plays a very very crucial role in mixing okay mixing or churning if you will the different gastric contents the food that we're ingesting and trying to break down and it also plays a very very important role with what's called emptying okay in other words trying to empty the contents of the stomach into the actual duodenum so we have to understand each individual function the storage function how do we do this now we have to talk about here's what I want you to do it's gonna make your life a lot easier when we

talk about the stomach here I want you to think about all these different functions with respect to the three phases of gastric secretion if you guys don't know what I'm talking about we have video on the cephalic the gastric in the intestinal bass but I want you to just think about it super super simply okay in the cephalic phase which is basically what so the cephalic phase was the sight of food was the thought of food was the smell of food the taste of food all of these things had the ability to activate the vagus

nerve the efferent fibers of the vagus nerve now if that's the case then these efferent fibers of the vagus nerve but what do they do look at this this happens before food even enters into the stomach it can come to this portion of the stomach right here and it can cause this portion of the stomach what is this portion of this on the college we should have a little breakdown here the anatomy this right here is called the cardia this portion here this portion right here is actually called the fundus this portion right here is

gonna be called the body and then this portion right here we're actually gonna say is the pylorus actually will go to will go up to about right here we'll say this is the pylorus okay so again what do we have here we have cardia we have fundus we have the body or the corpus and then again over here we have the pylorus alrighty here's what I want you to think about what the stomach the stomach is kind of weird it actually can act as two individual organs if you will the funding portion and the upper

aspect of the body can act as one specific have one specific function and then the remaining part of the body and the pylorus have another function here's what I want you to remember the pylorus and a little bit of the body play a role in the mixing and emptying function of the stomach whereas the fundus and a little bit of the upper part of the body play a role within the reservoir function of the stomach now this goes back into this first phase which is the cephalic phase so now we're going to talk about what

happens here in the cephalic phase first so we think about the food we see the food we taste the food we smell the food all of these things are happening before food even enters into the stomach when that happens it activates this vagus nerve the vagus nerve will come to the fundus now here's what's weird it stimulates nerves here to trigger the release of what's called vasoactive intestinal peptide and nitric oxide guess what that does to this part of the actual stomach smooth muscle it relaxes it so now if it relaxes it let's represent it

like this here let me get this on the way so we can really understand this I want to do it like this so now again what is it actually having coming here this is the vagus nerve cranial nerve 10 and it stimulates the release of basal active intestinal peptide and nitric oxide again what nerve is this this is cranial nerve 10 okay which is the efferent fibers of the vagus nerve don't forget that now when it releases this vasoactive intestinal peptide in nitric oxide look what it does it actually causes this Porsche I'm going to

represent it like this because this portion of the fundus and the upper part of the body to relax so now look what happened here it relaxed it went to this portion here this is that fun dick relaxation this right here where the stomach the fundus of the stomach and the upper part of the body of the stomach relax and response to the cephalic phase this is called receptive relaxation so what is it called receptive relaxation this is so cool the stomach is getting ready to receive the food and so it's starting to cause this dilation

of the relaxation of the funding smooth muscle prior to food even being in the stomach that's unbelievable it's accommodating it's getting ready now let's say that we follow the bowls to the next point so let's say here is our our bowl so here was the first part here okay so now the food is going to come down right it's going to come through the esophagus and it's going to come here into the stomach now it gets into the stomach and as he gets into the stomach the stomach is gonna start stretching it the volume is

gonna start increasing so as the volume starts increasing it starts causing some distension some stretching within the walls as it starts triggering some distension or some stretch within the walls remember what that does it triggers a local reflex to trigger the release of VIP and nitric oxide right as that happens then what is that going to do it's gonna promote even more relaxation so now look at this we're gonna accommodate the food even more now so now we stretched out an extra capacity here you know the stomach has a it can continue to occupy a

large volume of content without increasing in the intro graphic pressure so here's the important thing I want you to remember when this guy comes in this bolus it comes into the stomach it does something it actually increases the intra gastric volume starts stretching on the walls causing distension activating the my enteric reflex but also just realize that it's not just this reflex that can happen if you really want to remember do you remember that there is some stretch receptors here that can pick up the distension in the walls and they can come here and activate

