 Welcome back to our meds smarter lecture series where we're taking a smarter approach to preparing future physician Before we get started if you'll take just a quick minute and click that like button and also Subscribe and turn the bell on so that you'll be notified when we post new videos Today we're going to begin our discussion on immunology and the first thing that we need to do when we discuss Immunology is discuss some anatomy the organs of our immune system are divided up into primary organs and secondary organs Our primary organs are going to be our bone marrow and our thymus So with our bone marrow our bone marrow is where we see immune cells being produced and where we see B cells maturing Bone marrow typically going to be your sternum as well as your femur Long bones are very common to be a location where a lot of our bone marrow is a part of our primary immune system The thymus, which is up in the chest Posterior to the sternum as you can see right here that I've circled in red This is where our T cells mature beyond that our secondary immune system organs are going to be our spleen lymph nodes tonsils and pyrus patches We all know the spleen is going to be in the left upper quadrant Our lymph nodes are all throughout the body we have some under our arms and our neck around our gut and our Inguinal areas tonsils obviously going to be in your throat as you can see in this picture here and then pyrus patches are Located in the gut of the small intestine as you see in the bottom right hand corner So what all these secondary Immune system organs do these are all allowing immune system cells to interact with the antigen So they will go and find that antigen those cells will then present to that antigen and Will continue along down that immune system response line So let's look a little closer about some of our organs here We'll first look into lymph nodes. So we said the lymph nodes are all throughout the body So let's zoom in on just one lymph node here This is what a individual lymph node looks like at a close-up It is a secondary lymphoid organ as we already mentioned here that has many a ferrants Which means coming towards so your a ferrant limb here that everything is coming towards our Lymph node and then it does have one or more E ferrants, which means going away. So in this particular picture here, this is our efferent and everything is passing down out of that one particular lymph node each Individual lymph node is encapsulated and they're Tribecula they'd encapsulate them you can see these black lines around this particular Lymph node that we see here in this example and those are your Tribecula that will encapsulate the lymph node. So all throughout you have these Tribecula encapsulating. How do they function? They do non-specific filtration. So macrophages B and T cells circulate through and then our immune system response activates from this particular Location in the lymph nodes. We actually can break down the lymph nodes into Three different main structures the first being a follicle. So what is a follicle? Well first and foremost? This is where our B cells will localize and proliferate from the location of these are going to be in the outer cortex This one particular diagram doesn't have a great labeling of follicles, but we have primary and secondary follicles here Primary follicles are dense and quiescent meaning they're kind of hibernating or inactive And all of these like we said are going to be in the outer cortex. So you can kind of see them on Gross anatomy not so much in this illustration, but they look like a bunch of circles typically towards the outside of the Lymph node as you can see what I'm drawing in here. Okay The secondary follicles these are ones that have a pale Central germinal centers, and they are active. So if you saw a gross anatomy photo of a lymph node you'd be able to see those pale centers of the Secondary follicle where the primary follicle will just be very dense. We don't have those pale centers So you can kind of see as I'm drawing here onto this Example you draw some of them are very dense and packed together That's our primary follicles and then the ones that have dark outside almost just looks like an empty circle with a pale inside That is our secondary follicles the next structure the lymph node that we'll talk about is the medulla the medulla consists of medullary cords and medullary sinuses these are closely packed lymphocytes here and plasma cells and They communicate with the efferent lymphatics, which are whatever comes out of the lymph node so they communicate with the efferent lymphatics and they contain reticular cells and Macrophages so you can see in this diagram these medullary sinuses are going to be represented by the yellow lines You can see I'm drawing them in red now drawing over them So these are basically allowing communication within the lymph node between the rest of the lymph node and the efferent lymphatics and Like we said earlier, they contain the reticular cells and the macrophages Finally the third structure of a lymph node that we're going to discuss is the para cortex This is where we have our T cells located in the para cortex of the lymph nodes. This is Basically a region between the follicles and the medulla, which isn't very well Shown in this picture, but it's going to be the area down here. You