which system works day and night in order to keep us healthy well that's exactly what we're going to be talking about today we're going to be discussing the ait's version 7 portion of the exam more specifically human anatomy and physiology and we're going to be discussing the immune system let's get started among all the major body systems the immune system stands as a particularly intriguing one but you may be wondering why is it so intriguing it's because the immune system comprises of cells like macrofagos neutrophils and asops which are tirelessly collaborating around the clock to defend you against the Relentless onslaught of pathogens aiming to disrupt your health so when we talk about pathogens we're referring to a diverse array of different kinds of threats whether it's viruses bacteria fungi protus or even parasitic worms just to name a few your body is equipped with external defenses against these various threats such as your skin which acts as the first line of defense it forms a protective barrier to prevent pathogens from entering your body similarly mucus membranes like the lining that we find in our nose are also able to keep pathogens out this first line of defense is a non-specific defense because it indiscriminately blocks any potential Invaders from entering your body however these defenses are not invaluable and pathogens can sometimes breach the system when this happens the immune system is ready with numerous strategies to handle the invasion drawing on its extensive experience in combating such threats so if pathogens managed to breach those initial barriers we have a second line of defense that comes into play which includes things like inflammatory responses to put it plainly imagine that you accidentally pricked your finger on a thorn that carries bacteria this penetration of bacteria causes the cells in our body like mass cells to respond to the injury and the potential bacterial threat these cells are filled with substances that assists with allergic and inflammatory responses one such substance is histamine when released histamine causes the nearby blood vessels to dilate which is just a fancy way of saying widen and when it dilates it's going to make it more permeable or leaky this dilation and increased permeability makes it easier for various types of white blood cells like certain macres to reach and Infiltrate The affected area this allows these macrofagos to perform their quintessential role engulfing and digesting pathogens Additionally the body deploys a complement system which despite its name serves to enhance and support the immune system's functions this system can engage in both non-specific and specific immune responses in this case the release of compliment factors helps draw more macrofagos to the site to eliminate the pathogens once the signaling ceases that effective area is going to begin to heal and return toward its normal State as the pathogen has been eradicated however when it comes to our second line of defense this response is still nonspecific meaning that it reacts without knowing the exact nature of the threat like the unknown contents from that thorn this is what brings us to our third line of defense a more specific line of defense imagine that you're dealing with a cold virus spreading throughout your body this situation calls for a more targeted response for this particular kind of pathogen considering the need for a more specific and focused kind of immune response we're going to be stepping into the realm of an Adaptive immune defense when we talk about adaptive immunity we're talking about a more specific type of immune response that specifically targets antigens antigens are substances that the body recognizes as foreign often parts of pathogens adaptive immunity serves as the third line of defense where the two initial immunities known as non-specific defenses or innate immune responses are ultimately going to have failed to adequately control the pathogen like we'll see with the third line of defense we're going to explore two fundamental types of adaptive immunity we have cell mediated and humoral focusing first on cell mediated responses this is going to involve cytotoxic te- cells which is a specific type of white blood cell these cells can destroy other cells infected by a pathogen by by inducing apotosis which is a process of programmed cell death or self-destruction this is achieved by releasing substances like perorin which creates holes in the infected cell's membrane causing the cell to take in water and ions until it eventually bursts when infected cells are destroyed it's going to Halt the pathogen's ability to replicate within those cells the activation of cytotoxic tea cells requires specific stimulation for instance an infected cell may present a p P of the pathogen's antigen on its surface signaling that that cell has been compromised this flagging activates those cytotoxic tea cells prompting them to bind to the infective cell and initiate apotosis additionally cytotoxic tea cells can be stimulated in another way considering macrofagos that have ingested those pathogens these cells can process and present that pathogen's antigen to their own surface that's when we're going to start to see helper te te cells what the helper te cells are going to do is they're going to combine with that maccrage and with that combination they're going to start releasing chemical signals to activate those te- helper cells the activated te- helper cells are then going to release those chemicals and stimulate those cytotoxic tea cells which are going to set them on a mission to find and destroy any infected cell further amplifying our immune response DH helper cells play a crucial role not only in cell mediated respon responses but also in humoral responses acting as a significant supporter in both Pathways when it comes to the Adaptive immune response so what exactly unfolds during the humoral immune response going back to our scenario where a maccrage is going to engulf a pathogen and present a piece of the pathogen's antigen on its surface this maccrage is then going to interact with a helper T cell which in turn can activate a specific type of white blood cell known as a bees cell C B cells have the capability to produce substances known as antibodies antibodies are predominantly found in the blood but they also can be found in mucus saliva breast milk among other fluids there are several classes of antibodies we begin with IGG which is the most abundant type of antibodies found in our system IGG is found in our body fluids and it protects against bacterial and viral infections by enhancing phagocytosis neutralizing toxins and triggering compliment system components IGA is found in our mucous membranes lining either our respiratory or our gastrointestinal tract as well as saliva tears and breast milk IGA plays a critical role in mucosal immunity IGM is the first antibody produced in response to infection IGM is primarily present in the blood and lymph fluid and it's very effective at forming complexes with antigens and activating the compliment system IG is mostly associated with allergic reactions and responses to parasitic infections IG is found in our lungs our skins as well as our mucous membranes and then lastly we have igd although it's less understood than the other antibodies igd is mainly found on the surface of immature B lymphocytes and in our respiratory tract where they play a critical role in initiating early immune responses when when antibodies attached to an antigen they can neutralize this pathogen by hindering its movement reproduction as well as its ability to inflict damage this binding also acts as a signal to macrofagos to locate and devour that pathogen effectively marking it for Destruction activating B cells is a key component of the humoral response leading to the production of antibodies while B cells can be activated by a t- helper cell they can also be activated directly by free antigen that they encounter throughout the body it's important to highlight that memory cells play a significant role in both that humoral and that cell mediated response memory B and T cells are going to retain a memory of the antigens that they have encountered the differences is that memory B cells are going to initiate those plasma B cells which then are going to create antibodies and just like the name suggest memory te- cells are going to activate our cytotoxic te- cells which are going to Target and destroy our infected cells lastly we have active immunity and passive immunity which are two critical forms of immunity that protect our body from pathogens but they function in distinctly different ways active immunity occurs when an individual's immune systems produces antibodies in response to the presence of a pathogen so how is this type of immunity acquired well it's acquired through either direct exposure of the disease prompting a natural immune response or it can be through vaccination s or a dead or weakened pathogen is going to be introduced to stimulate an immune response without actually causing the disease active immunity is generally long lasting and can often provide lifelong protection after the immune system has developed memory of that antigen common examples of this could be developing immunity after you catch a cold virus or even receiving a measles vaccine and then we have passive immunity which is provided when a person is given antibodies from another Source rather than producing them through their own immune system this type of immunity can occur naturally such as when antibodies are transfer from a mother to her baby through the placenta during pregnancy or even breast milk it can also be acquired artificially through antibody containing blood products such as imunoglobulin therapies or anti- serums which may be used to treat specific diseases passive immunity provides immediate protection but it's only temporary as an antibodies are eventually broken down and do not result in the production of memory cells the protection might last a few weeks or even maybe a few months common examples of this could be newborns who are receiving antibodies from their mother or a person receiving a rabies shot after an animal bite I hope that this video is helpful in understanding everything you need to know when it comes to the immune system as always if you have any additional questions make sure that you leave them down below I love answering your questions head of nurse Chun store.com there's a ton ton of additional resources in order to help you Ace those atits exams and as always I'm going to catch you in the next video bye