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Blood Types Are WEIRDER Than You Think — Transcript

by Be Smart · 2,892 words · 424 segments · language en · Watch on YouTube

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0:02Hey, if you took out all the blood cells in your body
0:06and laid them out, end to end, you'd be dead.
0:10The average human adult contains about this much blood.
0:1515 pounds of my body is just liquid meat,
0:19and not all blood is red.
0:22Across the tree of life we can find blue blood, green blood,
0:26purple blood, even clear blood.
0:29Why does it come in so many colors?
0:32Of all the juices in your body,
0:34blood is by far the most important.
0:37But how much do you really know about it?
0:40Because without this stuff,
0:41we couldn't feed babies,
0:43cool off our bodies, eat, or even cry.
0:46Blood's the reason your pee is yellow,
0:49and also why your poop is brown.
0:51We're taking an adventure through this wild universe
0:54to learn all about blood and what it does.
0:57Why does blood come in so many colors?
1:00Why are some blood so rare, and maybe weirdest of all,
1:04Why is your blood different than mine?
1:13(uplifting music) Hey smart people, Joe here.
1:16Ow.
1:18Everyone knows blood is red.
1:20But ever hear someone say
1:21that blood is blue when it isn't carrying oxygen?
1:26That's actually not true.
1:27It's just an optical illusion.
1:29Blue light is better at reaching the surface
1:31of the skin than red light,
1:32so it just appears that our veins are blue.
1:35But some animal's blood really is blue, some is green,
1:39some is even clear.
1:41Blood in all of its forms is really super weird.
1:44But before we can understand all of those, we need
1:47to know what's in our blood.
1:51Blood gets around your body in many ways,
1:53through big arteries and veins that branch smaller
1:56and smaller, all the way to capillaries, the smallest
1:59of which are so tiny
2:01that only a single blood cell can squeeze through.
2:03Together, these form a closed loop
2:05that begins and ends at your heart
2:07and lungs, and there's a lot of ingredients
2:09to this little crimson cocktail.
2:12But that recipe starts with four main components.
2:16About half your blood is plasma, it's mostly water
2:18with the rest being proteins, fats,
2:21salts, and other chemicals.
2:22Its main job is to carry stuff where it needs to go.
2:25Things like nutrients, blood cells,
2:28and chemical messages all over the body.
2:30It also carries waste to your body's dump
2:32and recycling centers.
2:34And since it's mostly water,
2:35plasma also helps keep your fluid
2:37and electrolyte levels balanced.
2:39Without blood, you would overheat super fast,
2:42'cause when you're hot, water's absorbed by the blood,
2:45and your plasma volume increases to give you a reservoir
2:49for sweat making.
2:50That's right.
2:51Next time you're sweating,
2:53think about the fact that all the water
2:54dripping down your face
2:56was sucked out of your blood vessels.
2:58And that's true for pretty much every liquid
3:00our bodies make.
3:02Milk? Made from blood.
3:04The spinal fluid that cushions
3:05and cleans your brain, also made from blood.
3:08Saliva, that starts as blood too.
3:10Even tears, you couldn't cry without plasma.
3:14And our next three blood ingredients use plasma
3:16as a liquid highway to get where they need to go.
3:19You ever wonder why you don't bleed
3:20to death when you get a paper cut,
3:22or prick your finger?
3:24Platelets.
3:26They aren't true blood cells,
3:28they're more like cell fragments.
3:30When a blood vessel gets damaged,
3:31a chemical alarm belt draws platelets to that injury.
3:35They stick to each other
3:36and to the broken vessel,
3:38which creates a plug, like flex seal
3:40for your circulatory system, and you've got a lot of 'em.
3:44One drop of blood has millions of platelets in it.
3:48That's bonkers, but it's nothing compared
3:51to blood's biggest army: red blood cells.
3:55A body like mine has almost 30 trillion red blood cells.
3:59That's hundreds of times more blood cells
4:02than there are stars in the Milky Way.
