Pretend that your teacher told you to make a list of the most complicated machines that you could think of. You would probably write down things such as a space shuttle, a computer, and maybe a video recorder. But none of these are as complicated as the human machine—your body.
Lightly draw a 2.5 centimeter square on your arm with a soft pencil. Although you can’t see under or through that piece of skin, it is only as thick as a piece of paper and yet it contains 22 meters of nerves (about as long as five cars lined up end to end). It also contains an average of 10 hair follicles, 4.6 meters of blood vessels, and about 15 oil glands and 100 sweat glands. All this, remember, is within that tiny square of skin on your arm!
If you run a long time, you’ll notice that perspiration makes your feet damp. And if you’re nervous, the palms of your hands may get sweaty. Those areas of your body have the most sweat glands. They also have the fewest oil glands, which is why they get wrinkled when they’re in water very long.
Your heart is a miraculous pump that keeps your body alive by sending your blood through about 112,600 kilometers of blood vessels—and back—each minute. The average heart beats about 70 times a minute and rests between beats. That adds up to about 2.5 billion heartbeats by the time that you’re 70 years old.
An adult weighing 68 kilos has about 5.2 liters of blood in his body. A lot more than half your blood is water. When you play and exercise—and even sleep—your body loses water through sweating. It also loses water through the urinary tract. So it’s important to drink lots of water to replace what is lost so that your blood and organs can do their jobs properly.
In one day your body breathes in about 11,335 liters of air. With every breath that you take, your lungs pull in about .5 liters of air. Your nose is lined with moist membranes and tiny hairs, and it is their job to clean, warm, and moisturize all the air that you breathe in.
The tongue may sound like a funny thing to talk about, but just think of all the work it must do! You need it to breathe properly, to talk properly, to chew your food, and to tell you when something is sweet, bitter, sour, or salty.
Can you imagine a machine that could tell everything in your body how and when to work? It would have to tell you when you’ve touched a hot stove. It would have to tell you when you are cold and when you are hungry. Such a machine would make your heart beat without you even worrying about it and would signal your lungs to take each breath. It would make your arms and legs work, and it would do a great many other things. This wonderful machine would weigh only about 1.35 kilos. The machine that can do all these things exists—it is your brain.
But your brain is only one part of your body’s control center. The other, an invisible part of your body, controls your brain and everything that your physical body does. This part is called your spirit. The wonderful combination of your body and your spirit (see D&C 88:15) was designed by Heavenly Father and is one of your most valuable blessings.
By not abusing your body and by doing everything you can to keep it running well, it will last a lot of years and take you safely through the varied experiences of your life.