Our bodies are weird, and sometimes, you can end up with a bit more of you to love.

And no, I’m not talking about  love handles or a dad bod. Some people are born with extra tissues or organs, and others can even randomly  develop them as they age.

These bonus bits can be silent stowaways, your ticket to super powers, or wildly problematic and have to go, pronto. But the weird thing is that when they’re removed, they aren’t always tossed into the biohazard bin. So let’s find out what these extra pieces do, when they’re super powered versus super trouble, and who’s chomping at the bit to get them. [♪INTRO] Our first bonus organ is more  common than you’d think, because around 25% of you might have this  extra organ and not even know it.

The spleen is part cleanup crew  for your blood and part daycare for baby white blood cells, which play  a big role in your immune system. In addition to that, you can also have up to six extra pieces of splenic  tissue, called accessory spleens, which have a separate blood supply from your regular spleen but do all the same things. That’s true for 10 to 30% of the population.

Pretty much as common as blue eyes. Now, usually the extra spleens are not a problem and you’re just getting some free labor. But there are some conditions  where your spleen is doing too much and causing problems, even  if you only have one spleen.

People with some types of hemolytic  anemia need all the red blood cells they can spare, even ones  that a spleen might normally remove. And with sickle cell anemia, sometimes having a spleen  does more harm than good, since your abnormally shaped  red blood cells can clog it up. In either case, you may end up without enough red blood cells to bring oxygen to your tissues, which can cause fatigue,  pain, or even heart problems.

In these cases, you might be better off without any spleens, called a splenectomy. For those of us blessed with extra spleen, surgeons have to remove all of those as well, because once the main spleen is gone, accessory spleens can decide  that the show must go on, and start doing all the things  the main spleen used to do. Also because it’s so full of immune cells, spleen donations to others are pretty challenging, usually only done as a last  resort multi-organ transplant.

So most removed spleens are  destined for the biohazard bin. But there are scenarios where  accessory spleens can truly be heroes. If your main spleen gets evicted due to damage and not one of the diseases we mentioned, the accessory spleen can act like  a donor that’s already in you, growing from its usual  centimeter or two to the size of a regular ole spleen, and  taking over the full workload.

Definitely a super power to have accessory spleens when that happens. Other times, you might not be born with the extra, but trauma to the main  spleen will cause splenosis, where bits of the spleen go flying  off and hide away in the abdomen. Doctors will still perform a  splenectomy to remove the damaged organ, but might not be able to remove those extra bits, which then grow and do all the spleen things, just like the accessory spleen.

So an accessory spleen or two can be a good thing, especially if your regular one is retiring early. And our next bonus body part is  another example of how sometimes, more really can be better! If you have hereditary hemochromatosis,  the excess isn’t served upfront, but you are born with  the mutation that gets you there.

As you grow up and eat things with  iron in them, like meat, eggs, or green veggies, most of our bodies can take what we need and not absorb the extra. But people with hemochromatosis can’t do that, so their blood ends up with  boatloads of extra iron. And when it comes to iron, they can definitely have too much of a good thing.

Their bodies will stuff that extra iron into organs where it doesn’t belong, which causes problems like  liver disease or diabetes. When there’s plenty of iron to  go around, sometimes your body makes use of it by ramping up  hemoglobin production, so you can end up with more red blood cells than  your body knows what to do with. To prevent that extra iron, people  with hemochromatosis usually get therapeutic phlebotomy, which  helps remove the excess iron.

And there’s an upside to making  some extra iron-rich blood. If someone with hemochromatosis  meets all the normal donor requirements, then that removed  blood can be transfused into others. Plus, all that hemoglobin sort  of makes you anemia-proof, so the FDA allows hemochromatosis patients to donate even more frequently than usual.

So hemochromatosis might not be good for you, but it can earn you the super  hero title for helping others, which is at least something. Unfortunately, not all extra blood is helpful. Polycythemia vera is another  issue where you create too many red blood cells, which can cause itching, fatigue, dizziness, and nosebleeds.

And while that sounds like  you’d be able to single handedly be able to reverse the global blood shortage, the Red Cross isn’t interested  in those bonus red blood cells. That’s because it’s technically, uhh, cancer? Specifically, it’s a cancer in your bone marrow causing all that red cell proliferation.

So polycythemia vera patients also need therapeutic phlebotomy to ease their symptoms, but unlike with hemochromatosis, the blood can’t be donated to others. Unfortunately with this condition,  the best thing this extra part of you is good for is getting  on a first name basis with your local phlebotomists, since  there is not a permanent cure. But everyone has blood.

Not  everyone has our next bonus bit. And before we get into it,  all science needs funding, including ours. So here’s a quick ad break.

Thanks to our Presidents of  Science for allowing us to make longer videos about science  stories with more twists and turns. Charlie Stanley, McLaren  Stanley, and TJ Steyn help make that possible through  their support on patreon. It takes more time to research, write, edit, and fact check longer scripts.

Then it takes longer to film the whole thing, edit the video, add animations,  and make it sound great. That’s a lot more human work hours that go into our videos these days. And it’s worth it to tell complex stories.

After all, that’s kind of our  bread and butter at Complexly. But it also costs more money. And our Presidents of Science  help us pay everybody for that extra work.

To join them,  go to patreon.com/SciShow. You might wanna buckle up for this next one. There’s a kind of ovarian  cyst called a cystic teratoma, which contains, alongside the  other normal cyst-y stuff, hair… and teeth.

