1. Skin cells live 14 to 28 days, red blood cells live 120 days.
2. Humans share 99.9 percent of their genes with each other.
3. Humans and chimps share 98.8 percent of their genes: humans and fruit flies share only 60 percent of their genes.
4. Your body releases about two cups ( 400-500 ml of sweat a day 5. Identical twins are always the same gender.
6. Every minute, your body sheds 30,000 to 40,000 dead skin cells. 7. Skin is the thinnest on your eyelids, the thickest on your palms and heels.
8. Eighty - five percent of kids have acne.
9. When exposed to direct sunlight, the body makes vitamin D. which boosts bone health and the immune system.
10. Your sweat contains many of the same substances as your pee . 11. Fingerprints never change and no two are alike.
12. Five million hairs grow on the body, but the scalp contains only about 100,000.
13. The hair on your head grows about 0.01 inches ( 0-35 mm ) a day.
14. Hair on the top of your head grows faster than hair sprouting from the side of your head.
15. It takes 6 months to grow a fingernail, 18 months to grow a toenail.
16. Children's nails grow fastest during the summer.
17. More than 400 joints connect the 206 bones in a human skeleton 18. The average adult skeleton weighs 20 pounds ( 9 kg ).
19. The thighbone is the longest bone in the body, measuring about 18 inches 45 cm ) in an adult.
20. The shortest bone in the body is in the ear and is only o.1 inches ( 2.6 mm ) long.
21. Every day, your body produces more than 100 billion new blood cells.
22. There are 14 bones in the face.
23. Teeth are not made of bone, but rather of hard substances called enamel, dentin, and cementum, and soft tissue called the pulp.
24. Each hand has 27 bones; each foot has 26.
25. Babies have more bones than adults: as people grow some of their smaller bones fuse together.
26. Almost everyone is born with flat feet ( having no arches in their feet ).
27. The word " muscle comes from the Latin word " musculus, " which means " little mouse. " The Romans thought a flexing muscle looked like a rodent moving beneath the skin.
28. of the body's 650 muscles, the gluteus maximus ( or butt muscle ) is the largest.
29. The body uses 12 leg muscles to walk.
30. It takes 12 muscles to smile, 11 to frown.
31. All of an adult's blood vessels laid end - to - end could circle Earth two and a half times.
32. Blood travels 12,000 miles ( 19,000 km ) in one day.
33. The heart pumps blood through its largest artery at about one mile per hour ( 1.6 kph ). In tiny vessels, blood moves only 43 inches an hour ( 109 cm per hour ).
34. A soft tissue called marrow inside bones produces most new blood cells.
35. Blood itself is about 100.4 ° F ( 38 ° C ) -a little hotter than the average body temperature.
36. Blood is always red, but its shade varies by location in the body. 37. Being afraid and angry increases your heart rate by 30 to 40 beats per minute.
38. Squeezing a tennis ball with your hand gives you a good idea of how hard the heart works to pump blood.
39. The human heart weighs half a pound ( 0.2 kg ) in women, slightly more in men.
40. The smallest blood vessels in the body are much tinier than human hair and just big enough that red blood cells can pass through a single file