Gastrointestinal | Deglutition (Swallowing)

I ninja nerds in this video we are going to talk about deglutition or swallowing it is an extremely extremely important process and the reason why is if you think about it in order for us to be able to absorb for example the nutrients from a piece of pizza we have to be able to chew on the piece of pizza we have to mix it with the saliva we have to be able to swallow it in order for it to pass from our oral cavity to a pharynx to the esophagus to the stomach and then eventually

into the duodenum where we can absorb those nutrients so it is an extremely important process and clinically relevant all right so now what we're gonna do is we're gonna talk about specifically the three phases of deglutition so let's go ahead and get started alright so the first phase that we're gonna focus on is the oral phase so here's one thing I want us to understand it's not just important to notice and known of the physiology of these entire pathways the oral fringe on esophageal phase it's important to have a little bit of understanding of your

anatomy so when we talk about oral phases obviously the events that are occurring within a swallowing process that are specifically focused within the oral cavity but we should understand where does the oral cavity begin and where does the oral cavity end so the oral cavity specifically so I want us to understand like the boundaries so if I were to talk about the oral cavity boundaries I think that is really important for us to understand here so the oral cavity boundaries the first thing is anteriorly so if we go to the anterior part there's a space

between the lips and the teeth they call that the oral vestibule so anteriorly it's bordered by the oral vestibule so anterior it is actually bordered by the vestibule oral vestibule okay cool so that's the anterior boundary the posterior boundary will get a better look at this later when we take an anterior view of the oral cavity but there's an arch right here in the back part of the oral cavity it's called the pilato gloss arch the pilato gloss arch is the posterior boundary of the oral cavity so the posterior boundary is going to be the

palate o gloss ol arch and like I said we'll get a better view of this when we go over to the fringe you'll face because when I get to see a nice anterior view of the oral cavity okay so that's the boundaries the next thing we should understand before we even get into the events that are occurring inside of the mouth what do we have to do in order to put food into the mouth we have to open up the jaw so in order to oppress the mandible bring the mandible down so that we can

fit a piece of food into our goalie is we have to have muscles that are going to depress the mandible so what are some of those muscles that will depress the mandible all right so what are some of these muscles one of the big ones that I really want you guys to understand here is going to be the lateral pterygoid the lateral pterygoid is really important because he has a bunch of different functions but we're focusing primarily on the depression of the mandible so he depresses the mandible so he opens up the jaw now another

thing is we should not only just know the muscle but what nerve what nerve is innervating this guy this is primarily cranial nerve 5 but when we talk about this there is actually going to be a bunch of divisions of cranial nerve 5 one is there's actually the opthalmic the maxillary in the mandibular the mandibular is the third division so we can put a three here to represent that this is the fifth cranial nerve third division which is also the mandibular nerve another one is going to be the digastric so the digastric anterior belly this

is another one the digastric anterior belly if the high weight is in a fixed position it can also depress the mandible and this is also innervated by cranial nerve five and this is going to be again the v3 the v3 is going to be the motor branch of the trigeminal nerve the ophthalmic in the max layer and more for the sensory functions another one is going to be the Milo hyoid and the mylohyoid muscle is also innervated by the trigeminal nerve so we'll put cranial nerve five here and again this is the v3 division the

last one is called the genie Ohio and the genie Ohio 8 is actually innervated by the cervical plexus primarily that of the c1 ramus okay so this is innervated by the cervical plexus but primarily by the c1 part of the cervical plexus alright so all of these muscles are going to contract to depress the mandible now here's the cool thing when you depress the mandible you bring the mandible down right it stretches the antagonistic muscles to the depressors the elevators when you stretch those muscles that activates muscle spindles those muscle spindles appropriate receptors and they

respond to the stretch on the muscle when they're stretch it activates the eighth fare and fibers of the trigeminal nerve and sends that to the brain stem activates the motor fibers of the trigeminal nerve it comes out and causes the activation of the elevators and when you elevate the mandible boom it'll bring it up because the whole purpose is we were depressing to open up the actual jaw to put food in the foods in the mouth bang we crunch the food with the actual action of the elevators in the mandible what are some of those

muscles one is going to be the most powerful muscle which is the masseter muscle okay the next one is called the temporalis and this is a very interesting muscle - okay this elevates the mandible and elevates the mandible the next one is going to be called the medial pterygoid I don't know why I have a four in there okay but we got masseter temporalis and medial pterygoid what's nice is that all of these muscles are innervated by the trigeminal nerve which is cranial nerve five and again this is the third division okay this is actually

