Even if you think you learned everything that you needed to know way back in biology class, everyone has knowledge gaps. And often you’re not even aware that they exist. There are tons of things we don’t know—or incorrectly assume we know—about how the human body works.
To shed some light on this topic, internet users shared some of the creepiest and coolest facts about the human body in an intriguing AskReddit thread. We collected the most interesting, spine-tingling ones to share with you, and you’ll find them below. Scroll down to learn something new that might just change how you see the world… and yourself.
#1
The reason bleach feels “slippery” if it gets on your hand is because of saponification, it’s breaking down the fat in your skin and making it into soap. Always wear gloves when handling bleach. .
© Photo: nagisu
#2
When you tilt your head to the side, your eyeballs rotate so that the "top" stays oriented.
Want to be freaked out? Go look in a mirror and watch some stationary part of your eye, like a blood vessel. Then tilt your head and see your eyeball turn like a steering wheel.
© Photo: Preschool_girl
#3
Male and female genitals are made up of the same embryological components, just arranged differently, and with some bits growing bigger depending on hormone exposure.
One of the coolest biology-related things we’ve learned in recent years is that your brain gets ‘washed’ to flush out waste while you sleep. In a nutshell, based on research conducted by scientists at the Washington University School of Medicine in St. Louis, nerve cells coordinate to produce rhythmic waves, which then propel fluid through dense brain tissue, washing it.
“These neurons are miniature pumps. Synchronized neural activity powers fluid flow and removal of debris from the brain,” says the study’s first author, Li-Feng Jiang-Xie, PhD.
“If we can build on this process, there is the possibility of delaying or even preventing neurological diseases, including Alzheimer’s and Parkinson’s disease, in which excess waste—such as metabolic waste and junk proteins—accumulate in the brain and lead to neurodegeneration.”
#4
About 5% of our brain activity is conscious, and 95% unconscious.
That's not the creepy part.
The creepy part is that studies have shown the unconscious part of our brain making a decision up to several seconds before the conscious part thinks it's made a choice, and then retroactively justifying "why" with our conscious thoughts about it.
#5
Some may find it creepy i guess; maybe more... disturbing. Tinnitus can often be neurological rather than from physical damage, meaning you can be completely deaf and still have the ringing/buzzing in your ears. As someone who has Tinnitus, I've learned to filter it in day to day life, but it's hard to impossible below a certain level of ambient noise. Id quickly go mad if it was the only sound I could actually hear....
© Photo: theBaron01
#6
Your spinal cord is the same consistency as a banana.
© Photo: Shellona27
Meanwhile, the senior author on the paper, Jonathan Kipnis, PhD, stresses that it is “critical” for the brain to dispose of metabolic waste build-up.
“We knew that sleep is a time when the brain initiates a cleaning process to flush out waste and toxins it accumulates during wakefulness. But we didn’t know how that happens. These findings might be able to point us toward strategies and potential therapies to speed up the removal of damaging waste and to remove it before it can lead to dire consequences,” Kipnis said.
#7
It's a classic but humans are born with their baby teeth and their adult teeth, the adult teeth just hang on behind the baby teeth until their time comes, which means that a toddler's face is like 50% teeth and the skull images you can find on google are very unsettling.
#8
When you sleep your brain gets power washed with spinal fluid!
© Photo: Lumpy_Helicopter_758
#9
Everything in your house is completely covered by dead skin and is being eaten by something as we speak.
You also sleep in it :)
Sweet dreams.
What do you think, Pandas? Which of these facts impressed you the most? Which ones did you find the creepiest and why? Were there any that you already knew? What’s the most bizarre and impressive biology fact you know that wasn’t mentioned here?
Share your thoughts with all the other readers (and us!) in the comments at the bottom of this post.
#10
Babies grow and shed hair in the amniotic sac, which by the end of pregnancy is filled with.. old hair.
© Photo: alsotheabyss
#11
Finding out old scars reopen with scurvy haunts me.
© Photo: Any_Phrase_8121
#12
It takes up to a year for all the organs to go back in the right place after being pregnant. Also, during a c-section, they kind of just mush everything back inside and it all eventually goes back to where its suppose to on its own!
