special senses so there are five types of special senses so five types of special senses and they are known as taste smell the paste with your mouth smell your nose vision with your eyes hearing with your ear and also balance with your ear as well now the reason why they cause special senses is because the receptors for special senses are found in the head region and let's talk about the type of receptors so these receptors could be what's known as the receptors are receptors are chemoreceptors which has to do with chemicals and mechanoreceptors which has to do with pressure and photoreceptors which has to do with photons or light so we can say light mechanical receptors has to deal with pressure and chemoreceptors has to be with chemicals now let's talk about the different type of receptors involved with a different type of special senses so the first one is known as chemoreceptors they are going to be involved so these are involved with taste and smell and the chemo receptors are so the chemical senses what we can say is chemical sensors are stimulated by the chemicals in the solution and so a response of these chemoreceptors to chemicals and so we can say such as food dissolved in saliva so if your mouth is dry there's a good chance you can't taste your taste is not as heightened so your taste will be diminished somewhat and also this airborne chemicals dissolve in the mucus so when you if you have a dry nose so you notice that the mucosa in your nose nasal cavity help to keep the nose the nasal cavity moist and if you have a dry nose or nasal cavity there's a good chance your sense of smell is diminished now the mechanoreceptors are involved with hearing and equilibrium which is balanced and the photoreceptors are involved with vision all right so let's begin with the first special sentence which is smell so when you think of smell you think of basically is that smell is a very powerful sense and it it is very it's what is very unique about smell is that smell bypasses the thalamus so what we can say is this is a smell bypasses the thalamus so what that means is is that smell is transmitted directly into the cerebral cortex without the need to go through the balance so unlike any other sentence smell bypasses the thalamus so we know for a fact is a smell is detected by the chemoreceptors so which means we can say smell is detected by chemoreceptors and so let's talk about smell now in the nasal cavity there is what's known as the olfactory epithelium so this is this is defined as a sensory receptor organ found at the roof of the nasal cavity so now i want you to look at the image that finished on the right side now this shows you that this within the nasal cavity it shows you at the root of the nasal cavity you have what's called the ethmoid and you have these little openings called what both factory for remnant within the asthma now so the olfactory epithelium contains three different type of cells we can see what's known as first one is called the olfactory sensory neuron which is a bipolar neuron but this is a bipolar neuron which detects these neurons detects boulders now if you look at so the bipolar neurons have what's known as one dendrite and one axon so on the dendrite we have what's known as so on the dendrites you have what's called the olfactory hair which are defined as cilia projecting from the dendrites and these old fatty hair so the old fatty hair houses the chemo receptors so the smell receptors now the axon okay so the olfactory nerve so you can see right here is that you have the dendrite with these offense cilia so we these are hair and what they are this is that they contain chemoreceptors and they detect the smell or the chemicals within the smell and on the other end of the bipolar neuron there is an axon now when you look at a bundle of axons combined this makes it make up what's known as olfactory new olfactory nerve which is can be known as cn1 and the o fatty nerves are is composed of what's called bundles of myelinated axons so when you see all these axons combined they form what's known as cranial nerve cranial nerve number one now what we can also say is this is that the creole nerve number one project through the olfactory a ramen within the cribby form weight so to enter the old factory bow now when you look at the olfactory bulb right here you can see that this bulb could be found so the olfactory bulb can be found at the so the olfactory bulb you can see it's going to be found underneath the frontal lobe so this could be found underneath the frontal lobe but this could be found underneath the frontal lobe so this is a bulb right here oh ball i'm i enlarge this image for you to see so what once again let's go over this right now we can say that this is a bipolar neuron with one dendrite one axon and the dendrite has what's called old fatty hair but these are the cilia that contain chemoreceptors and on the other end of the soma you have the axon and when you combine all these axons together they form what's known as cranial nerve number one and the nerve cranial nerve number one project through the ethmoid through the opening in the fmoi which is called olfactory foramina to synapse with what's called the mitral cells so let's go back to that now within the epithelium the second one is called supporting cells you can see these in between the old factory cells you have the supporting cells and the main function would be [Music] they support the receptors so they help to maintain the receptors all right now let's go down to the next one so you can see within the epithelium you also have what's known as these um basal cells basically they're near