Embryology PDF

But we still need to understand the basics because you will have many answers of what's going on in clinical practice and understand why we do some things and we need to start from zero in order to build up. So I try to condense things as much as possible for you so that you're not getting lost. And...

But we still need to understand the basics because you will have many answers of what's going on in clinical practice and understand why we do some things and we need to start from zero in order to build up. So I try to condense things as much as possible for you so that you're not getting lost. And I know that although I'm saying all this, you know, open and philosophical, whatever things at the end, the question that comes always, what do we need to know from this for our exams? Okay, that's no matter how broad I want to be and discuss, the question is, okay, what do I need to know from this thing for my exam? So as I'm telling you, it's only the basic things that you need to remember. You need to focus definitely for the period parts where they're coming from and how they develop. So don't stress out too much in terms of getting into very details, but obviously you have the access to read more and understand more of what's happening. So we will overview a little bit. We have an overview on the periodontal, some terminology to understand things, understand why we need the embryology and how the processes work. So what are the four structures that make up the production? You need to know these by heart. I don't know if there's another word for that. So we have the gingiva, the PDL, the dental ligament, the root segment, and the alveolar bone. Okay, so this is what makes the periodontist. We're going to start breaking down those things. So if you see a patient clinically and you need to understand what's happening there, you will start seeing some terminology coming up, which is the first is the free gingival margin. So that's the margin we call it free because technically it's not attached in the tooth isn't the top of your gingiva. Then this part is the attached gingiva. So this below the free gingival margin you have gingiva that's attached on the tooth, the bone, etcetera. Then you're having on the top the redder color as you see in the bottom specifically, like more quickly the alveolar mucosa. So we have different structures. We will learn those in anatomy as well. What separates the alveolar mucosa and the attached gingiva? It's a very fancy word. No, it's the mucus gingival junction, mucosa. Gingiva. That's a junction. And. There it is. Excellent. So this is like a brief overview of how things are happening and then what's happening underneath the tooth. We have several structures. As we see here. We have this momentum, which is a thin layer of mineralized connective tissue. So we set about those four structures. We talked about the gingiva very briefly, and now we're going to the other three, the cement, which is a thin layer of this mineralized connective tissue that covers the external root surface. We have the periodontal ligament, which are dense collagen fibers that connect the tooth in the alveolar bone, and finally the alveolar bone, which is the bony housing for the tooth and all those three things, not the gingiva. Those three things are considered and termed as attachment apparatus make sense. So that's how we're breaking down. And we're going to go briefly on these each of these structure, how they're being formed. ET cetera. So regarding embryology, we just need to understand three basic terms induction, competence and differentiation as you're going to see. So the induction is the interaction at close range between two or more cells, cells or tissues with different histories, different properties. So these induction directs the development of various tissues, organs in the majority of the animals and embryos like the islands, the heart, etcetera. And one group of cells, the inducing tissue directs the development of other group of cells, the responding tissue. So having this induction, then we need to have competence, which is the ability of a cell or tissue to respond to a specific inductive signal. Some cells do not respond in that. So we need to have this ability and each compartment of cells must be competent to respond to the induction process. Otherwise the process won't move forward. Okay. And finally, we do have the differentiation. So we start with induction and end up with a differentiation. So with the differentiation is the process that populations assume particular function shapes rates and turnover. And the cells like of an individual stem for the zygote are compartmentalized and those generation of cells are in compartment and either remain constant or differentiate and change their characteristics, establish a new population of cells. So depending on the needs of what organ, what tissue we're talking about, we have different properties for those things. So as you see here, we have the induction and gradually we're moving into differentiation to have the final shape of tissues or cells that produce the properties that we want to. So why do we care about embryology and why do we learn about those things other than we have? Two is we know about how widespread those diseases are and there are major cause of tooth loss. And as we said, we need to go back to the basics and roots and understand where they're coming from and how we can help our patients with these kind of diseases. And since we know that those diseases can be treated fairly predictably, we may also consider, okay, we want to try to regenerate the tissues that have, you know, have been destroyed or lost. And this has led many, many people to go into research and try to find ways that, okay, you're losing a tooth, let's find a way to bring it back how it was. You're losing periodontal structures. Let's find a way to bring it back. And you may have heard about stem cells and how they try to work on those. Obviously, we don't have clinical applications as of now that are fixed for our population, but hopefully at some point. And a clinical example is this and again, you may or may not have heard about it, we use it in word ontology, which is like a normal matrix derivative. It's a