learning objective number one is to identify and provide a function for the I and accessory eye structures an accessory eye structure is a structure that is not part of the I itself but is found in the I region and plays some role in IE function a structure of the eye is contained within the eye or the eyeball itself so there are five accessory eye structures that we are going to take a look at I will highlight these on this image first along with their function and then I will post a recap of those functions on the next slides so you don't need to get too caught up on taking notes so we'll start with the eyelids which are also called the pelpa and the eyelids are these folds of skin here and here they sit above and below the eye and they work to shade the eyes during sleep protect the eyes from excessive light and foreign objects and spread lubricating secretions over the eyeballs we then have the ey lashes which extend from the border of each eyelid so our eyelashes are these parts here and here as well as the eyebrows which Arch above the upper eyelid so eyebrows are these part here both the eyelashes and the eyebrows function to protect the eye from foreign objects sweat and direct Rays from the sun we then have the lacrimal carun which is sometimes also referred to as the lacrimal apparatus and this structure is the pink mound of tissue that you find in your inner eye this tissue contains sebaceous or oil glands and sweat glands and when you wake up in the morning with sleep in your eyes this is where that sleep comes from the function of this tissue is to cover and protect the tear drugs or the lacrimal glands which sit just underneath this pink tissue lastly we have the conjunctival which is a thin protective mucus membrane which lines the inner aspect of the eyelids and passes from the eyelids onto the surface of the eye where it covers the Scara or the whites of the eye so taking a bit of a closer look at the conjunctiva and the conjunctiva is this brown part here so we have the pp conjunctiva which is the portion that lines the inner eyelid and then we have the Bulba conjunctiva which folds over onto the Scara and we have this both our upper and the lower segments of our eye the Bulba conjunctiva or the part that sits on top of the whites of your eye is vascular and contains blood vessels and it's the dilation and congestion of these vessels due to irritation or infection That's What Causes That bloodshot eye look the function of the conjunctiva is to keep the eye and the inner surface of the eyelids moist and lubricated allowing them to open and close easily without irritation the conjunctive are also functions to protect the eye from dust debris any foreign object or organism that could cause infection to the eyeball so those accessory structures and functions in written text form we have the eye lids which protect from light foreign objects and assistant in the lubrication of the eye we have eyelashes which extend from each eyelid they also function to protect from foreign objects sweat and light when something gets too close to your eye and touches your eyelash it can also initiate blinking which is another protective function we have our eyebrows that Arch above our eyes and again protect from foreign objects sweat and Light the lacrimal carun which is that pink Mount of tissue in the Inner Eye protects that underlying lacrimal tissue or our tear glands and then we have the conjunctiva which ensures lubrication of the eye and the inner eyelid now moving on to the structures of the eye itself or those contained within the eyeball and looking at this image here we have the anterior surface of the eye which is the part that would face out to the external environment and let in light and then the posterior side of the eye is this part down here which would be encased in the eye socket now when we look at the anatomy of the eye itself we look at it as being three layers of the eyeball and then everything internal to that so if we take a look here you can see nice and clearly those three layers of the eye the rest of the structures are then internal to those three layers so the outer almost superficial layer is called the fibrous tunic it consists of the corne the Scara and the canal of schlam the corne is this transparent layer here so it serves as a window to let light into the eye and then the Scara is actually continuous with the corn but it is white it's not seethrough and it provides protection for the eye as well as acts as a bit of an anchor for extrinsic eye muscles the canal of schlim which you can see is this little hole or duct here and also here is a sinus or a vessel which surrounds the cornal and collects aquous humor from the anterior chamber so we're jumping ahead a little here but the anterior chamber and the anterior cavity are these portions here they are filled with a liquid called the aquous humor and the canal of schlam collects this liquid so that it can be returned to the Venus system and be refreshed the middle layer of the eye is called the vascular tunic and it's made up of the choid the celery body and the iris so the choid is this brownie red layer here it's the middle portion running all the way around the eye it contains an extensive network of capillaries and so it supplies the retina which sits beneath it and also the Scara which sits on top of it we then have the celery body which is made up of the celery muscle and the celery processors so the celery muscle surrounds the lens and then the processors extend