50 Interesting Facts About The Human Body You Should Have Learned In Biology Class

human body facts

The human body is a perfectly constructed machine. Every ounce of our being serves a purpose, working in complete unison with every other body part to make sure we’re operating effectively.

And even after all of those text books your human body took during biology class, there’s still room for more.

A Reddit thread asked the Internet to share some facts about the human body that not many people knew and the responses were pretty wild.

From your body adapting to extreme climates to eyes, ears, muscles, feet, your brain, and every body part in between, here are some interesting facts about the human body that just might have you appreciating yourself in the mirror a tad longer today.




2. “When doing surgery where the doctors have to take out some organs, when placing them back, they don’t have to be put back In the exact position there meant to be, your body kind of just, moves the organs into the correct position after the surgery.”


3. “People who live in “extreme” conditions for generations adapt in extreme ways. For example people that live in high elevations often have larger lungs and different blood makeup. Or my favorite is the Bajau people that live on the water and spend a lot of their time diving, their spleens have become 50% larger in order to store more blood.”


4. “You hate the sound of your recorded voice because it’s missing the low frequency you’re used to hearing.
When you talk, you hear your voice as it goes to the air and back to your ear. It also goes through your skull to your ear, and this bone conduction mechanism transmits the low frequencies better than air does.

Your recorded voice only has the air transmitted sound. That causes the dissonance between what you think your voice sounds like, and what it really does. It’s also why your voice will (almost) always be higher pitch than you think.”


5. “Humans have, on average, just as many hairs on their body as chimpanzees, human hair is just a lot shorter and finer.”


human body


6. “Your eyes have a separate immune system from the rest of your body and in a lot of occasions if your body’s immune system finds your eyes, they will assume they are a foreign body and blind you.”


7. “Humans are bioluminescent and glow in the dark, but the light that we emit is 1,000 times weaker than our human eyes are able to pick up.”


8. “When you cry and your nose becomes runny, it’s actually your tears.”


9. “The reason it’s so easy to break your collar bone is because it’s designed to break.

The way it was explained to me is that it’s like a circuit breaker. It breaks there to stop the shock of impact from getting to your spine.”





11. “Alzheimer’s disease isn’t just gradual loss of memory. It physically exists in the brain. It’s a physical substance that attacks the brain. Like, if you were able to open the skull of a person suffering from Alzheimer’s disease to take a look at their brain, you would actually see this sticky, fibrous, grey physical matter overtaking their brain.”


12. “You can grow a new human being faster than most missing toenails can grow back.”


13. “You will sooner die from lack of sleep than lack of food.

You can live, depending on your current body fat and health level, for months without food. Estimates are you that you will die for lack of sleep within 2 weeks.”



14. “The surface area of the lungs is about the same size as a tennis court.”


15. “X-rays of childrens mouths are nightmare fuel. The second set of teeth to replace baby teeth are already grown and lodged in their skulls. So you’ll see two rows of teeth and its freaky looking. They don’t grow in when the old ones fall out, they are already loaded in the chamber waiting to get launched.”


16. “The appendix is not a vestigial organ. It actually protects good bacteria in the gut. You can live without it, but it’s not just chillin’ in there.”


17. “Every minute you shed over 30,000 dead skin cells off your body.”


18. “39% of people have an extra bone in their knee. 100 years ago only 11% of people had this bone.”


19. “In children under 11 (for some reason), cutting off the fingertip from the last knuckle will result in complete regeneration of the finger in 100% of cases, assuming the naibed is intact. There’s no explanation for why this happens, why it only happens to children under 11 and why it can’t sequence to fully regenerate/grow organs. It also occurs in many animals, as observed in test rodents.

I learned that in science class in grade 8 and my dad called me a liar. I showed him my science textbook and he threw it away and said it was fake.”



human body facts


21. “Scars are not made of “permanent” tissue (they’re held together by collagen) and are in a constant state of repair. This repair is facilitated by vitamin C (amongst other things). Yes, this means that people with scurvy (from vitamin C deficiency) will see all their old scars reopen into fresh wounds.”


22. “Humans have stripes, we just normally can’t see them. They’re called Blaschko’s lines and form along the paths of embryonic cell migration. The stripes are sort of U-shaped down our front, V-shaped on our back, wavy on the head and face and we have basic, simple stripes on our extremities.”


23. “Your body must warm fluids before absorbing them, so drinking ice cold water to hydrate is only burning more energy, and you’re not hydrating as quickly.”


24. “If you carry a lot of unprocessed trauma, it can cause psychosomatic autoimmune diseases.”


25. “The proportion of your vision that is actually in sharp focus roughly equates to the size of your thumbnail at arm’s length. The rest of it is just your visual cortex filling in the blanks.”



