this lab will be looking at the eye lots and lots of sensory receptors are found in the eye about 70 sensory receptors found in the eye um help pick up all that stimuli coming in through our window to the world uh lots of protection for that structure um there's quite a bit of fat around the eye if you're in lab we'll be doing an eye dissection well a lot of times there's quite a bit of fat still surrounding parts of those structures for the eye also of course surrounded by the bony orbit nice hard sturdy protection um lots of accessory structures to help keep things out of the eye keep things moist hopefully keep things clean so don't get infected since it is a potential entry point for pathogens so one of our accessory structures is called the lacrimal apparatus consists of lacrimal gland and then several ducts the lacrimal glands produce something called lacrimal fluid which we know as tears tears contain lots of wonderful things mucus antibodies lysozymes to help keep things moist and hopefully help keep things clean um so what happens let's actually go to our picture so we can see the second point drained to the nasolacrimal duct what's happening get rid of our boxes here so here's our lacrimal gland up here so superior lateral um to that eye produces that lacrimal fluid produces those tears and those little brown lines you see there those are our lacrimal ducts the fluid is going to go through there and comes on then release onto the surface of our eye and when we blink that will actually help move those tears that fluid across our eyeball so spreading out that fluid full of mucus and antibodies to keep things moist and keep things clean um come over here towards the lacrimal crunch that's always a fun word this little fleshy area here nearby there's two holes that those tears can drain into and the lacrimal chronicle though before we move on with that with those ducts produces oil that can also help with keeping the eye moist if you're not blinking a whole lot now sometimes if we're not blinking as much that oil that's produced by that crinkle can actually build up and then get sometimes called sleep in our eyes or i like to call them eye coopers that dried oil collecting there um so back to these ducks so those tears come across and blink they're going to drain into these ducks here and first then into well the first part you need to know lacrimal sac we see up here and down into the nasolacrimal duct so the name tells us where is it coming from that lacrimal sac down to the nasal cavity so if you think about if you have allergies and your eyes get really watery you also get a really runny nose which could be allergens doing that but also all excess tear being produced can make contribute intensify that runny nose or if you do get emotional near crying we get a runny nose because excess tears are spilling out of the eye but we have excess tears also going that duct into your nasal cavity there we go let's see another accessory structure the conjunctiva so this is a membrane we'll see covering um the inner portion of the eyelid and also the anterior portion of the eye also produces fluid mucus to help keep things moist hopefully help keep things clean um if it does become infected we get what's called conjunctivitis right most commonly or is commonly known as pink eye but point secret mucus help lubricate the eye because dry eyes can definitely be irritating and then other accessory structures that was on that first slide eyebrows and help divert sweat for instance from dripping into your eye eyelashes right help keep dust and small particles hopefully from getting in the eye extrinsic eye muscles so intrinsics mean they're outside of the eye um these allow our eye to move follow objects that are moving also the tension that they create on the eye helps maintain shape of that eye there are six extrinsic eye muscles um you need to be able to identify them there are two oblique muscles and four rectus muscles so giving us a hint what direction fibers are running so just starting here at the top we have the superior oblique muscle and i have another picture with the view we can see here momentarily it kind of comes over here at an angle hooks through the trochlea and attaches on the superior part of the eye we also have a superior rectus muscle so fiber's going straight again attach on the superior part of the eye here we have a lateral view of that eye which we see that nasal bone that's going to be medial to the eye so here's our lateral rectus muscle and rectus virals fibers running straight parallel to that midline it's not labeled but back here you can see the medial rectus we'll see it better on the next picture down here inferior rectus attaching inferior side of the eyeball and inferior oblique circling underneath an inferior part of the eye so all these muscles help to move that eye around in all directions so we saw the lateral rectus in this picture they've labeled lateral medial side for us we've seen lateral rectus superior rectus with my superior oblique again see it coming at the angle hooking through that trochlea here we have that medial rectus that we could see on the last picture but wasn't labeled