chapter 17 is over the special senses um special Senses weren't their own chapter because of all the intricacies that are involved in each one of the five special Senses so these sensory organs have special receptors that allow us to smell taste have Vision have Hearing and Balance or also known as equilibrium so special Senses their receptors are located within the head and they are very complex specialized structures that serve the role of these special Senses so the five special senses that we will be covering are going to be olfaction which means smell gastation which is taste Vision which is sight audition for hearing and equilibrium for balance now the key thing that that can be somewhat confusing is that the last two which is going to be your audition and equilibrium both of these occur in the ear so the ear actually has a dual function therefore the structures that we talk about in the ear I will differentiate for you which ones are for hearing and which ones are for equilibrium also known as balance olfaction then is the sense of smell um so the sense of smell is based on what are called odorants odorants are these tiny chemicals that you can't see in the air and these chemicals as they enter your nasal passageway get dissolved into the mucus that is is inside the nasal passageway essentially what happens is that those Orin stick to that nasal passageway and then they are going to be detected by the cells that are lining the nasal passageway in order for you to have a smell recognition for them in humans we typically don't have as much well powerful smell compared to other animals U many of our other animals have a much better smell sense than we do uh but we can which is is pretty awesome be able to distinguish a certain smell out of a thousand what this means is let's say that you walked into a um B Botanical center like a garden center all kinds of odorants are existing with all the plants that are there but as you walk through it you might be able to smell for example a lily or um a a rose through all of those odorants and if you can distinguish that amongst everything else that's there that's what this old faction can do for you another key thing that humans can do is have what's called adaptation meaning that decreasing sensitivity happens to odors and actually a very rapid rate if you go to a hog farm in the state of Iowa or in the case of when we dissected animals eventually that smell that really awful smell are going to not be noticeable by you because your um sensory fibers in your nose adapt to it quickly enough that you won't notice that it's there so so that's why often times when students are complaining about the smell and and of the dissections and trust me I know they have a very potent odor to them within a minute or 2 minutes you won't even notice that that smell is there even though it still is there you just have adapted to it now there are a lot of structures that we can go over in the ol faction or the sense of smell system but we're going to be focusing on main structures such as the olfactory epithelium the olfactory bulb which connects to the olfactory tract and then of course cranial nerve 1 which is the old factory um nerve that's going to play a role in your ability for old faction so in this picture here this gives you a illustration of the anatomy of these old factory receptors so let me get my little tool here going let's stop on the left side right there so the very top of the nasal passageway the nasal cavity is going to be the structure called the kior plate we talked about the copor plate when we talked about the ethmoid bones and the bone structure in the bone chapter and if you remember from this I described how there's tiny little holes in that plate and that's where nasal passageways for the neurons for olfaction are going to pass through from the nasal uh cavity into the space for the brain now it does not articulate with the brain what it articulates with is this first part of cranial nerve one which is called the ol Factory bulb so you can see this illustration on the right side has various neurons passing through those openings and then they are going to be synapsing on neurons found inside the olfactory bulb connected to the olfactory bulb is going to be a neuronal tract called the olfactory tract and then that will take it to the place inside the brain where you're going to be able to recognize whatever it is that you're going to be smelling the old factory epithelium then is this structure which is basically just a whole bunch of different cells that exist in that uh nasal passageway the old factory epithelium's role is to take those odorants and be able to recognize them via these Sensory neurons to transmit that odorant information all the way up to the oil factory bulb so then you recognize whatever it is that you are smelling and or tasting so your oil factory epithelium is going to consist of olfactory receptor cells which you see here and they're going to consist of the supporting cells which which help to support those olfactory cells and basil cells and so those are going to be the three main players of the olfactory epithelium so as I stated in the previous slide there are the three types of cells found in the oil factory epithelium uh remember the olda factory epithelium occupies the Superior part of the nasal cavity and it covers that inferior aspect of the kbor plate so the old factory receptor cells these are going to be a bipolar neuron and their role again as is for oil factory transduction of moving those odorants whatever those chemicals would be in the odorants that stimulate this neuron to get to the oil factory bulb then there are the supporting cells and the supporting cells role is that they're going to provide a lot of support electrical insulation nourishment for the olfactory epithelium basil cells are stem cells and they will divide into what will be new supporting cells and so their role is to to help with a turnover of the cells in that area so receptors in the nasal mucosa are going to send these transduction nerve impulses um through the olfactory nerve which is cranial nerve one again how it happens is that those bipolar neurons excuse me the olfactory receptor cells are going to synapse through the spaces called the Kor plate and then the Kor plate is going to be the place where these tiny little openings allow those neurons to connect to the old factory bulb then the old factory bulb is connected to the old factory track then the old factory tract is a series of neurons again that are going to be sending it to the primary o Factory area that's found in the cerebral cortex which is part of the temporal