Transcript for:
Histology Lecture Notes

okay so guys let's get started so the one that you're looking at right now on the screen here this is the slide of a the sebaceous gland and look before we talk about the cous gland before we can we talk about the cous gland you should first understand one thing that what is the difference between the epithelium and the epitheloid now I don't have to Del that what is epithelium the lining epithelium we've talked about the epithelium covering the body walls and body cavities from inside and outside but what is epitheloid and the reason I want to tell you about epitheloid is because it's not the epitheloid we generally talk about in the pathology that not not those the monuclear ftic cells those epitheloid that you must have read in your pathology part I'm talking about the epitheloid a normal cell epitheloid in histology what exactly is the meaning of epitheloid so understand it's it's a different epitheloid from what you read in the from in the pathology epitheloid are the cells which do not have free surface no free surface these cells they don't have a free surface and these are called as a epitheloid here right now they do they they can have a basement membrane they can have a basement membrane they can have a oppositional surface but they do not have a free surface their free surface is not available like you can see in the cous gland also they do not have a free surface if I give you some examples of what epitheloid are and these are good examples because they have been question asked on the epitheloid once it's a very old a question but you should know about it example for the epitheloid are like we have leading cells lutin cells eyet of langerin we will be discussing using eyet of langerin one of the slide will be where I will show you the eyet of langerin then another example for this would be uh the adrenal gland adrenal gland parenchima adrenal gland parena well adino hypophysis the anterior L of pitutary anterior low of the pitutary gland ER cells reticular epithelial cells or you can say epithel reticular cells epithel reticular cells of thus which again we will discuss I mean the one which I'm marking for you right now this this is the slide that I'm going to discuss with you in in the upcoming part that is eyet of langerin the ER cells of the the thymus and another example for this another good example here is itself is a cous gland about cous gland is also the example for for this so these are some examples Guys these are the cells which are they do have oppositional surface they they may have a basement membrane also but they do not have a free surface they don't have a free surface they're not facing outside toward the body cavity or toward the the Lumen of the asinus or toward outside nowhere they don't have any any free surface and that's the kind of arrangement that you see inside here also when you look at all these cells here well this is a cous gland and in the sebaceous gland what you see that we have these rounded cells the rounded cells with Central nuclei rounded C with Central nuclear and the way they look the reason they look clear because they are washed off with the alcohol when we when we prepared these slides this you know the the sebum inside it is basically washed with the alcohol so it looks like blank it looks like empty so it looks like these empty rounded cells with the Central nucle and they're filled with this lipid vacle right now which looks empty it is actually filled with the lipid vacle and that is the cous gland now you know if you look at the cous gland you know it is present toward the the base of the hair follicle if you look at this the portion the uppermost part of this cous gland you will see it is a portion where the cells will disintegrate the question which was asked in the exam actually they gave this picture and they asked what type of secretion is seen in this gland here cous gland is holocrine gland so this the epical portion that you're looking at here this is the integrating cell which is near the duct this is the disintegrating I should say this is disintegrating cell near Apex which tells us okay this is having what type of secretion it is having a holocrine type of secretion you know holocrine type of secretion in which the cell liis takes place the cell itself will be released as a Content that is holocrine like talking about holocrine guys if I if I may give you an example of the epoc and mocine gland as well because we have another slide coming up for that like epoc glands when I say epoc one of the example of theep what is ocine gland the apocrine reminds of of the word Apex here so you will see that there's a secretary vcle which will come out from the surface of the cell and that is the ocine epoc cell the example is the memory gland mamory gland so it's the membrane bound vicles it's a membrane Bound vcle in the ocine gland the membrane bound vicles are there which release the uh that's how they release their secretion whereas in the mocine gland the kind of secretion it is via exocytosis and one of the example of the of the mocine gland would be the the submandibular gland it will the submandibular gland yes you all know that that is submandibular gland or simply the the gland so the holocrine ocine mocine gland and just to cater the previous year question it was the sebaceous gland which was given in the picture and if I'm not wrong this question was asked twice that the question was just not about the identification of SP cous gland it was about okay the given gland will have what kind of secretion so sebaceous gland is a holocrine type of gland okay so with that guys that was our first slide U moving on to the second one the second picture that we are looking at right now this is a picture of a salivary gland but we need to find out that what kind of salivary gland is that is it Cirus is it mucus or is it a mixed well first of all guys this is a a mixed salivary gland the staining itself tell you you can see the two types of asinus inside it's a mixed salivary gland this here is a slide of a mixed salivary gland now first understand one thing guys when I say mixed C every gland we do have sublingual and even submandibular sublingual and submandibular they both are the mixed ly gland only but the thing is if I have to say what kind of slide is this one I mean if let's say if I have to choose between the sublingual and submandibular then I would say sublingual gland the reason is sublingual glands are the one which are predominantly mucous they're predominantly mucus and these are predominantly Cirus they are mixed they will have both Cirus and mucus asinus but if let's say you look at a gland and we looking at more of a the cus asinus and less of a mucus asinus then that's that's how you this is a this is predominantly a mucus now how come it is a predominantly mucous gland guys this here the lightly stained region this is representing the mucus asinus the mucus asinus how does the mucus asinus look like well let us say if this is one mucus asinas you will see the tall cinar cells are present inside not drawing the entire thing you have a tall colar cell inside and they have a flat basil nuclei the nuclei is flat and basil generally in the cinar cells we have the oval or rounded nucleus which is toward the base not exactly basil but toward the base in which you have a flat basil nuclei so the two feature that that I should write for this the mucus asinus is that we have these tall cinar cells we got tall cinar cells and then we have the nuclei is flat and basil flat and basil nuclei right so that's how a mucus asinus will look like lightly stained again it's a mucus which is washed off when we when we prepared these slides so it looks like like looks like empty only it looks like you can only see these flattened nuclear present toward the basil part otherwise the rest of the slide rest of the the asinus looks empty on contrary this is a mucus asinus the the Cirus asinus I'm sorry that is a Cirus asinus well how exactly the Asus asinus will look like we have what kind of cells we have these pyramidal kind of cells which are pointing toward the the central Lumin part here unlike the serus Asus which was having the colar cells so they having this pyramidal kind of cells again which are having a rounded nucleus toward the base only this time it's not the flat nucleus it's a rounded nucleus toward the base and what else we'll notice that at in the Apex region apical region of these cells you can also appreciate the zymogen granules we appreciate the zymogen granules here let me just write down the feature for the serus asinus as you can see in the diagram guys the serus asinus they have what type of nuclear they have the rounded nuclei rounded nuclei toward the base because we have a like xogen granule in the epical region so they are like more toward the base rounded nucle we the cytoplasm is basophilic I'm not putting any stain it so it's it's a basophilic cytoplasm basophilia is there basophilic cytoplas and as I said zymogen granules zymogen granules at Apex xogen granules at the Apex so that's that's how a serus of the mucus Asin is may look like here okay so um well s i I'll do that I'll mark the important slides for the in though I should not be doing because already I've just squee sque a slide to only 54 so like all these are important that's why we're discussing it here but still I I'll when I'll send you the copy of of this uh uh the annotated PDF I'll make sure I'll write all the important one there I'm sorry I'll not be able to cater the questions which are in in the telegram group right now because I'll be distracted and I may not be able to go with a certain pace so I'll I'll just look into your doubts and queries in the break or after the the session itself okay so guys this is you can see both cus and mucus asinus both are there but you know what this is a mixed gland so both are visible and in the mixed gland there is a histological artifact which is seen when I say hystological artifact that is called as a demun now it's a serus demun that you see here what is serus demun that when you have mucus asinus and they are CA with the cus cells look at this one which which I'm pointing right now this look at this one this is called as a a cus Demi LUN this is called a cus demun these demun they're actually not present cus demons they are a hystological artifact actually when we prepar the slide then these demun are formed here and when you call it a cus demun it means this the asinus is mucus and it is capped by the cus cells we also do have some mucus demun also the're very few in number but even mucus mucus demons are also there but generally that more the predominantly we have a cus demon present in which we have the cus asinus uh sorry mucus asinus which is kept by the serus cells here that's a cus the demun you're looking at and it's a histological artifact and it is a feature of a a mixed delivery gland so as I said you can see more of a mucous asinus in this and less of a serus asinus so it is a sub sublingual gland if you have to choose between the subband and sublingual both are mixed gland only so this is a mixed salivary gland just make sure that in in the in the in the cell that what