• Food will get to your stomach even if you are standing on your head.
• An adult's intestines are over 25 feet long.
• Those rumblings and gurling sounds are not really from your stomach being empty. The sounds are actually mushed-up food and gases moving through the intestines during digestion,
• It takes food seven seconds to go from the mouth to the stomach.
• You produce 1 to 3 pints of saliva every day.
• Listen to your teachers! If you swallow your gum by mistake, it will take 2 to 3 weeks to digest!
• It is not true that swimming immediately after eating causes cramps. In fact, long distance swimmers actually eat while in the water to avoid getting tired and muscle cramps.
  

• Every minute you breathe in 26 cups of air.
• Plants are our partners in breathing. We breathe in air, use the oxygen in it, and release carbon dioxide. Plants take in carbon dioxide and release oxygen.
• Adult humans breathe about 23,000 times a day.
• When you are sleepy or drowsy you are not getting enough oxygen, so your body takes a long, deep breath, a yawn.
• Hiccups are the sudden movement of the diaphragm. You can't control them.
• You sneeze to clear your breathing passages, so don't hold them back!
• 25% of people sneeze when they look at the sun, but scientists do not know why.

The main job of the muscular system is to help you move. There are three types of muscle tissues, skeletal, cardiac and smooth. Cardiac and smooth muscles are involuntary muscles, and we cannot control them. Skeletal muscles are voluntary muscles that we can control ourselves. Muscles work in a simple way. They tighten up, or contract, and then relax. Skeletal muscles are held to the bones with tendons.

• You have over 630 muscles in your body.
• Eye muscles are the busiest muscles in the body. Scientists estimate they may move more than 100,000 times a day.
• You have over 30 muscles in your face to help you smile or frown. It takes 17 muscles to smile and 43 to frown.
• The strongest muscle in your body is your tongue.
• It takes the interaction of 72 different muscles to produce human speech.
• The number of muscles in an adult does not increase with exercise. The cells simply get bigger.
• Want to try something odd? While sitting in your chair, lift your right foot off the floor and make clockwise circles. Now, while doing this, draw the number "6" in the air with your right hand. Your foot will change direction!
• Want another one? Rotate the index fingers of both hands in the same direction, slowly at first, then faster and faster. Pretty soon, they will be going in opposite directions!

• A newborn baby has 300 bones, but an adult only has 206.
• More than half of the bones in your body are in your hands and feet. Your face has 14.
• The thigh bone, the femur, is the longest bone in your body. The smallest is the stirrup bone in the ear which is about 1/10th of an inch.
• Believe it or not, humans and giraffes have the same number of bones in their necks.
• Enamel, which is the outer covering of your teeth, is the hardest substance in your body.
• There is no such thing as a funny bone! There is a nerve called the ulnar nerve that is next to the humerus bone. When you bend your elbow, if the nerve gets whacked, it sends messages up your arm creating a tingling sensation.
• Bones are not actually white. They range in color from beige to light brown. The white, sterile bones you've seen have been boiled and cleaned.
• The shark's skeleton is made from cartilage, not from bones, which is why they are more flexible than you are.

An alternative view of the digestive system
by David Dickson, with his kind permission

Think you know enough about your body systems? Test your knowledge with Bacterial Invasion by Mr. Nussbaum!

Can you put this human skeleton together?

Can you replace the organs in this game from Science NetLInks?