Lo so back when we talked about the central nervous system of the parts of the brain we talked about how in the temporal lobe this is where smell is going to be primary located at so here again is that pathway of how this happens so we have the old factory epithelium with those neurons synapsing through the O through the cior plate to where it connects to the olfactory bulb which is part of cranial nerve one to the olfactory tract so that's the olfactory tract and then it's going to pass through uh neurons until where it's going to synapse out here at the cereal cortex in the temporal lobe which is part of the primary oil factory area so the next special sense is gustation and gustation is similar to smell and the fact that the molecules that help you taste food are also chemicals so the chemicals also have to be dissolved and it's kind of a complicated mechanism beyond the scope of this class but essentially when you chew food you are releasing odorants and those odorants can be absorbed in your tongue but they also somewhat get up into your nasal passageway and you probably know that because if you've ever had the horrible cold that cut off your ability to smell anything um you probably didn't enjoy eating because when you were eating you couldn't taste anything and so basically all you were feeling from your tongue was a um texture sensation and so it's a combination of both uh the chemicals from olfaction and chemicals and gustation that allow you to do the sense of taste now it is accepted that in your taste buds the chemicals that stimulate these um tastes are five primary tastes sour Sweet Bitter salt and then yumami um you probably are familiar with the first four sour Sweet Bitter and salt and you've seen the maps I'm sure of tongues that show you where in the tongue potentially there's collections of the receptor cells found at well it's it's not as simple as that of saying um yes that's the location to where you taste sweet or bitter or sour it's been found that there are actually these uh receptor cells all over the tongue but what wins out for you in tasting something is basically how much of that chemical is detected in your tongue so for example if you have lemonade lemonade is both a combination of sour and sweet well if you have something that is in that lemonade if you're tasting more sour then the chemicals that bring about more of that sour taste to them is what is winning out as if you taste something more sweet which is that Sugar threshold that's what's going to be winning out to you U bitter and salty bitter usually comes from the idea of something like uh uh coffee it has a bitter taste to it salt with that um sodium chloride and when it comes to Umami this is somewhat of a newer in the world of gustan taste uh yumami is considered to be this very deep meaty or savory taste that comes about in the foods that you eat uh again still relatively new but we know that this is a part of the five primary tastes um when it comes to gustation so taste buds are what's going to be doing the role of gustation and they are going to contain um a whole bunch of tiny little gustatory receptors for the sensation of taste approximately about 10,000 taste buds are found not only on your tongue but you'll also have some of them on your soft palette some of them on your fairings and some of them on the epiglottis now most of them are going to be collected on the tongue which is where we talk about them within an individual taste bud I typically describe it looking kind of like an onion because within that onion there are a whole bunch of layers and that's what you will see in the next slide is a picture of what looks like that now each one of the tiny little layers of the onion might represent um the epithelial cells that are found part of the taste bud you have a supporting cell and the supporting cell's role is like it says to support the gustatory receptor cells and the gustatory receptor cells are what's going to have the neurons that project out of the taste bud to basically the surface of of the tongue and then they're going to have neurons that are connected to it to help form the pathway that will go to the brain in order for that gustatory Pathway to um exist for you to recognize the food that you are eating on the surface of your tongue you roughly have three different categories of taste buds and the fancy anatomical name for taste buds is called Pilla and so you have a combination of what's called um circum valate or valate foliate and then um fungiform sometimes there also considered to be a fil form Pell so they all kind of have a little bit of a different structure and rooll on the surface of your tongue so the top left that is why taste buds are commonly described as looking like onions because you see the the little hairs of the onion Parts which would be the roots and in this case this is the microvilli of the gustatory receptor cells right there and then within this structure of that taste bud again you have roughly about 10 thousands of these SC scattered throughout the whole oral cavity you're going to have a combination of cells so you have supporting cells that help support and you have the gustatory receptor cell so the gustatory receptor cells will have tiny little hairs up here and then that information as it's tasting will be transducted through the cell to then get to this first order neuron pathway where that will then articulate with other neurons in the pathway to ultimately end up in the primary gustatory area area of the brain which is also in the temporal lob so on the right is a histological picture versus an colored illustration again you can kind of see how it looks like an onion with the various layers to it and then the neurons are right there and then down here is a magnified picture of your tongue surface showing you of combination of these Pilla which remember Pilla means taste bud so there's filor fungiform Pilla there's your foliate Pilla and the circumvallate so they make your tongue kind of the texture that they are to be able to not only detect the odorant but also be able to feel um the temperature of something to be able to feel the texture of something that's a combin uh that's a large role of your Pilla is to help support not only the tasting but what food ultimately will feel like in your mouth the next sense is Vision so vision is known as the act of seeing and vision is somewhat of a a physics phenomenon in the fact that if we take all of these energy in the form of rays that radiate from the Sun there are many type of rays that we cannot see but on this spectrum there is a range in which humans can see and this is called the