These cysts can cause pelvic and abdominal pain, bleeding, swelling, and of  course, endless nightmares. Plus they can mess with your lab  results, develop into cancer, and can even come back after they are removed. And while these are just some  of the reasons to remove the unwanted cystic guest ASAP,  a 2021 paper says these nightmare pockets may have a  use case after all: teaching.

See, cystic teratomas don’t  just appear out of thin air. They’re germ cell tumors, which  means they start as stem cells and have lots of potential  to turn into other stuff. Hence the hair.

And the teeth. They can turn into pretty much  anything except sperm or eggs. So these little nightmares are  an in-vivo way to study things like tissue communication and engineering, disease modeling, and other stem cell topics.

A lot of that research is done  using animal models and grafts, rather than bits excised from people. But if you are having a  troublesome teratoma removed, you can always talk to your  care team about donating it for research or educational purposes. Because what self-respecting  scientist or med student doesn’t want to get up close and personal with a cyst that has hair and teeth in it?

So there is at least a little silver lining to these nightmare cysts, after all. Pretty much everyone has an extra  of this next organ. Technically.

Most people are born with  two kidneys, so you already have a spare built in, which  is good since they play an important role in removing waste  from your body through urine. But sometimes you might be born with more than just two vanilla kidneys. This can be a totally independent third kidney, which usually has some wonky  anatomy, but that’s fairly rare.

Those are true accessory or supernumerary kidneys, and only around 100 cases have been documented. They’re also bad news, and lead  to urinary issues, torsions, back pain, infections, and  requiring surgical intervention. Definitely not suitable for donation.

Less rare is extra kidney tissue or blood vessels glomped onto one of the normal kidneys. Rather than an entire extra kidney,  it’s more like a kidney plus. And while kidney-plus can cause or worsen problems like hypertension, it’s usually asymptomatic.

If it is discovered, it’s probably because you had imaging done or signed up to donate a kidney. And in those cases if the extra blood  flow is noticed prior to removal, surgeons will usually opt to give  away your other, less juicy kidney. If it’s noticed after removal,  then case studies have reported that the extra bit can just be carefully carved off before being  transplanted into a recipient.

So peaceful coexistence is possible  with supernumerary kidney parts, and they won’t disqualify you  from donating if you want to. Just beware of the dreaded third kidney! All of these other bonus parts  have been pretty hard to find.

But with this next one, all you  have to do is open up and say ahh! Up to 3% of adults have more  than the usual 32 teeth, earning a diagnosis of hyperdontia. If that’s you, you can get them  extracted, especially if they are causing issues like crowding or  they make it hard to brush or floss.

But that tooth won’t be transplanted to others, because we already have really  good fake teeth to use instead. What is a thing is tooth auto transplants, where you donate one of those  extra teeth to yourself. Like, say, if you are 30 years old and riding around on Heelys and you lose a front tooth.

If you have a suitable backup then your dentist can move the bonus tooth forward. Or maybe a regular tooth  is misaligned or malformed. A supernumerary tooth can be a good fill-in.

But if they aren’t cramping your style, you can always just keep them in. Or if you really want them  out, local dental schools or freaky tooth dolls are also good options. Compared to removing this next one though, tooth surgery is a piece of cake.

And now we’ve reached our final bonus organ. Uterus didelphys is when  you’re born with two uteruses, and it’s a very rare occurrence. Usually it goes undetected until puberty, when it can cause your first period to come along with a lot of blood.

They can sometimes go undetected  until you try to get pregnant, since having two uteruses is  associated with some fertility issues. At which point your doctor does a scan and then starts to wonder  if they’re seeing double. This don’t always cause these kinds  of problems, but if it happens, then surgery is an option, it’s  usually pretty tricky though.

Two uteruses means two cervixes, and usually some variation of two vaginas too. And since this condition is so rare, that can be pretty intimidating for  a surgeon who’s trying to remove and merge the right bits to leave  you with what you do want to keep. But it can be done, and if that  uterus is coming out anyway, who's to say it can’t go to someone who needs it?

Uterine transplants in humans started in year 2000 and are still super new. By  2017, only 25 had been performed. Right now, if you only have one uterus and still consider it extra,  then you can donate it.

But likely thanks to the rarity of  uterine transplants to begin with, combined with the difficulty of  surgery involving uterus didelphys, a didelphic uterus has never been transplanted. And that might be for good reason. Didelphic uteri can be smaller, look misshapen, and are associated with things  like preterm labor and miscarriage, so a lot of doctors don’t think  it would be safe or ethical to transplant when most recipients  are trying to carry a pregnancy.

That doesn’t mean it can’t be  done, especially if the uterus was anatomically normal and didn’t  show any fertility problems, but it’s definitely off the table while  safer donor options are available. And if you don’t opt for removal,  the other unique thing you might do with two uteruses is simultaneously  have a baby in each one, something called “dicavitary twins”. That might be the rare occasion  where having a second uterus might feel like a super power  rather than a curse.

Maybe. Some extra bits are definitely  safer for you or more donatable than others, but  whether valued or dreaded, learning about them can help  you know what to expect. It’s not always a bad thing to be  a mutant with extra body parts.

Although, if I had to pick, I’d probably opt not to have the terrifying tooth-and-hair tumor. Personally. [♪OUTRO]