towards the base and these basal cells are also known as olfactory so these are also known as olfactory stem cells and the purpose of these stem cells are they replace oh they replace old factory cells about every anywhere between 30 to 60 days so we know for a fact is that if you're if your chemo receptors aren't damaged by any chance they will regenerate so receptors cells so what happened we can say this is that we can say chemoreceptors regenerate now let's go on to something that is deep to the olfactory epithelium and this is called what's called a lamina propria in atlanta appropriate basically we can say it's deep to the old factory epithelium so as you can see you know it would be and what it does is this is that it's composed of is composed of areolar connective tissue so you should know that tissues is now it is a connective tissue which means this tissue contains this tissue contains blood vessels so negative tissue contains blood vessels and nerves and so within the lamina propria con it was called an olfactory or bowling gland so what we can say is these the olfactory glands are found within the lamina propria now the purpose of this blend is it forms mucus to cover the factory healing why you ask and the reason why is because the mucus helped to capture and exhaust the older molecules to stimulate the chemo receptors on the old factory philia or hair once again it says is that the mucus produced by the olfactory gland help to capture and dissolve the molecules the older molecules so to stimulate the chemoreceptors on the cilia so review this image right here now what we want to say see this is that you have cranial nerve number one and now olfactory tract so let's talk about the old fatty pathway so everything begins within what's known as the olfactory sensor neuron and this neuron basically is a bipolar neuron with one dendrite and one axon we know the dendrite contains the olfactory cilia with chemo receptors and the axon join joins with other axons of the olfactory sensory neurons to form cn1 so we can see right here is is that you have many axons of these neurons they form cn1 clear nerve one now crayon therefore one what it does is that it projects through the cribby form plate and enter the old fatty bulbs synapse with the mitral cells so you can see right here it says is that a synapse with the mitral cells within the olfactory bow within the old fatty bulb right here now the axon of the mitral cells so the olfactory tract is formed by is composed of axons of the mitral cells and the olfactory track what it does is that it transmits now information into the cns now there there's locations in which it carries it goes into in the cns into various locations in the cns the first location we can say is what's called the olfactory cortex and the purpose of this is the cortex allows perception of smell and also it helps to also it helps allows the identification the second location in which it goes to is going to be known as the limbic system and this limbic system is going to be involved so the smell helps to trigger emotion as it travels into the limbic system so when you think of a limbic system the limbic system basically is composed of many many structures in the brain and the limbic system is a functional system which means it's composed which means um it's composed of many many structures in the functioning system and is composed of many many brain structures and it is involved with emotion okay so when you smell something it may it may trigger some emotional output per se okay so what then was now we're moving on to taste it now taste is done within the mouth so we know for a fact that you taste with your mouth but what's more important is you what is involved with taste is taste buds okay so we'll talk about taste buds but first and foremost this there are five basic qualities of taste i'll start off with sweets that should be fine sweet salty sour good keep going bitter good one more and you mommy okay you mommy basically is is um it's kind of has a meaty flavor to it so it's it's meaty flavor and that is what yumami is it has a meaty flavor to it and when you think of you mommy you think of what's called savory taste i know a lot of you guys may say spicy spicy is not it tastes a quality of taste spicy is not a quality of taste instead spicy is a form of pain so when you think it's spicy basically what it does is that it can activate the pain receptors and so all right let's move on to the next one you say and then let's talk about taste buds we know taste buds contains receptors so we can say taste buds so let's go and taste buds so we know taste is involved in mouth but more so it's the taste buds in the mouth so let's go into taste buds so we know taste buds are going to be basically is are found the taste buds are found so taste buds found in the papillae on the tongue surface so you see these little projections so you were to look at yourself in the mirror and open your mouth and stick with your tongue you can see this little projection on the tongue now the pre so for that reason our tongue is never smooth it has some rough edges so the reason why it's rough edges is because of the papillae and so um so these the taste buds house the gussetory cells oh in general it has many cells because toy cells supporting cells and laser cells so you can see right here is this this is going to represent what's called taste buds right here so we i want to show you right here is this this is going to be this little papillae right here was in the papillae you had what's known as taste buds so this is going to be exactly what we have here is this now within the