kind of a gel as a protein based gel, and it's used to promote regeneration of lost tissue. So this is a material that periodontist when they're doing regeneration, the main fuze or bone grafting, or even if they don't use bone grafting to promote regeneration and rebuild the lost periodontal structures around the tooth. Either you have bone loss, you're losing all those periodontal ligament, the bone and everything that we said. So the base is why we do that is because we know how things form and develop. So eventually what we want is if I can have the very first cell that creates all this tissue, can I bring back what what is lost for our patients? And obviously this has been having application in the medical field as well with regeneration of organs. They try to regenerate tissue. So that's the concept behind it. So let's talk. Briefly about this oral embryology, about the things that we need to know. So the development of the phase starts around four weeks of the intrauterine life, and that's where we form this primitive oral cavity, this module, as we call, and this has those five facial swellings, the maxillary process mandibular process. So one frontal nasal process, two maxillary and two mandibular processes as we see over here. And that's the development of the phase. In five weeks we start having from the front end process to produce the medial and lateral nasal processes. And if this fails to Fuze, then that's when we have the cleft lip that some babies are having. And now obviously we can treat and assess and treat efficiently. And then in the six weeks of the intrauterine life, we have the nasal septum and the primary pilots that form like those two palatal selves. So we see here the primary nasal septum, the primary pilot and the two palatal shells that are trying to connect and come together. So both are derived from those frontal nasal processes and they try to develop behind that primary palate on the maxillary process. So these two keep in mind and for that pilot on the eighth, eight weeks of this intrauterine life, those two palatal shelves get into contact and they try to connect the palate. Again, if these fail to Fuze, we have like that cleft palate as well, another deformity that can happen in embryos. So that's how the process happens. Regarding the mandible, everything starts around the sixth week and this appears like a band of dense fibrous tissue. We call it like the cartilage. And this provides like the framework, if you're going to think about it, where the bone will form around it and how this happens in the six weeks it starts at the mental foramen over here, this little opening, and it develops backwards, front and upwards. Okay, that's where it starts and that's how the bone will start developing in the mandible. And as you go like backwards on the back part, you will start developing the small cartilages like the condyle and the coronoid process. When you go in the front anteriorly, you will have the symphysis and the two plates eventually connect and connect together and like Fuze and this usually form like a single bone around the age of two of the kid. And finally, when you go upward, that increases the height of the mandible and fall and forms the alveolar process that we know. And that will that will surround the developing tooth germ. Regarding the maxilla. And around the eighth week, we're having the ossification that starts at the area of the deciduous canine. So that's where the ossification starts and the remodeling and the growth actually of the maxilla occurs by remodeling of bone and by growth as it happens on the maxillary arch. And then the growth continues forwards and downwards and increases in size. And that's how the bone and the face and maxilla palate mandible forms. Okay, Basic things. I don't want you to get lost in that. Now, going to the tooth, how this develops, that's a super nice tool that even leaves the oral cavity. So the first sign of tooth development occurs around the sixth week as we see over here. And underneath the oral ectoderm epithelium, there is a condensation of mesenchymal cells where the teeth will eventually form. And in these areas the epithelium thickens and protrudes into the mesenchymal cells and forms the primary epithelial bond. And as we see here from this epithelial bond, you will have like this differentiation between the dental lamina where the tooth germ will come and the vestibular bond where the vestibule will form. If you think about the oral cavity right at the bottom of the vestibule, that's things will form. And more specifically about the development of the tooth germ. This happens like in three stages the bud, the cup and the bell. Okay. And what we need to know about those things, I'm pretty sure my accent has been super bad for those three words, but it's okay, you can read it. So these are clumps of mesenchymal cells that induce the dental lamina to form swellings. And this is what we call the enamel organ's in the cup stage you're having. The inner aspect of the of the enamel origin which forms the inner anomaly epithelium. You're having the outer aspect of that which forms the outer enamel epithelium, and underneath that you're having this condensation of mesenchymal cells over here, as you see over there, which forms the dental papilla and eventually the pulp and all these capsule, the dental follicle that's going to form around it, that's eventually going to go and make the PDL. And by those 14 weeks at the end of the bell stages we see over here, the enamel organ consists of the following the inner enamel helium, the stratum epithelium, the stellar ilium and the outer Cilium. So things to keep in mind. And in the late stage of the bell over there, the dental lamina disintegrates and is ready for the formation of the dental heart tissue and the dentin formation always precedes the enamel formation. Okay, now the three parts of the tooth germ that we need to keep in mind, the enamel organ makes the enamel, the dental papilla makes the dentin and the pulp. And finally the dental follicle makes the three structures we said the symptom, the PDL and the alveolar bone. That's what I need you to remember. Okay, so a little more information about those three parts of the tooth germ to keep in mind