visible light so scientists will put this on on a spectrum called the electromagnetic spectrum and you can see there the examples of gamma rays x-rays UV rays infrared Rays microwaves radio waves you can't see those but they exist they come from the Sun what you can see is the visible light so anywhere from 400 nanom to 700 nanom which is the wavelength of light you can see the Spectrum there of visible light of what humans are able to make out so the accessory structures of the eye because the eye obviously is where the vision takes place but the accessory structures are going to be things like eyelids for protection of the eye eyelashes also for protection eyebrows serving for kind of collection of O uh sweat oil also for protection as well and then you also have the lacrimal apparatus the word lacrimal means tears so this is how your uh eyes are going to be producing the fluid that crosses them in order to clean off the the surface of your eye it's also how crying happens too and so we'll talk about the lacal apparatus structures that help serve that purpose of cleaning off the surface of your eye and producing tears and then externally to control the movement of you your eye you have extrinsic eye muscles you also have intrinsic eye muscles which means the muscles that are found within the eye extrinsic means they are found outside the eye and they attach to the eye itself the fancy name for um eyelids and the structure that makes them up is called palpal so you have an upper and a lower eyelid when you blink shade your eyes close your eyes fall asleep you are lowering your upper eyelid and so the palpal muscles are what's going to be controlling your eyelid movement um the one that's going to be on the top of your eye is called the levator palp superioris so you every time that you open up your eye which is hopefully what you're doing looking at this lecture you are Contracting this muscle to keep this eyelid open then on your eye you have six extrinsic eye muscles that play a role for moving your eye itself in all directions and we'll talk about that in an upcoming slide on the surface of your eye is a very thin piece of mucous membrane called the conjuctiva the conjuctiva is a piece of tissue that's made up of stratified squamous epithelium and this covers the outer part of your eye that faces that you can see when people have um conc divitis or like allergies it's inflammation of this tissue and the reason why this is an important piece to know is when we talk about the Scara which is the WID of the eye the Scara is a vascular meaning that there is no blood supply to the Scara but when you look at one's eye it looks like there's blood supply and that's because the blood supply is in the conjuctiva um so that kind of gives it a a bloodshot look to it it's not actually the Scara it's the conjuctiva now not only does your eyelid need to have muscle in it to keep it open it also has to depend upon a structure known as a tarsel plate the tarel plate is this thick piece of connective tissue that help gives form and structure to the eyelids at the end the Taro plates there's going to be tarso glands which are going to be secreting a basically a sebaceous oil that's going to prevent your eyelids from sticking together um so it has a little bit of an oily substance to prevent that the two eyelids from adhering to each other when your eyelids are closed so a couple structures here that we talked about in the previous slide let's first identify the palra which is going to be your eyelid so right through here eyelid upper eyelid lower eyelid there and then we have on the surface of the eye the conjuctiva so the conjuctiva is this orange piece that you colored illustration that you see here and even though it looks like it only goes so far it's covering all the part of the eye that you see facing forward again this is where you're going to find the vessels that actually give your eyes that uh bloodshot look or the inflammation that can occur because the scarid does not have a blood supply to it and then the green tissue here is called the Taro plate and the Taro plate and the Taro glands are kind of one and the same and they are going to be right near where your eyelashes are so that way those tarsal glands can secrete their product onto the surface of the eyelid to prevent your eyelids from sticking together the lacrimal apparatus is a group of structures that um collects produces and drains the lacrimal fluid also known as tears from your eye how this begins is that in the lateral Superior part of your eye you have the lacal glands and the laal glands are going to be secreting fluid onto the surface of your eye and as they secrete fluid onto the surface of your eye you blink naturally you do this throughout the whole day and as you blink that pushes fluid towards the medial aspect of your eye as it gets to the medial aspect of your eye you have two tiny little openings that you probably didn't know had a name to them or didn't know what the name was these are called the lacrimal puncta so when you look inside a mirror and you look very closely at the medial aspect of your eye you're going to see those two tiny little holes the electral punctus role is to actually absorb the fluid of the lacal tiers and move them into structures called the lacal canicula the laal canicula are going to unite inside the nasal passageway in What's called the laal sac and then the laal sac is going to empty down into the inferior nasal cona through the nasal lacrimal duck of your nose so every time you cry your nose is automatically going to run because the tears are being absorbed through those lacrimal canicula into the lacal sac via the nasal lacrimal duck into your nose so it's just automatic the tears contain lysozymes which is going to be a protective bacterial enzyme every time you touch your eye you will could potentially be putting bacteria or some sort of microbe in your eye so the lysozymes part of your lacrimal tissue is very powerful at destroying bacteria now mind mind you it doesn't always it's not 100% perfect but it does a very good job because imagine how many times you stick your fingers into your eyes without you washing your hands first additionally it helps keep your eyes nice and moist um because that's important for movement if you have ever had dry eyes you can attest the fact that it feels kind of like sandpaper every time you blink and so your lacrimal apparatus plays a role in making sure that that is going to stay nice and moist so the six extrinsic muscles of the eye these play a role for eye movement and again um if we have the eye here we're going to have six muscles all four rectus