hi everybody and welcome back to miss Angler's biology class I am Miss angler in today's video we are going to be doing an updated video on the commodation of the eye I have originally shot this video during lockdown in 2020 but I've decided to update the video and make it more current and more precise so it's always easy for you to understand these more complex topics now if you are new here don't forget to give this video a thumbs up and make sure you are subscribed with your notifications turned on because I post every Tuesday and Thursday if you are interested in also getting your hands on my cheat sheet study guide you can find that at Miss anger. co.za I have one for Life Sciences mathematics and very soon everyone I'm going to be releasing some very exciting subjects so keep your eyes locked on my social media as I will be posting updates on that very soon one other very exciting project that I do have if you're interested is my Smart Start series it is a workshop it's a self-paced workshop that you watch and you progress through as you prepare for your exams and your finals it's different from the YouTube channel in that it is more structured and you're learning as you progress through the topics as you do the questions I've provided so you can actually establish whether you are ready for your exam and that is also on Miss anger. co. now to dive in on this video we are going going to focus in on the anatomy of the eye that we've already covered in a previous video but what we are going to focus in on is specifics now when we are looking at the eye and we're talking about accommodation we are talking about this area of the eye over here that needs to change its shape in order for us to bring an image into Focus so to make it clear now it's important to know that you can't change any other aspects of your eye in other words you can't change the shape of the cornea which is this outside layer you can't change the retina which is this inner yellow layer the only that you can change in order to see an image more clearly is going to be this structure here which is the lens now the lens is really important because it is the point at which light is going to refract and when I use the word refract or refraction it means bending and when we bend light we want it to converge or meet at the back of our retina we want it it to converge at the back over here and the best way to do that is with the lens so essentially the lens is bending light so that you can see an image more clearly now what exactly is accommodation accommodation is when you are changing the lens shape to accommodate for more or less ref fraction and we're going to go into exactly how to explain that and what is going to get you full marks in your exam so to begin we need to start with what exactly is actually happening in the eye the structures that are actually going to do all the changing and so what I have here is an image of your eye and we're focusing right at the front of the eye we've taken everything away we've taken the iris and we are looking straight through the pupil now and this over here is is the lens surrounding the lens these long filament structures are the suspensory ligaments and their job everyone is as the name suggests to suspend the lens so to hold it in place and then right around the edge this ring is the CER muscle and the cery muscle is linked to these suspensory ligaments and it pulls or relaxes and changes what the ligaments are doing now to give you a nice side view or a crosssection we can also look at it like this here is our cery muscle on the either side here is our lens once again and there are those suspensory ligaments one more time so that you can see them nicely now I want you to know that the natural state of your vision which means when your eye is actually at rest is when you are using distance vision and what counts is distance Vision anything that is 6 M or more than 6 m is distance vision and in an exam you are often going to be asked something like this they'll say um you are looking at a book and then you hear a noise in front of you and you want to look up at the object far away that is accommodation but looking far away distance vision and then going to ask you what changes happen in the eye that enable you to look from your book up and look at the board or look at an object that is being thrown towards you and you can see it clearly so this is our first step when we explain it we are going to say that the CER muscle relaxes and going back to our image alongside remember here is our cery muscle this outer ring of muscle over here that is going to relax and whenever that muscle relaxes an opposite effect happens to the suspensory ligaments which brings me to my second point the suspensory ligaments pull tort now what does tort mean this spelling of T and this meaning means that they are pulling tight on one another and that means that the lens if you look at this lower image these are the suspensory ligaments down here they are pulling on the lens and they are going to change the shape of the lens and so I want you to imagine we're going from a fatter lens so the lens is more bulgy like this and we're going to make it thinner and flatter and skinnier so that brings me to our next point that we must mention the lens becomes flatter now a lot of matrics just stop right there and they don't explain anymore but there is actually more to this and you must mention the next point because the lens is becoming flatter there is less refraction which means there's less light bending remember we spoke about that earlier it's all about bending the light right more or less and because there is less refraction we can now form a clear image on the retina and this is exactly how you are going to explain it in an exam these five bullet points is what you need to give and so to just recap before we move on to near Vision it's all about the lens changing shape and it is done by the suspensory ligaments and the cery muscle in this instance the muscle contracts and so what happens is it's pulling upwards which pulls on our suspensory ligaments they pull tort and the lens now goes from being a fatter chubbier lens to a skinnier lens and in doing so it reduces the refraction which means less light is being refracted and you can now actually see further away more clearly now we're moving on to near vision and hopefully we can see some physical differences between the previous picture but you'll notice the cery body over here is a lot thicker and that's because it's Contracting whereas our suspensory ligaments hopefully you'll notice they're like squiggly like this and that's because they are relaxing now if we give you a side image that you can see it is as well hopefully we can notice here that the suspensory ligaments have relaxed and they're more squiggly and you'll Al notice that the lens here has got a lot fatter and chubbier now the beauty of learning this for an exam is that when we do near Vision which is anything less than 6 M you're actually just learning the previous answer in the opposite so this time we would say that the CER muscle is going to to contract and we can see it Contracting in the image next door because it's got this really thick band the next point is the knock on effect is the suspensory ligaments slacken and you'll notice I don't use the word contract or relax with the suspensory ligaments because those words are reserved for muscles only we don't use that for a ligament a ligament can't contract or relax it can pull t or it can slacken and that then allows the lens to go from being skinny to being more bulgy right so wider and bigger and so we need to say that the lens becomes fatter but a better word for fatter so I don't really like to use it um the word fatter or bulge is actually the word convex it's a better word to use so the lens becomes convex there is more refraction and if there is more refraction we end in the same point as we did in the previous one a clear image is formed and we must always say where on the retina that is really important a lot of people forget that last bullet point and and that's accommodation now as always I like to finish off these lessons with a quick terminology recap and you can use these as a list of words to learn or flash cards as well we first spoke about the general structure of the eye that's going to play a role in accommodation and we spoke about first of all the cery muscle and the cery muscle is the ring of muscle that sits around the lens remember so the lens sits in the center and it is attached with suspense ligaments to the lens and remember those suspensory ligaments were those long wavy like structures that held or suspended the lens in the center and it is their relationship between each other the muscle and the ligament where one contracts and the other slackens or the other one pulls tort and that one relaxes whichever the way it may be that relationship changes most importantly the lens and the lens either is thinner or bulgier depending on whether we're looking close or far away and that fixes an image back on the retina so that we can see clearly at the back of the eye and accommodation refers to refraction which is light bending in the eye you either have more light bending or less light bending depending on whether you're looking close up so when you're looking close up near Vision you need a lot of detail think about it so there's lots of refraction when you're looking far away there is a a lot less detail you need so you need less refraction now if you like this video don't forget to give it a thumbs up and make sure you're subscribed with your notifications turned on because I post every Tuesday and Thursday and if you have any questions or you want me make a video on a specific topic then leave it in the comments section below and I might make a video answering you I'll see you all again soon everyone bye