25 Extremely Interesting Facts About The Human Body That They Definitely Did Not Teach You In Health Class

25 Extremely Interesting Facts About The Human Body That They Definitely Did Not Teach You In Health Class

Julia Corrigan

Thu, December 18, 2025 at 2:16 PM UTC

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Recently, I came across two posts on the popular Ask Reddit page that turned out to be intriguing, weird, and, honestly, pretty informative. In it, users Mindless_Reality_14 and alwaysclimbing5 asked, what are some lesser-known facts about the human body that would surprise the average person? And I thought that if I didn't know all these, surely many other people didn't, either! So, I decided to share. Here are some of the most interesting and best answers:

Person in a stylish swimsuit, showing part of their back and side, promoting body positivity and self-acceptance — Tatiana Maksimova / Getty Images

1. "Humans can be divided by how their body reacts to exercise. Your gut either moves (pooping from exercise) or shuts down, and your stomach refuses to empty, and exertion can make you throw up."

Hands are placed on a hoodie pocket, fingers spread slightly, conveying a casual and relaxed pose — Andrii Medvediuk / Getty Images

—u/vrosej10

2. "The bone that supports your eyeball, called the orbital floor, is paper-thin and has a large empty cavity, called the maxillary sinus, on the opposite side. When you get hit hard in the eye, instead of your eyeball itself rupturing, the bone underneath your eye breaks, which is called an orbital floor fracture. This releases the pressure from the impact and saves your eyeball. If you crush a beachball against a concrete wall, you can pop it, but if you try to crush it against a styrofoam wall, the wall breaks, but the beachball is fine. An amazing evolutionary adaptation to protect your eyesight."

A person with a shaved head wearing a checked shirt stands in front of a blue background, surrounded by various eye collages — Klaus Vedfelt / Getty Images

—u/ddsmd

3. "The reason the navel and the area around it is an erogenous zone is because [they share] nerve pathways with the genitals."

Close-up of a person's torso with water droplets on their skin. Hands gently rest on their waist, wearing a plain undergarment — Bymuratdeniz / Getty Images

—u/SabrinaDelgado

4. "The diver reflex. When your face is submerged in chilled water and you hold your breath it causes your heart rate to lower and blood supply to be increased to vital organs such as the heart and brain. This is useful to help increase the amount of time you can hold your breath, but is also useful in helping to manage PSVT (paroxysmal super ventricular tachycardia) which is characterized by occasional bouts of high heart rate."

Person snorkeling above a vibrant coral reef, visible under clear water with light streaming through — Ippei Naoi / Getty Images

—u/UCantHearAnEnzyme

5. "Your brain is basically the main 'sex organ.' Stress, lack of sleep, anxiety, [and] feeling unsafe or judged can tank arousal way faster than anything physically 'wrong' with you, which is why feeling relaxed and emotionally okay makes such a huge difference."

An MRI scan of a human brain, showing detailed cross-sectional imagery — Paul Biris / Getty Images

—u/RipBackground204

6. "Fallopian tubes aren't attached to the ovaries; they have little tendrils at the end and can kind of flop around towards the ovary that's releasing an egg."

Illustration of a human uterus with ovaries and fallopian tubes, highlighting anatomy for educational purposes — Mohammed Haneefa Nizamudeen / Getty Images

"I had my tubes removed two years ago and asked my doctor what would happen during ovulation; apparently, my eggs are just kind of shot into my abdominal cavity and eventually reabsorbed by my body."

—u/annekecaramin

7. "Natural redheads require increased doses of anesthesia, due to some connection with the mutated melanocortin-1 receptor. I’m a natural redhead myself, and developed a fear of dentists because I’d always feel what they were doing! Eventually, I had an issue that couldn’t be ignored, and I had to find a new dentist. At my first visit, he took one look at me and said, 'You’re a real redhead, huh?' 'Yup.' '(Hygienist), get me 4x the novocaine!' I knew I’d found my man, and he’s been treating me ever since... also shed my fears, since dental work is much less unpleasant when you’re actually numb before they start."

Person with short hair gazing thoughtfully at the camera, head resting on folded arms, creating a serene and introspective atmosphere — Guido Mieth / Getty Images

—u/LollyHutzenKlutz

8. "Message from your middle-aged Auntie: In perimenopause and menopause, women produce less hormones like estrogen/estradiol and testosterone. This can cause the labia minora to fuse with the labia majora and is considered vaginal atrophy. This can lead to increased UTIs or PH imbalances that can cause 'yeast' infections."

A surprised woman with blonde hair and blue anchor earrings looks forward — Warner Bros.

"It also causes the mucus tissues throughout the body to shrink and dry out. This can lead to vaginal dryness/irritation/itching, fine lines on the skin, and bad breath, surprisingly. A lack of testosterone can also cause the clitoris to recede, and in some women, completely disappear.

As many as 70-80% of menopausal women will have vaginal atrophy. This can ALL be prevented or reversed with proper hormone management and replacement. It’s best to start at the earliest signs of perimenopause, but vaginal tissues can be rejuvenated with proper hormone management even after menopause."

—u/mariahmce

9. "You know the smell of rain, or disturbed soil? It's a compound produced by bacteria called Geosmin, and the human nose is extremely sensitive to it. We can smell it at as low a concentration as 5 parts per trillion."