if you think about a compass that's how that they are identified so you have a superior rectus at the top you have an inferior rectus at the bottom just like north and south and then if this is the nose side over here is going to be the medial rectus and over here is going to be the lateral rectus so those four muscles attached to each one of your eyes just like that the superior oblique and inferior oblique they're called oblique because they attach to your eye at an angle the superior oblique comes from the top medial aspect to attach laterally and same thing with your inferior oblique it comes from the U medial aspect and attaches laterally so all six of these muscles are found on both eyes and you have to have all six of them in order to move your eyes so delicately intricately in the way that humans can so that is all about the accessory structures of the eye let's look at the actual eye itself and talk about the structures that make up each one of your eyes so the eyeball now what you see when you look at somebody and their eyes is roughly about 1/ 6th 1 7th the size of the actual eyeball so the eyeball is actually quite huge it's just that you can't see it because your eyelids protect posterior aspect from what you can see there is considered to be three layers of the eyeball you have the fibrous tunic the vascular tunic and then the inner layer which it can be called the neural layer or sometimes it's just strictly called the retina the word tunic means layer that's all it's referring to or coat and so it goes from outside to inside and um the fibrous tunic is made up of the external structures of the coronary cornea and the Scara the vascular tunic is made up of the choid the ciliary body and then the iris and then the neural layer is strictly made up of all the neurons that do the role of vision so let's talk about each one of these layers so I would suggest that you get familiar with this particular picture showing you um what these structures are it's a great illustration over the structures we're going to be talking about there's also um some videos on blackboard of some models that will be helpful for you to identify these particular structures okay so we're going to look at the cornea the cornea is going to be part of that um external fibrous tunic and then next to the cornea the other structure that's part of the fibrous tunic is going to be the wi of the eye called the Scara then we get to the next layer called the vascular tunic and the vascular tunic is going to consist of the choid which in this picture it looks Peach but it's actually more of a blackish color in real life then we have the structure up here called the ciliary body and the selary body is going to consist of a couple different um substructures sary muscle and the selary processes also part of the vascular tunic is going to be the iris and then there's going to be the opening of the iris that's going to be called the pupil that's how light gets in there attached to the um sillary body are going to be suspensory ligaments that are going to adapt the structure here called the lens then the innermost layer is called the retina and the retina is going to be where all of the neurons are going to be found at what we'll find on the retina is there's going to be a structure called the macula ludia and this is a really important structure to see through here because do you see this black line coming right there that is where your vision is projecting to it's not coming in and projecting over here or here or here your vision and the purpose of the cornea in the lens is to project it to the very back of your retina right here to where it hits the macula ludia because within the macula ludia you also have What's called the fobia centralus and the fobia centralis is where you have a collection of cones that is where your best visual Acuity is therefore the reason that you would have glasses or contact is to help those light rays end up right here and nowhere else on the retina now the retina does have have rods and cones scattered throughout but this is where your best visual Acuity is at we will also talk about the optic disc which is known as a blind spot this is where the neuron is going to attach to the back of the retina you have a blind spot from this but you can't tell that it's there because the rest of your retina makes up for that tiny little blind spot and I'll talk more about that coming up then lastly we're going to talk about some compartments so there are two main divisions we have the anterior cavity and then behind where we see the iris is going to be known as the posterior cavity the anterior cavity is subdivided into chamber so you have an anterior and posterior chamber and then the posterior cavity back here is going to contain a fluid called the vitus fluid which is what's going to give your eye its shape and support so the first layer of the eye is the most superficial layer and it's called the fibrous tunic it's called fibrous because it's a pretty strong layer of protective tissue and tissue of the eye itself there are two main structures of it the Scara which is known as the white of the eye this is a dense connective tissue that's made up some some collagen and fibr blasts the purpose of the Scara is it's a very strong tissue for anchoring for those extrinsic eye muscles to move your eye but also it helps maintain the eyeball shape and so it it's a protective mechanism making it more spherical and creating a little bit more rigidity to otherwise a gelatinous kind of structure on the anterior portion of the FIB fibrous tunic is the cornea the cornea is a transparent um kind of lens in of itself but it's not the actual lens that we refer to but the way that you see is a series of two lenses that are channeling the light rays from that are entering your eye and making them so that they project to the very back of your eye onto that macula ludia in the fobia centralis area because that's where your Best Vision is going to take place you've probably heard of an astigmatism and an astigmatism occurs when an individual has an irregularly shaped cornea next layer is the vascular tunic this is the middle layer of the eyeball and it's vascular because this is where the blood suppli is at um vascular tunic is made up of quite a few structures but the main ones for you to know are the choid so the choroids layer is going to line the or be the middle layer of the eyeball itself the choroid contains melanocytes and melanocytes in this case are not the melanocytes that we talk about when it gives your skin uh pigmentation as far as uh you know absorbing the Sun or not um melanocytes in this case is going