Enamel is hardest substance in the human body.
61
Your thumb is about the same size as your nose.
124
It takes about 20 seconds for a red blood cell to circle the whole body.
102
An average heart beats 100,000 times a day, pumping some 2,000 gallons of blood through its chambers. Over a 70-year life span, that adds up to more than 2.5 billion heartbeats.
73
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
The average sperm cell swims at 8 inches per hour.
76
It takes twice as long to lose new muscle if you stop working out than it did to gain it.
127
There are times when you're walking that the pressure on your feet exceeds your body weight, and when you're running, it can be three or four times your weight.
62