4:04You have four times as many red blood cells
4:06as all your other cells combined.
4:09If you were to count them one by one,
4:11it would take you almost a million years.
4:14So your body's basically all red blood cells
4:18with a sprinkling of other cell types.
4:20A red blood cell's main job,
4:22of course, is carrying oxygen from the lungs to the rest
4:25of the body, and then helping move carbon dioxide back
4:28to the lungs so that you can breathe it out.
4:31And that oxygen carrying job is done by a literal atom
4:34of iron inside a protein called hemoglobin.
4:38Just like rust,
4:39iron is what gives our blood its red color,
4:42and also what makes it taste like metal.
4:44The smallest blood vessels in your body are just 1/10th
4:48of a human hair across, that is tiny.
4:51So red blood cells have to be tiny too.
4:53They're about a million times smaller
4:56than one of your muscle cells.
4:58There are around a billion red blood cells
5:01in just one drop of blood.
5:03Your body makes about 2 million
5:05new red blood cells every second.
5:07Old blood cells constantly being replaced
5:09by new ones, because well red blood cells are kind of dead.
5:13See, like all your blood cells,
5:15your red ones get their start in the bone marrow,
5:17and as they mature, the nucleus gets thrown away.
5:21This is a big trade-off.
5:23Not having a nucleus makes red blood cells flexible enough
5:26so they can squeeze through those tiniest of blood vessels,
5:29and it leaves more room to pack the cells
5:31full of hemoglobin.
5:32But, it also means they have no DNA blueprints
5:36to repair, damage, or make more of themselves.
5:39So one red blood cell only lasts around four months,
5:43which really isn't very long compared
5:44to all the other cells in your body.
5:47It makes you think in some ways they kind
5:49of don't fit our definition of living cells at all.
5:52Your biggest cellular army is basically
5:54a hoard of oxygen-hungry iron zombies.
5:56And finally you've got white blood cells, a huge family
6:00of cells whose main job is about figuring out self
6:03versus non-self, what belongs in your body and what doesn't,
6:08and putting up a fight to attack anything
6:10that shouldn't be there.
6:11So, that's our basic recipe for blood,
6:14but each of us has our own special twist on that recipe.
6:19Pop quiz hotshot, what's your horoscope sign?
6:23Okay, you probably know that.
6:25Now, what's your blood type?
6:27I'm willing to bet a lot
6:28of you did not know the answer to that one.
6:31More Americans know their astrological sign
6:33than their blood type, which is pretty wild,
6:36because only one of those things
6:37could potentially save your life,
6:39and it ain't your horoscope.
6:41This test is gonna tell me my blood type.
6:44Even though all
6:45of our blood does the same jobs, I might not be able
6:48to give you mine.
6:50Why is that?
6:51Scientists are still trying
6:52to unravel this blood type mystery.
6:55And the story starts about 200 years ago.
6:58Back in the old days,
6:59doctors were really into mixing different bloods together,
7:02different people, different animals,
7:04sometimes people blood with animal blood,
7:06and it didn't usually end well.
7:08They noticed sometimes combining different bloods
7:11made them clump up.
7:13It's called agglutination, basically Latin
7:16for glued together.
7:18One Austrian doctor, Karl Landsteiner,
7:20wanted to know if this happened
7:22because there was something wrong
7:23with the blood,
7:24or if this sticky situation was something blood
7:27was doing on purpose.
7:28So he did what any normal person would do,
7:31he asked some friends for some of their blood,
7:33and got to mixing it up.
7:35He found that there were rules patterns to the clumping,
7:38and after studying those patterns,
7:40it seemed like human blood could be split into three groups.
7:44When he mixed plasma from group A
7:46with red blood cells from group A, the mixture stayed nice
7:50and liquid, and the same for group B.
7:53But if he mixed plasma from group A
7:55with red blood cells from B,
7:57or vice versa, the mixture clumped up.