to absorb stray light rays and so that prevents uh additional scattering of Light Within the eyeball as a result this layer has the tcy to be kind of a blackish layer and especially when you dis like a coow eye for example you are able to see the blackish layer of the choid that's absorbing those um scattered light rays then there's the structure of the ciliary muscles the ciliary muscle is found in the structure totally called the ciliary body the ciliary body contains more structures just outside the sary muscles but the sary muscles have tiny little threads attached to them called the suspensory ligaments and the suspensory ligaments role is to either tighten to contr ract the lens to make it tall and skinnier or loosen it to make the lens um fatter and wider so this dispensory ligaments are ultimately what's adjusting that lens based upon your near Vision versus far vision and what's um causing this dispensary lenses to or spensor ligaments to change in their totness is theary muscles so here's um the layer of the coroy you can see in the image it has kind of a pinkish layer to it but it's actually more of a blackish layer in real life additionally there is blood so there's some red and blue to represent the arteries and veins that are there and then up here we have the ciliary muscles so you can see the muscle fibers there and muscle fibers here and then they're attached to the suspensory ligaments that are going to adjust the um size and shape of the lens additional structures on the vascular tunic is going to be the eye the iris is the colored portion of the eyeball and its role is that it actually is going to contain two muscles the two muscles that are going to be found in the iris are going to be one for constricting and one for dilating the eye and what it's really controlling is the pupil so the pupil is the opening in the center of the iris and the role of the pupil is to control how much light is going to be entering the eye itself those two muscles that are surr rounding it are going to either contract or relax depending upon the presence of light so if there's a lot of light your pupil is going to constrict if there's not a whole lot of light the pupil is going to dilate the third layer of the eye in the deepest layer is called the retina which can also sometimes be called the neural layer all the retina is is a whole bunch of neurons roughly about 10 layers of different types of neurons they're going to be stacked one on top of the other to be able to transmit that visual Pathway to the occipital lobe in the back now the retina we could talk about all the layers but the items or the cells in particular that I want you to be familiar with are What's called the photo receptors the photo receptors photo for light receptors for The receptors here they are going to consist of rods and cones you have roughly about 6 million cones and roughly about 120ish million rods Rod's role is that they're going to allow you to be able to see dim light um rods do not provide any color vision and so it helps to enhance the black and white and all Shades of Gray in between they really come into play when of course when it's dark outside then you have cones the cones are for color so always remember the C in cone and the C in color there are three colors of cones blue green and red and this is a common place where students want to associate the primary colors that you've learned which are blue yellow and red but please fight that urge because it is green instead of yellow that's part of the cones so how you're able to see in color is by the proportion of um shading that's coming out so if you're seeing for example like a oh gosh yellow yellow would be great there's probably going to be a little bit of red that's stimulated in there a little bit of blue and maybe even a little bit of green depending upon the shade of yellow that you're looking at so each one of the colors that are reflected back to you stimulate one of these um cones in in combination with other cones that are there now the retina is going to have all these photo receptors Converge on one spot and the axons are what's going to form cranial nerve 2 well where cranial nerve 2 is which is the optic nerve that attaches to the eyeball is called the optic dis this can also Al be sometimes called the blind spot as I mentioned when I was describing the anatomy of the eye in a previous Slide the blind spot is called blind spot because you don't have any Vision out of that particular spot but because it's so small you can't tell where your blind spot is at unless we are testing for it so we'd be doing that in a lab scenario um you would have two basic uh dots and you'd have to move the book until um one of the dots disappeared and that's where your blind spot is at but as it stands right now you wouldn't be able to tell where your blind spot is but that is where your optic nerve is attaching to the back of the eyeball via the retina and then there is the macula ludia so the macula ludia the word macula means small ludia means yellowish this is um a structure in the exact center of the posterior portion of the retina this is where your greatest visual Acuity is at because the fobia centralis is the small depression in the middle of the macula ludia and this structure contains nearly only cones with just a few rods so this is where your colors your main colors here are going to be able to see the best so the fobia centralis is where you get your best sharpness of vision and the main reason for this is that when you move your head and eyes while looking at something um it places the images right on your fobia C trus and that fobia andalus is where that sharpest vision is so all lenses contact lenses glass lenses role is to reflect your light rays onto the surface of the fobia centralis inside the macula ludia so here's a picture looking at the very back of the eye looking at the retina itself so what's kind of fascinating about it is you can see a couple structures so over on the left side here is the optic disc so that is the blind spot this is usually an easy to identify location because this is where you see blood vessels entering the eye so not only does the optic disc have um if circular structure you can see the origination of blood vessels in that area as well then we have the macula ludia when again which is where your vision is projected and then the greatest visual Acuity right there is the fobia centralis so that is where your vision is the sharpest two conditions to talk about here this slide and the next slide there's macular degeneration and macular degeneration comes from that macular ludia in macular degeneration what is