we are going to be looking at the second type of white blood cells known as lymphocytes in this video um and of course unlike fagos sites you do have to know the formation and the maturation of the lymphocytes formation is pretty simple just like fyes the lymphocytes are also formed in the bone marrow which is inside the bones and it starts off with the blood stem cells divide ing continuously through a process known as mitosis now when the blood stem cells divide uh they will specialize into two groups of lymphocytes some of the blood stem cells will specialize or differentiate to become something known as immature B lymphocytes and another one is called the immature T lymphocytes I'm representing them as different colors it doesn't mean that the B lymphocytes are orange and T lymphocytes are green I'm just you know it's just a clear way of looking at them right then of course you might be asking the question why are the lymphocytes um classified into B and T the answer to that question is because of the place where the lymphocytes become mature now some students will ask what exactly does it mean by cell maturation maturation of the cell just means that um they are quite small when they are newly divided and the cell starts to become larger you can link it back to your cell cycle which is the G1 phase in interface by the way anyway so the main thing to know about bosy is that the B lymphocytes mature in the bone marrow and the bone marrow the first letter of bone marrow is uh b as I have highlighted over there so that is why B lymphocytes are called such because B lymphocytes mature in the bone metal simple stuff and the te lymphocytes however they will mature in an organ known as the thymus now students may be asking the question where exactly is the thus located the thus is an organ which is part of your lymphatic system you don't have to know that don't worry and the thus is located behind your sternum your sternum is just the bone that is in the middle of your chest all right uh so it's just good to know where the timer is located but um will they asked for the location of the timers no so because T lymphocytes mature in the thers the first letter the first alphabet of timers is T we call that t lymphocytes it's as simple as that okay you do have to know the formation of the two types of lymphocytes and you do have to know where they mature this is important for the exam now another very important thing that you have to know is when the B lymphocytes ENT T lymphocytes mature something interesting happens one obvious thing that happens here is the size increases obviously if you compare the immature B lymphocytes immature T lymphocytes with the mature ones with their mature counterparts the mature counterparts are the mature cells are larger but what is very interesting is the mature lymphocytes have receptor proteins on their cell surface membrane so what are the functions of these receptors on the cell surface membranes so that is what we want to look at now a very important thing to understand here is each lymphocyte whether it's b or t lymphocytes have receptors which are complementary to one type of antigen only what do I mean by that if you look at each of the cell yes they have multiple receptors but in each cell The receptors are the same shape now why is this important is because now I'm drawing out a pathogen at the bottom here remember pathogens are the harmful microorganisms and on the surface of the pathogens they have the antigen antigens are foreign substances here is where something important happens B lymphocytes and T lymphocytes are highly specific now what do I mean by highly specific you see under normal circumstances white blood cells are supposed to attack anything that have antigens we understand that we saw that in the previous videos but lymphocytes are highly specific for example I'm drawing out one lymphocytic the shape of the receptor on the lymphocytic they are not complementary so that no so they will not respond third lymphocytes at all thus they will not respond the fourth lymphocytic and the antigen matches in the sense they are complementary to each other the moment they are complementary to each other that's when the lymphocyst you are something that is foreign in our body and the same thing happens with the T lymphocytes as well the T lymphocytes have receptors and they are only complementary to one type of antigen that's the first important thing that you have to understand about lymphocytes they are highly specific all right they only respond to a specific type of antigen all right so that's the first thing that we have to know so then of course you might want to ask the question what's the difference between B lymphocytes and T lymphocytes then well obviously the first thing is we knew that their area of maturation is different B lymphocytes mature in the bone marrow and T lymphocytes mature in the thyers and also their immune response which means to say how they respond to the antigen is going to be very different as well and we will be looking at that in the next video