[Music] hello and welcome to Insight oftalmology this is Dr Amrit welcoming you to the anatomy of retina in this video we will be studying the 10 layers of retina in such a way that you will never have to remember them you can understand them very easily and logically so without any delay let's get started in order to understand the 10 layers of retina we must have a good understanding as what is meant by the inside and what is meant by the outside so as we all know that this is the witous cavity and the witous cavity is present inside the eyeball and covering the eyeball what we have is the quarts of the eye now the one which I have drawn over here in orange color is the retina so the retina is the innermost coat of the eyeball and the blue over here is the ska which is the outermost quat of the eyeball and in between what we have is the choid so in this diagram we can see that retina is the innermost and anything which is towards the ca is the outermost structure now the retina itself is divided into about 10 layers right yeah so before we understand those 10 layers it is very important to know about the three important cells which are present in the retina the first is suppose the cone okay the cone is nothing but the photo receptor there are two photo receptors which are present in the retina one is cone and the other one is Road rods the cone is considered uh the cone is concerned with the color vision and the rods are concerned with the night vision so the cones which are the primary receptors for the vision they will relay next with the bipolar cells and then the bipolar cells will relay with the gangon cells similarly the rods also will relay now with the bipolar cells and these bipolar cells will again be relaying into the gangon cell so this is the primary arrangement of the cell which is present in the retina and it is present in such a way that the photo receptors are actually located in the more outer region of the retina right so as you can see over here this is the cone right so cone is the cones and the rods are the outermost then we have the bipolar cells and then we are going to have the gangon cells so in this diagram let us consider this is the image of the eye this is the optic nerve what did I tell you anything over here is the outside that means towards the retinal pigment epithelia right so let me tell you what is meant by the retinal pigment epithelium there are three quotes of the eye number one retina then we have choid and then we have the sca the retina is actually divided into two parts the outer part is the pigmented epithelium or the retinal pigmented epithelium and the inner part is the neuros sensory retina okay the inner part is a neurosensory retina the retinal pigment epithelium actually consists of a pigmented cells right which have macras function which have metabolic functions right however the neurosensory retina is itself again divided into nine layers and why it is called neuros sensory is because the three cells that I told you the photo receptor cells the bipolar cells and the gangon cells they are going to form these other nine layers of the neurosensory retina and since they are neurons and they have sensory function of vision that part of retina is called a neurosensory retina so which cells are present towards the outermost side these are the photo receptors the con the cones and the rods so over here let us see first these are the cones okay and the cones are then uh relaying with the bipolar cells and bipolar cells are relaying with the gangon cells this can be seen in this image right so just see the arrangement of these cells in the retina cones relaying with bipolar bipolar relaying with the gangon cells right similarly the uh the rods also will be present they will also relay with the bipolar cells and then we are going to have the gangon cells right so this is how you can see that the basic Arrangement is same photo receptor to bipolar bipolar to the gangon cells and as we know there are millions and millions of these neurons they are going to form the retina okay so what happens finally to our uh gangon cells uh is that these processes that you can see over here are nothing but the processes of the gangon cell layer right and these processes of the gangon cell layer are actually called the Nerf fiber layer and so these nerve fiber layers are going to finally come like this from the retina okay the Gang from here from here from here all these places they are going to finally form the the nerve fiber lay and that nerve fiber LS are going to finally go into the optic nerve right and they're going to form the optic nerve okay so this is the picture which is denoting the cellular arrangement in the retina the outermost which is drawn at the bottom over here is the pigment epithelium right and then we have the rods and cones the bipolar cells gangon cells finally forming the optic nerve fiber so like this we are going to actually divide the entire retina structurally into about 10 layers so let us see all of them one at a time so the first uh layer which is the outermost layer is the retinal pigment epithelium that is drawn over here right so the retinal pigment epithelium is basically having few functions like number one they are pigmented okay so anything which is pigmented will have what will have melanosomes right and these melanosomes contain