kind of cell you're looking at more and that kind of mixed salivary gland you have to mark the answer based on that okay now guys moving on to our next question which is also one of the the pyq it's one of the inct pyq only and it is a a picture a electron micrographic image of a a skeletal muscle well I'm pretty sure you must have read about the skeletal muscle in your physiology also in detail you're looking at a skeletal muscle fiber well if you look at this line over there this one and this one this is called as a zed line or Zed band that's called as a z line or you can call it a zband and guys between the two zline this is one functional unit we're looking at that is called a sarcom so from one Z line to this another Z Line This is one sarcomere the functional unit and the sarcomere is is a functional unit so let's say if they ask you this question in this format that okay the functional unit of the skeletal muscle it lies between which two Lin so it's a z line from one Z line to another Z line that is a the one sarom are looking at and that is a functional unit the line that you this look at this dark line that you see in the center here this is called as the M line this here is the m line look at this area which I'm pointing at right now this Darkly stained region in between here guys this is called as an N isotropic band or a band you know the reason we call it a band is a is for the an isotropic so it's an an isotropic band or a band and what exactly this a band represents these a band represents the length of the myosin filament here and if some some something is representing the length of the myosin filament the myosin filament itself here the length of that band will be constant skeletal muscle contraction is based on the the sliding filament theory we know when it's about the sliding here the two filaments are sliding so it's not the change in the length of the actor of the masin filament it is basically the sliding on over each other and that's how the muscle is Contracting so this a band it represents what it represents the length of length of myosin filament and because it represents the length of the myosin filament so it is fairly constant it is constant that means the the size of the a band will not change whether the muscle is Contracting whether the muscle is relaxing so something which is constant in this in the sarcomere is the a band which is not going to change okay now if you look at the either side of the Z Line This is the I band look at this this band here is the I band that is called as an isotropic band or I band from here all the way to here this is a i band a is an isotropic i is isotropic that's an isotropic band what this isotropic band is representing it is not representing the entire length of actin filament no no it is only representing the UN overlapped part of the actin filament look look at this you can see the overlap part also look at this very dark area that's the overlap part also we're talking about only the UN overla part of the actin filament so I band represents un overlapped part of actin filament and when I say un overla part of actin filament that means it will change when the muscle will contract obviously the IE band will get shortened so guys if you look at this entire this the EM of this skeletal muscle what you'll notice that the two a band is something which is constant but the thing which is not constant or will change with the contraction muscle or will decrease with the muscle contraction are two thing one one is the H Zone where is H Zone this is the H Zone look at this till the end of these actin filament here and this portion here this is called as H Zone again H zone or H Band whatever you call it so this H Zone number one and then what band that is the I band H Zone and I band they are one which will decrease they will decrease during during contraction they will decrease during the contraction of the muscle so hzone and I band will decrease during contraction a band is representing the length of the myosin filament and that's why it is it is fairly constant it is not going to change sarcomere is from one Z line to the another right so this is a picture of a skeletal muscle and look at this all this dark light dark light dark light thing this is something which creates this trition the the feature of the skeletal muscle I mean this is electron microscopic image let's say if you would have got a picture of an H stain or something in which the skeletal muscle will look like this you will see the parallel bundle of the skeletal muscle our next slide is actually cardiac muscle so I should tell you about the skeletal muscle here so you will see the parallel unbranched bundle of in the skeletal muscle which are having a very very prominent cross Tri and these cross trition because of these dark band and eye band uh this light band that we're looking at here so we have these cross Tri which is a very very Pro minent feature of a skeletal muscle absolutely yes sir you're right and the type of nuclei which is present in here is the the flat and peripheral nucleus the flat and peripheral nucleus that's how a skeletal muscle if you get a picture of the hystological this H stained slide of a skeletal muscle so you will see the the parallel bundles parallel unbranched bundles I should say parallel un branched bundles very very prominent cross striations we do have cross striations in the skeletal muscle in the cardiac muscle also but they're not as prominent as the the skeletal one and the nuclei which are present in this they are again different from the the cardiac muscle these are the flat and peripheral nucleus flat and peripheral nuclear flat and peripheral nuclear if you find let's say if you find like I'm going a little bit more Pace or something in in that case here anyways you're going to get these slides immediately after the session itself so don't worry about that so pay more attention on understanding rather than just noting down the things right so guys this is the skeletal muscle the fibers that that is if a normal h& stain image is given to you and that is an electromicroscopic picture well guys moving on to our next Slide the next slide is the slide of a cardiac muscle now when you see a cardiac muscle how do you differentiate this cardiac muscle from the skeletal muscle first of all you can see the branching right this is a picture of a cardiac muscle in the cardiac muscle the branching is to be noted here you can can you can look at this all these fibers are branching these are the branching to be noted so they are branched number one number two their nucle are they Central and they oval nucleus like they're not at the peripheral that doesn't look like just you just draw a flat line of the periphery of the skeletal muscle you can see the nuclear present inside they round to they could be round they could be oval and these nuclea are placed centrally we have a centrally placed we got a centrally placed oval nuclei oval to round you can say oval to round nuclei there we do have cross striations there are cross stri in the cardiac muscle also but these are very faint I mean that is not one of the identifying feature of the cardiac muscle because we do have a cross trition but they are very faint here skeletal muscle cross tration though you can see even if the slide is not good then still you'll be able to see those cross Tri here so cross trition are there but they are faint okay then what is the what is the one important thing guys which is which we need to discuss here and the one on which the question is also asked well that is about look at this the areas which I'm pointing at here this one here this one here this one what are these these are all inter caled disk that is a intercalated disk what is a question asked on the intercalated dis from the cardiac muscle it is about the type of junctional complexes which are present over there you know what what this intercalated dis is representing it is representing like a zline of a skeletal muscle it is like a z line only so it is basically a zline of a cardiac muscle just like we have a z line in the skeletal muscle this is z line of the cardiac muscle only so it's a zline of the cardiac muscle but see what is what is important to understand here is that the type of junctional complex is present so if I just kind of elaborate this one picture of a intereted dis what do you see here we have let's say one fiber connected to the another one and this in between is the let's say this is intercalated dis here this area this this Furrow here it is nothing but the intereted disk the type of junctional complexes present in this we have we got fascia adherence the type of junctional complexes may we have fasia adherence we do have desmosomes here we go these are the desmosomes are there and the most most important that is the gap Junction the most important one that is the gap Junction so the question asked here that what are the junctional complexes present at in the intercal disc so we got the fasal ader we got desmosomes and we got the Gap Junction and and what makes this Gap Junction as I said the most important because Gap Junctions are the one which allows the movement of the ion from one one cell to another and that's why these Gap Junctions they are acting as a electron coupling there's a electronic cou coupling the electronic coupling is because of the Gap Junction and that's why this intercol dis is also called as a a functional syum guys it's a functional syum here because we can have movement of ion from one cell to another so that's say it is a it is a let me write that also it is a functional syum functional syation so this is the slide of a cardiac muscle you're looking at cardiac muscle as I said unlike the skeletal muscle they are branched they do have a centrally placed nuclear oval nuclear overal to round nuclear you may notice there the cross trition are present but that as said is not the identification feature because these cross trition will be very faint then we have intercalated dis which are the functional syn and the type of junctional complexes present at the intercal disc are faser and desmosome and the Gap Junction that's that's the I would say the most important question in the skeletal muscle about the junctional complexes well guys moving on to our next Slide the next slide is and the next few slides are on the cartilages and you know no matter as I said this cartilages and lymphoid they're never out of fashion I mean no matter whether it's a ug exam or it is a PG entrance examination it is like whatever you talk about all of them in every single exam the cartilages and lymphoid I always keep them as a as a top priority that cartilages and lymphoid in the histology are important and they always will be so we are starting with this very first slide in the in the cartilage and this is a slide of a a Highline cartilage so this here is a slide of a Highline cartilage now when I say Highline cartilage I need to tell you one thing here guys this is a Highline cartilage and this is actually nonarticular Highline cartilage that you're looking at let us say if they give you this picture like this in the exam and they ask you okay where it is present here don't choose the surface