Science quiz

Skin The skin covers about 20 square feet in adults and accounts for about 15% of your body weight

Tooth enamel Tooth enamel is even harder than steel, though it can still be damaged by acids in food and drinks

Pancreas The pancreas produces about 1-2 million tiny clusters of cells called islets that make insulin

Stapes Located in the middle ear, the stapes is only 3.3 millimeters long and weighs about 2.5 milligrams

Cerebellum The cerebellum contains nearly 50% of all neurons in the brain despite being only 10% of its volume

Heart The heart beats about 2.5 billion times in an average lifetime without ever taking a break

Liver The liver can regenerate up to 70% of itself if damaged, returning to full size within weeks

Jaw muscle The masseter (jaw muscle) can close the teeth with a force of up to 55 pounds on the incisors

Lungs If all blood vessels in the lungs were laid end to end, they would extend for about 1,500 miles

60% The brain and heart are composed of 73% water, while the lungs are about 83% water

Smell The olfactory bulb has direct connections to two brain areas strongly implicated in emotion and memory

Hyoid bone Located in the throat, this U-shaped bone is essential for speech and swallowing

300 As a baby grows, some of these bones fuse together, resulting in 206 bones by adulthood

Middle finger Fingernails grow about 3.5 millimeters per month, with the middle finger growing the fastest

10,000 Taste buds are replaced every 2 weeks, but this ability decreases with age

Nose and ears This continuous growth is due to gravity and changes in cartilage tissue, not actual growth of bones

98% This small 2% difference accounts for all the major distinctions between humans and chimps

17 It takes 43 muscles to frown but only 17 to smile, which is why smiling requires less energy

Lungs This floating ability is due to the air spaces within the lungs, making them the only naturally buoyant organ

60,000 If laid end to end, these blood vessels would circle the Earth more than twice