regarding the enamel organ. This is composed of the outer enamel helium. We mentioned that before the inner enamel, helium, the stellate and the stratum, the stellate ridiculous and the stratum intermediate. As we see over here, these cells give rise to a mellow blast which produced the enamel. So these are mellow blasts have been used in many research projects in order to try to regenerate the enamel because that's the strongest part we have in our bodies. And being able to regenerate, that would be again, a breakthrough in what we do. Obviously, we're not there yet. Hopefully we may I don't know the location where the outer enamel epithelium and the inner enamel epithelium meet and joins, we call it the cervical loop. And finally, the growth of the cervical loop cells into the deeper tissues that form the Hedwig Hedwig's epithelial root sheath, which determines the root shape of the tooth. And we have the different shapes of the teeth and the roots as well. Regarding the dental papilla that contains cells that develop into a blast, they form the dentin of the tooth. The junction between the dental papilla and the inner enamel epithelium determines the shape of the tooth crown. Previously we have the shape of the roots. Now we have the shape of the tooth crown. And finally we're having those ectomy cells with the dental papilla that are responsible for the formation of the tooth pulp. And lastly, the dental follicle. The dental follicle gives rise to those three structures. As we said, the segment of glass, which will form eventually the cement of the tooth, the osteoblasts. We will play a role in forming the alveolar bone alveolar process. And finally the fibroblasts, which play a role in the formation of the PDL. Those three periodontal structures, the attachment apparatus, as we said in the very first, second slide or so. Okay. And then to close up these origin parts regarding the formation of the gingiva, which is the fourth structure of the tumor, as we said, the gingiva is the connection between obviously actually the connection between the gingiva and the tooth. We call it the dental gingival junction. And this has three types. We're going to learn more about that in our next lecture. Thing is for anatomy, which is a gingival the Sackler and the Junctional epithelium. This makes if you understand the basis of that, you will understand how the gingiva works around the teeth, how it forms in health, in disease, variation of health, what we're aiming to do with treatment, etcetera. And obviously we have mass amount of epithelial cells that are forming that epithelial cuff between the tooth and the mouth and the junctional epithelium that's derived like from the reduced enamel organ epithelium, the enamel organ divides rapidly. So the junctional epithelium is actually what starts to attach on the tooth. Okay, I'm not going to confuse you now because next time you will have also the visual with the picture. But as you're having your epithelium, your gingival cilium, you're going to your cellular epithelium in that, right? Below the free gingiva. We said in the beginning, you're having these small sulcus that forms the cellular epithelium and which is not attached on the tooth, right? It's very loosely. They're just resting. That's why you can probe around it. That's why you can put your instruments. And right there where this epithelium connects on the tooth, which is usually at the cement or enamel junction area, that's where your junction be. Helium attaches on the tooth surface. And finally, as the junctional epithelial layer increases in size, the remnants of the amyloid blast become isolated from any source of nutrition and degenerate. And they forming these sulcus the cellular epithelium. As we said, that's how gingiva is formed. Regarding cement and cement Genesis, we're having these cement blasts that differentiate from those follicular cells. They can reach the surface on the tooth, on the tooth only once the Hedwig's epithelium root sheath has begun to deteriorate. And what we need to keep in mind is that a cellular momentum forms first, which is what are we over here? So that's the denting. That's where the tooth is. That's bone PDL, A cellular forms first and then the cellular cement forms afterwards and develops this cellular cement after most of the tooth formation is complete and after the tooth occlude with the tooth and the opposite arch and the cement or blasts that are forming the last layer become trapped in the cement. And sometimes you can see those in the microscope as well. And. Okay. So what we need to keep in mind because with the cement, it's a weird thin structure that around the tooth and sometimes we don't understand why it's part of the tooth and why it's part of the periodontal and everything. But you need to understand its functions. And we're talking about a super, super thin layer on that side. So those meant to secrete find those collagen fibrils along the route surface, they start migrating away from the tooth and after mineralization, those segmental blasts move away from the cement and join the forming periodontal ligament. And that's what you see in those slides, like the microscopic, the microscopic ones. And as the cement blasts move, more collagen fibers and more collagen actually is deposited to thicken those bundle of the fibers and forms the cement afterwards. Okay. And regarding the PDL. These are like fibroblasts that differentiate from those follicular cells as well. They secrete collagen, interact with fibers on the surfaces of the adjacent bone. And this momentum and leading to this attachment in between which we call the PDL and the occlusion continually affects the formation of the PDL. So how do we know that? How do we have clinical signs for that? Any idea? About the occlusion and the PDL. Mm. Widening. So let me give you some background. If you see an x ray radiograph of a patient, you will see normally a tooth. And maybe I could have I'll put it in the next lecture. You're having the alveolar bone, the tooth and the root and right between the bone and the tooth, you see is super fine. 0.2, three, four, five millimeters of a fine line. Right? And that's how normally you see the PDL. If you don't see that line, that's when you're