from the muscle to the lens to hold it in place and pull it tight to change the shape of that lens when it's required so the muscle is this part here and here which is all the way around the lens the processes are like these little strings that extend from the muscle to the lens the iris which is actually a little bit hard to see on this image but kind of sits here and here is the colored part of the eye that sits in front of the lens it contains blood vessels pigment and smooth muscle and the smooth muscle can dilate or contract to let more or less light into the eye the opening in the middle of the eyes that changes shape when that smooth muscle either contracts or dilates is called the pupil the innermost layer of the eye is called the retina you may also see this termed the inner tunic and the retina contains rods and cones which are our photo receptors or the specialized light receptors the macular lutea the FAA centralis and the optic disk so the rods and cones or the photos receptors we will look at in more detail in a few slides but these are the receptors of the eye they take the light that enters the eye and turn it into a neural signal that our brain can process the macular lutea is a small yellowish region of the retina at the back of the eye now when you focus on an image the center of the macular lutea the center of the lens and the image that you are looking at are all lined up in a straight line and then in the very center of that macula is a depression called the FIA centralis and this part of the retina contains only cones which again we will speak about shortly but a specific photo receptor responsible for Sharp and clear color vision in the fva centralis there is also no blood vessels which can get in the way or interfere with the photo receptors and vision so when light is reflected specific typically on this little part of the eye that's where you'll have the most sharp and detailed Vision lastly we have the optic disc this is the part of the retina that's found at the very back of the eye where the optic nerve exits and therefore there are no photo receptors in this space because there are no photo receptors we have no vision when the light hits this area and for that reason the optic disc is often called the blind spot the optic disc is also where major blood vessels will enter and exit the eye because they're not getting in the way of any of those photo receptors now within the eye so under our fibrous tunic our vascular tunic and then the retina or the inner tunic we then have a number of structures that are important to be aware of we have the anti ior cavity which is made up of the anterior and posterior Chambers so I know that's a little bit confusing this portion here is our anterior cavity and it's made up of our anterior chamber which is this portion here in front of the lens and then this portion here which sits behind or beside the lens the anterior cavity is filled with aquous humor which is a clear liquid that provides nourishment to the interior eye structures and also helps keep the eyeball inflated we then have the posterior cavity which can also be known as the vitus chamber or the vitus body and it's this entire back portion of the eye so if this is our anterior cavity everything behind that is our Vitus chamber or our posterior cavity the posterior Cav is filled with Vitus humor which is also a clear fluid but it's thicker and more jellylike than the aquous humor and its function is to maintain the round shape of the eye and actually hold the retina in place the last internal structure that I want you to be aware of and one that you might know a little bit about already is the lens so the lens is this part of the eye here and the function of the lens is to transmit light and focus it on the retina so a written recap of O eye structures and we have the corne which is the clear front portion of the eye which provides a window of light to enter the eye we have the Scara which is continuous with the corna it's the whites of your eye and provides protection and acts as an anchor for our extrinsic eye muscles the canal of schlim with those little holes or or sinuses that I pointed out these drain aquous humor from the anterior cavity and the anterior chamber the choid is that middle layer so that brownie ready layer it contains an extensive capillary Network which supplies both the retina underneath it and the scera above it the celery body includes the celery muscle and then the processors or the little fingers which hold the lens in place and we have the iris which is the colored part of your eye and contains blood vessels pigment and smooth muscle which can adjust the diameter of your pupil on our inner layer we have the macular lutea which is that yellow spot in the center of the retina that allows for high visual acurity a really sharp detailed Vision the FIA centralis is a little depression in the very middle of the Mac macular lutea this is where we only have cones as our photo receptors so it allows for the highest visual accurity our optic disc also sits at the back of the eye and is where the optic nerve leaves the eye so it's sometimes also known as our blind spot we have the anterior cavity which contains the aquous humor which nourishes the eye structures the posterior cavity which is the back of the eye and contains the vitus humor which maintains the shape of the eye and holds the retina in place and then we have the lens which is at the front and it focuses the light that passes through it onto the retina