taste buds you have different type of cells you have gastroy cells you have in between supporting cells and then you have what's known as basal cells so let's go let's do one by one so we know fourth fact is this is that investigatory cell so i want you to zoom in okay so zoom in and you must zoom in to give you a better view of this you can see the dust toy cells right here the gusset toy cells what it is is that it is the so the best toy cells has this little hair that comes out the pore so we can say the gasket cells has what's called long micro view line which are here extend through taste pores to the surface of the epithelium okay so it comes out of the taste pour you can see this opening into the epithelium so this is represent a taste bud right here and so it these little hair hair come out into the ceiling now what we can say is this is that these microvilli contain microvilli contain chemo receptors now what happens is that these molecules tasty molecules are dissolved in the saliva so to stimulate the chemoreceptors on the micro new line i know i repeat a lot but the thing is the more i say it the more it will stick to you and these cells the ghost toy cells they have a very very short lifespan so if you were to damage your chemo receptors let's say you burn your tongue from eating hot food now there is a good chance so you always have except experience this moment where you just reach over and you taste things because it smells good but yet you don't realize that the consequence of tasting something that's really hot can burn your tongue and what happened is that you lose the the sense of taste you know during that moment and also this but over the days you regain some sort of sense of taste and so the reason why is that these chemoreceptors are they regenerate all right now let's go on to the supporting cells once again they support the receptor cells so they support these support the gussettory cells these so by the way keep in mind this these gospel cells contain chemo receptors so chemoreceptors regenerate the basal cells that you see here represent what's known as stem cells so these basal cells replace gussettory cells so if you by any chance damage your burn your tongue because you are tasting hot food and what happened is that the these gus toy cells will regenerate now let's go up to the next one it's gonna be let's go on to the next one um so we're moving on to the pathway so let's look at a pathway really quick in this case okay so this is your tongue now we know this is that on the tongue you have what's called gustatory cells now these desktop cells what it does is that it is going to um you know it would be triggered by what is known as these molecules from the food and what these cells does is that they they disgust toy cells they transmit information so they transmit um taste information to the primary sensory neuron now the primary sensor neurons contain axons studies so these primary sensory neurons contain axons so what we can say is is that the creole nerves are composed of axons so we can say is that the cranial nerves are composed of axons of the primary sensory neuron so these cranial nerves are just defined as bundles of axons of the primary sensory neuron so they're composed of primary extension neurons so in essence these cranial nerves these cranial nerves are composed are bundles of axons of sensor of primary sensory neurons and these cream nerves the cream nerve cn 7 9 and 10 transmits taste inflammation so as you can see 7 9 10 they transmit case information into the medulla now in the medulla itself in medulla the primary sensory neuron synapse so the premise so to be quite frank we can say is this the axons i should say the absence of the primary sensor neurons your naps um so we can say this in so we can say so let's say in the medulla in the medulla finally the axons of the primary sensory neurons which are the cranial nerve so let's use the word cranial nerves synapse with the secondary the synapse with the secondary synapse for the secondary sensory oh that's used to a secondary neuron so what that means is is that we can say that these axons they synapse with the secondary neuron now so what we can also say is this is that the secondary neuron the secondary neuron continued to transmit this information throughout the brainstem and into the thalamus now in the thalamus in the thalamus the secondary neuron synapse with the tertiary atlantic neuron and these tertiary thalamic neuron transmits information case information into the transmit information uh into the insula and the limbic system so once again let's talk about the insula in the limbic system so the insula first and foremost you have heard of this right so the insulin could be found deep to the lateral sulcus that's the first one and the insulin what it is is it contains gustatory cortex which allows us known as which allows us known as taste perception so which allows what's known as taste perception you can actually taste what you are so whatever you're tasting you can perceive it now the limit system what it does is that it triggers so if the information goes into the limit system the taste information triggers emotional attachments with food in the limbic system let's do once again is this is first and foremost is this the gus toy cells sends the message to the cranial nerves and the cranial nerves are composed of axons of the primary sensory neuron so if you remember what i taught you guys is that nerve is composed of axons so nerves in general are composed of axons um now what we can also say is this is that these axons these nerves i should say carry the information