of the joint here like the head of the humorus the head of the femur non-articular now why it is a non-articular if it is Highland cartilage how come it is non-articular here it is non-articular because what you can see here is the peric chondri in the nonarticular Highland cartilage in the non-articular Highland cartilage there is no peric condum there is no peric condum but in this case the peric condum is seen understand this so it is a Highland cartilage but it is nonarticular because in the articular Highland cartilage I should write like this in articular Highland cartilage this will give a false impression in the articular Highline cartilage peric condum is not present that's why the Regeneration power is is not good you when the when the joint surface are eroded why don't they they regenerate by themselves and like get automatically regenerated and will get rectified because there is no peric condum but in this slide you can see peric condum and there are two layers of peric condum guys if you notice this this here is a fibrous layer this is the fibrous layer and just below that you can see all these cells present here the small small condr blasts are present here that's a Condren layer you can call it or you can call it the the Condren layer like fibrous layer is outer layer and a inner layer is a cogenic layer inner layer is cogenic area so this is the perondi so exception we said it is an articular Highland cartilage which is not having a parond otherwise when you compare the cartilages Highland elastic and fibro cartilage we do have peric condum in the Highland cartilage and we also do have this peric condum in the elastic cartilage but even fibro cartilage will not have a peric condum we'll see that the one upcoming slide is that only the type of collagen fiber that you'll appreciate inside is a type two collagen fiber predominantly it's the type two Collision type two Collision is predominantly seen in the Highland cartilage and see what is the future guys whether it is a Highland fibro or elastic cartilage obviously the condro sites are present inside and these condro sites are present in the leuna again when you treat them with the alcohol these cells will get shrinked and you will see a space around them and that is a leuna so if I mark one cell for you here this is the that is the condr sites in Lacuna cro and like if if I draw it for you separately it is something like this so you'll see a space all around it here that's a cont Lea what makes the Highland cartilage I mean what is the identifying feature of the Highland cartilage which makes it different from the elastic and the fibro cartilage you will see all these Contra sites present in the Lea they're present in the groups and clusters have a look at this guys can you see the cluster of like 4 to five again cluster of 4 to six ctil is there the Clusters they're all present in the Clusters here and these clusters these clusters are called as cell Nest that is referred as cell Nest this is called as cell Nest generally these cell Nest have four to six qu sites come together that is called a sness and and it's a very nice SL so you can appreciate all those things in this if you look look see around the cell nist we have a Darkly stained Zone around them here and that is called as a territorial Matrix territorial Matrix territorial Matrix it is Darkly stained it is Darkly stained but when you see the two cell Nest like it's like an island which are present over there cell Nets are like the island they have their own territory territorial Matrix is there in between them we have inter territorial M look at this lightly stained zone I'm marking point this is this is the inter territorial Matrix that is a inter territorial Matrix and Inter territorial Matrix is lightly stained it is lightly stained because of this Condren sulfate it is a glyos amog glycin which is predominantly present in this part and that makes it lightly stain here the condrin sulfate is present and that is making it lightly stain we don't have to know that that kind of detail to be honest you just need to know that if you're looking at the these islands of these condr sites clustered together that is called as cellest and between these cell Nest we do have this lightly stained region called as interterritorial Matrix here so guys this is a picture of a Highland cartilage now once you know the okay what cartilage is having it is having a peric condum the outer lay is fibrous inner lay is cogenic and and then more you move toward the central part you will see the condid starts increasing in size I mean you can see these are the condr blasts here in the cogenic lay these are condr blast it looks like a flat cells only but the more you go toward the central part you can see the cells are larger in size the condro sides present in the Luna how it is different from the other slides the very next slide that you're looking at is a slide of a a fibro cartilage and this is again one of the neat question only a fibro cartilage well what makes this fibro cartilage different from the another first of all guys we already know the examples of Highland cartilage when I say articular Highland cartilage well we do have Highland cartilage in and Joint surfaces like on the head of the humorus head of the femur and when we say non Artic Highland cartilage like the one which we saw the previously one of the finest example would be in the like trachea the trachea or the the primary and secondary all the broncus they do have these Highland cartilage which is which is obviously nonarticular Highland cartilage must be having peric condum fibrocartilage guys what is not there if I give you some examples fibrocartilage first like intervertebral disk is one example uh libram like lium of the glenoid cavity the librum which is present on the acetabulum of femur librum uh the pubic symphisis puic symphisis menis Skai and in fact the articular dis guys in TMJ the articular disc is there articular disc of TMJ temporal mandibular joint it is also fibrocartilage and because there was a recent question on this so I should tell you although it is not a hystology question articular dis of TMJ it is an extension of lateral teroid tendon it was a lateral teroid muscle lateral teroid tendon extension which is forming the articular disc of TMG but they're all fioc cartilages interal dis the librum The Joint the the laum which is present on the glenoid cavity netum pubic symphasis menai Artic the examples of fibrocartilage what do you see in the fibrocartilage guys we do see the collagen bundles are there these are all parallel bundle of collagen fibers it is a fibrocartilage the word says fibrocartilage obviously we have the loads and loads of collagen fiber bundle present in there and and when I say collagen Fiber Well it's type one predominantly unlike Highland cage where it was type two it is fibrocartilage type one collagen bundles are predominantly present in the in the in the fibrocartilage and these collagen bundle see collagen fibers how they're different from elastic fibers collagen fibers they do the bundle branching but they don't Branch individually understand what I'm saying if this is one collagen fiber here's another one here's another one here's another one so these collagen bundle and then you may see these bundles will Branch like this like some of the fibers will turn to this side and some of the fibers will turn to this side here and that's how this is called as the bundle branching the term that we use for them is the bundle branching they branch in bundles like say if you have 10 fibers in a bundle then five five they will Branch like this here individual fiber will not Branch that's not the property of the collagen fiber the individual fibers don't Branch individual fibers branch in case of elastic fibers now another important thing to be not here guys there is no peric condum there is no peric condr there was a peric condum present in the Highland cartilage there will be peric condum in the next slide that is elastic cage but there is no peric condum in this in the fibro cartilage and because of this like we have so this huge and thick collagen bundles condro sites which are present inside you can see condr sites are there also we do have quides there but all these quites are squeezed it's like if you just if you just put these cont Ides here at one place here scattered and then you have parallel bundle of collagen fiber running in there occupying majority of the space so all these collagen this condro sides they actually get aligned because they are squeezed between the collagen bundles and they get arranged in a line and that is the property of the that is the property of the fibrocartilage that you see the condr sites and these condro sites are present in rows look at these quides guys so condr sites in Rose is a special special feature of fibrocartilage condr sites present in clusters having Territorial and interterritorial Matrix that was in the Highland cartilage and condr sites present in row is a feature of a fibro cartilage coming to the next next one guys the next slide that we have is a slide for the elastic cartilage we talking about the cartilages so we should cover them all here so we're done with Highland we're done with the fibro and now we have elastic cartilage but just to give you a statistic here that in the recent time in the exam it was a fibro cartilage which was given in the exam but you never know Ian they've given the fibro cartilage the next time they might give you the elastic or the Highland cartilage also I've seen people at time getting confused between the Highland cartilage and the elastic cartilage fiber cartilage will not confuse you yes guptas I like your the way you have put your name on telegram so this here is the elastic cartilage once again okay once again what do you see you can see peric condum peric condr is present same thing guys outer layer is a fibrous layer this is a fibrous layer and then we have this cells you can see that's a cogenic layer so peric condum is there having fibrous layer and the condic layer no change in there once again we have the condres in leuna condr sites are present in leuna now guys one way to differentiate them the condr sites are present in now see neither you see any cell Nest here let me just put it this way when you compare it with the Highland C fibbr cartilage first of all there is no cell Nest right there is no cell Nest number one they're not present in cluster you can see they're individually present here so there is no territorial or interterritorial Matrix you can see it's fairly the the same kind of stain that you can see throughout the parenchima when you compare it with this one here look at this you can see dark light dark light in between here the islands of the dark and the then in between you have the light State interal Matrix so in this case there is no territorial or interterritorial Matrix no territorial or interterritorial Matrix right and no collagen bundle there is no collagen bundle well it's a slide of elastic cartilage so what Collision bundle will do here so no Collision bundle here but understand one thing that in the h& staining even elastic fibers are not visible like I cannot see the elastic