The human body is an amazing machine, so to speak. The way in which all of these functions work simultaneously as well as the level of cognitive function humans have is unlike any other known species. There are things our body does we are unaware of but matter a great deal. Here are 15 cool facts about what's happening inside.

1. Semen ejaculates at 27 mph, making it illegal in school zones.
2. If a pregnant women suffers damage to her organs, the fetus immediately sens stem cells to the damage organ to repair it. This is pretty amazing. The human body even has a plan B for every major issue that could happen.
3. Our bodies are ready for staying underwater for long periods of time as soon as our faces touch water. This is called mammalian diving reflex. Your heart rate slows down immediately when an impact with water is made, even with newborns. 
4. The human body contains enough bones to make an entire skeleton.
5. To slow down the blood stream during intense fear or stress, the human body makes it easier for blood to clot.
6. The inside of your cheek is made of the same tissue as the inside of the vagina.
7. Saliva acts as a protective shield against bile and stomach acid that might come up when you've gotta hurl. Your body actually automatically ups saliva production to maximize protection against harmful stomach acid in your throat and mouth.
8. Human vision isn't that great. There is a spot on the retina where the optic nerce is located and it actually is considered a blind spot on the human eye.
9. There are no pain receptors in the brain itself. So it, by itself, can feel no pain. But everything around it can.
10. Your forearm is the same length as your foot.
11. The liver can regenerate if a chunk of it were to be taken out. In fact you could take off three thirds of it, and it would still regenerate into a whole liver.
12. Humans are pretty much the only animals that can throw objects properly. This has been a major factor and has had a huge impace on our evolutionary path. 
13. The tongue is the only muscle in the body connected at one end.
14. The average adult human is just tall enough that falling forwards/backwards with the body rigidly straight will impart enough kinetic energy to kill you when you impact the floor head first.
15. The brain actually only requires the equivalent amount of power than a 10-watt light bulb.