into what's known as the into what's known as the medulla now in the medulla the cranial nerves synapse with the secondary neuron in the medulla and the secondary neuron continues throughout the brainstem and into the thalamus where it synapsed with what's known as the tertiary thalamic neuron and the tertiary thalamic neuron will transmit inflammation into the insula and the limbic system and the insula is involved what was called a will give what's called taste perception and the limbic system is one that is gonna give you what's called emotional attachment with the food so for example this is that when you taste something you know you and i can taste the same thing but we may not feel we are feeling for the food may not be the same so you taste something that remind you of what your mother cooked for you or your grandmother cooked for you when you were a kid and it might bring it you know it's like some sort of emotional attachment with that and you might shed a drop of tear if not to drop at least more than one drop right um so i may i i may taste the same thing but it doesn't have any meaning to me whereas it may mean something to you so just wait so when you think of the limbic system you think of the um emotional system of the brain and now the limbic system is a functional system which means that it is composed of many structures involved with the formation of emotions so once again i magnify this just to show you what's going on is that you can see that these are going to represent what's known as so these white cells are called gustoy cells and these cells itself what it does is that if they provide what's known as so they provide what's known as um they can not provide they contain they contain what's called gustoy hair and this hair emerge from the pore onto the surface of the of the mucosa and on the surface what it does is that it detects the molecules you know from the food and what it does is that it triggers you know what it does is that once that is detected what it does is it passes the um the information on to the cranial nerves onto the primary sensor neuron i should say and the axon of the primary sensing neuron will form what's known as cranial nerves seven nine and ten and these cranial nerves will carry the message into the medulla to synapse with the secondary neuron and the secondary secondary neuron continues to transmit information into the thalamus and in the thalamus the secondary neuron is going to synapse with the tertiary neuron which which then uh transmit information into the insula and other structures within the brain that form the limbic system all right so we're done with that let's go on to the next one it's gonna be vision so we finish we finish so far smell and we finish what's known as taste let's move on to what's known as vision so vision basically is involved with what's called photoreceptors and the photoreceptors do not regenerate so as you when you were a kid your parents always tell you do not look directly into the sun is oh at the sun i should say do not directly look at the sun and the reason why is because the strong blood rays in the sun can harm your photoreceptors so the uv rays in the sun can harm your photoreceptors and that's the reason why it's never recommended to look straight at the sun now let's move on to the next one okay let's move on to the next slide i should say so vision basically is involve the eye so the eyeball is enclosed in the bony orbit so this is the bony orbit the eye socket when you think of bone orbit you think of eye socket now within the eye socket there are fats within the eye socket and the fat help to cushion the eyeball so when you cushion the eyeball you minimize the the damage to the eyebrow the shock you know so what it does is it helps you cushion the eyeball now we can only see the anterior 1 6 of the eyes surface so whatever you see in the front is 1 6 of the the surface of the eyeball itself now vision we know four factors is vision is the dominant sense in human now look at how amazing this is oh seventy percent of the body's receptors are found in the eyes that's massive amounts and 40 of the cerebral cortex is involved in processing visual information that is a lot of involvement and so we know for our scientists is that vision is the dominant sense in humans so we use our vision more than our hearing you know um so it's just something it's a darn scent in humans now if you remember what i taught you in the last uh powerpoint i said that we have what's called neuroplasticity if you lose your vision by any chance your hearing become heightened which means your hearing will take over so you can survive now let's talk about how we organize our visual structures so we organize it as into two categories one is the eyeball the second is the accessory structures so let's talk about about the function of the eyeball when you look at the eyeball itself this is the eyeball itself and the eyeball itself its main purpose is to protect or to house and protects the photo receptors now keep in mind this these photoreceptors are very very delicate and they do not regenerate so you want to protect it as best as you can now what we also have is what's known as accessory structures and these include extrinsic eye muscles eyebrows eyelids eyelashes conjunctiva and lackable apparatus just let's use apparatus and so and this includes the glen as well so we'll just leave it as that now the function of of the accessory structures are going to be the functions our first function is to prevent boring objects um coming into contact with vi and the second function is to keep the surface of the eye keep the