You probably never think about all the things going on inside of you. Don't you think it's about time you got to know yourself a little better? Here's your chance. This is all about you—by the numbers.


Your Hair:

- A healthy head of hair has anywhere from 80,000 to 150,000 hairs; brunettes tend to have 115,000 hairs, blondes have 140,000, and redheads have about 100,000.

- Your hair grows at the rate of about a half inch every month.

- You lose 50 to 150 strands of hair per day.

- Half of us will be 50 percent gray by the time we reach the age of 50.

- Your genes determine whether you'll go bald. If baldness is on your genetic plate, you're not alone: About 60 percent of all men will be bald by the time they're 50.


Your Eyes:

- Each of your eyes measures about one inch in diameter.

- 20 percent of all people are nearsighted.

- If you have 20/20 vision, when you go for an eye exam you'll be able to read letters on the chart from 20 feet away.


Your Ears:

- Any sound that's louder than 85 decibels puts you at risk for hearing loss. (A rock concert checks in at 80 to 100 decibels; a jackhammer that's three feet away from you registers in at 120 decibels.)


Your Teeth:

- You have 32 permanent teeth, 16 in each jaw.

- At present, half of all 65-year-olds have lost all of their teeth.


Your Body:

- 15 to 20 percent of your body weight is from fat.

- On average, water makes up 60 percent of your body weight.

- You can determine roughly how many calories you burn just being alive by multiplying your weight in pounds by 12.

- Your muscles reach their maximum mass between the ages of 25 and 35.

- To find out whether your body is a pear or an apple, determine your waist-to-hip ratio: Divide your waist measurement by your hip measurement. For women: If the outcome is greater than .80, you are more like an apple; if it's lower, you're more pear. For men: If your calculations show a number larger than .95, you are more like an apple than a pear. (Unfortunately, "apple-shaped" individuals may be more susceptible than others to hypertension and heart disease.)


Your Heart:

- At rest, your heart beats 60 to 80 beats per minute and will contract more than 2.5 billion times in your lifetime.

- Your heart pumps out about 12 pints of blood per minute.

- When you exercise, your heart can beat up to 200 times—and pump out 100 pints of blood—per minute.


Your Skin:

- Your body is covered with two square yards of skin.

- Collagen—a tough, fibrous protein that holds together cells and tissues—makes up approximately 90 percent of your skin.


Your Bones:

- You have 206 bones in your body.


Your Hands and Feet:

- Your fingernails take approximately six months to grow from base to tip.

- Toenails take almost twice as long to grow out.

- Nails tend to grow faster in hot weather.