remember I drew the follicles up here in the perimeter while the area down here Inferior to those but not all the way into the medulla is where we have the para cortex in this area We have high endothelial venules through which the T and B cells will enter from the blood and then a Clinical correlation with this is patients that have the George syndrome Don't have a very well-developed para cortex in their lymph nodes. So what we see With the para cortex is that it enlarges When they have a very strong cellular immune response So we have Epstein bar virus or other viral infections You can actually feel the lymph nodes of the patients that have that infection because we're getting the para cortex to enlarge So para cortex enlarges leads to pericortical hyperplasia and that is lymph adenopathy. So when you can feel a Lymph node Typically, it's because of lymph adenopathy Oftentimes due to inflammation associated with the para cortex. So let's talk a little bit about the spleen in General as we know from our regular anatomy This is located in the left upper quadrant of the abdomen as you can see in this picture right here. This is Residing anterolateral to the left kidney. So our left kidney is going to be a little bit more inferior and posterior from the spleen and It is protected by the ninth to the 11th ribs It is somewhat difficult to injure your spleen. You'd need a pretty strong blunt force trauma To be able to injure the spleen because of those ribs. It does have a very small portion of the spleen that could be peaking out underneath that 11th rib that could be exposed To certain damages and blunt force traumas. So let's talk about the spleen more closely here So the spleen is made up of sinusoid which are long vascular channels Within our red pulp of the spleen and it has a fenestrated barrel hoop basement membrane So as you can see in this picture the letter B points to the red pulp the Sinusoids are within that red pulp area. We can find T cells in the pals area or the peri arteriolar Lymphatic sheath pals and that's going to be within the white pulp which is under letter A on this diagram B cells are often found in the follicles within that white pulp and the marginal zone between those two So if we drew a zone right around the edge here, the marginal zone is where we see macrophages B cells antigen presenting cells all come in and capture blood-borne antigens that are able to be recognized and seen by the lymphocytes and It is noteworthy here that within the spleen the macrophages are what removes encapsulated bacteria This is important for people that no longer have a spleen Because that encapsulated bacteria would then no longer be able to be removed. So let's get right into that So if you have splinic dysfunction Such as you've had to have a spleen removed For whatever reason you could have maybe had an auto splectomy where Patients that have sickle cell disease the spleen gets damaged and enlarged so much that it is no longer functioning Or you've injured your spleen Then we have to remove that So one of those two states is the most common thing you'll see. What do we have happen here? Well With a spleen dysfunction. We're gonna have low IgM Low IgM will cause us to have low complement activation without the activation of complement our C3b optionization will become low and That in turn gives us our high susceptibility to our encapsulated organisms So let's say we have a patient that is Post splenectomy he had to have a spleen removed due to trauma and bleeding and internal bleeding injuries What would we see in patients that are post splenectomy well First thing we'll see is how old jolly bodies. These are nuclear remnants and as you can see in this particular picture here There is a big blue Nucleus piece that is a remnant inside that red blood cells remember red blood cells typically don't have a nucleus inside of them So the how jolly body is the nuclear remnant due to the splenectomy We can also see target cells If you remember back to your red blood cell anatomy red blood cells have That biconcave shape with that central pallor there this here We are actually seeing more of a Target so it looks like red white red and almost like a bullseye that is called a target cell That is a finding of our post splenectomy patients as well You'll also see some thrombocytosis here where we can have loss of sequestration and removal of the platelet cells and Then lymphocytosis here is also common in post splenectomy patients due to the loss of sequestration So what do we need to do to patients that have had their spleen removed or have undergone autosplenectomy? Because of their risk of encapsulated organism infections when we need to vaccinate them Vaccinate these patients against those encapsulated organisms. So what are they encapsulated organisms that we have a vaccine for? Well, that's gonna be our pneumococci our hemophilus influenza type B and meningococci So we need to give all of our post splenectomy patients whether it be Surgical post splenectomy or autosplenectomy due to something like sickle cell disease Get them vaccinated with these particular vaccines to help against pneumococci Hib and meningococci If you found this material helpful for your studying Please like and consider subscribing to the channel also share this video so that more people can benefit from it like you have