surface i used to keep the surface of the eye to stay clean and moist so when you think of this in these cases is that um our eyes should be [Music] moist it should be dry and uh if you have dry eyes and there's a good chance you can scar your cornea so everything should be moist that's the first thing now if you notice in this case this is that if there's any dust particles blown into your eyes what will happen is it would trigger some sort of tears and tears are meant to cleanse everything keep the surface of the eyes to be clean so it's very unique in the sense of this is that these accessory structures help to keep the eyes clean and prevent foreign objects from coming into contact with the eye so let's show this right here this this right here is the conjunctiva the eyelashes you can't see the lacrimal apparatus on this but i'll show it to you in a moment you have the eye the eyebrows you have the eyelids all right and get the muscles and we'll talk about the muscles in a moment so let's begin with the first one so we have what's called the eyebrows oh what exactly are eyebrows well the eyebrows are touchy eyebrows look at the eyebrows look at the eyebrows look at yourself in the mirror and observe your eyebrows so the eyebrows are coarse hairs on the um super ciliary arch i hope you remember what that is this is eyebrow arch yes it is and what it does is is that the function of the eyebrow is the eyebrow prevents sweat from entering the eye oh entering into the eye so what it does is the eyebrows help channel the sweat away from the eye so moving on to the next one is that eyelids okay so eyelids for the eyelids the function of the eyelids first and foremost is the function of the eyelid arm is a protective covering of the eye now the eyelids is made of made of tarsal plates and when you think of the tarsal plates you think of and then i'll talk more about the tarsa plate in a moment or big layers alkaline i hope you know that and the thin skin okay now let's talk about tarsal plates target plate basically is this intense tissue within the eyelid so this connected tissue is the framework of the eyelid so basically we can say the framework of the eyelid now we can also say this when you look at the eyelid so you have the upper and the lower eyelids and they meet at these two junction and so we can say the eyelid meets at the medial and lateral campus or commissure so when you think of campus and commissioners so let's use the word campus and commissure so come or campus represent the junction where the eyelid meet and merge so you have two commissures you have the medial commissure on the medial side and the lateral commissure on the lateral side now there is a flip in between the eyelids and so we can say the eyelids are separated by how people t-shirt so we can say with this is slit in between the eyelids okay so far so good now that's the first thing parsa plate now orbicularis alkaline what it does is this is that it's just a muscle that you see so you can see right here it says orbicularis aqualine and this muscle and circles around the eye right here and what it does is it squeezes on the eyelids to prevent the eyelids from opening so we know and you know i taught you is that i said this muscle itself orbicularis alkaline what it does is that it encircles the eye to prevent the eyelids from opening so you use this and this muscle is innervated by cn 3 the muscle's innervated by sin 3 muscle innervated by stem 3 all right good fantastic moving on now let's go on to the next one so we can say the next one is going to be what's known as levator palpebral superioris now first and foremost this eyelid when you look at what eyelids is also known as the pebble braid well palpable means one papa bray means many all right now let's move on to the next one levator palpebral superioris you can see this muscle right here is going to be known as the levator how people superior is so this muscle itself is going to be involved it pulls the eyelid up so it pulls the eyelids up so pull the eyelid up and up and up right so this is the eyelid value it's going to be pulled up by what's called the levator palpebral to purus so this muscle is a skeletal muscle innervated by cn3 oh by the way by the way i made a mistake orbiculous alkaline is not innervated by scene 3 instead it's innervated by cn7 so correction is the orbicularis alkaline is innervated by cn7 so i just want to clarify myself on this so once again it says the orbicularis aqualine is innervated by cn7 so so make a correction on that because if you miss out exam i made a correction so i am i'm going to hold you to it that you have to make a correction this is innervated by cn7 the levator palpebrus appears is innervated by cn3 so now what muscle contracts what does this is that this this muscle itself will raise the muscle raises the upper eyelid so one can open his or her eyes okay and the upper eyelid not the lower eyelid so so just keep that in mind this because i could ask you questions about which nerve innervates the muscle to open your eyes and which muscle in which nerve innervates to keep the eyes closed so keep that in mind now let's move on to the so the eyelashes extend from the margin of the eyelid so the eyelashes extend from the margin of the eyelids and the function of the eyelashes is to prevent the function of the eyelash to the function of the eyelashes i should say this function is going to be at prevent the eyelashes prevents the objects from coming into contact with the eye so we can use wood foreign objects number two is going to be the next one is that it can also eyelashes can initiate blink reflex all