Sixth Grade
Worksheets
Your Amazing Body
You might be amazed at some of your own measurements. Did you know that your heart is only about the same size as your fist? When you were first born, your heart had a mass of about 19 grams (about seven-tenths of an ounce) and beat nearly 120 times per minute. As an adult, your heart will probably have a mass of 255g (nine ounces) to 312 g (eleven ounces) and beat about 70 times per minute.
Although you had only about 250 ml (a little more than 1 cup) of blood as a baby, that amount will increase to almost five liters (about five quarts, or two-and-one-half two-liter soda bottles) by the time you are an adult! An adult's heart pumps nearly 4,000 gallons of blood each day. This blood is pumped through about 60,000 miles of blood vessels. That's more than twice the circumference of the Earth!
Your brain reached its full size of about three pounds when you were six years old. A newborn baby's brain will almost triple in size in the first year of life. To accommodate this huge growth, babies have a "soft spot" on the tops of their skulls. There are gaps between bones of the skull. These gaps will close by the time the baby is about two years old.
