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Young's anatomy class is not to be uploaded or distributed to any social media sites or streaming sites and not to be used without permission of dr. young welcome to chapter 15 special census in this chapter we're gonna be looking briefly at all the special census but we're gonna focus mainly on vision and hearing vision and hearing both contain a lot of structures there's a lot of structures to the eye and there's a lot of structures of the ear whenever we're looking at taste smell those are basically just sensory receptors so there's not quite as much structurally when we're looking at those special senses so that's why we're mainly gonna be focusing on the eye in the ear when we're looking at the special senses we have olfaction which is smell gas station is taste we have vision audition is hearing which we usually just call hearing and then vestibular sensation this is basically our balance or orientation with your own body and that's gonna fall right in with hearing whenever we look at our ear all right looking at olfaction or smell first so olfactory system anything with old fact Ettore or olfaction OLF is gonna have something to do with actually smelling this is gonna be pure chemoreceptors so it's completely sensory with neurons basically just embedded within that nasal cavity and whenever a chemical activates that receptor activates that neuron it sends information to the brain and then we interpret that as a smell so we have our olfactory nerve which is that first cranial nerve it's attached to a bulb and then a tract leading up to the brain and here's just a nice little picture showing those neurons embedded within that nasal cavity so you have the actual neuron itself you have a little bulb and then you have the track that leads all the way up to the brain there so like we said before those chemicals bind to those receptors send that message up to the brain and then the brain activates it and then we can smell whatever that chemical is taste taste is next so taste is gustation so anything that starts with gust g ust is gonna have something to do with taste taste is very very similar to our our olfactory senses to our smell we're gonna have taste buds located within the tongue and here again these are just gonna be sensory receptors so essentially chemical binds to that taste bud which is basically going to be the neuron and that information gets sent up to the brain and then we interpret whatever it is or whatever chemical it is that's activating that neuron so here's a picture of the actual taste buds and they're called taste buds because they do look like little buds but essentially they're just neurons neurons they're to actually bind chemicals so here again that chemical binds to it sends that information up to the brain and the brain interprets what we're in the taste all right getting to the anatomy of the eye so the eye has a lot of physical structures it's not just straight neurons so there's a lot more to look at literally when we're looking at the eye looking at the eye so we have two eyeballs that are located within each orbit when we look at the bones there's actually multiple different bones of the skull that's gonna be making up those orbits the eyelids are palpebrae are located above the eye basically just folds a tissue most people are familiar with eyelids they help to protect the eye so whenever we see something coming towards their eye really fast we instinctively and just with a reflex close that eyelid to protect the eye so there's a lot of structures that actually go into making up everything that goes around the eye and helps to protect it we're not gonna look at all of them we're mainly going to focus on that eyelid and then the my lashes so eyelashes there again are there to protect the eye so if anything's coming towards the eye hopefully those small hairs can kind of bat them out of the way and get whatever it is coming towards us not to go into the eye now the only problem with eyelashes is that sometimes they fall out and actually get in the eye themselves so sometimes that can be a problem conjunctiva so this is gonna be a thin epithelial lining that actually covers the eye this is gonna be the part that gets infected in pinkeye so conjunctivitis is pinkeye it's a bacterial infection spreads like wildfire mainly because it causes your eye to be itchy to burn sometimes and you rub your eye get the bacteria on your hand and then touch everything else someone else touches it ends up with pinkeye kids spread it really really easily kids are little germ factories and they might rub their I just touch their friend's face or touch their friends eye you never know luckily we have antibiotic eyedrops that can clear this up relatively fast but any conjunctivitis you're probably looking at a pinkeye lachrymal act apparatus anytime you see lacrimal has something to do with tears so we have a pretty sophisticated tear duct setup where we have a passageway leading all the way down to the very medial corner of the eye a collection system for the tears and then a way to actually drain it the lacrimal gland that produces the tears is actually on the superior lateral portion of the eye so it's on top a little bit more towards the outside of the body but still setting right on top of the eye there so when we look at all the difference that structures associated with it you don't have to memorize this entire pathway I just wanted to have all the definitions up there so you can actually see it or look at these definitions before we look at the picture so here's our entire lachrymal setup we have that lacrimal gland on the kind of top outside of the eye all of our tears are gonna drain to that medial corner of the eye because their eyes are slightly slanted down into the middle all those tears are gonna drain into our entire lacrimal apparatus there so we have a nice big lacrimal sac with nasolacrimal duct that leads down to that nasal cavity so when people really really start to cry a lot and then the nose starts to run a lot the reason why that nose is running so much is because you're literally crying out your nose those extra tears go down into that nasal cavity and literally are running out your nose along