going to be the third division or the mandibular division now when we depress the mandible by those depressor muscles stretch it activate muscle spindles trigger the elevator muscles to contract and crush the food it utilizes our teeth you know because the mechanical digestion is we're just trying to there's a whole bunch of different things with mechanical digestion you're not breaking any chemical bonds you're just trying to break the food down into smaller pieces well our central incisors and lateral incisors are good for like cutting or nipping at pieces of food the canines are good for

tearing or piercing into the food and the molars and premolars are good at being able to grind and crush the food so the combination of our muscles of mastication and the teeth what are we doing we're breaking a big food molecule like a piece of pizza down into smaller pieces that's really good because there's a important reason for that we'll talk about it out to the salivary glands but the last thing is once we activate those muscles and those muscles contract there's pressure receptors that can pick up and there in the oral mucosa so the

gingiva even the tongue and whenever there's a high pressure from you pushing down on that food it activates nerves sensory nerves that go to the actual brain stem and inhibit the trigeminal nerve and the motor fibers gum going to the mandible elevators will be inhibited if they're inhibited what will happen they'll relax and the mandible will drop back down to a resting position that's one of the cool things about this next thing is not too much about this just realize that you have salivary glands and there's two types there's intrinsic which only account for about

10% of the salivary secretion of secretions and the extrinsic and this was the one that was the pirat of the submandibular and the sublingual salivary glands in this accounts for about 90% of the salivary secretions but more important that is what is the purpose of this saliva the muscles over here pretend here's a bolus and we make our way here and here's a piece of food so here's a big glob of food and they get broken down by this chewing process when they get acted on by these muscles here it breaks the big food food

particle down to smaller food particles then what happens is the saliva is going to lubricate all of these actual food particles and there's mucin molecules and different types of digestive enzymes that will combine with this moisten the food lubricate the food soften the food and make it more into a nice compact mass so it's not so big and that little mass that we now have here is going to be called a bolus okay there's two reasons that I wanted to mention this by doing this process mastication and the salivation mechanisms it gives us two really

important things one is it increases the surface area for chemical digestion okay and this would be by salivary amylase which is a carbohydrate digesting enzyme and lingual lipase which is a fat digesting enzyme and the other one is it decreases abrasion of GI lining particularly the pharynx and the esophagus try imagining put swallowing a potato chip hole you're gonna frick your stuff up that's not what you want okay so that's the big thing that we want to know here for that process now let's assume that we've done these things thus far we've done these events

so now we took the big bolus I remember the big piece of food we ingested it we broke it down by the mastication process we mixed it with the saliva and now it's a nice compact mass here which we're gonna refer to as a bolus the next event that has to happen is we need the tongue to take on a special shape so you have ma souls of the tongue they're called intrinsic muscles of the tongue and what they do is they change the shape of the tongue in such a way that they form like

this central trough it's like a longitudinal central trough so imagine here here's the tongue and here's my little trough here that's one thing that the intrinsic muscles the tongue are going to do they're gonna form a central trough the next thing is there's going to be other muscles and these are the extrinsic muscles of the tongue and the extrinsic muscles of the tongue are actually going to elevate the tongue so that the tip of the tongue touches the actual palate that's low so cool so not only informed as nice little longitudinal look we can do

it like this actually look this is actually a lot better here we'll have the tongue up like this and then we'll have like imagine like a little tunnel there there's like a little kind of like longitudinal tunnel the bolus is sitting right here in this okay so two things have happened one we elevated the tongue so we had to elevate tongue second thing is we had to form a trough so the second thing here is we had to form central trough the elevation of the tongue is carried out by the extrinsic muscles of the tongue

and the central trough is formed by the intrinsic muscles of the tunnel and we'll label these when we go over there of Tom okay cool now once we've done that we have the the actual tip of the tongue at the hard palate look what this does there's a whole purpose of this it creates like a nice little downward slope so there's like a little slope that this bolus can just be like we write down into the pharynx so we create this downward slope that'll allow for this bolus to move post tearily into this area which