occurring is that the person's central vision because that is where the macula is located at is deteriorating and often times this occurs as you get older and it's unfortunate um because you can't see centrally you can only see peripherally you can see in the bottom right picture what it would be like to potentially have macular degeneration and then color blindness so color blindness is warranted to talk about here because color blindness means that you are lacking one of the cones remember cones are part of the retina that are going to be for the color vision so some people are lacking um basically uh one of the three types of cones the most common one is a red green color blindness in which your either your red cones or your green cones are missing and so as a result the individual has a hard time distinguishing between red and green in the bottom right you can see some examples of what it would look like if you were missing a combination or one of these particular varieties of cones in the bottom left this picture we would be testing this in what's known as ishihara's color plates ishihara's color plates are particularly designed to test to see if somebody has color blindness color blindness is XL which means this is carried on the sex chromosome so sex chromosomes are either XX for female or XY for male so color blindness is carried on the X and it is much more common in males because in order for males to be color blind they only have to inherit One X and this x always comes from Mom the Y always comes from Dad so a a man who is color blind did not inherit it from Dad it inherited it from his mom in order for females to be color blind they have to inher inherit two x's that have color blindness on them and that is a rare situation if they just have one x with color blindness then they are not going to be color blind they're just simply going to be a carrier for that color blindness trait so we can compartmentalize the eye into two cavities the anterior cavity and then the posterior cavity the anterior cavity um basically sits right along the board of the iris and the anterior cavity can be further subdivided into Chambers so there's an anterior chamber and then a posterior chamber the anterior chamber is between the iris and the cornea and it's filled with a fluid called the aquous fluid you are producing Aquas fluid all day everywhere all day every day it is a fluid that your eye needs in order to have the structur stay liquidi moist the lens to be nice and soft that's what the purpose of the aquous humor is going to be the posterior chamber is behind the iris but in front of the lens and this is also going to be filled with eus humor so the fluid flows between the two of these Chambers and then when you're done with it your body will absorb it as you're making new aquous humor the other cavity then is called the postor cavity sometimes this can be called the vitus chamber because this is full of a different type of fluid called the vitus humor so aquous means liquidy or watery Vitus in this case is referring to a gelatinous material you are born with as much Vitus humor as you're going to have and it's what makes up a a large part of your eyeball in a cow eye dissection you would be able to see this substance come out and it has a consistency for lack of a better term like jello is what it basically has a consistency of and because you're born with as much Vitus humor as you're going to have if there's ever any damage such as like a torn retina or the floaties and they're called floaties you all know what I'm talking about when you are looking and it looks like there's a piece of fuzz in Your Vision but it's really in your eye they're actually called floaties and they're inside the uh Vitus humor it's basically your body's way of processing those items so again to uh clarify these divisions we have the anterior forward posterior in the back and we have the anterior cavity the vitus chamber also called the posterior cavity and then the anterior cavity divides into the anterior chamber and posterior chamber so right here to here is going to be the posterior and basically here to here is going to be the anterior and fluid is going to be formed and basically flow and flow and flow all the way between those two structures as the aquous humor whereas the vitus humor posteriorly is going to be made once gelatinous material that's present there so the process of vision goes through quite a few different structures initially it's going to go through the cornea and from the cornea then it will be projected through the anterior chamber through the pubil through the posterior chamber through the lens through the vitus humor then onto the retina so there's a whole pathway that it has to get through of structures in the eye and on the retina the structure again that it's aiming for is the macula ludia so what helps the macula ludia U be able to get its proper light rays to it is the lens the lens has the capability of changing shape depending upon if you're looking at something close or something far away again what changes it is going to be the suspensory ligaments and then attached dispensory ligaments are going to be the sillary muscles they work to accommodate your vision so when you have normal 2020 Vision as you can see right here on the top left notice that those light rays go through the cornea and they go through the lens and they are projected back there onto the macuda or the fobia centralis if you are somebody here depending upon your lens accommodation you can see that the lens is flat flattened it's taller and wider which means you're looking at something far away this is the point in which which you should be able to see but notice that it sits in front of the retina so for this individual you would have to add a lens that would then move that crisscross back here onto the retina and so then you'd have one two one 2 three basically sequences of lenses in order to get that projection for your vision on the back part for the retina in the macula ludia and then down here when you're looking at something up close you can see that the lens gets wider and fatter and right there again is where those Rays should be found on the retina but because they're not you again would give the person a lens to move these Rays to fall right there in the retina and that why you can see so after the pathway gets into the optic nerve what happens is that the optic nerve is going to go through a series of neuronal connections and ultimately end up in the very back of the brain in the occipital lobe at the primary visual area so you can see the neuronal pathways that come from that optic nerve all the