with Tunney mucus or snot anything you got along with your nose also clears it out now the functions of Tears they're mainly there to help to lubricate the eye we're moving the eye around all different directions all the time so those tears really help to lubricate the actual eye but they're also gonna spread nutrients and help to get rid of waste so they can distribute oxygen they can distribute basically anything ions that that conjunctiva on the outside the eye it may need to keep healthy and then also it can help to get rid of waste a lot of times if we do get something in our eye we produce extra tears to help to kind of flush out whatever it is that we got in the eye looking at the eye muscles we do move our eyes in all different directions we have six different muscles that are actually gonna help to control that eye movement and as we saw with the cranial nerves we have three different cranial nerves that are gonna lead to these different muscles to help to control the movement even though we have six of them the names aren't too bad because we have a superior and inferior a lateral and a medial rectus so literally just name for where they're at and then add rectus to it so super is on top inferiors on the bottom laterals to the side and medial is on the inside our second two are gonna be superior oblique and inferior oblique so we had our first four and then these are the next two so superior oblique is on top and runs obliquely and inferior oblique is on bottom and runs obliquely so six muscles total actually helping us to control that eye movement and just to remind you here's your three cranial nerves helping to control them so we have that ocular motor nerve we have the trochlear nerve and then we have that abducens nerve so three cranial nerves helping to control all those eye movements and here's a picture of all the muscles so you can see all four rectus muscles in you then you can also see how those oblique muscles literally run obliquely and they Renel Bleakley because we kind of hold them with little bands of connective tissue there when we actually start getting down the eyeball itself we're gonna have three major layers making up the eyeball we have a fibrous layer a vascular layer and then a neuron layer the fibrous layer is gonna run towards the outside of the eye the vascular's kind of sandwiched in the middle and then the neural layer is gonna be the very inside layer here we can see the fibrous layer is made up of the cornea which is a protective very outside portion of the eye that really helps to protect the iris the pupil the lens to some extent and then also the sclera that wraps all the way back to the back of the eye is just connective tissue that sclera is the white of the eye the cornea is gonna be completely clear the vascular layer is made up of the iris little ciliary bodies that are actually gonna connect to the lens that helps us to focus and then the choroid layer which is where all the blood vessels are going to run the neural layer is the retina so that's where all our neurons are going to be located which are responsible for detecting and picking up that light and sending that information down through the optic nerve cranial nerve number 2 to our brain to interpret and that's what we actually end up getting this vision so four of your fibrous layer here's your sclera and cornea actually written out for you it's the same thing we just talked about just written out here's your vascular layer with your choroid where the blood vessels run those ciliary bodies it's gonna help to basically focus the lens the iris is gonna be on the next slide so here's your iris and your pupil so still part of that vascular layer iris is the colored portion of the eye and then the pupil is the actual hole in the middle of the iris so here's just another picture recapping that fibrous layer and that vascular layer for you within that iris we do have little bitty papillary sphincter and a papillary dilator muscle this is gonna control the size of that pupil what's kind of odd if one pupil changes sizes the opposite pupil will change size and we're probably gonna do this in lab we're gonna have a little light shine it in one eye it's called a consensual reflex when you shine the light in one eye that pupil constricts but the opposite pupil off also constricts I'm gonna show you in the pathway of our vision how our nerves actually cross over one another so whenever you activate one nerve the opposite nerve automatically gets activated it's a neat system how its set up but it can get complicated relatively fast and here's just showing that consensual pupillary response so we do have those sphincters and those muscles that do help with dilation and constriction whenever we shine a lot of light into the eye that iris and that pupil will actually constrict so last slide can get in when there's loelai situations it relaxes and dilates so more light can get in you we do have a couple special areas in that actual neural layer the macula this is gonna be kinda a slightly darker slightly yellow region where we have found find a lot of photoreceptors collected in one place this one little area is actually responsible for a lot of our color vision it's where a lot of our cones which is the receptor responsible for color vision are going to be packed we also have rods which are a different type of receptor that are more responsible for low-light night photochromatic type of vision then we have the optic disc the optic disc is actually where the cranial nerve and all of our arteries branch into the eye this is a blind spot we don't have any receptors there we don't have that pigmented layer that soaks in the light because we have to have at least one area where things enter and exit so that's gonna be at the optic disk and we can actually see both of this there both of these areas we can see the macula we can see the object disc just through a normal eye examination so here's a picture of the actual eyeball like we were looking into someone's eye doing an eye examination with up with an ophthalmoscope basically just shines a light into the eye and we have a little magnifier that will magnify that image Horace so the optic disc always shines up like a nice big Sun cuz there's no