we're now going to refer to as the oral pharynx so that is the significance of elevating the tongue and forming a central trough the whole purpose is to create a downward slope that is the significance there so now oral phase we have the boundaries next thing is we have to have the mastication process okay and remember there's four muscles of mastication we mentioned a lot over here but the main ones that are involved lateral pterygoid medial pterygoid masseter and ten poor Alice and remember all of these were innervated by the trigeminal nerve and if you

really want the actual third division or the mandibular division so that was significant the next thing that we had to remember is the salivation process and the whole purpose of the salivation was helping for two things one is the chemical digestion of the food okay and that was the carbohydrate process of sound Larry amylase and the lipid breakdown by lingual lipase and the next thing is to actually soften the food okay and form that nice compact mass called a bolus and the last thing that we wanted is we wanted those intrinsic and extrinsic muscles of

the tongue to be able to contract and the whole purpose of that it was to create a downward slope of the tongue and again if you wanted to remember the intrinsic muscles and extrinsic muscles of the tongue are innervated by cranial nerve 12 which is also known as the hypoglossal nerve if you really want to know really quick the extrinsic muscles the tongue to elevate the tongue is primarily the stylo glosses and the genial glosses the intrinsic muscles of the tongue are like the soup a longitude no inferior longitudinal vertical and transverse muscles of the

tongue okay another muscle that can help in this creating the elevation of the tongue is also the mylohyoid - if you wanted to know that also but again trying to get the basic parts here so that is what we consider to be a part the oil phase now here's what I want you to know I've gone to the next diagram remember I told you that it was bordered the posterior border here I'm gonna create like a little border here this we said is the plateau glossa larch once the bolus comes into contact I mean he

just even touches this area here boom we are no longer in the oral phase we're gonna go into the Ferengi phase now okay so that is what I want you to remember once the bowl touches this Pilato glosso arch we are no longer the oral phase and now we're gonna go into the fringe will face okay so now we have to hit the Ferengi Elise so what did I tell you before I said it had to first hit what structure the pilato the law sole arch so now what I need to do before we continue

to go on throughout the fringe of faces you need to know what is the pelota gloss alarge so come over here a little bit with me and look at this structure here so what you're looking at here is you're looking at this is the lips right lower upper lips and you're looking into the oral cavity like if I had you guys open your mouth and you're looking in I'm looking in this is what you're gonna see this little sucker right here the freken speedbag that's your uvula okay then there's an arch right next to it

this one right here and that one right there the one towards the midline in this case but really in reality it's in the back this one right here this arch so I'm gonna put here one okay and then I'm gonna put here two one is specifically the pilato pharyngeal arch and two is the one that's a little bit more anterior that is the palate oh glosso arch remember I told you once you hit number two the Pilato glosso arch we are no longer in the oral phase we're in the fringe of phase there's a reason

why there's a bunch of nerve fibers a bunch of different sensory receptors that are super super concentrated in this area here at the Pilato glosso arch the pilato pharyngeal arch even in between so you see how there's a space where these little green structure is that's space right there we'll write that down here in a second but that space right there is even called the tonsillar fossa so here look I'll put number three that little space in there that space is called the tonsillar fossa that area and even one more area which is the posterior

pharyngeal wall all of these structures are super super innervated by a special cranial nerve that cranial nerve is going to be the glossopharyngeal nerve or cranial nerve nine so this is what happens I want you guys to imagine I'm just gonna put it kind of like in this area I'm gonna put like a nice blue fibers here and these blue fibers are just literally representing all of these fibers right here I just don't want get the diagram too cluttered and I'm gonna bring this up here it actually goes to a special gangly on and then

goes into the central nervous system and again what is it picking up remember what it touched what touch this area right here look here this guy right there this little dude right here that's our bolus so once it touches it stimulates the glossopharyngeal nerve fibers the a ferrant fibers once it does that it stimulates action potentials down this axon and goes into the central nervous system so these fibers are gonna come up into the central nervous system and they're gonna activate technically they will activate a bunch of other structures like the nucleus attractive solitarius which

then can stimulate the nucleus ambiguus what I want you to remember is is the this glossopharyngeal nerve is gonna lead to the activation of another cranial nerve vagus nerve cranial nerve 10 now I remember the nucleus there is technically the nucleus ambiguus but again we're not trying to overload ourself with that which is focusing on a fair fibers of the glossopharyngeal nerve here are being stimulated cranial nerve nine coming up activating the vagus nerve the vagus nerve is then going to come down into a bunch of different things but before I start going in and