way to the back to the occipital lobe the next structure in the special senses is the ear now the ear is incredibly important because it plays a role in both hearing and equilibrium which is another word for balance so your hearing is for detection of the sound waves it's also for identification when you move your head around sideways up down left right you can tell that your head is in that particular position the nerve that plays the role here in your ears is cranial nerve 8 which is the vestibulo clear nerve so vestibulo is for equilibrium clear is going to be for hearing so that's where those that name combined creates the um cranial nerve 8 so they both will go to the ear and then divide their respective structures similarly to the eye um there are three layers but instead of it being three layers of the ear it's actually three spaces you have your external ear your middle ear and then your inner ear so the external ear middle ear and internal ear I would suggest you get to know this picture here um roughly the external ear will go from the Oracle that's catching the sound waves right up until the tanic membrane and then the middle ear is going to be where you find your ticles in the opening of the um oval window and then the inner ear is going to contain your ca and the semicircular canals as well as the vestibular clear nerve externally the structure that's going to be catching the sound waves is the external ear and the external ear can sometimes also be called The Oracle or the P that's another name for it um this is just going to be the place where those sound waves are collected and then those sound waves are going to be moving into um a structure the opening that is called the external acoustic meatus sometimes it's called external auditory canal this is a bony tube but when you are not looking at the bones what you're going to see is that it's going to be a tube covered by skin and that's again what we call your external acoustic meatus or the external auditory canal at the very middle or most medial aspect of this uh Canal is going to be the tanic membrane T tanic membrane is also called an eardrum uh the word tanic comes from the word tempany like you're playing the drums that's where the name comes from for that the tanic membrane plays a role for hearing in the fact that it's going to vibrate as sound waves hit it its role then is to project those vibration vibrations through your middle ear bones called the oses and it will create more of a vibration through those in order to project the sound waves to the middle and then ultimately to the inner ear so the border of the tanic membrane is where the outer ear external ear ends the middle ear is the small cavity that's going to be containing the auditory osal so the malice the incus and the stapes Ole means bone these are the smallest bones of the body there are also going to be two windows you have the oval window and the round window both of these play a role as the sound waves project from the middle ear to the inner ear to allow those sound waves to get into and out of that inner ear then coming up in this space is an opening that connects your ear to your throat and there's lots of names for this it can be called the auditory tube it can be called the fingio tanic tube it can also be called the usaan tube the fingio tanic is a great word to describe the fact that it goes from the ferx which is part of your throat to your tanic area which is where your tanic membrane is at so this is a tube that goes from your ear down into your throat one of the reasons is that if you ever need to pop your ears what you are actually popping is the air bubbles that are found in this particular tube so it's good for Equalization of pressure within the head additionally um when people have ear infections or chronic ear infections um one of the ways that that virus can get to the ear is this opening comes from the throat and so that virus or bacteria can work its way up this to go into the ear when you are little if you happen to be a person who is frequently getting ear infections it commonly is to the fact that this particular tube is more horizontal and with it being more horizontal fluid that accumulates in your ear have no way to go nowhere to go as you grow older your ustation tube becomes more vertical I'm not exactly sure how vertical it gets but it's vertical enough that any fluid that's in your ear will drain down into your throat and so that's why you're less likely to have ear aches um and ear infections as an adult so this is a magnified um picture of the middle ear remember the outer ear external ear ends right here the tanic membrane then we have the three ticles the malice the incus and the stapes and we have the two openings to the inner ear the round window and the oval window and then right here is the auditory tube also called the E uh ustan tube also called the fingio tanic tube and right there you see it is as well and that connects down into the throat just a little bit about those three bones and they smallest bones of the body uh the auditory oces so you have the malice the incus and the stapes their role is to vibrate and transmit those sound wavs that have hit the tanic membrane to get them into the inner ear the malice is the first one that you would get to if you're moving lateral to medial it's attached to the tanic membrane and this is um I believe commonly called The Hammer um when people talk or give different names to this because of the way that kind of looks like a club then the incus is the middle one it represents a Anvil is commonly what it's described at so you have the hammer the Anvil and then the last bone is called the stapes which looks like a Stirrup stct so all three of these structures are the smallest bones of your body you have one on either side and their role again is to transmit those sound waves from the outer ear to through the middle ear into the inner ear okay so the inner ear is where it gets a little bit more complicated because it's not just playing a role in the process for hearing it also will be playing a role for equilibrium so the structures that mainly are going to be for the hearing are going to include the ca which is the snail-like structure as well as the structure called the vestibule um the three semicircular canals are what's mainly playing the role in equilibrium which means helping you to keep your balance so here's a picture of the innermost structures uh you can see that this is the oval window and round window that's part of the stapes this is the vestule that's going to be part of the differential iting between the sound waves and then we have the ca which is