the a ferrant the efferent fibers of the vagus nerve can activate the efferent fibers and trigger this long reflex so remember there can be long reflex arcs and short reflex arcs either way both are important but again within the cephalic phase it's the site thought taste smell of food food is actually not even in the stomach yet in the stomach is already relaxed and receptively expanded and dilated to receive the food then the food gets into the stomach increases the inch or gastric volume distends the stomach stretches the stomach again triggers either a long reflex

arc or a short reflex arc which causes even more relaxation more opening up or dilation of the stomach and this actually is called adaptive relaxation so this one is called adaptive relaxation these are both important because they play a role in what's called accommodation so these both play a role in what's called gastric accommodation an accommodation is important because what that's saying is whenever there's an increase in inter gastric volume the pressure the intra gastric pressure stays constant to a limit okay obviously there's certain point at which the volume is too much to where the

pressure will start rising usually that's somewhere around to where this actually can't play a factor when it's greater than 1.5 liters then the pressure starts rising but again super important to understand here the reservoir function of the stomach remember treat the fundus in the upper part of the body is the reservoir how does it do it so phallic face sight thought taste smell food food that hasn't even gotten to the stomach trigger this vagal response to cause the relaxation of the smooth muscle to receptively relaxed food enters into the stomach starts ascending the walls of

the stomach as it starts to standing the walls of the stomach it activates either a long reflex arc or a short reflex arc which causes the smooth muscle to relax and even dilate even more that's called adaptive these to play a role within gastric accommodation which is as food is in the stomach the volume of the stomach is increasing but the intra gastric pressure is staying constant to a certain degree until the volume is greater than 1.5 liters then the pressure starts rising there's one more thing that we should understand with respect to the gastric

phase so this one was the distension right so this was our distension and that was the first one the other thing is let's say that this bolus is high and partially digested proteins if you remember partially digested proteins were able to activate particular cells located within the lower part of the stomach like maybe in the body or and the answer the stomach and these were called in Tarot endocrine G cells and these G cells are releasing particular chemicals what were those chemicals that they were releasing they were releasing gastrin and what you need to remember

is that gastrin has the ability to come over here and stimulate the actual smooth muscle to relax even more so it also plays a role in this adaptive relaxation response okay so gastrin has the ability to cause this fundus to relax even more and continue to expand it also does play an important role within the antrum of the stomach to cause the answer I'm sorry to antrum of the stomach to contract and empty so it has two roles one is it can cause fun dick relaxation and it can cause the antral pump to start contracting

so that's the big thing there so now we know the cephalic we know these two things let's play a role in the gastric phase and then again these two things work distension and high partially digested proteins which if you remember played a direct role with increase in pH all right now we talked about the last thing which is the intestinal phase with respect to this reservoir let's say that the stomach is emptying its contents out here and the contents that is being emptied out here into the small intestine is rich in protons it's rich in

fat it's rich in peptides is rich in carbohydrates all these different things this is all that kind that we put out here when it does that if you remember there were certain entero endocrine cells that could be stimulated by these different factors one could be cholecystokinin which was primarily in response to fats and partially digested proteins see Cretan which is primarily responding to a siddik hime GI P which is called gastric inhibitory peptide or glucose dependent insulin autotrophic peptide and that was primarily responding to carbohydrates all of these actually play a crucial role in doing

the same thing they like to cause relaxation of the stomach primarily of the fundus in the upper body to allow for the stomach to start relaxing collecting the food storing the food for a little bit longer until the duodenum is prepared itself for this kind contents that the Doge somebody is trying to pump out okay so that's important to understand there one other thing we'll actually get to that a little after we'll talk about another reflux called the entero gastric reflux but we'll get to that a little later okay so I think we have a

pretty good idea of the storage function of the reservoir function now we're going to cover this mixing function and emptying function they actually go hand-in-hand if you remember we said let's do this one in this actual blue color here and a portion of the stomach usually let's say like right here let's say right here and the body of the stomach the mid-body of the stomach there's special cells in this area that are generating a constant electrical rhythm this portion here is where you're gonna have those pacemaker cells so this is where the highest concentration of

