Blood types | Human anatomy and physiology | Health & Medicine | Khan Academy
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Blood types | Human anatomy and physiology | Health & Medicine | Khan Academy

– [Voiceover] Let’s say that
this is a red blood cell. What makes up the outer
layer of this red blood cell? Since it’s a cell, it has a cell membrane, and that’s made up of lipids. But embedded in those lipids,
there’s all kinds of proteins and molecules, some of
which I’m drawing here, that have all kinds of
different functions. There are two of them that are sort of more important than the others, at least for this topic that
we’re going to talk about, and those are the A
molecule and the B molecule. I think you’ll be pretty
happy with those names, not too hard to remember. I’m actually calling them
molecules and not proteins because they’re actually not proteins. They are actually something
called glycolipids, which I actually didn’t realize at first. Glycolipids, glyco meaning a sugar group, lipid meaning a fat group, so it’s some kind of
mix of a sugar and fat. You can look it up if you’re interested. What’s interesting, is that not all people have both of these
molecules, these glycolipids, on their red blood cells. Some people do have both,
but some have only one. For example, some people
might have only the A, or, as you can imagine, some
people would have only the B, and some people, can you figure
out the last possibility? Some people have neither A nor B. Of course, all these people
have all kinds of other proteins and molecules embedded
in their red blood cells. The reason why we care about this and why I’m talking about
these As and these Bs, is that in medicine, we often have to give blood transfusions. Let’s say you got in a car accident and you lost a lot of blood. You’re rushed to the hospital. If you’ve lost enough blood, they’ll give you a transfusion of blood. Transfusion just means they’ll
put a needle in your vein and pump blood into your veins. It turns out that you can’t
just give any blood to anyone, and it has to do with
these A and B groups. For example, it turns out,
and we’ll explain this, but for example, it turns out that if you are the kind of person
who has this kind of blood that only has As on your blood cells, then it turns out that you
can’t get a blood transfusion from someone who has this
kind of blood, As and Bs. Let’s learn why. If you remember from the immune system, there’s something called an antibody. We usually draw it in this shape here. If you remember from the immune system, your body has something called antibodies, and it uses these
antibodies to fight things that it doesn’t want in the body. For example, if you have a bacterium, I’m drawing one here,
you’ll have an antibody that will bind to that bacterium. The purpose of that is
that now your body knows that is should destroy this bacterium. This antibody is kind of like a tag that marks this guy for destruction. But your body is very careful not to make antibodies against itself,
which is obvious, right? If your body made
antibodies against itself, then it would start to attack itself. For that reason, someone
who has this kind of blood, which means that all of
their red blood cells have As and Bs on them, that person would not want to make antibodies against the A and the B molecule,
because if they did then their body would attack
all of their red blood cells. These people don’t have these antibodies. But, let’s say if you
have this kind of blood, then you might not make
an antibody against the A molecule, but
you can make it against the B molecule, because
the B is not in your body, and so there’s no risk that
your body is going to attack itself by making an antibody
against the B molecule. So these guys don’t have the A antibody, but they do have the B antibody. These guys, on the other hand, they can have the A antibody, but they don’t want the B antibody because then they would attack themselves. This final guy, can you guess what he has? He can actually have
both A and B antibodies. He actually will have both, because that’s the way
your immune system works. It makes antibodies against
pretty much anything that is not you, that is not yourself. A and B molecules are
not part of this guy. He has none of them, so he’ll
make antibodies against them. Let me ask you, what
would happen if this guy, someone with just A blood, type A blood, got in a car accident
and needed a transfusion? Let’s say they’re rushed to the hospital and you give them blood from
someone with A and B molecules. What would happen is that
this guy’s antibodies again B would go and
bind to the B molecules on the blood that he’s just received, and then his body would start to destroy all of these cells that he just received. That’s bad because, first
of all, it’s a waste. You gave this guy blood and now he’s just going to destroy it. But second of all, it’s
going to cause a huge amount of inflammation,
because this guy’s body is going to suddenly
see all these antigens that he thinks are really dangerous, and it’s going to cause
his whole immune system to rev up, and that will
actually be bad for him. Let’s go through all the
different possible transfusions between these different kinds of people. Let’s go through them
methodically by drawing a table. On one side of the table
we’ll have the donors. Bear with me as I draw this table out. We’ll have AB donor,
A donor, type B donor, and do you know what we
call this kind of blood? We can’t call it type B or type A because that’s these guys, so we actually call this O, type O. Then we also have the same
guys as possible recipients, so we have type AB blood recipient, type A blood recipient,
type B blood recipient, and type O blood recipient. Let’s make this into a table. Here are our donors, blood donors, and here are our blood recipients. What did we say before? We said that someone with type A blood cannot receive blood from
someone with type AB blood. So that means that A recipient
with AB donor is no good. Well, how about someone with AB blood? Can they receive blood
from someone with AB blood? The answer is yes, because
the guy with AB blood has no antibodies against A or B, so he won’t attack the AB
blood that is given to him. Why don’t you pause the video for a moment and try to fill in the rest of this table? Hopefully you’ve paused for a second and tried to fill in
the rest of the table. Now we’ll fill it in together. Someone with AB blood
can receive blood from A, he can receive blood from B, and he can receive blood from O because he has no
antibodies to either A or B, so he won’t react to any of these guys. Likewise, someone with type
A blood can, of course, receive from A, B can receive from B, O can receive from O, but B cannot receive from AB, nor can O. Nor can B receive from A, nor can O. Nor can O receive from B,
nor can A receive from B. But O can give to everyone. Something interesting
you’ll notice here is, as we just said, O can give to anyone because the O blood type
has no As or Bs on it, so no one’s going to react to it. For that reason, we call
O the universal donor. The other interesting thing you’ll notice is that AB can receive from everyone. For that reason, we call
him the universal recipient. All these things, by the way, AB, A, B, O, these are blood types. So when someone asks
you for your blood type, this is what they’re referring to. This is why it’s really
important to know your blood type if you’re ever going to
require a blood transfusion.

