What’s the coolest thing you know about the human body?

1. Clenching your buttocks/sphincter stops you from crying.
   — living_with_mumNdad


2. Infants can hold their breath when they're underwater. This is instinctual and not taught (one of the few).
   — eyekwah2


3. If you take too big of a shit, you can overstimulate the vagus nerve which can cause your heart rate to slow and can even make you pass out.
   — azure-panda






4. Infants are born with a super strong grip, and can support their own weight from a chin up bar. They lose this ability pretty quickly, and can't do it again for years.
   — Scrappy_Larue


5. Our bodies are incredibly loud, our ears tune out most of the noises.
   — FappinPlatypus


6. Your immune system is a helluva thing. Take for instance your adaptive immune system. This includes things like antibodies and T cell receptors (TcR) that can recognize specific pathogen antigens (molecular patterns that are unique to viruses, bacteria or other disease causing organisms). There is an estimated 10^8 possible pathogen antigens, which your adaptive immune system must be able to recognize and target to prevent you from dying. However, the amount of DNA required to encode for 10^8 different antibodies would be far too massive to even fit in a cell. To overcome this, your T/B cells use something called somatic recombination. Basically, your antibodies/TcR are composed of a number of chains and segments that each have multiple gene segments. The antibody is then produced from a combination of different gene segments for each of the different chains. This allows your body to make over 10^11 different possible antibodies with only a modest amount of DNA aliquoted for these genes. In addition, B cells can do something called somatic hypermutation, which creates point mutations in the antibodies which can increase the number of different possible antibodies even further.
   — boultos






7. That we essentially have a second brain in our digestive tract. Processing food is so important that our digestive tract has brain cells so we can continue to process nutrients.
   — crabby1990


8. Inside of the skull is a silver/blue/purple-ish pattern, similar to some sea-shells, almost sparkly in some people. It's actually quite beautiful.
   — SaintOfPirates


9. I read it on reddit and it's quite useful - holding your breath helps stopping boners
   — SupremeNoodle






10. The liver is like the human body's Wolverine. It literally heals itself.
    — slightlycharred2


11. In certain brain injuries, you can become "blind" but still be able to navigate obstacles. In [this](http://scienceblogs.com/notrocketscience/2008/12/22/blind-man-navigates-obstacle-course-perfectly-with-no-visual/) patient, his eyes still work and still see but his brain can't interpret the information, so he isn't aware of any sight. But his eyes are still telling him to go around obstacles.
    — roweira


12. A baby's knees/legs look weird because an infant's knee is made completely of cartilage and does not start ossification until age 3-4.
    — _eyeballer






13. Something about our sperm is faster than a polar bear? I don't remember... Check that other thread.
    — DooleyBoyDooleyBoy