pigmented layer so none of that light gets absorbed so it actually gets reflected back atoms coming out through that optic disc we should be able to see our blood vessels coming out through there they should be relatively big we want to see a lot of them we want to see their small branches if we don't see those real small branches that sometimes can be an indication of a disease process diabetes is a big one we're always concerned with because diabetes cult kills off the small blood vessels throughout the entire body which includes the eye so vision problems eventually leading to blindness can happen with be teased so we want to see all those real small branches and we want to see those vessels looking nice and healthy in there the fovea is that darkened area within the macula so might be said that macula is gonna be the area that we find packed with cones responsible for a lot of our colored vision all right as we work our way down to the lens here the lens is gonna be used to focus light or bend light we're gonna focus it by bending it the lens when you look at the modeling lab don't confuse it with the cornea they're both clear discs the cornea is larger in diameter but thinner the lens is smaller in diameter but thicker the lens doesn't protect anything the cornea protects the lens so don't flip-flop them when you're looking at them that lens is actually going to be located underneath the iris the way we're gonna focus it is with the ciliary bodies so when we're looking at something up close those little ciliary bodies with ligaments attached to them will they're basically just little muscles they contract and actually pull the lens so it's more of a elongated shape when we're looking at something far off in the distance they're going to relax so we can see whatever it is far off in the distance now this is where the problem comes in as we age with being able able to read things like menus relatively up-close as we age those muscles aren't as strong anymore and can't contract and we can't pull that Ling lenses elongated as it used to be able to so when we try and focus on things up close they're not as in focus because those little muscles have basically worn out now when people have vision problems when they're younger it's usually due to the shape of the lens to start with so especially if you're trying to see things in the distance and they've always been blurry and you need contacts or glasses well that's because that lens was never the right shape so whenever those ciliary ligaments just relax the lens actually doesn't go back to the shape it should be in to focus on those faraway objects so that's why we use glasses or contacts to compensate for that slightly wrong shape of that lens so here's a picture HAP you can see the lens you can see the pupil which is the actual opening to the iris to get down to the lens you can see those ciliary bodies with those little ligaments attached to the lens so those ciliary bodies are just little muscles that contract and then pull those ligaments which pulls the lens and it actually gets us to focus like I said on either things up close or things far away we also have two big cavities in the eye so we have a posterior cavity and an anterior cavity these are both gonna be filled with fluids in the posterior cavity which is the larger cavity behind the lens this is gonna be vitreous humor this is gonna be a fluid that's almost more like a gel it has proteins floating around in it it helps to keep the shape of the eye the aqueous humor in the anterior cavity which is located in front of the lens this is also filled with a very similar fluid as a vitreous cat fluid is going to be found in that posterior cavity this is gonna actually help to keep that iris nice and healthy and there again distribute nutrients get rid of waste from that ciliary body area this is gonna have actually a little drainage area called the scleral sinus the scleral sinus will recycle this fluid because the epithelial cells are continuous gonna be continuously making this fluid in there so we're always going to be making some and replacing some if that sclera sinus gets blocked that fluid is gonna build up and the pressure inside the eyes build up that can actually be very dangerous and cause blindness it's usually really painful though so people usually get it seen about before it actually causes too much damage but if you've ever gone to the eye doctor and they do that little pup test where they blow the actual air into your eye it's like a little puff what that does it's measuring the pressure in the eyeball that air has the eye it bounces back to the Machine and it can measure that pressure and what it's measuring is a pressure of the fluid in that entire cavity as long as that's draining like it should they should get a nice constant pressure within a range the pressure is too high there may be a problem with that drainage you with these last few slides of the eye I wanted to show you the visual pathway so this is something you don't have to remember but I just want to show you the entire setup this can get relatively complicated fast so the neurons that supply each I threw those cranial nerves the outside or lateral neurons are actually gonna be responsible for your medial vision so that vision we see right there in the middle so those run up on either lateral side of the eye and then they make you see that very inside medial vision the neurons that actually run to the inside of the eye they cross over so the right side crosses to the left and that left crosses to the right then they ran up the medial of each eye and those medium neurons are responsible for the lateral vision now this can really help us determine where eyesight problems are sometimes if the problem is actually with the neurons themselves if someone has a lesion right in the middle of where those neurons crossover this is called the optic chiasm if there's damage there then what people end up with is tunnel vision because if those medial neurons get damaged where they cross over the lateral vision doesn't work so you just end up with tunnel vision now if there's damage up higher to both tracks going to one eye then you just have vision problems in that one eye or if the problem is just with the medial