these pacemaker cells are gonna be okay those interstitial cells of conduits are located in between the inner circular I'm sorry the middle circular in the outer longitudinal layer they generate those action potentials right so they're the ones that are sending out those action potentials when they send out these action potentials it causes the stomach smooth muscles to contract and usually these contractions start off within the body of the stomach now here's the thing the contractions increase in intensity and in force as you work your way down to the pylorus that's what you have to remember

so for example let's say that we talked about the contractions at just this point here it might only be little rippling contractions it might not be very strong okay then you move your way down here to like the lower aspect of the body maybe it's a little bit stronger contractions okay then you move in here to the pylorus these contractions are super intense almost to the point where they occlude the actual lumen of the stomach so now look at the bad boys so this is what I want you to understand if you work your way

down from the actual upper part of the body all the way down to the pylorus the intensity of the contractions are increasing so don't work don't forget that so for example we'll have like a mini diagram right here let's say here you start off with the stomach here and then you have another one okay and then we'll have one more right here again keep it keep it simple here when you start up here the actual contractions are gonna be kind of shallow kind of a rippling effect then you work your way down here to like

the body and they're gonna be a little bit stronger then you work your way down to the pylorus and they're pretty much occluding the actual lumen okay so that's the important thing to remember that as you're working your way down from the let's say upper body a then you work to the lower body let's say that this is part b and then you work your way down to the pylorus this is part C the contraction intensity is increasing so what does that mean when you start up here at the upper part of the stomach all

right these pacemaker cells generate an electrical potential about three to five about the basic electrical rhythm that they have their basic electrical rhythm is about three to five action potentials per minute so that's gonna generate about three to five contractions per minute now when they generate these action potentials it spreads to this part here contracts when it contracts here what it does is at this upper part of the body is it pulls and Yanks some of the climb out of this reservoir from the fundus out into the body to mix it with a lot of

that actual gastric juices here then it comes into like the mid part of the body contracts and again tries to push the actual climb to the next part so right now the chyme is moving in this direction then we get to this part here the pylorus this is where it is super crucial we really need to understand at this part what I'm gonna do is I'm gonna actually break the pylorus up into three little segments here so I break it up into three individual segments right here and right here is gonna be one so let's

say we go over here this is the proximal portion this is gonna be the middle portion and this last part here is going to be the distal portion so again we have distal we have middle and we have proximal now when the actual kind gets here at this point here in the proximal aspect of the pyloric antrum when this part of the pyloric antrum contracts it really squeezes down and ACLU's the lumen behind it what's the purpose of that to prevent any of the actual climb from back flowing into the stomach but this part here

distal to the proximal aspect of the antrum relaxes so that the chyme from the proximal antrum can get pushed into the terminal or distal antrum okay that's important okay now let's assume that this has a mixture of particles maybe it has some big particles in here maybe it has some small little itty bitty particles in there but there's a lot of solute particles the significant thing here is that in order for substances to travel through the pyloric canal here they have to be less than two millimeters in order to pass so if this thing hasn't

been if these chemicals are these solutes haven't been reduced in size to at least less than two millimeters in size they can't get passed forward so when the proximal pylorus contracts it pushes the contents forward into the terminal antrum right now the next one is you're gonna have the middle Antrim the middle aspect here it's going to contract when it contracts it takes all of the climb that it might have in this area okay all the kind that it might have in this area and it pushes and forward okay so the proximal Antrim would push

all of its kind which has different solute particles into the terminal Antrim then the middle Antrim will contract when it contracts it pushes a lot of its particles which might have again some big particles here or it might have some itty-bitty particles in here but it's gonna push its substances through the pylorus canal the reason why is when the middle Antrim contracts the terminal Antrim is still relaxed and open so it pushes out a good chunk about three to four milliliters is pushed out here into the actual duodenum here's the thing though at the same

time when the middle Antrim contracts and pushes things through the pyloric an island out into the duodenum it also pushes a lot of that time back here into the back part of the stomach why to continue to keep mixing with a lot of the actual gastric juices to continue to reduce those particles down in size now what particles really be moving through here the particles that would pass through would be the particles that were tiny you know in other words they were less than two millimeters in size some of those larger particles that weren't able

