Here is a concise summary of the content:
**Human Body Facts Summary**
* **Anatomy & Structure**
+ Heart valves create the heartbeat sound
+ Horns (nails) don't receive blood, getting oxygen from air
+ Largest molecule: first chromosome, made of 10 billion atoms
* **Brain & Senses**
+ 100 billion neurons in the brain
+ We use almost 100% of our brain, not just 10%
+ Sense of smell sends direct signals to emotional & memory centers
* **Health & Functions**
+ Stomach produces new blood vessels every 6 days
+ Liver filters blood, but doesn't store oxygen
+ One lung uses only 15% of breathed oxygen
* **Interesting Statistics**
+ 7 octillion atoms in a 70kg human body
+ 5 million hair follicles, with hair growing 1.27cm/month
+ Eyes blink 15-20 times/minute (5 times/minute when looking at screens)
* **Myths & Trivia**
+ No regions on the tongue for specific tastes (it's a myth)
+ Veins appear blue due to light scattering through skin
+ Fingernails grow twice as fast as toenails
+ Heart has its own electrical system, beating independently
Here are the extracted key facts, numbered and in short sentences, excluding opinions:
**Human Body Facts**
1. There are approximately 100 billion neurons in the human brain.
2. The human body has around 60,000 miles of blood vessels, long enough to circle the Earth twice.
3. The brain uses almost 100% of its capacity, not just 10%.
4. The brain is composed of about 70% water.
5. The brain needs 20% of the oxygen entering the body.
6. There are approximately 700 types of bacteria and 6 billion bacteria in the human body.
7. The largest organ in the human body is the skin.
8. The surface area of the skin is roughly equivalent to 2 bath towels.
9. New blood vessels (1.6 km long) are produced every time you take a step to provide oxygen and nutrients.
10. The stomach produces new blood vessels every six days to aid digestion.
**Senses and Organs**
11. The sense of smell sends a direct signal to the part of the brain controlling emotions and memories.
12. The protrusions on the tongue are not taste buds, but mushroom-shaped protrusions.
13. Each taste bud contains 5 taste receptors.
14. There are approximately 10,000 taste buds on the average person's tongue.
15. Elderly persons may have around 5,000 working taste buds.
16. Enamel is the hardest substance in the human body, made up of 96% minerals.
17. Humans have two sets of teeth in their lifetime, unlike crocodiles which change teeth over 45 times.
**Other Biological Facts**
18. The heart's electrical system is self-contained, allowing it to beat independently.
19. One lung uses only 15% of the oxygen we breathe.
20. A 70-kilogram human body consists of approximately 7 octillion atoms.
21. It takes 6-8 hours for food to reach the stomach and small intestine.
22. Muscle contractions, not gravity, help nutrients reach the stomach.
**Development and Growth**
23. Teeth begin to form before birth but appear between 6-12 months old.
24. Hair grows 1.27 centimeters every month.
25. Fingernails grow twice as fast as toenails, taking 7 months to grow 2.5 cm, compared to 15.5 months for toenails.
**Miscellaneous**
26. The human body can detect more than 10,000 smells, contrary to previous beliefs.
27. There are approximately 3 million sweat glands in the human body, mostly on the soles of the feet.
28. The heart beats at a speed that allows it to reach the brain in a few seconds, traveling at 6 kilometers per hour.
29. The average person blinks 15-20 times per minute, decreasing to 5 times per minute when looking at a computer screen.