© Photo: yourremedy94
#13
When you're in a plane at cruising altitude and lose cabin pressure, you have about 15 seconds of useful consciousness before hypoxia sets in. That's why they tell you to put your own oxygen mask on first - you'd pass out trying to help others.
I'm a pilot and this fact still gives me chills.
#14
Pretty much all the different fluids your body can leak. My wife got a poorly placed epidural (2 natural births and finally caved on #3 and it got messed up and was awful) and was leaking spinal fluid. Read a story about a guy who had a runny nose, but it was brain fluid! So now I feel like I'm an old truck and I'm just going to start waking up with random leaks under me :D.
© Photo: MaDrAv
#15
Not too happy with the fact that there’s a bunch of hollow tunnels filled with mucus exactly just right behind my face.
© Photo: Aromatic-Side6120
#16
The feeling in your stomach when you go down on a roller coaster is your organs lagging behind your body.
© Photo: Moo-Mungus
#17
Your brain can’t actually feel pain.That’s why surgeons can perform brain surgery on awake patients. You can feel pain in your skin, skull, and meninges but the organ that interprets pain itself feels none. It’s unsettling to realize the thing that screams “OUCH” can’t experience it at all.
#18
Your internal organs itch; your brain chooses to ignore the sensation!
#19
When were in an unfamiliar environment, we sleep with half our brain at a time kinda like sharks and that's why we wake up easier.
#20
Some women can actually feel pain when they ovulate. It’s called mittelschmerz, a German word that means “pain in the middle.
#21
When having an operation doctors move your organs around to get to where they need to go. Once they are finished they dont put them back. They return back all on there own. Same with being pregnant. If you have a baby in there it moves your organs out of the way to make room. Once you give birth they start to realign back into place on there own. Like they remembered where they were.
#22
Some people are walking around with 3 or more kidneys because when you get a transplant, unless medically necessary, they leave the old ones in there.
© Photo: daemonhat
#23
If you’ve ever worked in an OR, the smell of cauterization is similar to cooking steak/pork. We’re all literally walking meat sacks made of electrical signals.
© Photo: WowzerzzWow
#24
There are tiny mites that live in your eyelashes all the time.
#25
You can be internally decapitated. The neck breaks and your head literally is only connected by soft tissue.
#26
Your body produces cancer cells all the time.
#27
The ovaries aren’t physically connected to the fallopian tubes. The eggs shoot out into the fallopian tubes. This also means that certain other things (👀) that may go into the fallopian tubes ultimately just swim out the ends and end up floating around in the abdominal cavity.
#28
Young children can fully regenerate the the tip of a finger if it is severed or amputated.
Apparently the younger they are, the more active stem cells the have to promote this process which we adults lack.
© Photo: MysteriousWon
#29
There's a fun little thing called Prions, which are a incorrectly folded protein. It has given us some fun diseases, like the Mad Cow Disease, Zombie Deer Disease, Kuru, and FFI (Fatal Familiar Insomnia). While these diseases are either genetic or spread by eating tainted meat, FFI has a fun little cousin called SFI, or Sudden Fatal Insomnia.
While extremely rare (only 3-5 known cases world wide, AFAIK), it can happen to anyone. Suddenly, in your late 30's, you start to lose the ability to sleep. Sleeping pills and such work in the beginning, but over time they no longer do the trick. Once you can no longer sleep (which can take anything from a few months to a few years), you only have a few weeks to live before your body breaks down.
#30
Evolution hasnt fully ironed out the whole walking upright thing. Its literally bad for your hips and back.
#31
Brain matter smell is hella gross. Source: I'm a paramedic.
#32
I work in an emergency room. The sheer amount of patients that come in with literal maggot infestations is, well, disturbing.
#33
Your intestines and other organs are always squirming and moving around but your brain ignores it.
#34
Probably posted already but there are a few people born with all organ asymmetries on the opposite side (pancreas, liver, aorta position, etc.). This isn’t creepy until you try to diagnose appendicitis .