fiber between I I do know that we have elastic fiber present in between but there are elastic 5 not to be seen we need silver stain arent stain to stain the elastic cartilage so if you if you happen to get a slide on the Argent stain which is to be honest less likely then you might see these black colored fiber you know elastic fibers which are running inside if I have to draw that they'll look something like this that's how the elastic fibers will look like and I told you elastic fibers are the one which which will do the individual branching here if this is a elastic fi I'm just looking one example here if at all elastic fiber is seen inside you can see an individual fiber will be branching and then curling that's how the elastic fibers will be seen running inside that's how the elastic fibers are right and you know when you go from peripheral to Central let's say this arrow is representing this is a periphery that's obviously peric Quantum side here that is a periphery and this is toward the center the number of elastic fiber will increase we have more number of elastic elastic fibers are more densely pled in the central part of the the elastic cartilage compared to the periphery like more do go toward the center it is more number of elastic fibers are there well talking about the elastic cage obviously if I have to give you some examples of the elastic cartilage one of the the better example is the ustation tube or the auditory tube then you have the epig glotus epig glotus although epiglottis is fibroelastic cartilage it is generally referred as a fibroelastic I mean we categorize the lenal cartilages in two type we categorize them as Highland and elastic cartilage but if you look into more detail actually epiglottis is more of a fibroelastic cartilage it's not Pur elastic then external ear and if I give come it's like nasal septum many examples all these are the examples of the elastic fibers what I was saying for the elastic fibers are that there unlike collagen bundles collagen bundles show the bundle branching a bundle will get branched here in elastic fiber the individual fiber will get branched so if this is a elastic fiber looking at then you will see that the end of the elastic fibers they look like this they're branched and they're curled also like this so throughout the parena the way the elastic fibers are run running and the way the collagen fibers are running if you can see them in the stain here it's not difficult to identify them here if you see the parallel bundle running collagen if you see the fibers which are curling and then branching that is elastic so guys this is about the cges we saw the Highland cartilage the fibro cartilage and that is the elastic cartilage as I said when I'll I'll share these slides with you I'll try to share some alternative pictures also with you so that you can also have a another view of a different kind of slide if you get sometime there's a variation in the staining in the peric condum is shown not shown so that ways you may have a difficulty in you know comparing one slide to another but no worries like we'll look at the multiple slide and that will resolve it for us it's not it's not visible because it is a h& St I told you to to to stain the elastic fibers we need the Adent tiin stain we need the there are other special stains are also there to stain the elastic fiber in not in the h& stain you can't see it so based on the elastic fiber is visibility you cannot identify the elastic elastic cartilage here you clearly know it is not a Highland cartilage there is no cellest you clearly know it is not a fibro cartilage so it has to be what it has to be the elastic cartilage because I can see the contro sites inside Highland cartilage location is articular cartilage guys think of any articular cartilage that is Highland cartilage only the end of any long bone you can think of that we have a Highland cartilage that is the articular Highland cartilage non-articular Highland cartilage you can write an example like trach and broncus coming to the very next very important I would say probably the most important section I believe that is in the histology is about the lymphoid guys when it comes to lymphoid the kind of slide that you're likely to get it is either they give a lymph node they can give you the spleen the peltin tonsil or thymus so these are the four major slides that you can expect to get in this region how to differentiate them what are the common features that you will see and then what is that one specific feature that you look at and you'll okay you'll say the moment you look at that slide and I identify these couple of things and they'll say okay this is Highland cart this is I'm sorry that's a lympho lymphatic nodule or it's a lymph node or it is a spleen so we basically need to like focus on those features well guys this is a slide of a a lymph node let's understand that why it is a slide of a lyph node what makes it a lymph node first of all you can see there is a capsule present here we have a very defined capsule in this lymph node then deep to the capsule and deep to the traul if that is a capsule you can see this this is a traul that's a branching over there so this is called as a Trula that is travic and I'm sure you all can very clearly appreciate that space which is present deep to the capsule like this this this whole Space here and deep to the travic this is called as a subcapsular or subicular sinus and that is a feature of a lymph node here you will not see that kind of space in the spleen or thymus or anywhere else this space which is present deep to the capsule this is called as a subcapsular or subicular sinus that is subcapsular on subicular sinus right deep to the capsule and deep to the the tribul also it runs along with the Deep to the capsule and along with the trab also so we call it sub capsu and sub tricular sinus and this is this is a unique feature of a lymph node again it's a unique feature of a lymph node what else well lymphatic nodules can be seen of course lymphatic nodules can be seen well lymphatic nodules guys they can be seen in the spleen also lymphatic nodules can be seen in the paltin tonsil also the lymphatic nodule that you will see in the slide of a lymph node these lymphatic nodules are present only in cortex only in cortex that means a slide of a lymph node can clearly be divided into the cortex and the medula wherever you see the lymphatic nodules are present toward the peripheral area that is a cortex area so guys this here is a cortex if I just mark it like this from the capsule till this area where the lymphatic nodules are present that is a cortex this area is cortex furthermore deeper area this here is the medula I'm still leaving some part in between this is medula so lymphatic nodules are present only and only in the cortex you will not see in the medula you cannot see any lymphatic nodule present lymphocytes are present there but it is not in the form of a lymphatic nodule but guys when you look at a lymphatic nodule talking about a lymphatic nodule how how a lymphatic nodule look like well it is it is like we have these lymphocytes present and if it is an active lymphatic nodule you will see we have densely pled lymphocytes is present on the periphery and we have very few which are present in the center here that makes the central part lightly stained and the outer part Darkly stained here because of the number of lymphocytes present over there in the lymphatic nodule it's predominantly the B lymphocytes that you will see B lymphocytes predominantly the B lymphocytes are present in there and this centrally lightly stained region is called as a germinal center germinal Center if you're looking at a germinal center in the lymphatic nodule it is an indication you're looking at an active lymphatic nodule guys it is an active lymphatic nodule if it is inactive then you will not see a Geral Cent In it will all look fairly the the similar kind of you know um this dispersal of the B lymphocytes will be seen then at the junction of the CeX and the medula this area guys the one which I'm trying to highlight with a different color here I hope that I'll be able to do that yeah this one I hope you can see that this region here in the in the junction of the cortex in the medula this is called as a paracortex and there is a question asked on this area also this is called as a paracortex at the junction of the medula in the cortex that is paracortex what is paracortex known for paracortex is known for the location of the T lymphocytes it is known for the location of T lymphocytes and that's why the cortex is also called as the thymic dependent Zone it's a thymic or thymus dependent Zone because it's a t lymy so obviously T lymphocytes are producing on thymus so it's a thymus dependent Zone here now that exactly was a question asked in the exam that in the lymphatic nodule what is a thymus dependent Zone and that is a paracortex not the cortex not the medula it's the paracortex which is a thymus dependent Zone because St lymphocytes are predominantly situated in that region well guys in in the medula we have medary cords and sinuses well in in this lightly you know if you want to see the medary cords and sinuses they have to give you a very high you know magnification picture like something like 100x or something and I don't think they're going to give you the picture on the 100x because then they only will be able to see the medula only they cannot show the in 100x they can show you the entire slide that is not practically possible but let's say if they ask you some question about the medula part so this is the region where we have medular cords and medary sinuses what is medary cords and sinuses we do not have lymphatic nodule present in this region we have lymphocytes clusters present like this let's say if I say we got a cluster lymphocyst lymphocytes have cluster of lymphocytes present throughout this medular region and they are lined by the endothelial cells these are all endothelial cells in between so this is called as a medary cord these lymphocytes that is a medary cord and these are the Middy sinuses so that's that's what you're going to see in the Middy cords and sinus if you magnify this area you will see the cords and sinus the spaces in between these are the sinuses and these clusters of the lymphocytes like present in a random manner that is called as the medary cord so guys if it is a slide of a lymph node then obviously in the lymph node what we expect to see we are in the lymph node we are basically bound to see the the capsule we can see travic the sub capsule and subicular sinus we'll see the lymphatic nodule present and lymphatic nodule is present only in the cortex part lymphatic nodule may show you the germal center like you can see the germinal center in this case these These are the germinal centers to be seen here right this is a Geral Center that's a Geral Center and germinal Center tells you it's a active lymphatic nodule we looking at then we got a paracortex where we have t lymphocytes lymphatic nodule is mainly known for the B lymphocytes and T lymy is present in the paracortex called as a thymus dependent Zone okay moving on guys the next slide that we have yet yet another slide of