where hearing takes place and then the semicircular canals which is going to be for your balance and your equilibrium one of the most complicated uh aspects of hearing is actually where the hearing occurs which is way down in the intricate structures of the ca so there's a lot more structures um outside of what's mentioned here but to give you a brief idea of what's occurring to help with hearing is that those sound waves that have been projected through your external ear through the tanic membrane through the middle ear ticles in through the oval window now are into the CA and the ca is basically three tubes that are coiled around another to form that kind of snail-like looking structure out of the three tubes the most important one that has to do with hearing is the CER duct because the CER duct is where the fluid is that's going to be disrupted when things are shifting so the VES cellular membrane is going to be a membrane that separates the ccar duct from another tube there called the scalopus tiuli the basil membrane is going to be separating the cular duct from the other tube called the Scala tempany resting on um the baser membrane is the spiral organ also called the organ of cordi the Spiral organ is a coiled sheet of cells that include about 16,000 hair cells and these are where the hearing is taking place is via those um organ of cordi as a result of that Toral membrane moving and vibrating because the Toral membrane is kind of a gelatinous material when it moves it causes those hair cells to be disrupted and therefore they convert the mechanical vibrations of sound into electrical signals and that then is going to be synapsing with the clear division of cranial nerve 8 and then send this information to the primary auditory tube or auditory lobe auditory area in the temporal lobe blah all right so this is really deep inside the ca so in the previous slide I talked about the vestibular membrane with the Basler membrane and the Toral membrane so the pressure waves are going to get through the vestibular membrane and enter into the coar duct so the coke layer duct is essentially what you're looking at right here and on either side there's two membranes the Toral membrane and the Basler membrane you can see that the tectorial membrane sits a top of the tiny little hair cells right there again roughly about 16,000 of them and as they move due to the Toral membrane moving that causes the hair cells to be activated which that sends a message down those neurons that you see right there and then those neurons will group together to form the clear division of the vestibular clear nerve that is used for hearing so the hair cells found in your ear are incredibly important for hearing and you can't really uh do anything to them if they've been damaged so you can see on the left side what normal healthy hair cells look like and on the right side what happens when you listen to Too Much loud music it can cause those um hairs to break off entirely which limits your ability to hear appropriately so here are roughly the nine steps for hearing in the process of how this occurs step number one is how the Oracle is catching onto the sound waves and causing it to get through that external auditory canal to cause a tanic membrane to vibrate which is Step number two um the tanic membrane is going to vibrate which will then send the vibrations via the middle ear through the malice the incus and the stapes and then that's going to cause in Step number four the stapes to move back and forth and that's going to be um into the opening of the oval window the oval window then is going to vibrate and that's going to cause the fluid behind the oval window called the paril lymph of the CIA that's going to start to vibrate and as a result that will pass through the C structure of the CIA as those waves get transmitted to the Scala vestibuli and the Scala tempany and ultimately it will go to the center of the ca called the heloa and then those sound waves can project out so all along and by the way the CIA here is relatively uncoiled um so all along this pathway sound waves here in the black you can see that they're jumping into those various scalas or tubes of the ear so after the pressure waves cause the vestibuli the Scala vestibuli and Scala tiany to move they then are going to dissipate through the endolymph and that's going to cause those sound waves to basically exit right here via the round window and the sound waves are done the other main role of your ear is going to be for equilibrium so equilibrium is how you're going to be able to maintain your balance um body movements that cause um receptors for equilibrium to be stimulated with thing would be things like acceleration de acceleration the movement of the head the proprioception of the body there are two main divisions of equilibrium we have dynamic equilibrium and then static equilibrium dynamic means your ability to maintain your body's position relative to gravity so it's making sure that you can withstand whatever pressures have being put on it from Gravity dynamic equilibrium is going to be based upon your body's movements how you are able to maintain balance if you suddenly move the structures that help with the equilibrium we can call the vestibular apparatus and the vestibular apparatus is the structure that will help maintain the balance and equilibrium the main organs that make up the vestibular apparatus is going to be the SACU um and if in the SAU you see tiny little ois so ois are the crystals that exist exist up there and then there's the utricle which is also going to contain tiny little oo lists and then we have the semicircular canals which is where these structures are going to be found at the very end in What's called the ampula so the three semicircular canals are basically at right angles to each other and their role is to um detect any sort of acceleration and de acceleration inside the head when your head rotates the semicircular ducts and the hair cells move within it which causes disruption of the fluid that's going to send an Impulse down cranial nerve 8 so the vestibular ccar nerve division called the vestibule division which means equilibrium in this case and that's how that movement will be detected so you can tell where you are at at any given time and so inside those semicircular canals at the structure called the ampula is where we find um the ability to do the detection of the movements of the head the acceleration the de acceleration the odal list movement the pressure that are occurring there um this is going to give you the positioning of your head your body and rotational forces of acceleration and de acceleration