to get through there they'll actually get pushed back here into the body of the stomach to continue to get mixed with the gastric juices to reduce them in size okay then you get to the terminal antrum when the terminal antrum actually contracts it's the interesting one okay it's the really interesting one when it contracts again what kind of time could be right here there could be large solutes there could be some little itty bitty solutes kind of mixed in here all over the place but when the actual distal aspect of the antrum contracts it pretty

much closes off because when it contracts here it's pretty much right next to the actual pyloric sphincter so when the distal or the terminal antrum contracts the pyloric sphincter also contracts and closes off this lumen so now any substances that are in the terminal antrum can't go out into the duodenum they only have one direction that they can go in what is that direction they get pushed back here okay now there's a reason why I'm telling you this the proximal when it contract it pushed substances into the terminal antrum that part right there just that

aspect that is carried out by the proximal antrum this is called propulsion it's just trying to move the solutes again a lot of these solute particles along the middle antrum what did it do when they contract right here when it contracted it tried to push a lot of the solute particles out into the duodenum transpile Oracle II about three to four mils and then some of it backwards this going backwards and actually going outward is important because it plays two roles one is it plays a role within the propulsive function you know emptying the stomach

contents but also it pushes it backwards to mix with the gastric contents and this right here is going to be that mixing effect so it has a propulsive effect and then that mixing and grinding like effect then the terminal antrim when it contracts remember it's so darn close to the pyloric sphincter that it the pyloric sphincter contracts with it occludes the actual pyloric canal now no chyme can exit out all the time can only go in one direction and that's back into the actual stomach body to get mixed up with the gastric juices and this

is going to be called retro polishing okay and that's important that we understand that now because of all this think about it again what would happen if we were to think about this in the cephalic phase and the cephalic phase what we be doing we're getting ready to ingest food if we're getting ready to ingest food what are you going to want to do you're going to want to be able to cause this food to just stay here no you're going to want to empty it so that we can make more room for the incoming

food so in the cephalic phase what would you expect to happen in this area it's going to start causing a lot of contractility of the pylorus a little bit of the body what about in the gastric phase well food is in here what is gonna happen it's gonna be distension which is gonna cause fun dick relaxation and there's also going to be a lot of partially digested proteins that's gonna cause the release of gastric gash and will cause fun dick relaxation but gastrin also has a emptying effect an acetylcholine which is coming from the distension

that'll also have a contractile effect but then the intestinal phase what were chemicals were releasing cholecystokinin secreting GIP all of these things what were they doing they were actually acting to inhibit the pyloric and contractility because they don't want a lot of this time to get empty down into this area because just dumping all that stuff out into there could cause some really really nasty effects so another mechanism that actually helps to protect us from that as you have receptors out here that pick up the significant distension and they actually go and activate your sympathetic

nervous system when the sympathetic nervous system is activated these nerves come here and they stimulate the pyloric sphincter to really really contract when it contracts it closes off the pyloric canal prevents any more substances that are being able to be released into the duodenum this right here is called the entero gastric reflux the entero gastric reflux it's a sympathetic reflex we talked about it already in the gastric secretions okay that's important now one last thing that happens that we need to talk about what the stomach is let's say that some little kid ingest a penny

all right and wanted to ingest that penny obviously those things are really big they're greater than two millimeters how does that penny actually get out because obviously we need to excrete that substance right well there's something else that happens in what's called the fasting state and we need to make sure that we don't forget this one this happens in the fasting stay so let's write this one down in the fasting state or the inter digestive period we have what's called a m/m/c this stands for migrating motor complex this happens in the fasting state when we're

not eating there's a hormone that's actually released called mote Ilyn we'll talk about this phase more in the intestines because it is important but what Motel and can do is is it's been found to stimulate this migrating motility complex it's a peristaltic wave basically and the peristaltic wave kind of starts here at the body of the stomach and just moves its way down the pylorus and tries to empty a lot of the contents out of the stomach into the duodenum what it can empty out is it can empty out a lot of the chemicals that