8:00He noticed something even weirder about group C.
8:03Adding plasma from this group to either
8:05of the others' red blood cells resulted in clumping,
8:08but C type red blood cells could be added
8:10to plasma from any group no problem.
8:13Now it's been more than a hundred years
8:14since those early experiments,
8:16but Landsteiner work is still the basis
8:18for the major blood types we use in medicine today,
8:21the ABO system.
8:23And today,
8:24we know why these different bloods
8:26don't always play nice together.
8:28Comes down to our immune system.
8:30Your immune system is constantly tasting bits of cells
8:33and debris looking for foreign invaders
8:35and other bad stuff that it should attack.
8:38These bits that it tastes are called antigens.
8:40Not all antigens come
8:42from outside of our body like viruses.
8:44Some we make ourselves,
8:46and your red blood cells are covered in them.
8:48Your specific flavor
8:49of blood antigens depends on which genes you inherit.
8:53Your immune system learns not
8:55to attack your own red blood cell antigens,
8:57but it means that it is ready to attack any
9:00that don't match.
9:01Today we know there are hundreds
9:03of different red blood cell antigens,
9:05but what this test is looking at
9:07are called the A and B antigens.
9:10This is the blood type that most people think of.
9:12Blood group A has A antigens on its red blood cells
9:16with anti-B antibodies in the plasma.
9:19Blood group B has B antigens
9:22with anti-A antibodies.
9:24You can mix A blood with A blood
9:25and B blood with B blood because the antibodies
9:28and antigens are never gonna clash blood.
9:30Group C has neither A
9:32or B antigens, which is why it was renamed O,
9:35after the German word for without.
9:38Landsteiner was able to put O red blood cells
9:40into any group's plasma,
9:42because without A or B antigens,
9:45they don't trigger an immune system alarm.
9:47And that's why O is the universal red blood cell donor.
9:52But, O plasma does have both anti-A
9:56and anti-B antibodies ready to attack,
9:59so you can't let it mix
10:00with other red blood cells from other groups.
10:03The opposite is true in AB blood.
10:06It has both antigens on the red blood cells,
10:09but that plasma won't attack either A or B blood cells.
10:13That's why the universal human plasma donor
10:16and the universal blood acceptor is AB.
10:20That's why when Steiner mixed plasma from one type
10:24with red blood cells from another, bad things happen.
10:28The immune cells swimming in the plasma recognize
10:30the antigens on the red blood cells.
10:32That clumping was the immune system going into battle mode.
10:36A person's combination of antigens
10:38and antibodies
10:39is what determines your blood type in the ABO system.
10:43(narrator sighs) I gotta prick my finger again.
10:48Ow.
10:50All right, now we just need a little bit of blood.
10:53Here we go.
10:58(upbeat music)
11:02This card contained antibodies against A antigens
11:05and B antigens on red blood cells.
11:08My blood didn't react to either,
11:10which means I don't have A or B antigens.
11:13In other words, I've got type O blood.
11:16But there's something else.
11:1840 years after this initial discovery,
11:20Landsteiner, and his colleagues
11:21found another way to categorize blood,
11:24by whether or not the red blood cells
11:26also carried a different
11:27antigen, called the rhesus factor.
11:29If your red blood cells have the RhD protein on them,
11:33your blood type is positive.
11:35If they don't have it, your blood type is negative.
11:38That's why if you're RH-negative,
11:39you can have a similar immune reaction to RH-positive blood.
11:44This test tells me
11:45that I do have the RHD protein on my blood,
11:48so I'm O-positive.
11:50These eight blood types are just ones we get from the ABO
11:54and RH systems,
11:56but there are more than 30 systems
11:58for categorizing human blood
12:00just depending on what doctors are looking for.
12:03And humans aren't the only animals with blood types.
12:06Dogs have more than a dozen of 'em, so do chickens.
12:09Horses have seven main ones,
12:11and many primates even share components
12:14of the ABO system with us.