inferior rectus and then of course our inferior oblique so the eyeball itself slightly irregular hollow sphere we'll find three tunics forming the wall of our eyeball the fibrous vascular and neural layers or tunics so we'll look at those one more closely um internally we have a couple cavities filled with fluids we call humor so we'll see those today too and then the lens separating the front and back cavities segments from each other so let's look at that so high eyeball so there's our lens anterior to the lens we have what's called the anterior segment contains um aqueous humor about the consistency of water it's pretty thin stuff it's constantly being created and reabsorbed um the point the benefit of this is it helps supply nutrients to structures that are avascular like our cornea here no blood vessels here so recycling that aqueous humor constantly can deliver nutrients um to that cornea remove waste also posterior to the lens we have the posterior segment and this contains what's called vitreous humor this is has more of a gel like consistency um it's gonna help with um maintain the shape and the pressure of that eye aqueous humor helps with maintaining pressure within the eye also um but bitter humor definitely does that gel like material if we're doing here for the cowboy dissection in class well most of the eyes have the victory humor so we'll actually get to see that all right so then our layers so the fibrous tunic is the outermost layer of the eye and has two components the sclera and the cornea so the sclera is opaque it's the white of the eye and we can see a little bit of it anteriorly but most of it's posteriorly making up a lot of that part of the eyeball that we can't see because it's in that socket surrounded by fat surrounded by that bony orbit and of course skin and stuff anteriorly will find the cornea which is clear and will allow eye then to of course enter i allow light to enter the eye so the sclera some nice tough connective tissue that gives more protection to the eye and it also gives a nice sturdy attachment point for those extrinsic muscles so where you saw those muscles attaching to the eye that was the sclera and of course the cornea let's light in there's that clear cornea the anterior part of the eye and i mentioned earlier is a vascular um blood vessels potentially right block our view the aqueous humor being recycled helps provide nutrients remove waste as we need to from that tissue and then all this sclera nice dirty connective tissue maintain shape and allow sturdy attachment point for those muscles the middle layer the vascular tunic consists primarily of what's called the choroid has three regions chloride still everybody and the iris three major regions of that tunic so major part of the choroid very vascular lots and lots of vessels to supply nutrients oxygen move waste to surrounding layers that are avascular heavily pigmented also so helps absorb light as it enters so if it's not landing on receptors for instance it's not bouncing around in the eye which could stimulate receptors too much and then make it hard to see right we're stimulating them a lot um let's look at that oh and part of the ambassador tunic we find the iris color part of the eye right we're probably pretty familiar with this in the middle of that colored part of the eye we find the pupil the opening of the iris so allows light to enter the posterior segment of the eye to that lens back to that posterior segment so the light will pass through the cornea that aqueous humor through the pupil on back to the lens and posterior segment anytime light passes through a structure of fluid it will refract or bend that light so like the cornea for instance refracts light quite a bit as it enters the eye as we try to get it onto photoreceptors focus it on the back of the eye at the pupil we can alter the size of that pupil by altering the smooth muscle and contracting a relaxing smooth muscle in the iris so what we'll see with close vision or if lights really bright peoples will constrict so that some of that smooth muscle contracts and the iris making the opening smaller constricts it distant vision dim light peoples will dilate with as much light as we can right to stimulate more photoreceptors so get bigger bright light constricts so we're not um bombarding those photoreceptors with too much light so let's grab the boxes here swing see whoops what's going on here so most of that middle layer is choroid this dark stuff we see here lots of blood vessels again highly pigmented um let's see iris talked about that already this part here is the color part of the eye it does also consist of smooth muscle so it is controlled by the autonomic nervous system and then people that opening in the iris so again light will pass through the cornea gets bent aqueous humor going through fluid could potentially refract also through that pupil to our lens which we can see here now there's this other structure here called the ciliary body and this is a ring of tissue that surrounds the lens more smooth muscle and then going from that ciliary body we have what are called suspensory ligaments that go out and attach to the lens let's