a pigment which is called melanin so melanin is basically responsible for the absorption of extra light so when we look at a bright object and uh our photo receptors are going to perceive it okay perceive that light however we also need to protect our retina from that excess light okay and from the excess photo damage right phototoxicity so that damage will be prevented because of the uh pigmented epithelium because they have this melanin and melanin will absorb the extra light now second function is that whatever waste products are actually generated by these cone cells and Rod cells they will also be taken care of by the pigment epithelium cells now before going into the details of the other layers after the RP so let us just have a look at the basic structure of the rods and the cones right so the rods and cones are nothing but they are the photo receptors of the vision okay so they are the photo receptors or the primary sensory organs of vision right so these are going to be again divided into the nuclear part and the segment part okay so the this is the nucleus of the rod and the nucleus of the cone right now again they have this part over here which is the segment so we have over here the outer segment which is also called the transductive region okay the outer segment of the cone and the outer segment of the rod now again we have one more segment which is the inner segment and which is uh responsible for the maintenance of the cellular homeostasis okay and why it is responsible for the maintenance of cellular homeostasis you can see over here that they have mitochondria and we know that mitochondria is associated with energy production so all the energy that these photo receptors need to see is being supplied from the inner segment right yeah and then it is being transferred to the outer segment outer segment is just a transductive region which is actually made up of so many discs right and eventually as the cells will age by doing work these discs are going to be eliminated like this okay so you might ask why are these discs are not getting accumulated in the retina because what did I tell you where is which is the most outermost region of the retina it is the retinal pigment epithelium so retinal pigmented cells the RP cell cells are going to present like this you know very in very close association with the outer segment of the rods and the cones and when these discs are actually released they are going to be taken in taken in by the RP and the RP cells are going to phagocytose those discs okay fyos is nothing but they're going to eat up all that waste material right so we have the outer segment which is in contact with the RP then we have the inner segment okay and these two are going to form the segment region of the rods and cones then little bit inner side what do we have we have the nucleus and finally we are going to have a transm missing uh transmissive region okay and that transmissive region is the synaptic endings of the rods and synaptic endings of the cones so the first uh layer was the RP layer and let us now come to the second layer of the retina from outside to inside the second layer of the retina is going to uh compose of the second segments of the rods and cones only okay the important point that you must remember is the segments only the segment is present in the second layer that is the outer segment which is in contact with the RP and the inner segment which is having the mitochondria okay in both rods and the cones the nuclear part is not included in the second layer okay so only the outer segments and the inner segments are present in the layer of rods and cones now just inside the layer of rods and cones which has the segments of the rods and cones is the outer limiting membrane okay as the name suggests it is an outer limiting membrane because it is to present towards the outer layers of the retina that is towards the RP we are also going to have an internal limiting membrane about which I will tell you later and why are what are these limiting membranes also I will tell you later right so you can see that these limiting me membrane is actually bisecting the area of rods and cones at the level of their nucleus next what we have is the outer nuclear layer okay that means there might be an inner nuclear layer also right so the outer nuclear rare is going to consist of the nuclei of the rods and the nucleus of the cones right so again you you must remember that the segments are present in the layers of rods and cones and the nuclei of the rods and cones are actually present in the outer nuclear layer right so the outer nuclear layer is having only the nuclei of the rods and cones next we have the outer plexiform layer now if you see here what did I tell you the photo receptors rods and cones are synapsing with what they synapsing with the bipolar neurons right so the synapses which are formed between the rods and the cones and the bipolar neurons okay they are going to consist of the axons and dendrites right right so the Ison and ddes they look like plexus okay and there is no nuclei which is present here because in this layer there is no nucleus and only plexus this is called the outer plexiform layer okay which is consisting of only the synapsis between these bipolar cells and the rods and the cones next what we have is the inner nuclear layer okay so let us