telling you all the different things here's what I want you to do to make your life ten million times easier think about where the bolus could go from here it technically has three different areas that it could go it could go up into the nasal pharynx up here is the nasal Ference right it could go where it's supposed to go which was down into the pharynx and then eventually into the esophagus or the bolus could not good though could go down into the larynx and we don't want that so technically there's three destinations of this

bolus let's focus on each one individually so first thing is we're going to focus on this one now the first one is how do we prevent food from going up into the nasal cavity via the nasal pharynx pacifically so let's go ahead and do that okay so let's say that the bolus is right here then here's our bolus dude and he's like who don't want to go into the nasopharynx so what happens here remember that we said it'll activate the plateau Glaus large plateau fringe arch the tonsillar fossa the poster Forenza wall of these nerve

fibers and again if you want to remember you go back you can say this was cranial nerve nine the glossopharyngeal nerve stimulated it send an action potentials into the brainstem into the medulla and eventually leads to the activation of cranial nerve 10 the vagus nerve now what the vagus nerve is first gonna do is is this is going to come out here and it is going to stimulate this muscle here so here let's do this in red so we know that it's a muscle look we're gonna have this guy right here it's actually doing this

maroon color so we can distinguish him so here's our little punching bag right here here's the uvula we're gonna stimulate the uvula and cause the uvula to contract now watch what happens if this guy contracts he's gonna go upwards if he goes upwards now this is the next position so this was the first position pointing down now he's going to go up look what he just did if he goes up here it's gonna be hard for the bolus to get up into the nasopharynx such a beautiful mechanism so now that's one thing so the first

thing I want you to remember is activation of the uvula uvula lifts up blocks off the nasal pharynx second thing as it goes to this muscle right here there's muscles of the soft palate this one right here is called the Levitt or veal I pala tonight so Leavitt or veal I pallets and I and when this puppy contracts this muscle right here it's going to LA it's going to pull up on the soft palate as you pull up on the soft palate it's gonna increase the distance between the bolus and the soft palate so not

only is it going to be hard to get up into the nasal pharynx but now I pull up the hard palate farther away from the bolus we're making this impossible for that guy to get up there another one is there is the trigeminal nerve again the trigeminal nerve he actually can have fibers that come out and innervate this guy again this right here can be cranial nerve five the trigeminal nerve and again this is actually going to be v3 the mandibular division it'll come and innervate this muscle this muscle right here is called the tensor

veal I Paulo tonight and what this guy does is he tenses he tenses the soft palate if you tense the soft palate it's going to accentuate or enhance the action of the leavitt or villi Palatine so now it's going to elevate the soft palate even more so three things total have happened one thing is we elevated the uvula second thing is we elevated the soft palate via the laboratory lap Alton I third thing is we tense the soft palate via the tensor veli palatini which accentuates the action by elevating the soft palate boom we prevented

the bowls from getting into the nasal pharynx amazing next thing we need is we need to make sure that this bolus doesn't go into the larynx this can be extremely deadly if a bolus goes into the lyrics it can go into the trachea and it can cause us to choke all right we don't want that we don't aspirate we don't have to do the Heimlich maneuver on anybody so now the next thing we have to think about is how do we prevent the bolus from saying and going down to this area what do we do

here two mechanisms so now what we have to do is I want to zoom in on this uvula and I'm sorry zoom in on the larynx a little bit better over here so we're gonna take a kind of look over the larynx over here two things are going to happen at this point so let's put here first one and second one first thing most important thing it always happens when we slaw a low whenever you swallow then the food gets the right away okay and naturally there's your vocal cords right these little green things right

here these little green guys are called your vocal cords your true vocal cords okay and these things are normally important for like phonation they vibrate and whenever they vibrate it pursues buzzing sounds which helps to produce speech but another thing is whenever these vocal cords whenever food is coming down we don't want to focus on speech so what happens is there's actually some muscles around this area you know there's a lot of different muscles around this area and these are called the lateral one of them is called the lateral cricoarytenoid x' okay lateral cricoarytenoid another

one that's also here is you have your transverse and even and the oblique arytenoid muscles now so when these muscles contract they actually approximate or another word is add duct the actual vocal cords so these guys are going to approximate now there's a space the space between these two bits the space between the vocal cords that space right there it's called the glottis so it's the space that will actually eventually lead down to the trachea so the first thing we want to do is we want to approximate the actual vocal cords and then decrease the