go back to our picture here so everybody so we have celery muscles ancillary processes so still muscle lots of capillaries here um and then anchored in those ciliary processes we have suspensory ligaments those little thin white lines here we can see them down here also so when the smooth muscle in our ciliary body contracts and relaxes it'll change the tension on the suspensory ligaments which will then change the shape of the lens this can also be helpful with refracting light and trying to focus it in the back of the eye so this picture is just giving us another view of that ciliary body and lens so here looks like we have a frontal section open up so we're looking on the back side of the front part of the eye okay so there's that ciliary body and within that cellular body we have vasciliary muscle ciliary processes okay so smooth muscle and those white lines there just for orientation right we see retina choroid sclera but all these white lines we see going in a ring between that ciliary body that smooth muscle and our lens it's going all the way around that structure and again the muscle contracts relaxes changes tension on those ligaments altering in the shape of our lens your last layer the sensory tunic or neural layer more commonly known as a retina probably heard that word before um does consist of two layers very very thin very very delicate the more outer layer is pigmented so again helping to absorb light prevent scattering the light in the eye so we're not stimulating receptors too much or when we don't want to be neural layer contains a bunch of receptors particularly what are called photoreceptors light stimulates those receptors and then it gets passed on to neurons particularly bipolar cells and ganglion cells or bipolar cells you mentioned bipolar neurons are pretty rare we find them generally in special senses boom hello eye special sense so retina oh this stuff here this yellowy layer we'll look more closely at how those receptors and neurons are arranged with each other so within the retina a couple areas to be aware of one is the circle here called the macula ludia since we're going to find a high concentration of photoreceptors in particular cones but then there will find an even higher concentration super high concentration of photoreceptors in the lobelia centralis or phobia centralis right there smack dab in the middle of that macula so when we're refracting that light as going through the cornea adjusting that lens for instance that's usually where we're trying to focus it on is back here in that macula particularly on that fovea now there are photoreceptors scattered all throughout the retina except here what's called the optic disc also known as a blind spot this is where the optic nerve exits a bunch of axons of our neurons all travel back here and exit the back of the eye forming the optic nerve remember a nerve is a collection of axons in the peripheral nervous system where those are exiting no photoreceptors and that optic discs also has a blind spot of course i would like to you to name it the optic disc if i'm asking you to identify so photoreceptors that we mentioned there are two types rods and cones rods seem to be stimulated in dim light conditions um we'll find a lot of them towards the kind of periphery of the retina so use quite a bit with peripheral vision cones respond to bright more intense light and these are going to help us with high accuracy and color vision and again we find a lot of those in the macula ludia and the phobia centralis not exclusive to here but we find a lot there so we look at a picture here and let's come in just a touch so we're focusing in on that retina so high photoreceptors rods and cones they're actually closer to the back side of the eye which is kind of interesting so here we have that little pigmented layer of our retina okay pick up that light that scatters so essentially if that light doesn't land on a photoreceptor it's going to go back into this pigment and later layer and be absorbed so it's not bouncing back out stimulating receptors um unnecessarily but our receptors are going to synapse with these bipolar cells and they're going to then conduct that input those impulses to what are called ganglion cells another neuron type we're seeing here and the axons of those ganglion cells will all start traveling towards the back of the eye so you can see all those lines there are ganglion cells so we're finding around all that retina okay and their destination is here all those ganglion axons are traveling towards the optic disk where they're going to exit as that optic nerve excuse me so i already talked about those things ganglion cells helping to form that optic nerve where they exit forms that optic disc so come in here all those lines again axons of our ganglion cells coming together from the optic nerve how cool and then cow i will be doing if you are on campus dissection of a cow eye um so there's some slides in here to help you review those structures when we are not in class and then just a big review picture of all the structures we just talked about so there to help you quiz um yourself work on being able to retrieve that information