a lymphatic uh system and this time it is a slide of a spleen let's understand what makes it a spleen this is a slide of a spleen guys now first of all what is there in the spleen and what is not there in the spleen first of all there is no differentiated cortex and medula there is no differentiated cortex and medula you cannot appreciate any cortex and medula in case of spleen and that's why the lymphatic nodules are present everywhere look at this slide guys and you can see you got a lymphatic nodule here also here also here here everywhere you in the entire parena you will see the the lymphatic nodules are present that's why because there is no cortex differential cortex and medul we do have branched and very very thick traic capsule will be there for this obviously not shown in this picture but there are branched and thick travas unlike the lymph node where the travic was present only in the cortex and just like present in between the the lymphatic nodule here it is Branched present throughout the parenchima and it is very very thick here I can see only some patches over there guys it is one patch or I can see it is one one here like this one these are just nothing but the travic only this a branch and thick tribul again to be seen throughout the parena itself what makes this slide special guys what makes the what is the important thing in there well again you can see the lymphatic nodule is present there's a lymphatic nodule to be seen but this time the lymphatic nodule that you're looking at so there is a lymphatic nodule which are uh to be seen this in this lymphatic nodule can see gal Center guys this is the germinal center to be seen and the special feature of the spleen is that we do have the arterial present inside and that is called as a splenic arterial here when the lymphatic nodule was inactive it was in the center when it became active and the lymphocytes they start migrating toward the periphery even the blood vessel this lymphatic this arterial is also shifted toward the periphery now look at this arterial guys that is a splenic arterial that's a splenic arle so you you check out on any lymphatic nodule like again you can see the gal Center in this one here the gal Center and look at at the peripher you can see the splenic arterial the splenic arterial when you're looking at ly lymphatic nodule guys lymphatic nodule with splin arterial let me just try to highlight them with the same color ly lymphatic nodule with splenic arterial that makes it a slide of a spleen only presence of lymphatic nodule is an indication it is a white pulp why white pulp guys wbcs white blood cells so it's a white pulp this is called as a white pulp area and the presence of artery inside the lymphatic nodule is an indication of a closed circulation so as of now I can see that in the spleen we have a li ltic nodule that means it is a white pulp and we do have blood vessel present inside so it's a closed circulation here but the moment these blood vessels they come out of the lymphatic nodule they spay their blood into the parenchima also I hope you can appreciate this red tinge over there can can you see this all this red tinge it's it's a red and pink color that you can see this rbcs which are actually spreading into this paren area because it is also an indication of an open circulation these blood vessels when they come out of the lymphatic nodule they spay their blood into parena and that's why you see all this red tinch Pres present over there which is indicated as the red pulp red pulp so lymphatic nodule are representing the white pulp and the area in between where the all these rbcs are seen because of the blood is played into the parena that is the red pulp area right red pulp present presence of red pulp here that is obviously tells you that it is in also having what type open kind of circulation so open circulation is also there open circulation is also there so in the spleen we do have a closed circulation we do have a open circulation also closed circulation is represented the moment you see the artery so it's a closed circulation but when you see the blood is present in the parena it is a Clos and open circulation so both kind of circulation to be seen in case of the the spleen okay as I told you guys in the lymphatic nodule about this arterial let me let me write that also that in the splenic arterial if the splenic arterial is present Central if the lymp itic arterial is inactive but this spenic arterial will be shifted toward the periphery it's peripheral when it is active when it is active it is on the periphery so guys if you're looking at a picture of a lymphatic uh if you're looking at U if you have a lymphatic nodule present that gives you an hint okay this could be the slide of a lymph it could be a slide of a spleen it could be a slide of a paltin tonsil or you may see a lymphoid the lymphatic patches like par pairs patches present in the IMM also but I don't think that you will confuse the the the pairs patches with these so the lymphatic nodule can confuse you between these three slides the spleen the the what do you say the tonsil and the spleen uh this lymph node in the lymph node lymphatic nodules are present but they were present only in the cortex no arterial nothing like that here if you see they're present throughout the parena everywhere because there is no cortex in medula then it is a slide of a spleen and also we do have this very special feature that is a splenic arterial present and that is present toward the periphery in the in the in the active lymphoid follicle with the Geral Center in the in between now if we compare it to the third one this is the peltin tonsil the very next slide that you're looking at it is a slide of a peltin tonsil and how to differentiate the peltin tonsil with this one guys it this is actually quite simple in peltin tonsil again I can see the lymphatic nodule with the germal center I can see this lymphatic nodule here with the Central germinal Center the Geral Center again looking at the lymphatic nodule the doubt could be is it a lymph node or is it a spleen well it is not a spleen because there is no artery there I cannot say any arterial present in there I cannot see this any red bulb in this so obviously it is not a it is not a the slide of a spleen it is not a lymph node also because see what differentiated it because the the slide of a Palatine tonsil closely it can be kind of you know confused with the lymph node not with the spleen spleen it's very easy to differentiate with them every time they give you the picture of the ptin tonsil they will make sure that they will give you the oral epithelium also the oral lining epithelium of the Palatine tonsil is a stratified scus epithelium like look at this huge layer of the stratified Schamus epithelium there the stratified Schamus epithelium presence confirms it is a slide of a paltin tonsil so if I just once again if I put it in the context here guys lymphatic nodule present in the cortex and then we have only in the cortex here lymph node lymphatic nodule present throughout the paren with the blood vessel it is a spleen lymphatic nodule present and then we have what do you have what do you say again there's no cortex Med it just again lymphatic nodule is present and we have a surface epithelium or the oral epithelium is the stratified SAS epithelium that is in case of the ptin tonsil okay and you know if you get a picture of a paltin tonsil there are also a very good chances that they will give you the picture ptin tonsil with a tonsil Clift I mean if you look at the ptin tonsil guys there is this surface which is the lateral surface present toward the superior constrictor muscle that's why you can see toward the basil part if the entire slide is shown to you toward the basil part you may also appreciate or toward the lateral surface you may see some skeletal muscle also because Superior constrictor is forming the tonsil bed and the oral surface of the peltin tonsil is having all these Crypts and one of them largest one is called as a tonsil or clip also this is a tonsilar Clift so very likely if you get a picture of the ptin tonsil they will show you the stratified simus epithelium going inside and coming out that is a tonsil Crypt or Clift they will show it to you that is again a feature of the peltin tonsil not to be seen in obviously in the lymph node or anything else okay coming to the last one guys that is the thymus this is a slide of a thymus well thymus it's it's not difficult to identify thymus when it especially when you look into the lymphoid system because thymus it is different in a way that in thymus in case of thymus there is no lymphatic nodule so first thing is that there is no lymphatic nodule in this year okay but look when you see these traic guys connected tissue septum connected tissue septum in case of thymus they're running throughout the parena and they're dividing it look at all these septum guys there are multiple long septum that you're looking at here running throughout the slides here these are all connective tissue septum running in between they're all the connected tissue septum running through and because of this connected tissue septum the entire thymus slide is divided into small small lobules so we have like thus thic lobe is there and then you can divide the thymus lobe into small lobules over there like if I just highlight one for you this is one lobule that you're looking at here this is one lobu one thing another thing when you look into the lobu let me just just try to draw it for you separately let's say if it's one lobule here now in this lobule you will see incomplete septations inside we have very fine septations these are incomplete SEPTA which are extending into the lob part like this so it is it is a lobule that we're looking at and then we have these incomplete septations and because of the septation the entire lulle can be divided into the cortex and medula this Central lightly stained Zone will be the medula part here this will be the medula and this is the cortex and you can see cortex is the one which is divided it's a it's a cortex which is divided by the scepter the medula is common so in a lymphatic nodule when you're looking at the medula is common but we have a individual cortex which is present around them here no lymphatic nodule but lymphocytes are there so you can see the densely PL lymphocytes are present over there can you see that lymphocytes over there then you can see a small SEPTA there there's lymy then we have a Septa there lymphocytes the SEPTA there lymphocytes they're present in the cortex so we have majority of the lymphocytes most of them are present in the in the in the cortex part here so this is the cortex part guys if I if I just use a different color to mark that that is a cortex cortex cortex cortex and you can see that like incomplete divided by the SEPTA but when it comes to medula that is more or less the common in between in the medula well it it is a low magnification so obviously will not be able to appreciate this in L low magnification that's why I took a separate picture for that if I look inside the medula what you'll see you will see a special feature of the thymus and that is the presence of thymic corpal or