right now let's move on to the next one let's move on to the next one the glands so there are different glands that we have one is called tarsal gland and this actually when you think of it with tarsal that means that we can say this gland um to be found within the tarsal plate found in the tarsal plate and the function of the gland is what it does is that this gland secretes oily secretion at the edge of the eyelid to prevent eyelids sticking together so the torso gland secretes oily secretion at the edge of the eyelid to prevent the eyelids from sticking together and so when you have a pimple that is um cause that's blocking so let's say you have a police in a style so we'll talk about a pimple on the eyelid just know it's your style right so so it's just a style in the eye um let's go on to the next one cilary gland are found so these glen are found in between the follicles of the eyelashes and the glands secretes these glands secretes lipid or fatty substance that adds to the tear skill so the the moisture in the eye so to slow down the evaporation of the moisture in the eye unique that is it just tells you that what it does is it adds a bit of the lipids onto onto the filmy layer of the eye to slow down the evaporation of the moisture in the eye to keep the eye moist so think of the side the thinner side what exactly is thigh have you ever had a sky before think of that okay so we can say this is that when you take a slide so and when you think of that this is just a pimple on so it is a boil okay or a pimple on the edge of the eyelid so it's like a pimple on the edge of the eyelid it's like any painful except it's on the eyelid and most of and the reason behind it is because it's blockage of the ducts so for that reason the oil does not come out and so i just a clog up in the depth to the glands all right now let's talk about the lacmo car rumble so what exactly it is a lack of car wrong going all right let me show you right here this is nearby to the medial commissure of campus okay so keep in mind this medial commissure of campus and so keep in mind campus oh come sure same thing all right now so the black car renko is an elevation so you can see it's a reddish elevation so if you look at your eyes the mirror near the middle campus of your eyes we can say it you can see a small pink reddish lump so it is going to be defined as a reddish elevation or you want to say small pink math tissue that's fine at the meteocampus now what it does is this is that the car wrong contains gland so the carbon goes still is amount of tissue so to be more precise we can say we can rephrase this amount of tissue nearby to the medial canvas and this tissue contains that's secrete [Music] whitish one yeah whitish oily secretion so you notice that when you have that little eye booger you know near the middle campus where people where people pick your eyes you know it's normal um that is the secretion produced from the car wrong so it's a whitish oily secretion and what it does is this is that the purpose of that is it traps the dust particles so whenever you blink what happens is that whenever you're blinking you're washing what's on the surface of the eye from lateral towards the medial so you're washing everything from out towards inside so the oily secretion what it does is that it helps to trap the dust particles and for that reason when people pick their eyes they tend to go towards the medial canvas and this is where they pick your eyes and they pick what's called the eye booger and now let's go to the conjunctiva so the conjunctiva is going to be defined as a transparent it's not conjunctive it's conjunctiva it's defined as a transparent transparent means that you can see through it mucus membrane now the purpose of this conjunction is function wise what it does is that it secretes mucus to lubricate and hydrate the eye so the eye has to be very very very moist now what we can say is this is that the conjunctiva you can see is a membrane that covers the eye now it has two parts so the conjunction has two parts and the two parts connect or to form a conjunctival sec okay so let's go with the first one how people conjunctiva how people conjunct the what it does is that it covers the popular conjunctive so what the word palpebral means eyelid how people conjunct with what it does is that it covers the internal surface of the eyelid so you can see right here this is right here represent what's called how people conjunct the it covers the internal surface of the eyelid same thing goes down here as well the boba conjunctiva covers the anterior aspects of the sclera but so you can see the white part of the eyeball is called a sclera it covers the anterior aspect of the sclera but it does not cover the cornea but it does not cover the cornea so as not to interfere with the light passage across the cornea so here's what happens is is that the boba conjunctiva covers the anterior surface of the sclera but not the cornea now keep in mind this the coin and the sclera are continuous but this the conjunctiva the boba from gentleman does not cover the cornea and the reason why is so so it would not interfere with the light passage across the cornea because if the conjunctiva were to cover the cornea it may interfere with the light passage across the cornea so in this case since it doesn't cover the cornea it does not interfere with the light passage across the cornea and once again it is we can say the how people and when you put your contact lens on the contact lens goes into the little opening pockets i should say which is going to be known as conjunctival sac but this is a pocket all right very good