The human body is an amazing machine, with some oddities."
You can brush your teeth too aggressively. This can wear down the enamel and make your teeth sensitive to hot and cold foods.
Goosebumps evolved to make our ancestors' hair stand on end, making them more threatening to predators.
Wisdom teeth are useless. They are remnants from hundreds of thousands of years ago. As the brains of early humans grew, they reduced the space in the mouth, thus eliminating that third set of molars.
Scientists aren't sure exactly why we yawn, but it may help regulate body temperature.
Your nails don't grow after you die.
If they were placed end to end, all the blood vessels in the human body would circle the Earth four times.
Humans are the only animals with chins.
When you breathe, most of the air enters and exits through one nostril.
Every few hours, the workload shifts to the other nostril.
Blood makes up about 8% of total body weight.
The human nose can detect approximately 1,000 billion odors.
You have two kidneys, but you only need one to live.
Navels grow special hairs to catch lint.
The satisfying sound of your joints cracking comes from gas bubbles popping in your joints.
The skin is the largest organ in the body and can make up 15% of a person's total weight.
Thumbs have their own pulse.
Your tongue is made up of eight intertwined muscles, whose structure resembles that of an elephant's trunk or an octopus's tentacle.
Genetically, all humans are more than 99% identical.
The foot is one of the parts of the body most sensitive to tickling.
The extraocular muscles of the eye are the fastest muscles in the body. They allow both eyes to flip in the same direction in a single movement lasting 50 milliseconds.
A surgical procedure called selective tonsillohippocampectomy removes half of the brain's amygdala, and with it, the patient's sense of fear.
The pineal gland, which secretes the hormone melatonin, gets its name from its shape, which resembles a pine nut.
Hair grows rapidly—about 15 cm per year. The only thing in the body that grows faster is bone marrow.
No one really knows what fingerprints do, but they can help remove water from our hands, prevent blisters, or improve our sense of touch.
The heart beats more than 3 billion times in an average human lifetime.
The blush is caused by an adrenaline rush.