or Hassel Corpus thic or Hassel Corpus how does this Hassel scorpus look like if you look at the central part of the H Hassel scorpus there is a Highland Mass present in it there is a uniformly stained Highland Mass present in the center which is surrounded by these cells and these are the re cells guys reticul epithelial cells re cells which I told you is one of the example of EP epitheloid only here there is re cells the dying reticular epithelial cells are the one which comes toward the center and they have this the central Highland masses there and then you have surrounded by this re cell that is the Hassel scopus so if I just try to like draw the Hassel scal for you it is like this we have a central Highland mass and then you have the cell surrounding it are cells surrounding it here that's the Hassel Corpus the older the person they get obviously we have more Hassel corpal in that so thic corpal or hesel corpal is a feature which is present in the mum so so generally when you look at a slide of a thymus you different you have to differentiate a slide of thymus based on that okay it is not a lymph node because there's no lymphatic nodule there's no it's not a spleen again same it is not a paltin tons lymphatic nodule is not there but lymphocytes are there slide is divided into this trules or the septum running through these long connected septum which is dividing it into the lobules and in individual lobule if you look at this one lobu here then we have small small septations which is dividing the cortex only they're not extending into the medula so medula is kind of common and then we have a cortex divided into Parts okay CH sir moving on the next slide that we have again a very simple one but again because it was asked in the exam so we got to keep it in our discussion this is a slide of the thyroid gland this is a slide of a thyroid gland well guys thyroid gland what do you see in the thyroid gland first of all you're looking at this a thyroid follicle here this is thyroid follicle generally it is like .9 mm in size okay the type of cell if if you're looking at thyroid follicle it could be active it could be inactive active or inactive thyroid follicle what the difference would be the one that you're looking at right now in the picture it's active thyroid follicle why it is active or what what makes you identify it as an active we have the cuboidal cells a very predominant cuboidal cells can be seen inside in the staining obviously you'll not be able to see the margin of the cell but you will be able to see the centrally placed rounded nucleus but when it compare it with the inactive one inactive thyroid follicle is the one which is having more of a a squamous cell present in it here scammer cells present inside what do you see in the center guys this is the the colloid there is a colloid present in the center nothing but the thyroglobulin only and this colloid look at the borders of this colloid it look like serated border the scallet Border we call it it they are all scallet borders it look like serated borders and these are scalloped borders scallet borders is seen in case of the active thyroid follicle in case of active thyroid follicle we see the scallet poers so it is like if you see like this the borders of the Collide is like this that is scallet borders are there then it is if it is a inactive one you will see a uniformly present or non- scallop border there's no sered borders of this colloid in case of inactive thyroid follicle and obviously it look larger in size because the cells are Squam cells so it looks like more space in the center this is the inactive one guys look at we have a smooth borders of this the colloid in case of the inactive one and we have a scallop Borders or the serrated Border in case of the active one the picture that we have with us is a active thyroid follicle looking at in between in between the thyroid follicles we have these par folicular cells guys this this is the area just if you look at in between here these are the parap folicular cells present the paricular cells the C cells producing the parol calcitonin producing cells and they are relatively pale staining they're pale staining again I'll share a picture with you in which you'll see it better that if they stained like comparatively in this you it's not easy to differentiate this the one with from the thyroid follicle only you can see the one which is lining the the follicle is a thyroid follicle cells and the one in between are the the parol cells but on the basis of the stain it is not a very good slide to show it parap folicle cells guys there is a question on the embryology also this where they are derived from and they're derived from the neural crest cells neural crest cell is always your best answer better answer than what Ultimo brinkle body ultimum brinkle body is a remnant of the fifth fenal pouch so if both are given in the option and ask that parap folicular cells are derived from where you got to go with the neural crest cell as your single best answer I'm sorry guys I'm not able to look into this messages in the telegram group I I'll just look at all them together only right so that's thyroid gland and it's a active thyroid follicle that you're looking at CH moving on the next slide which is again a a kind of recent question only pancreas and kidney they have created a little you know confusion in in the recent time there was slide they asked for the pancreas and then they SL slide as a slide for the kidney and people end up marking the kidney to the pancrea mark end up marking the pancreas on on the kidney slide so I I gave both in the in in the picture although there should not be a confusion between the kidney this the slide of a pancreas and the kidney yeah pancreas can be confused with the pared gland that is possible if the eyelet of langerin is not visible then it is difficult to differentiate between the pared gland and the pancreas but one should not confuse between the pancreas and the kidney we'll discuss that so guys this here is a slide of a pancreas that's a slide of pancreas what do you see in the pancreas um they do have cus asinus present inside now that's why it said it can be confused because cus asinus if if I may remind you again once again cus asinus were like this and serus Asus can be seen or are seen in the per gland also per gland is a predominantly a serus type of gland so we do see in the pered gland also but how the serus asinus in the pancreas are different from the the one in the pered gland though you will not be able to appreciate in that this kind of section you have to again you have to take a very very high magnification you have to like Focus The Examiner has to focus on one individual asinus to show you that difference here which is not to be appreciated here but I should tell you that how it is different the serus asinus is present this type of serus asinus is present in peroid gland I'm just trying to differentiate with the peroid gland how the seriousness will be different in case of the pancreas well guys in the pancreas it's the same only again we have these pyramidal kind of cells present there same Central or slightly basil oval nuclei with the xogen grenes but what what special you see in this in case of the pancreas you will see the ducts are starting from inside the asinus only and because duct starts from inside the Asus so obviously ducts are also having their own cells ducts are lined by the cuboidal epithelium ducts are lined by the cuboidal epithelium so we do have these cuboidal epithelium ducts to be seen inside the Asus and these cells which are present inside these are called as what centroacinar cells Centro asinar cells look at the name guys croar Center of Asus centar cell so in the serus asinus of the pered gland you will see the Cirus asinus like in the center there's nothing but in case of pered gland you will see various serus Asus in which you will see the cells you can see the nuclear inside the Asus only apart from the cells which are present on the periphery you will see some nuclear present in the center that's a center as in our cell they the they are the basically the the the nucle of the ducts which are present starting with that from inside the Snus itself here so this is the feature of the serus Snus in the pancreas if let's say this question is asked theoretically to you or maybe they'll give you a high magnify picture for that here I can show you one kind of one in this if I enlarge this picture and let me take your attention to this one guys look at that I hope you can see that in the center we have these cells of the Snus and these are the centrar cells can you see that you can see the SNS and you can see the cells in the center itself a center SNR cell some of the more SNS can be identified like that but this kind of arrangement you will not definitely not see in case of the pered gland but what generally is is like given in the picture to make you it easy to identified that is the eyet of langerin look at this lightly stained the pale stained Zone in between that is called as is eyet of langerin that is eyet of langerin these ey of langerin they are pale staining of course they're pale staining Zone number one and mostly present where in the tail mostly in the tail of the pancreas see that makes the tail of pancreas such a important region tail of pancreas is very close to the highum of the spleen you know the pancreas is retrop peronal but tail of pancreas is not retr peronal tail of pancreas via loral ligament reaches the HM of the spleen and that's why in splenic toy our major concern is always to save the tail of pancreas the first our primary goal is to okay mobilize the tail of pancreas before we do the splenic toy because majority of theet of langerin are present toward the tail of pancreas here eyet of langerin this slightly this pale stained Zone that you looking at here in which the central portion if I just Mark like this I mean again you cannot differentiate IED that easily the central portion is the one in the is of larance which is mainly having the beta cells so 70 to 75% cells are the beal cells and you find them predominantly in the central part here but when you look at the peripheral part here the outer portion in the peripheral part this is where you have these the Alpha and the Delta cells alpha cells like if I go with that like around around approximately 20% and 8 to 10% of the cells of the detal cells which are seen predominant in the in the peripheral area of the iset of Larin so do not confuse a slide of the pancreas with the pered gland and I'm pretty sure the examiner is not so cruel that they will give you the picture of the pancreas without the IET of langas they have not done this and I hope they will not do that but let's say if they do this if they go to that extent here understand that if you're looking at a serus asinus and if you're looking at a magnified picture of serus asinus make sure that look for the cent in ourselves present inside because that will decide it is not a slide of a pered gland it is a slide of a pancreas okay moving on guys the next slide that we have this also is one of the image based question asked well I'll respond to whatever you're writing in the telegram