were actually greater than two millimeters in size so if someone swallowed a penny or like on a chicken bone or something like that it could actually be pushed out because when the migrating motility complex occurs it actually has a way of relaxing the pyloric sphincter to empty a lot of those contents out another reason for the migrating motility complex is what is in this area a lot of gastric juices a lot of hydrochloric acid digestive enzymes the cells in this area the surface epithelium they're constantly undergoing so much damage that we have to regenerate those

every three to six days so there's a lot of D Squa mated cells or cellular debris so it's just taking all of these substances that are remaining in the stomach after we've eaten and just yanking all that that cellular debris any remaining time any things that weren't able to be reduced less than 2 millimeters in size and pushing it out here into the intestines so that we can eliminate it so it's kind of like a housekeeping function if you will so there is a disease that can actually plague this unfortunately this right here the pyloric

sphincter my fiancee actually had this condition and it's called hypertrophic pyloric stenosis and this condition is usually the result of the hyperplasia which means that you have more smooth muscle cells or the hypertrophy the cells are bigger of the pyloric sphincter so what is it usually it's hyperplasia and hypertrophy of pyloric sphincter pyloric sphincter this is usually more common in boys they genetically traced it back to that's more common and in boys and they might believe that there are some environmental aspects that can be related to a lecture in people who use antibiotics like certain

macrolides they've also seen that it can cause this pyloric stenosis somehow when we look at this let's look at what's actually going to be significant about this the pyloric sphincter we know is responsible for allowing for controlling and regulating the climb exit let's say that this thing is so stenosis the notices what does that mean it's narrowed okay it's to the point where this thing is so darn thick that it is including the pyloric canal and now substances aren't able to exit the stomach if these chemicals are substances are solids whatever's in the stomach isn't

able to exit what is gonna happen the stomach's gonna stretch and stretch and stretch and stretch and eventually it's gonna activate the efferent fibers of the vagus nerve send those information up to a specific area in the medulla called the emetic center and trigger vomiting so one of the tell-tale signs that you can see with these people who have hypertrophic pyloric stenosis is that they're gonna have what's called vomiting and not just like I'm not talking like normal vomiting I'm talking like exorcism type of stuff I'm talking oh I like projectile all right that's one

telltale sign another thing with this hypertrophic pyloric stenosis is usually their stomach muscle it gets so thick because it's working so hard to try to empty these contents out but it's not and there's so much distension if you remember the more distension there is the more it activates those sub-threshold waves and bring them above threshold which increases the action potential which increases the contractility over time the smooth muscle gets thicker and it gets to the point where if you watch you can visibly see the stomach undergoing peristalsis and you can even feel it too another

thing is if you do your physical examination you palpate right around the epigastric region they have what's this called this olive shaped mass in the EPI gastric region all right and then one last telltale sign here is if you do some blood work what you'll notice that the patient's pretty darn dehydrated but they're also showing signs of what's called metabolic alkalosis which is where their pH within the blood is really hot because they've lost a lot of their hydrochloric acid a lot of the chloride and so because of that that can cause metabolic alkalosis also

they're losing a lot of fluid so they're gonna be dehydrated they're gonna have some electrolyte imbalances so this is really important so what they usually do with the patient is they send them to do an ultrasound obviously they look at all the history and the physical in the lab work but then they'll actually send them to do an ultrasound and if the ultrasound shows some thickening of the actual pylorus area then they know okay then what this person definitely have some pylorus noses usually this happens a couple weeks after birth okay and with that said

what they usually do is they do what's called a pile or oh my Oh Tomi okay they cut the pyloric sphincter to open up this area and allow for more of the contents to be emptied out into this into the duodenum okay so that is a little tidbit on the situation some certain types of GMO Tilly disorders that can happen with respect to the stomach I hope that made sense I ninja nurse so in this video we talked a lot about the GMO tality of the esophagus and stomach and we talked a little bit about

the fundamentals of motility again we're going to continue to this discussion and we're gonna talk more about the geometry within the small intestine large intestine in another video and I hope to see you guys there I'm excited to continue to keep talking to you guys about that stuff I hope all this much stuff made sense I really do hope that you guys enjoyed it if you guys did please hit that like button comment down the comments section please subscribe also you guys get a chance go check out our Facebook Instagram the movie on our patreon

account iron engineers as always until next time you [Music] you [Music]