26. “If you say haaah your breath comes out warm,but when you say Woooh it comes out cold.”


27. “You can poop out of your mouth if your intestines get backed up enough. It’s like vomit, doesn’t look like actual poop per se, but it’s still disgusting.”


28. “The reason it feels weird when you or someone touches the inside of your belly button is because the nerves actually go to your spinal cord. These nerves lie at the same level that relay signals to your urethra and bladder. So when you feel like you have to pee when you touch the inside of your belly button, that’s why.”


29. “Human eggs are small but big enough to be visible to the human eye.”





31. “30% of body waste is excreted via skin.”


32. “You can live “normally” with half your brain. In some severe drug resistant epileptic syndrome in young kids, the only option to stop the seizures is to remove a complete brain hemisphere.

After a while, with proper reeducation and all, the children can go on to have a normal life without cognitive deficit. They will have a limping, blindness from one eye and a very weak arm but can lead a normal life and not end up cognitively impaired.

One of the earliest sign of Alzheimer’s disease, before the memory loss, could be the loss of the sense of smell. It’s also the case with Parkinson’s disease.

Our brain looks wrinkled because it is actually “folded” inside our skull in order to fit a maximum of surface and thus neurons & cell communications. Some animals like rodents have a completely smooth brain.”


33. “The average adult has 22 square feet of skin. Perfect size for a nice rug.”


34. “Jaw muscles are the strongest in the human body.”



35. “If you faint at the sight of your own blood you may have an oversensitive vasovagal response. The theory is that this developed as a survival mechanism, kind of like an opossum playing dead.”


36. “When you have a bowel movement, your heart rhythm shifts temporarily due to a vagus response. The reason Elvis died on the toilet was because his heart was beating 200+ bpm and the quick rhythm change caused a myocardial infarction. People with low heart rates have been known to pass out on the toilet because their bodies can’t handle the shift.

It’s also why EMTs will absolutely not let you use the bathroom before getting on the ambulance. Especially if the bathroom is a standard 5’x8′.”


37. “Each one of your eyes has a blind spot where the optic nerve exit your eye into your brain. You can’t see it because your brain tricks you not to see, it covers the spot with some made up image of what it thinks fits better with the rest of it.”


38. “Babies can break their collarbone during delivery. It happens quite often, but heals quickly. My teacher told me that (if it happened to you ofc) you may feel a slightly higher spot on your collarbone, called the callus where the fracture grew back together.”

– u/jaelIlii/Reddit

39. “Your brain likes stimulation, if it doesn’t get any it will make some up, some people are more susceptible to it than others, the colors you see before you fall asleep are a common mild occurrence, there are several classes of these hallucinations, closed-eye visuals, which are caused by leaving your eyes closed for a long time, hypnagogia, which is caused by the onset of sleep, prisoners cinema, which is caused by looking into a dark place for a long time, ganzfeld effect, which is caused by blocking out all external stimuli, and Charles Bonnet syndrome, caused by sight loss.

Most are these are simple phosphenes but some can be whole imagined scenes, or more abstract fractal-like imagery.”




41. “Babies don’t get knee caps until 2-6 years old.”


42. “Apparently not everyone knows that women grow a new organ while pregnant.

In addition to growing a child, they grow the placenta.”


43. “When you get conditioned to physical activity, your circulatory system adapts — more blood, more vessels, more blood cells. But your lungs really don’t. This is because no matter how much blood your heart is able to deliver to your lungs, the lungs still have no problem oxygenating it. This is why your oxygen saturation doesn’t drop during exercise (unless you have a heart defect.)”


44. “Most reflexes never make it to your brain. The sensory aspect travels to the spinal cord and the spinal cord itself sends the muscle movement signals to your limbs.”


45. “There are tiny cilia that spin in a certain direction. If they spin in the opposite direction while you’re developing in the womb early on, that is how you get organs transposed onto the opposite side of your body.”


46. “In theory, humans could breathe a liquid if it was super saturated with oxygen. It wouldn’t be easy because the density of liquid being so much higher than air so after 15 mins or so you would be too fatigued to continue breathing.

The hardest part is getting all the liquid out of the lungs so the person doesn’t get pneumonia.”


47. “Apparently about 20% of people have a bony ridge on the roof of their mouth. Most people’s pallettes are smooth with a very slight ridge.

The 20% like me have an exaggerated and more pronounced ridge. Apparently it’s most common in women and Asian folk, and I’m neither so that’s neat. I always thought it was totally normal.


48. “You can calm yourself down by splashing cold water on your face to trigger the mammalian diving reflex.”


49. “The hyoid bone is a bone not attached to any other bones in the human body and is only considered the anchor of the tongue.”