group later because I need to post this video on YouTube also well guys this is uh the picture of of the the tongue papilla you're looking at now when I talk about tongue Pap then we have filiform Pap the fungiform pap the foliate pap and the circum valet valet Pap now let's let's have a very quick discussion that what is the difference between these kind of Pap and what's what what is the like one basic identifying features when you looking at and and then you will be able to identify uh just by looking at that you'll say okay it is what type of papill is that now is is it a foliate or is it a circum valet or is it a fungi form papill so for that before we start with that you can utilize the space on the side the tongue papill well guys in the tongue papilla if I first start with the Philly form the Filly form papill now in the filiform pap when you look at the lining epithelium you will see these conical projections conical keratin projections coming from the surface no taste wordss to be seen there all you see is a conical keratinous projections from the surface that will be seen in the Philly form papill okay the next one we got this fungi form now I don't have to tell you what kind of lining epithelium is that when I talk about this lining epith whether it's fungi form fil form filate or foliate or anyone this lining epithelium that we looking at guys over there this is what lining EP that is a stratified Squam epithelium so as I said I don't have to tell you that that this is stratified Schamus epithelium that we will be talking about in this slide or in the in the one which which are coming up that is stratified Schamus in fact anything and everything in the oral cavity it is lined by stratified Schamus epithelium whether it is a tongue lining epithelium the tonsil the pallate the upper border of epiglottis you know valul all the everything is lined by the the stratified Schamus epithelium then the fungi form papill in the fungi form papill what you see the lining epithelium will be showing these indentations from the surface the perpendicular indentations like these again stratified com as epithelium and these are and do have taste Birds also guys but those taste birds are present The Taste birds are present on the surface on the dorsum of the tongue or on the surface you will say taste parts so we have these gustatory pits we can call them gustatory pits or taste pits here these are the pits the gustatory pits can be seen from the surface lining epithelium the vertical pits can be seen and but you will see the taste birds are present on the surface that's important The Taste birds are present on the surface on the dorsum surface not inside the pit that is in the fungi form papill foliate papill when it's about the foliate papill the shapee like fungi form papill only I mean once again from the surface you will see the indentations like this vertical indentation inside that you'll see in the foliate papill but this time what is the difference guys the difference is we do have taste wordss present inside the Gest in inside this gustatory pits or The Taste pits here taste buts are present inside gustatory pits inside gustatory pits and then finally we have a valid Pap or circum valid valid or you can call it circum valid Pap when we say valet or circum valent P they just like I mean as I said our job is main to identify them here in the valet or circum valent papill whatever you just see in the follow papill just more or less the same more or less like them only here but they're mushroom they're huge from the surface they look like circular that's a circum valet here but when you just Trace them into the bottom they're tapering downward so they're mushroom shaped so if I got to draw it it is something like this that from the surface you will see them tapering down in this manner guys look at this that is how it is present so once again the The Taste SPS are present in the pits Only The Taste SPS are present in the furrow just like the foliate papill only but the only thing is they are mushroom shaped they are mushroom shaped right the circumvent papill so if you see conical keratin projection on the surface the fil form if you see the vertical indentations and the tast SPs are present on the surface as we saw in this one that is a fungi form here FID papill you will see the taste birs present inside the fur the vertically running Furrow and when the furrow is like the the gustr pits or fur they are kind of tapering downward inside giving it a mushroom shape and having T SPS again inside the fur that is the circum valent papill just keep that in mind yeah all have same lining EP they are all stratified scas tongue is having a stratified scam epithelium when I say The Taste Birds guys when I talk about the taste bird you should know that the taste bird is present throughout the epithelium like I just marked like this if this is a lining epithelium here so taste birds are present like this so we have all kind of cells we have gustatory cells we have taste cells present inside and they are lightly stained the way you identify the taste birs are they are lightly stained from the rest of the epithelium they're lightly stained you you can you can see that here let me just enlarge this picture for you first of all guys by looking at the shape here by looking at the shape only two things come to our mind is that this one is either it is a Fung form you can see the vertical gustation this far there so it is either fungi form or it is foliate Pap let's check out if I look at the surface here I do not see the taste bird there you will say okay they look like a taste bird only no they're not taste bird guys if they are taste bird they must be opening on the surface here taste bird should be present throughout the epithelium you cannot have taste bird like in patches like that here it looks like something which is light slightly stand over there but they are not taste but taste buds are present throughout the epithelium and what do you see if I look inside the furrow if I look inside the f look at that now look at this guys I I'm I hope you can see all that look at these are the taste parts here look look at this lightly stained region they are all taste parts here this is telling you that we have taste parts present in the vertically oriented F so it is a slide of a foliate Pap The Taste birs the taste bus the taste buds when I'll share this PDF with you you can always enlarge it and then check it out this one is a slide of a foliate in the exam the question was asked on the foliate pill and many people end up marking is a circum valent papill guys many people end up marking it as circum valent papill the circumvent Pap is the next one and and what else you can see you can see some Cirus glands also present inside the one abers gland can you see this cluster of cells look at this the big cluster of the Cirus cells can be seen inside and these are the one abnur gland these are serus gland you know how the serus ASAS look like these are serus glands and in the bottom part because you know tongue is is a having skeletal muscle inside again in the bottom region you may appreciate some skeletal muscle also not to be seen in this picture here so this is the foliate papill this one and if you look at the next one the next one here is the circum valet papill because again fur can be seen you can see there is no taste but present on the surface so it is not the fungi form so it is either foliate or is it the circum valid and look at this orientation guys look at this how it is kind of tapering downward here it is going projecting toward you can see the the surface is very broad here and the bottom is kind of narrow here that is telling it is kind of mushroom shaped and that's why it is a circum valid papill circum valid p and again you can see all these look at numerous numerous numerous T SPS over there t spur present in pits and mushroom shaped I can tell you one more thing there although again when it comes to the basic identification that is not needed guys if if you start discussing all these slides in detail I mean you can go into the extreme detail of every single slide we can talk about what kind of susten cells we have in the guest these taste Birds what are the supporting cells they look like what are the main uh you know these taste cells they look like and they're appendages but that is all together if you go into that detail now look at one thing guys if if you look at this connective tissue present in this this lamina propria region here that that connected tissue and the indentation this lamina propria is making here it is very faint kind of indentation this is this is something which is again very helpful here if you see a very faint kind of indentation very like they're indenting into the L this lining epithelium but faintly they just go for a certain extent and coming back here it's a faint indentation into the lining epithelium it is again a feature of what circumvent papill but you if you see a very strong indentation into the lining epithelium that will be present in the the folate look at that guys have a look at this can you see the strong indentation inside a very deep indentation into the Ling epithelium that is again to be seen in what in the the foliate papill so another confirmatory Point although just looking at the shape you can identify the two differentiate the two here but this could be another feature that you can notice that when you look at this this connected tissue there it is indenting into the the this lining epithelium and the very deep uh indentations are there in case of the foliate which are quite shallow when it comes to the circumvent papill CH sir moving on the next slide that you're looking at well uh in the git system the two slides the the reason I chose the two the main two slides here is for one one specific reason guys when we talk about any slide in the git we divided into what we divided into the mucosa then we divided into the muscularis mucosa then we divided into this the sub mucosa and then muscularis external generally that these are the four layers we have like this this area here this will be the the the mucosa there then we have this muscularis mucosa is present after muscularis mucosa then there will be the sub mucosa part here and then finally we have a muscularis externa where we have this all these circular muscles and longitud muscles are present here the slide of the esophagus and deum I chose the slide of the esophagus and deum here the reason is because generally when we talk about the mucosa we have a lining epithelium we have the lamina propria there and in the lamina propria we have the glands present most of the intestinal glands gastric glands are present in the lamina proia that means somewhere here this is the area this is the lamina propria guys now first look at this I'll tell you what slide is this is the lamina propria and in the usual slide of the G8 whether it is if I talk about stomach or the deodor not the deod sorry the stomach or the um the the J iium colog you take a slide of anything you will see that majority of the glands the gastric glands the intestinal glands are present in the lamina propria but that is not the case in esophagus and in the