actual glottis we don't want food to go down into the actual trachea and as a result that results in apnea so air can't actually go down so we can't breathe so the small moment of time when we're actually not able to breathe when we're swelling is called deglutition apnea but again remember first thing here that is significant is we need to approximate the vocal cords okay and by doing that that narrows the glottis and prevents food from being able to come in so it add duct so results in the adduction this is another word for

is with so besides approximating is add ducts and that decreases this space now and it will decreases the chances of food going in the second thing is this little flap right here whenever the bolus is coming down that way it can run into this epiglottis when it runs into the epiglottis you know I pick a lot of made up of elastic cartilage so here's our EPI glottis it's made up of elastic cartilage which has a lot of resiliency you can stretch it it can recoil so when the bolus touches this it can actually kind of

bend the epiglottis downwards that bending is called retro version of the epiglottis there's another thing that happens there's muscles imagine these there's muscles right around this edge they're called the aryepiglottic muscles and when they contract they pull the aryepiglottic folds closer to one another and that helps to it again accentuate the pulling back of the epiglottis so first thing happens approximate the vocal cords this is more important than the epiglottis one okay second thing is we're gonna say retro version of epi glottis okay and this become becoming in contact with the bolus or it can

be via the muscles called the aryepiglottic Asst which approximates the aryepiglottic folds so that's what we want to happen here that's preventing the food from going into the larynx so that's that pathway boom we've already covered two pathways now the next thing is we want to make sure that the pharynx openly welcomes the food into the we want to make sure that the pharynx openly welcomes itself into this bolus so we want to make sure no matter what that this bowls doesn't go this way doesn't go this way but that it perfectly goes this way

so there's a bunch of muscles that help that process okay what are some of these muscles one of the muscles that we talked about it over here we talked about the arches so if you look here we have the pilato Ferengi arch in the Palazzo colossal arch there's muscles around those arches the Palazzo Ferengi's and the pilato glosses the pilato glosses and the plateau Ferengi's imagine these walls coming closer together if these walls are coming closer together it's making sure like imagine here is like a little slit here's a little slit here's a little slit

when we want to push this bolus out here so imagine here is the bolus we want to push the Bowls out here it has to go through this slit two of them technically if we really want to think about it so imagine here's the first slit and then here is the next slit so that's to go through this one and then after that has to go through this one an order for it to get through this slit the pilato glosses will contract when it contracts it approximates these walls these slits come to these areas come

together and it squeezes the bolus into the next segment then the next muscle is the plateau for in GEOSS he's gonna have to contract and he'll approximate and make sure he squeezes a small bolus into the pharynx isn't that a beautiful mechanism I think that's so darn cool so remember that so big thing to remember here is that the plateau glosses and the Palazzo ferengi asar going to approximate the walls to make sure that the only the smallest Bowl as possible goes into the pharynx the next thing is like I said we want to make

sure that the pharynx is openly welcoming this bolus so you know what we're gonna do we're gonna bring the pharynx to the bolus let's do that so there's a whole bunch of muscles over here we're gonna categorize this group of muscles we're gonna categorize just this group right here boom this whole thing right here these are the outer like longitudinal muscles so these are the outer because there's two layers we'll talk about the circular next but the outer longitudinal layer okay and these muscles there's a couple of them one is the stylo foreign geus another

one is called the South Pingo for NGS and there's another muscle here that we're going to talk about because remember that muscle the palate ofer in Geus it also is a part of these this longitudinal layer here too so not only does it approximate the walls to make sure that the bolus smalls bowls is passed through but it can also do another function with this outer longitudinal air so we have they'll plateau for angeas so this is a double-acting muscle right approximation and this next function what do all of these guys do they're so gracious

they do two things they elevate the pharynx they pull the pharynx up and they elevate as a result the larynx so they can do two things they can elevate the pharynx and they can elevate the leg so now it's gonna pull upward and at the same time it's gonna pull the larynx upwards so two things there with this outer longitudinal air next question I have what nerves innervate it Vegas so the vagus nerve is going to innervate these outer longitudinal layers just like the pilato glosses it's also if you remember down here the plateau glosses

it's also interviewed by the vagus nerve - oh cool so that's one way one way is we're going to elevate the larynx and the pharynx to openly welcomed that bowls the next thing let's squeeze the pharynx to make sure that only the smallest we can make sure that the balls not only is received but we can make sure that we can start propelling it downward that's another thing that's where these bad boys these chunky muscles come in so let me move this glossopharyngeal nerve here because we're gonna need this space right now so now look