suspecting, Oh, baby by tooth is unclosed, right? So you wouldn't want to get this tooth out. You would like to just give it there because it's going to be a pain. So sometimes when you're having excessive forces, this spacing, we will learn about it. How it responds to forces starts to remodel in order to adapt on those excessive forces. And what you see radiographic is that this space starts to become wider. So you see a wider black space because it doesn't have the mineralized tissue of the bone and the cement that you have on the tooth, right? And the moment you see that, that's something that you may want to check the occlusion clinically. You may have other findings like mobility and other things, but that's something that you would see radiographic. And that's how we had our first signs saying, okay, something is happening in this space when we're having excessive forces on those teeth, okay? And you will see that the PDL is like the key for regeneration for US presidents. And yes, we do a lot of procedures and surgeries and all these things, but if we fail to regenerate the PDL, which takes like a lot of time, has a slower, slower turnover rate along with a bone et-cetera that's when we fail to truly regenerate those periodontal tissues and that's why we try to use materials, the membranes, the gain, as we said, and other materials in order to create that space and lead to the regeneration of the periodontal and finally the formation of the alveolar bones again, osteoblasts differentiate from those follicular cells. As we said, the collagen fibers are secreted on the surface near to the tooth, and then they remain there until they mineralized and attached to the periodontal ligament, the PDL. And we need to know that the alveolar bone is modified throughout life. We have this remodeling, we're sitting here, we are all remodeling our bone, we're having the osteoclasts preserving the osteoblasts, creating new bone. We're going to learn about that. And obviously there can be processes, diseases, medications and etcetera that can change that turnover and remodeling rate leading to diseases. And that's why we have medicate like osteoporosis, for example, and that's why we have medications that try to fix and balance that turnover rate, which could have side effects, you know, becoming more like Petrovic bones. ET cetera. We will learn about those things. But what I need you to understand from all those things before we finishing up is that everything comes from those, like production wise, I mean, from those follicular cells, there are a lot of cells that differentiate with specific roles, try to produce their fibers, collagen, etcetera, creating that balance of the periodontal and how all these things play a role in forming that and maintaining that through life. And obviously other processes, inflammatory processes can take play a role over there to create the imbalance and leading to the disease that we all know as President of disease. And before finishing up, we learned that the animal induction system guides the tooth development and the formation. Can we reproduce that? Not yet. Maybe at some point we wish this would change the lives of many, many, many, many people. Okay. That's when they first. That's why I'm talking about embryology and how things are. The moment you understand how these things develop, that's when you go start to start from the beginning to try to build things from scratch. So as of today, we were not there yet. Maybe, maybe not. Who knows? But that's pretty much so, as I told you, a short lecture today. Any questions in that? What I need you to remember from this is where things are coming from. Basic things, basic things of development don't get crazy. Okay? Usually we say, Yeah, you need to. I mean, if you want to feel free. But I'm not gonna ask like all those super little details about embryology, but I need you to understand the basic where they're coming from, what cells are being produced from where and what they're forming. And obviously you will see that in the anatomy class. Those things will start making more sense because they will be putting more information on that. Any questions? No. Yeah. No. Okay. Sure. The exam. I was sure about that. I was waiting for this question. Do you want to have. The midterm or the final? Yeah. And then some. Yeah. How? How often? It depends. If you make me angry, I will have it. No. No, no, no. Um, I don't have a fixed number. I usually vary from 3 to 4 per semester. Unless for some reason you say I need more. Okay, let me do some more. The reasons is, as I told you, mainly to. Urge you to start reading a little bit. So after the first half of the lectures here, there will be a quiz saying, you know what, we're going to ask those questions on, I don't know, anatomy, embryology, microbiology. So you start reading a little bit about this because I know how overwhelming your schedule goes. And again, I'm repetitive. I know how it is. I was doing the same mistake. So but I didn't have somebody who was pushing me this way saying, Oh, you're going to have a quiz now, so you need to study. Okay. And again, I don't want to stress you out too much. You're going to it's going to be at home open book, have whatever you want. It's mainly for you to start looking up at the materials so you don't have to panic the day before the exam. But I'll give you plenty of time. I will say it will be everything will be announced on Blackboard. So, you know, a quiz will be available from that day to that day and what it's going to include so that you know where to study and not get lost. Any other exam question? Not yet. Okay. Before you leave, let's take the attendance one second. Please know. Okay. Do I have to make it bigger? Yes. No, I don't know. Yes. Okay. Wait a second. Where is my thing? It should be this one, I guess, right? No. Yeah. Button top. Right. Okay. What should I do? Top right. Top right. Oh, I can't see. The magnifying glass, so. Okay, I found it. Okay, You're right. Somewhere there. You click on it, and then it's. Pulling it the. Okay. I'm making it too difficult. This one. Ah, Wow. Did it work? Okay. Have a good day. See you next week. It's not 10:00 yet. Can't start. Did you guys not have parallel this morning and early?