deum now first of all this is a slide of a esophagus well that's a slide of esophagus and there are just couple of things which will help you identify that number one again the lining epithelium look at this stratified squamous epithelium there the studified squamous epithelium as we all know that esophagus having a certified sampas with respect to the rest of the the G where we have a cinar kind of cells then in the lamina properly there is no gland present then you go deep and you can see this layer this is a layer of the muscularis mucosa that is muscularis mucosa and then obviously the next layer here is the sub mucosa and that makes it special that we have the cells we have these the the mucus asinus the mucous cells present into the sub mucosa these are the mucus asinas to be seen you know how the mucus asinus look like that's a mucus asinus we call them esophagal glands these mucus Asus are nothing but the esophagal glands and the important thing mucous asinus or these esophagal glands are present in sub mucosa they present inside the sub mucosa so that is one important feature which will help you differentiate the slide of this esophagus the when you looking at the esophagus look at the lining epithelium the stratified scus epithelium I cannot see any V over there so I cannot confuse it with any diod or J anything like that and then you're looking at the glands which are present in the sub mucosa so this is a slide of a e figus so this is the main feature guys that one is a stratified scus epithelium number one and number two the esophagal gland located not in the lamina propria but in the sub mucosa in the sub mucosa same ways if I go to the next one again I chose this slide here because this see this is a slide of the small intestine small intestine we have a jumm and deum we have this this long longest will which are present in the in the jum so we have these this is a slide of the the deinum there is a slide of a deinum well guys what makes it a deodal SL see first of all look at these closely packed Willi so the moment you see the V so it is a small intestine obviously it's a closely pecked vli and the lining epithelium in the v here would be I mean if I just draw it for you the lining epithelium because you cannot appreciate the lining epithelium very well in these in in in these kind of magnification so we have a colar epithelium and in between the colar epithelium we have these goblet cells also present inside so the lining epithelium is the the tall cinar cells are there the cinar cells and we got goblet cells in between so goblet cells just look like a empty spaces if you see these goblet cells they look like an empty spaces and you know if you get a comparative picture of the if I go from the deum to jum to iium to the colog the number of goblet cells will keep on increasing the more you go toward the distal part the number of goblet cells will keep on increasing here so if you look at the slide of I we have more number of goblet cells and by the time you reach the colog it look like that epithelium is just a goblet cell only if you just just you can Google this slide off any any any slide of the colog and you will see the in the historical section of the colog the lining looks like all looks like continuous goblet cells been seen we have like more number of like huge huge number of goblet cells to be seen in them once again guys it is to be noted that I hope you can see this red tinge here which is corresponding to the muscularis mucosa muscularis mucosa and this time you can see the lightly stained gland are present over there so guys we these gland the lightly stained gland the mucus glands these are mucus gland these are lightly stained glands the mucus glands also called as a bruners gland and these Bruner gland are present where again in submucosa in sub mucosa had it been the section of the iium or the section of the stomach or something then the gland will not be seen in the sub mucosa the gland will be seen in the lamina properly that is above the muscularis mucosa here so for the slide of this small intestine if at all you get a slide of a small intestine look for the muscularis mucosa look for the V and then look where the glands are present if you see the mucus glands these lightly stain mucus gland you can easily identify these mucus gland if they're present in the sub mucosa well it is a slide of a the diod which brings us to our next slide which is the second last in the historical part and this is a very recent question also now this is what happened guys last year when they asked this question on the kidney well majority of the people got it right but some people accidentally marked this slide as a pancreas because they just saw a central portion between which looks like an eyelet of langerin although it doesn't look like eyet of langerin if if you if you look carefully and they thought it is a slide of a pancreas so this is a this is a mistake which many people did and I want you to be careful with that well guys this is a slide of a kidney and let me just give you a couple of important point to identify this one well this that you see in between here that is the glomerulus this is glomerulus and in the Glarus you can even see the bom space also can you see the space over there between the paral layer and this glomus you can see this is the bombin space can be seen that kind of space obviously not not nothing like that to be seen in the slide of a pancreas so it is a bomb in space to be seen there a moreover obviously when you see the Glarus in the surrounding region you will see the pcds and dcds also guys when you talk about the proximal convol tuule and distal convol tubu see how histological they are different in PCT and DCT the lining epithelium is the same it is a cuboidal epithelium only in PCT also it is a cuboidal epithelium in DCT also it is a cuboidal epithelium present cuboidal epithelium is represented by this rounded nuclei like if it is oval nuclear it could be colar if it is a rounded nuclear it is a cuboidal epithelium but in case of the PCT the Lumin looks very hazy and it looks hazy because of the the micro light the brush B in in the PCT we have this brush B like this that is a micro and that's why the Lumen is quite hazy in case of PCT and there is no micro present in the DCT so the Lumen looks quite clear and that's the easiest way to identify the P and D if you look at this picture have a look at this one guys this is a PCT this also is a PCT well they are P why because you can see the the the central nuclear can be seen these are rounded nucleus that is telling you it is it is a cubal cells and look at the Lum guys it's quite hay nuclear which are present this Lumin inside they're all PCD that I'm showing in here but the one which looks quite clear especially this one a little lightly stained also comparatively this is a distal convoluted tuule DC obviously you'll see less number of DCT and more number of pcts there close to the glomus region so if you see something which is having a clear human unlike the one which is in the PC so in the PCT you can see first of all the staining is also dark we have DCT the staining is relatively lighter we have Micro present in case of PCT that's why the Lumen is is is is hazy and and DCT is a clear Lumin so it is a slide of a kidney so like nothing to be confused with the slide of a kidney for sure guys with that we move on to our last slide in the histology part here and that is something again which is repeatedly asked I mean no matter how much you know about this slide you I pretty sure if the question is asked on this slide a cere cortex here you will be able to answer it but you know something which is important is to be revised frequently this is a slide of a cerebel cortex and now they mix and match the questions of the cerebel cortex histology slide with the gross anatomy questions also well there are three layer of the cereal cortex as you can see guys this layer here the one which is lightly stained having very few cells present inside this is the outermost layer we are going from outside to inside this is from outside this is outer to Inner this layer present outside this is called as the molecular layer and in the molecular layer in the molecular layer we had two types of cell present we got the state cells and basket cells both are supporting cells the state and basket cells and both are inhibitory cells Sate and basket cells are present these are supporting cells present in the molecular layer here difficult to differentiate between the state cell and basket cells especially when it comes to the H staining then the middle layer is just made up of perja cells and that's why the layer is also called as a peringer layer so this one here is a perking layer perinel layer which is having these large flask shaped peringer cells also inhibitory and then look at this layer it looks like all granules are there that's why it's called as a granular layer this innermost layer here having all these granular appearance so it is called as the granular layer it is the granular layer and even granular layer is having two types of cell present inside well what two type of cell guys we have the GGY cells and granule cells G cells and granular cells again GGI cells are inhibitory and that makes the granule cells important because they are the only excitatory cells present in the cere cortex in the entire cere cortex the only cells which are excitatory are the the GLA this this granule cells and that's why cereal cortex is the largest collection of inhibitor neuron you compare this cortex with any other area in the central nervous system we will not find as many inhibitor neurons as we have in this cere cortex it's the largest collection of inhibitor neuron in central nervous system pering cell guys perin cell if I just take one example in here like if you look at this perin cell the dendrites are spreading above in the layer like this that's a dite I'm putting D for the dite here and exone of the peringer cell is the one which which will leave the cortex and will come into the white matter will come into the white matter now that's a question also that Perkin cell are the only cells which are forming the ephren from the cortex once they Fe the ephr from the cortex when they come out of the cortex they will go to the white matter and in the white matter they are going to project on the Deep cerebr nuclei they projects onto the Deep cerebellar nuclei dentate emboli form festial all these are deep cereal nucle so peringer cells out of all the cells we saw inside Sate basket granul GGI not to be differentiated only perja cell can be appreciated I mean in this a low magnification h& staining so perja cells are the one although you not able to appreciate these dendrites and exons but yeah the exons of the this perin cells are the one which will leave the cortex will come to the white metal and will project to the Deep cereal nucle and then the Deep cereal nucle is the one which will project outside the cerebel will project into the the other areas outside like to the red nucleus to the thalamic nuclei to the reticular nuclei outside to the cereal so this is a slide of a cereal cortex so guys with that we're done with the hiso part