Yawns are more contagious among people with closer relationships.
163
Enamel is hardest substance in the human body.
61
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
Stress can result in more headaches as a result of the body rerouting blood flow to other parts of the body.
92
One human hair can support 3 ounces.
191
After age 30, the brain begins to lose about 50,000 neurons per day - shrinking the brain .25% each year.
55
The human brain is very soft, having a consistency similar to soft gelatin or firm tofu.
13
Cracking your knuckles does not actually hurt your bones or cause arthritis. The sound you hear is just gas bubbles bursting.
18