vision but you can see fine laterally then the problem is probably just with one of the lateral neurons so it can actually help us to trace down where the problem might be but once those neurons actually make it into the brain then they're gonna go to nuclei more towards the center of the brain and then those nuclei have neurons that branch all the way to that occipital lobe so we have a relatively complicated path wave or vision like I said this isn't something you need to memorize but I at least wanted to show it to you because we have half our neurons that stay on the same side we have half our neurons that cross over and go to the opposite side then it has to branch back to nuclei then it has to branch back all the way to that occipital lobe so relatively complicated vision pathway but it does help us to sometimes figure out where that problem is and here's just another basically some really slight summary slide looking at how that vision pathway is going to work and how that brain actually interprets vision all right up next is the ear when we're looking at the ear we're going to have three big major sections we have the external ear outer ear the middle ear and then our inner ear you so looking at that externally er like we said the Oracle is gonna be that your your lobe if you remember we also had Oracle's to the heart with those atriums so those atriums kind of look like I always call them elephant ears kind of look like elephant ear lobes our ear opals are in the our ear lobes that external auditory canal or external auditory meatus is just the hole you can stick your finger in it you can stick q-tips in it here we're gonna find ceremonious glands which just make cerumen which is earwax earwax actually helps to lubricate that inside portion of the ear and keeps it from drying out sometimes if people use q-tips too much it can actually dry out that inner canal and cause some irritation and some bleeding so some Mira wax is actually good too much earwax as a bad thing there especially with elderly patients sometimes they'll come in with hearing problems and it'll be because they have so much earwax that it's literally blocking that entire canal so here's your outer ear that Oracle and basically that external auditory canal tympanic membrane this is the end of the outer ear the beginning of the middle ear so tympanic membrane is eardrum make sure you call it tympanic membrane it's not a natural eardrum it's a tympanic membrane this is going to be connected to auditory ossicles which are gonna be three little bones so the way this works the tympanic membrane vibrates which vibrates the auditory ossicles which then send those vibrations to the inner ear where the receptors are going to be located then the receptors are going to interpret those vibrations into our actual hearing so middle ear there's not too much going on there except for the tympanic membrane the auditory ossicles it is filled with air and this is where that Ferren go tympanic tube or eustachian tube is really going to come into play and here's your fanfare and go tympanic tube written out so remember eustachian tube is the same thing let's yours a little bit common more commonly used this is going to be used for drainage down to the thrill and also used to help to balance that air pressure so if you've ever been going to Branson going up and down the big Hills that air pressure is going to change as you go up and down the hill and sometimes you can feel that actually in your ears same thing if you're flying on a plane and you start coming down to land that air pressure changes and sometimes it can really hurt the ears the fairing go tympanic tube eustachian tube is made to equalize that outside pressure with the inside pressure to that middle ear also used for drainage if we get an ear infection especially behind that tympanic membrane it can drain all that infection the swelling sometimes pus actually down into the throat a lot of times we swallow it don't even know it and stomach acid can actually break it down problem we get especially with kids is this eustachian tube or forego tympanic tube is relatively small to start with it can get blocked so if it swells too much if there's too much infect infection that tube gets blocked and there's nowhere for that pressure to go can actually rupture that tympanic membrane this is when we put tubes in kids ears we literally make a small incision tympanic membrane so that fluid can then drain out of that external canal instead of down that you station to the tubes work relatively well I have a picture coming up here in a second but it can cause some damage to that tympanic membrane and they can also get dislodged kids are bad about messing with them if they're running them planes sometimes they can just come out and then they have to be repositioned auditory ossicles are the small little bones attached to that tympanic membrane it's the malleus incus and stapes stay piece is a little kind of pitch fork shaped bone a little bit stay pieces is actually the smallest bone in the body Jeopardy type question you don't have to memorize a name to all these small bones you can just call them auditorium chuckles they connect to that inner ear to an area called the oval window we do have little bitty muscles in here too called the tensor tympani and stapedius muscles these are some of the smallest muscles in the body they actually help to dampen real loud noises when they hit that tympanic membrane so it actually helps to try and protect it prevent it from getting damaged a little bit but if you're at a real loud concert that tympanic membrane is taking a real big beating it still might take a little bit of damage plus it helps to dampen those waves actually going to the cochlea and that's where we're really concerned about we're really concerned about damaging those receptors that are picking up all those sensations those vibrations from that hearing so here's a picture of that middle ear you have that tympanic membrane you have the auditory ossicles that attach to that inner ear at that oval window that little stabies and then that nice tube leading down to the throat which is that fair and go tympanic tube or that eustachian tube and here's a picture oh Titus media so this