yeah we'll put the glossopharyngeal nerve to the side okay okay there's this inner circular layer okay so this layer here is the inner circular layer and these are your Ferengi instructors so there's the superior the middle and the inferior laryngeal constrictors I'm gonna put P c p c p c so you have the superior this one middle and inferior for injeel' constrictors this is the circular layer so now watch what happens the bolus is gonna come down once it comes down these muscles are going to undergo what's called peristalsis so they're gonna undergo a process

called for NGO para stall sis which is just like that alternating wave of contraction and relaxation to push the bolus down such an amazing mechanism so this is going to push the bolus down okay one more thing that is such a cool thing that helps in this perennial phase and it's another thing that kind of its kind of not just with the fringe you'll face but it also helps to it not only associates the food going into the pharynx but it also again helps to prevent food from going into lyrics also you have some other

muscles right here these muscles here are your super high weight muscles so what are these ones right here that I'm gonna kind of like engulf here this is the Supra hyoid muscles and there's a bunch of these digastric anterior belly I'm not gonna go over all these are just you know super hide muscles digastric anterior belly posterior belly stylohyoid genial hyoid mylohyoid what's the significance of this when they contract they pull upward on the hyoid bone when they pull up on the hyoid bone it pulls the larynx upward and in he really so these muscles

here what's the function what's the overall get up with these guys so this is a third thing is we are going to have lyrics elevated and moved anteriorly so if you think about that if I move the lyrics upward and entierly it's just making sure that the food doesn't go into the lyrics and it just drops right in to the pharynx so that again is another beautiful thing last thing that I have to talk about here with the fringe of phase is at the lowermost part of the inferior fringe of constrictor this one right here

there's a muscle that's we say is actually a part of it's like the lowermost part so here I'm gonna kind of connect these guys here because technically these guys are actually kind of connected so this is the in fear pharyngeal constrictor the lowermost part of the in fear fragile constrictor there is a special muscle here and this special special muscle here makes up most of this sphincter here this muscle is called the cry co Varinius the cricopharyngeal acts as this sphincter here which is called the ue s the upper esophageal sphincter is the primary muscle

of the upper esophageal sphincter now peristalsis is occurring it's moving the downward as it goes downward remember as you go down the descending axons will relax the lower most part so that the Boles can be received so that we want the bowl is to just kind of beep fall right into the esophagus right that's what we want but not only is it just gonna be the natural peristaltic mechanisms but look what you did to the larynx you moved it upward and anteriorly that also kind of also opens up the esophagus - that's a cool thing

also so the fourth thing that I want you guys to remember is the cricopharyngeal who do you think he's innervated by cranial nerve 10 vagus nerve when this guy relaxes due to the peristaltic mechanism the descending should always relax it and lyrics moving upward and interiorly it allows for the bolts to now move into the next segment which is the esophagus okay so now we need to do is we need to kind of blow through this really quick and describe what we just said in just the most basic things so what do we want to

do here first prevent bolus from going into nasal facts that was the big big thing we don't want that okay next thing is we want to prevent bolus from going into larynx and we had all the mechanisms that we discussed there we want to ensure bolus enters the pharynx through the mechanisms that we discussed and the last thing is we want to make sure that the upper esophageal sphincter ues relaxes that is the significant partner if you remember the UAS we can really say it cuz mainly it's the cry co Ferengi assits really the lowermost

part of the in pharyngeal constrictor but it makes up most of the upper esophageal sphincter that is the primary components of the fringe of face now really really quickly farik's there's actually three parts we talked about it in our half head Anatomy model there's the nasal pharynx which is technically from here all the way up to the uvula then from the uvula all the way down to the epiglottis like in this imaginary line here that's the oral pharynx and then from the epiglottis downward until we get into the esophagus is the low Ringo Fang so

we have nasal pharynx oral pharynx Lorraine go pharynx so that is the borders of the fringe you'll face once you hit the actual moving for a below the upper esophageal sphincter we're now in the esophagus so it's a beautiful mechanism you should be thankful though because the esophageal phase thank goodness it's so easy so now we uh we have the bowls right here the Bullis is right here we're having it moved down the esophagus look he's he's crying you want to know why look at this he freaking he knows there's a whole bunch of hydrochloric