12:16Huh, it's almost as if we share
12:18a common evolutionary ancestor.
12:21And there are some humans
12:22that have special super rare blood types.
12:25About 1 in 1 million people in Europe
12:27and 1 in 10,000 people in India
12:29have what's called the Bombay phenotype,
12:31a rare condition where they don't have any
12:33of the blood types in the ABO system.
12:36They live normal lives as long
12:38as they don't receive blood from someone
12:40who does have those antigens.
12:42RH-null lacks all of the antigens in the RH system.
12:46It's sometimes called golden blood,
12:48and it's so rare
12:49that it's likely more people win the Powerball jackpot
12:52each year than are born
12:53with this blood type.
12:55Like the Bombay phenotype,
12:56people with this kind of blood can only get transfusions
12:59from others who share their unique trait.
13:03Scientists still don't fully understand
13:05why blood types even exist.
13:07Many evolutionary biologists think
13:08that having these different blood types
13:10gave certain populations
13:11advantages in particular habitats
13:14or helped 'em survive certain threats.
13:16For example, type O people are more susceptible
13:18to plague, cholera, mumps,
13:21and tuberculosis, when people with type A
13:23are more susceptible to smallpox.
13:26As various groups of humans faced these
13:27and other challenges in the past,
13:29certain blood types
13:30could have provided a local survival advantage.
13:33And people with type A blood are more prone to blood clots.
13:36That's a health risk today,
13:38but imagine in times without hospitals
13:40and modern medical care,
13:41this could have been an advantage in childbirth
13:43or in response to injuries.
13:46Even today, some simpler animals like jellyfish
13:48and sponges survive without any blood.
13:52They have slow metabolisms
13:53and really high surface area, which means they can absorb
13:56and release important molecules
13:57and nutrients directly through their skin.
14:00Insects don't have blood either.
14:02They use a similar fluid called hemolymph
14:04that transfers gases
14:06through openings in their exoskeletons.
14:08Across the tree of life,
14:10we think that blood or something like it
14:12first showed up more than 500 million years ago.
14:15It's also likely that blood evolved many different times
14:19in different types of animals creating unique,
14:22and sometimes strange blood recipes along the way.
14:26The blood of some ice fishes is completely clear.
14:29Their cold ocean habitat has a ton of oxygen
14:31so they can survive without hemoglobin or red blood cells.
14:35The green blooded skink has lime colored life juice thanks
14:38to a pigment made
14:39when red blood cells break down; it's the same thing
14:42that makes your bruises turn green.
14:44And the blood of some marine worms
14:46and brachiopods carries a protein called hemerythrin.
14:50When it grabs onto oxygen, it turns purple.
14:52And you might owe your life to the literal blue bloods
14:56of the world: horseshoe crabs.
14:59These ancient animals use a different blood protein,
15:02hemocyanin, to bind into oxygen,
15:04and it gets its blue hue from using copper instead of iron.
15:08Horseshoe crab blood also has a superpower:
15:11it holds a chemical that can detect bacteria
15:14and certain toxins at super low concentrations.
15:18It's used to make sure that drugs and vaccines,
15:19and medical devices are safe for humans.
15:23Despite how much we've learned about blood
15:25in the past few centuries, it still holds many secrets.
15:29That's why humans have never been able to accomplish
15:31what many scientists view as the Holy Grail
15:34of biomedical research, creating synthetic blood.
15:38Because, like everything in our bodies,
15:40blood is more than just the parts that make it.
15:42It's a flowing universe of cells
15:44and molecules that interact
15:46with each other in these really complicated ways
15:48that we're still figuring out.
15:50So, the next time you see a drop of blood,
15:54don't get the ick.
15:55Remember that there's a universe of complexity inside,
15:59one that fuels us, defends us, heals us,
16:02and connects every corner of our bodies in ways
16:06that we rarely appreciate.
16:08Stay curious.
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17:28Not messing around this time.
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