#35
That when you twist your wrist, your forearm bones overlap. It's biomechanically normal, but it's kinda gross to see in simulation.
#36
Unborn babies can cry inside your womb if you are pregnant.
#37
I have three:)
1.Ribs can regrow. It’s a problem they have to watch for if ribs are being removed for medical reasons. The tiny bud left behind on the rib cage starts a new bone.
2.Humans typically have one spleen, located in the upper left abdomen, but it's relatively common (around 10-20% of people) to have extra, smaller spleens (accessory spleens or splenunculi) due to developmental variations or the body's natural ability to regenerate spleen tissue after injury, a process called splenosis. I’ve read cases of people having six. Unless you have surgery near them, they rarely cause issues and you are unlikely to ever know they are there.
3.Children under a certain age do not have knee caps.
#38
Look at anything around you. Your tongue knows what it would feel like to lick it.
#39
When you gain body fat, as much grows internally as externally.
#40
When a bone saw cuts into a preserved human skull it smells frighteningly similar to cool ranch Doritos.
Yes, I still eat cool ranch Doritos.
#41
Human bones stay wet for a very long time when left to dry naturally. (I worked in an osteology lab in college).
#42
That you can live without basically half of your organs. By that I mean 1 kidney, half a spleen, 1 lung, etcetera. Not going to be a great life but you can live.
#43
Bones aren’t naturally white. They can be cream, yellow, brown, red, or even black depending on minerals, medical conditions, or environment. There’s a real case where a woman’s bones were black, and it was only discovered after an accident during surgery. Most people never know their bone color unless bones are exposed. So you can have black bones for all you know 🤷♀️.
#44
After the placenta is delivered you have a dinner-plate sized wound in your uterus.
#45
Your BRAIN is what makes your skin prune in water, your skin does NOT do it automatically.
© Photo: oonastellaluna
#46
Your skeleton isn't inside of you. You are inside your skeleton, since your brain is inside of your skull.
#47
The “baby smell” that young babies have generally fades around two years of age. Coincidentally this is also around the time that babies skull finishes fusing together to get rid of the soft spot, leaving scientist to believe that what you’re actually smelling is baby’s brain.
#48
Human cheekbones evolved to be thicker to withstand punches to the face better.
#49
Your stomach is full of warm vomit.
You can thank another reditor from last week traumatizing me with that one...
#50
That if the chemicals expressed by the pancreas are blocked from the digestive tract (by gall stones) those chemicals just eat the pancreas itself.
#51
We almost all have eyelash mites that are a type of arachnid. Spiders live in your eyes.
#52
Well its not really about a living human body, but like literally a body.
Apparently a decomposing human body emits a "sweet scent", the type of overwhelmingly sweet scent that makes you instantly nauseous, even tjose that have often smelled it get nauseous by it, many thta smell it for the first time often throw up.
Thing like eating way too much sugand and getting a stomach ache, but then all that sugar is a scent in the standing air.
#53
I'm always amused that the colour purple doesn't exist, our brains invented it.
Purple is not violet as purple is a mixture of red and blue where as violet has a definite range of wavelengths.
When our brains see blue and red, which are at opposite ends of the spectrum, it sort of joins these opposite ends together and invents what we see as purple.
#54
Galen (c.129–c.216 CE) would dissect piglets live , and their screams bothered him . He found that by running his knife along both sides of the wind pipe he could sever a nerve that made the screams stop. I mean the pigs were still screaming , but their vocal cords made no noise .
And that's how we learned about the recurrent laryngeal nerve and its function.
#55
Our bodies replaces most of its cells over time, yet our fears nd trauma can stay unchanged.
#56
Your bladder is connected to your bellybutton. There's a condition that can cause your bellybutton to "open" and leak pee.
#57
The fact your eyes are invisible to your brain and if they ever found out they existed they’d destroy them!! Can happen if you get a strong enough eye infection and you can say goodbye to your sight forever!! 😳.
#58
Every time you smell someone else's fart, you are literally inhaling bits of their fecal matter.