is basically an ear infection if that your drum tympanic membrane gets infected it should look like all the way on the left is a nice healthy tympanic membrane its connective tissue so it should like kind of white relatively shiny the middle picture is of an infection it's red kind of bloody looking a lot of times it may kind of be bubbled up if there's a lot of pressure behind it kind of pushing out and then the picture on the very right is a picture of a tube actually in the ear so that eustachian tube going down to the throat gets blocked we put a tube in the tympanic membrane so while that extra fluid can actually drain out of the ear getting to our inner ear so our inner ear is going to be made up of several different parts it's all surrounded though by a bony and membranous labyrinth blown on the outside and then membrane on the inside this is gonna hold a fluid called endolymph this fluid is what's gonna activate all our receptors in the inner ear so when you're thinking about the inner ear I always think of it kind of like a Snell the first section we start with is the head of the snail or the vestibule the vestibule contains the oval window which the auditory ossicles connect to so this is what's going to receive all the vibrations that eventually lead to the cochlea the utricle and saccule is where we find the actual receptors to the special table what this vegetable is really gonna be responsible for since it's filled with that endolymph that fluid it's gonna have receptor so every time we move our head in a certain direction it is going to pick up the movement of that fluid with inside that vegetable and actually interpret that depending on which way we're moving the big thing that the vegetable is going to pick up is going to be linear acceleration and gravity type movements so linear acceleration when you first take that step walking forward you can kind of feel that sensation of movement the vegetable is responsible for picking up that sensation when you start to fall you get the sensation of falling the vegetable is also responsible for picking up those type of movements so linear acceleration gravity type movements so because when you move your head it moves the fluid which activates the receptors sends that information to the brain and the brain can detect what you're doing semicircular canals are kind of like a little horns of the snow these are gonna be literally semicircular canals they're semi circles and they're canals you're filled with that endolymph fluid still at the base of each one of these we're gonna have three an anterior posterior lateral we also have receptors the this is again again all based on fluid movement so this to basically helps with your balance and body position whenever you move your head a certain way or if you're hanging upside down or you're laying down the fluid will move within those little semicircular canals and activate the receptors at the bottom of each canal these help to pick up more rotational type of movements so actually spinning in a circle are you hanging upside down up right are you sideways any type of circular type of movement is what these semicircular canals really help to pick up so here's a picture of the entire inner ear and you can actually see that endolymph in it now so we've talked about that very head portion of our snail the vegetable and we talked about the semicircular canals up next is gonna be the cochlea cochlea is kind of set up like a snail shell it's in a whining vortex kind of looking circle there so our cochlea is going to be responsible for a hearing this is where all our hearing cells are actually going to be located at so what happens as a vibration moves through the tympanic membrane the auditory ossicles it sends that actual air vibration into the fluid then it turns into a fluid wave that wave then activates the actual receptors in the cochlea and will send that information to the brain and then our brain is going to interpret that the receptors in that copia are located in an area called the organ of Corti or sometimes a spiral organ a lot of times you're probably gonna see organ accordi Cordy discovered it named after himself and call it the organ in Cordy here's a picture of that actual cochlea kind of cut up and we can see it so within that endolymph is gonna be a whole bunch of these little organs accord ease and that vestibulocochlear nerve that cranial nerve the vegetable branch goes to the vegetable of the ear picking up the semicircular canals and that vegetable for balance and movement and then the cochlear division actually branches out through the cochlea and you can see that here it's gonna have a whole bunch of branches all going to different little organs accordi where those receptors are located so as that fluid moves on top of the organ of Corti those little receptors it's gonna stimulate the receptors differently depending if it's loud soft high-pitched low pitch will all move the fluid different which moves the receptors different and that signal that movement of the receptors gets sent through that cochlear nerve to our brain and our brain can then interpret all those different movements as actual sounds now within the organ chord Eva little receptors are usually called hair cells or hair receptors because they're so small they do look like little hair sticking up we don't want to damage these if that fluid wave is too big due to a really large sound via this is the part that actually gets damaged it gets pushed down too hard and if those get pushed down too hard they're not gonna bounce back up and we actually have hearing loss associated with that so once you dam us up damage those receptors that's it so that's why we try and stay away from loud noises or wear earplugs here again big problem concerts a lot of the times people go to them music is too loud and sometimes you even get that ringing in your ears that can ask for a day or two literally what that ringing is why you're hearing that is those little hair cells actually popping back up and your brain is detecting that movement as a ringing type of sound so that ring is happening it probably means some of those hair receptors are popping back up some of them probably apart there's probably some damage there somewhere