Child in red boots splashes energetically in a muddy puddle outdoors, creating a fun, carefree moment — Catherine Falls Commercial / Getty Images

—u/nonions

10. "Testicles move on autopilot. The cremaster muscle constantly adjusts their height like a built-in thermostat — rising when you're cold, stressed, or about to sneeze (yes, that last one is real)."

A person holding two eggs in their hand, with denim jeans visible in the background — Intek1 / Getty Images

—u/saadaintsalad

11. "You mostly breathe out of one nostril at a time, and the ‘dominant’ nostril switches every hour or so."

Person pressing their forehead with their fingers, possibly experiencing a headache or stress relief technique — Prostock-Studio / Getty Images

—u/thecuriousdigest

12. "Your hands and feet alone account for more than half of all the bones in your body."

Person in a relaxed pose sits on a bed, stretching arms upwards. Room is minimalistic with plants on a shelf — Fiordaliso / Getty Images

—u/gianthooverpig

13. "Vaginal lubricant is mostly blood plasma."

Person in lab coat and gloves adjusting an IV bag of yellow fluid in a medical setting — Nadya Tkach / Getty Images

—u/Commercial-Yak-2964

"All bodily fluids are derived from blood, including breast milk."

—u/Damn_Dog_Inappropes

14. "There is erectile tissue in the nose that resembles the erectile tissue in the penis, so sexual arousal can trigger nasal symptoms like congestion, sneezing, or runny nose. It's called 'honeymoon rhinitis.'"

Animated character with a long nose looking surprised, wearing a hat with a feather, and a blue bow tie — Walt Disney Productions / RKO Radio Pictures / Via giphy.com

—u/Whoosier

15. "Your heart rate increases about a minute before partaking in exercise. It is known as the anticipatory rise and happens involuntarily."

Woman practicing mindfulness, lying on a yoga mat, eyes closed, hands on chest, in a serene setting — Maskot / Getty Images/Maskot

—u/wizzkidjay

16. "A small percentage of people are 'super sleepers' and are fully recharged after 2 to 4 hours of sleep each night. They get to burn the candle at both ends!"

Person sleeping peacefully on white bedding, wearing a striped pajama top, lying on their side with a relaxed expression — Roos Koole / Getty Images

—u/lokensnarm

17. "There's zero proof of pheromones in humans despite all the talk around it."

Close-up of a person's shoulder and hand with water droplets on the skin, conveying a refreshing and soothing moment — Flavia Morlachetti / Getty Images

—u/atalantafugiens

18. "Apparently, yeast infections can be contagious."

Red lips in a kissing shape on a white background — Hannatverdokhlib / Getty Images

"As a dumb college kid, I wasn't aware my gf had one (I choose to believe she didn't know, either). We went to the ER because my dick wouldn't stop flaking skin, almost like a croissant or something. Simple meds and an ointment did the trick, but FYI. 🫡"

—u/DruAL

"This is a good PSA. I too have panicked over an unexpected case of French dick. The treatment, per the urgent care, was just OTC athletes foot cream."

—u/AcuteMtnSalsa

19. "Orgasms burn calories (but not that many). Technically, you're burning some energy, but don't quit the gym just yet. Think a few jumping jacks, not a full workout."

Two people exercising outdoors with arms outstretched, focusing on a fitness routine in a park environment — Nick David / Getty Images

—u/Massive_Debt_6102

20. "Some people will cough if they put something in one ear, a very small percentage will cough if something is in either ear. It is called Arnold’s ear-cough reflex."

Person covering mouth while sneezing, sitting indoors with a blanket draped over shoulders, suggesting a cozy or unwell moment — PonyWang / Getty Images

—u/ArtEclectic

21. "Out of curiosity, I [looked up] why males have a 'head' on their penis. It's because it acts exactly like the rubber tip on the plunger of a syringe. In the same way you can draw out a fluid with a syringe, during sex, the penis has the ability to draw out... semen in the vagina that was deposited by a different male, increasing the chances of its deposit being the one to impregnate the female."

The CW

—u/One-Ball-78

22. "Orgasms can cure hiccups."

Person with long hair, surprised expression, covering mouth with hands. Wearing a long-sleeve top, rings, and purple nail polish. Green foliage background — Herstockart / Getty Images

—u/Xadith

23. "Some people are born with extra ribs called cervical ribs which grow from the C7 vertebrae in the neck. It's a weird and rare mutation that a lot of people don't even know they have, although it is also a cause of thoracic outlet syndrome, which is where pressure is applied to the nerves, veins and arteries running into the arms. It can be really painful, and in some rare cases can cause gangrene in the arms. If left untreated it can kill you if you're really unlucky."

Person in a bikini holding a tablet displaying an X-ray image of ribs in front of their torso — Klaus Vedfelt / Getty Images

—u/winterf19

24. "Some people sneeze as a reflex when aroused. It doesn’t happen every time but if it happens to you or you learn to identify it in your partner, then you’ll know. Achoo."

A person sitting on a couch sneezes into a tissue, wrapped in a blanket, with bookshelves and lamps in the background — Milorad Kravic / Getty Images

—u/ViceNSpice

25. And finally: "Eye immune privilege: Your immune system doesn't know your eyes exist. There's a chance that if you get an eye injury or an infection near your eyes, the immune system will think your eyes are a foreign body, and you'll go blind."

Close-up image of a human eye with detailed iris and eyelashes — George Pachantouris / Getty Images

—u/kubrickfan

Is there a body-related tidbit of information that you love to share with people to shock them? Let us know in the comments below.

Please note that some responses may have been edited for length/clarity.

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