About James Carlton

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30 thoughts on “Blood types | Human anatomy and physiology | Health & Medicine | Khan Academy

  1. Hey guys so it's pretty hard to get noticed on youtube but I was really hoping that you guys would give my channel a chance. I make educational videos in hopes that it will help students as well. You don't even have to subscribe if you don't want to but it would mean a lot to me if you took a look! Thanks so much in advance for your time!

  2. You wouldn't believe all the things about cells we learned in our first week of paramedic training. It was astounding. It was positively overwhelming. 
    I went to school for a year plus the training I got.
    Antibodies, I never understood well enough IMO to understand anything other than anaphylaxis and allergies well enough to pass the test but not at the highest level.
    I lived with a doctor at the time and he said immunology was never his strong suit, which I found more astounding than learning cell structures. He understood more than I ever did.

  3. I think you ought to put the information in the description in bold letters. Or at least tell them you have to have licenses to do any part of medicine. You're not allowed to practice any medical care without a license, especially these days. 

  4. But when someone with blood B or A donate to AB
    the donated blood (from A or B)will have antibodies for A or B which will attack the recepient's blood AB (since it has both antigens)

  5. Instead of the Ys for the antibody it would help if you used the actual A or B. I get that you used the same colors but I'm a very visual learner and the Y antigens kept throwing me off. Thank you for the video and explanation.

  6. this is really interesting, my mother found out that she has a really unusual blood group known as AD negative, does anybody know anything else about this unusual blood group?

  7. Whats the difference between the positive blood types and negative blood types?

    Im A+ and i want to know how that's different from A-

  8. I was wondering if, since those 'a' and 'b' molecules are on red blood cells, is it possible to donate plasma and white blood cells to anyone and receive from anyone? Because I know they rarely give a full transfusion these days.

  9. I was expecting this is more on the GalNAc and Gal present in the ABO blood groups type of discussion but thanks anyway

  10. Just a quick sum, AB can receive from any other blood types donors and O can donate to any other blood types receivers. The rest is just a matching game Period!.

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