see what is it the inner nuclear layer which is inside the OU the plexiform layer what does it have it has the bipolar neurons nuclei okay so only the nuclei of the bipolar uh cells is present in the inner nuclear layer however there are other cells also which are present at this level as you can see here and these cells are the horizontal cells and the amarine cells you can see over here this one cell which will go syapse here it's Amrine cells and this is the horizontal cell still in this in this layer since only the nuclei of these cells are present and predominantly the bipolar neurons nucleus is present this is called the inner nuclear layer right so don't forget that we have an outer nuclear layer and an inner nuclear layer the outer nuclear layer was formed by the nuclei of the rods and cones and the inner nuclear layer because it is present towards the vitus is formed from the nuclei of the bipolar cells ocine cells and the horizontal cells next what we have is the inner plexiform layer now again move inside sides from the bipolar neurons what did I tell you the bipolar neurons are synapsing with the gangon cells right so now the the synapsis between the bipolar neurons and the gangon cell neuron again consist of only the axons and ddes again there is no nuclei present and therefore it is called a plexiform layer now because this plexiform layer is present towards inside of the retina that is towards the vus this is called the inner plexiform layer finally we have one more layer which is the gangon cell layer it is called gangon cell layer because here only the gangon cell nucleus is present okay and as you can see in this insert that only the gangon cell nucleus is present and this is called the gangon cell layer then as I told you that the gangon cells are going to send those processes which are going to form the nerve fiber layers okay so the last layer or sorry the ninth layer is actually the nerve fiber layer okay which is formed by the processes of the gangon cell and these are going to go and finally form the optic nerve so they they can also be called as the optic nerve fiber layer finally we have one more layer which is the innermost layer which is the inner limiting membrane okay now I told you that there is one outer limiting membrane also so the outer limiting membrane was actually present in between these segments and the nuclear right so that means in between the uh the layer of rods and cones and the outer nuclear layer right so there we had one membrane which was called the outer limiting membrane and the innermost layer was the inner limiting membrane now let me tell you what is meant by this inner and outer limiting membrane now in all the 10 layers of the retina that I told you I basically talked by talked about the the rod cells the cone cells the uh the gangon cells and the bipolar cells okay so these were the main cells that we were talking about the bipolar gangon and the rods and the cones and then again in the inner nuclear layer I told you that there will be horizontal cells and the Amrine cells also right so all this nervous tissue has to be actually kept together by a certain kind of cells which are called supportive cells right so these supportive cells are called the gal cells right and and these gal cells since they are supporting this nervous tissue of the retina they're also called the neurog gal tissue or neurog gal cells now we can give a name to this neurog gal cells and that name is the m cells so Muller cells are nothing but the neuroglial cells which are going to keep all these nervous tissue together right so it acts as a supportive framework and along with that it will also act as a nutritive function right and these cells are actually present vertically so as I told you in my video that how what is the arrangement of these cells the cells were basically arranged horizontally right like this however these word cells that is the neurog cells that's the Muller cells will actually have a vertical Arrangement right and in through this vertical Matrix of the neurog cells or the M cells all our retinal cells are going to pass like this right so at a point that is uh they are going to perforate it at two points right the outermost uh part where it is perforated by the rods and cones will actually form the outer limiting membrane okay so that is the outer ending of the M cell and the innermost part of the M cells where the retina is Perforating okay where it is separating the retina from the Vitas is the inner limiting membrane right so the outer and the inner limiting membranes are nothing but are the perforations which are present in the arrangement of the vertical Muller cells okay through which the rods and cones are passing and through which the nerve fiber layer is actually passing okay so it is just a supporting it is just a supporting structure to the retina so this was about the layers of retina and you can see the OC which is nothing uh which is actually u a hystology which is similar to hystology right OC is like invo histology it can actually show you all the 10 layers of the retina starting from the nerve fiber layer inside gangon cellay okay the inner plexiform inner nuclear Outer plexiform Outer nuclear then okay then we are going to have the rods and cones lay cells RP okay then we have the Brooks membrane and the choid now in the case of e e