acid and pepsin just waiting for him and he does not want to go down there but sorry buddy you do you're gonna have to go down so remember the esophagus is extremely muscle or muscular and when it contracts its muscularis externa will contract it undergoes peristalsis but here's the beautiful thing the peristalsis that was occurring in the pharynx it's there's just a continuation of that down the esophagus isn't that so cool so what I want you to remember here is the peristalsis occurs in the pharynx the ones that occur in the esophagus is just a

continuation of the Ferengi lols so remember this right here so the peristalsis there's a technical word for this that we should mention it's called primary peristalsis is continuation of Ferengi peristalsis so just imagine like a wave starting at the superior Firenze will constrictor and just traveling its way down and not only goes down the pharynx but the peristaltic wave goes all the way down through the esophagus and again remember what nerve innervates all the muscularis externa of the esophagus cranial nerve 10 vagus a lot of this area here is supplied by the friend Joe plexus

we talked about a lot of these nerves here more in the cranial nerve video so if you haven't seen those go watch those you'll have a little bit more info on this stuff okay primary peristalsis we know the next thing that we have to know is the poles gets here and it's kind of like squeezed it can't get into this area well remember we said there's peristalsis as the peristalsis moves down remember the descending most muscle here of the muscularis externa has to relax and the ascending part has to contract so that it produces a

constriction ring right here behind this bolus and it produces an open space right here in front of the bolus right here so now or we can say after the Bowls down here we wanted to relax here we want it to constrict behind it so if that's the case then we need this muscle right here they call this one there's a whole bunch of names for it I'm gonna say lower esophageal sphincter le s there's two other names the cardiac sphincter and the gastro esophageal sphincter it can be affected because in GERD it can actually come

back up because the people who have like hiatal hernias because the esophagus actually runs through the diaphragm there was called the esophageal hiatus so lower esophageal sphincter has to relax now when this muscle relaxed guess what buh-bye bolus he is going to come down in here and look at him he's gonna be in pieces I know this is graphic I'm sorry but what we're gonna do is we're gonna start breaking that guy down now here's the last thing I need to tell you here let's say you I don't know you try to swallow like a

huge hamburger hole and you're trying to swallow it sometimes it happens it happens to me a lot but when I swallow something sometimes they can get feel like it's stuck and it's having a hard time going down it's not that you're choking it's just it's stuck and the peristaltic wave the primary peristaltic wave just wasn't strong enough to push the balls down if it gets stuck there's a really cool mechanism here we talked about this in the enteric nervous system video if you haven't seen it go see it here we're gonna have that Bowl so

let's imagine that for a second that bowls got stuck here it is he's stuck when he's stuck there he's going to stretch because naturally the esophagus is kind of like collapsed but whenever foods coming down it opens up it's gonna stretch the esophageal walls right and then it's gonna activate these stretch receptors here this purple one right here this is a stretch receptor and what the stretch receptor will do is he will do two things one is he will stimulate these blue neurons and inhibit these green what do I mean the blue neurons are going

to do what if you remember we're not going to go into super detail here but it inhibited the longitudinal layer above this bolus and stimulated the circular layer above the bolus the descending axons did what they did the exact opposite so now let's come to like this segment right here it's going to do what - this one stimulate the longitudinal layer and inhibit the circular layer if I do that it will contract up here and relax right here and this will help to ensure that the ball moves down that right there is called secondary peristalsis

so secondary peristalsis is basically your local reflexes the local reflexes through your my enteric this blue and green structure is your my enteric plexus if bolus is stuck and then also remember a part of this primary peristalsis I'm gonna put it in kind of like a red here so we understand is the lower esophageal sphincter relaxes as a result of this primary peristalsis all right ninja nerds so thank you guys so much for watching these videos I thank you guys so much I really do I appreciate it I hope that you guys like this video

hope you learn something if you got did guys did please hit that like button comment down in the comment section and please subscribe also I just want to take a second guys and just say thank you so much for supporting us here at the engineered science it means so much to us we really do love to hear from you guys and hear how much we're making a difference in you guys's academic life it means so much to me it means a lot to our crew here and I just thank you guys so much for that

also these videos would never ever ever be possible if it wasn't for robber beach one of the guys who controls all the filming all the editing all the audio all the uploading the exporting so guys please throw some comments down the comment section for this guy cuz this channel would not be possible without him our engineers as always until next time [Music] you [Music]