Our Bodies Are Heroes!
Many things outside our bodies are dangerous.
But
our bodies have lots of ways of protecting us:
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Skin keeps things from getting inside our bodies. |
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Tears keep eyes clean. |
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Nose hairs help to clean the air that goes into lungs. Mucus in noses traps and washes away some of the nasty little things that manage to get by. |
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Coughing and sneezing helps get rid of some invaders. |
Some harmful things -for example, bacteria and viruses -- will always sneak by these defenses. But our bodies have an army of special cells. It's called the immune (im-yoon) system. These cells patrol our bodies and search for invaders.
The immune system can tell the "good guys" from the "bad guys" by what they
wear!
For
example, your body is made up of cells, like the dish-shaped red blood
cells in this picture. They carry oxygen to every part of your
body. The other scruffy looking cells are part of the immune
system army.
The outsides of cells are marked by lumpy, bumpy molecules. (They're too small to see here.) Your cells are wearing your team uniform -- a lumpy, bumpy uniform! No two people on Earth have exactly the same uniform! Your special pattern of molecules tells your immune system that these cell are yours! Don't attack!
Other things that enter your body wear
different uniforms. The immune system army checks everything
that comes in. It recognizes that some are okay and lets them pass.
When the immune system army finds an enemy, it goes into action. The army itself multiplies very fast. Cells work together to find the invader. Then they attack. They squirt the enemy with powerful chemical weapons that can heat them up and destroy them. Then they eat them!
The big blue cell in the photo below is called a
macrophage (mac-row-fage). The word macrophage means "big
eater"!
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For example, when you get a cut,
it gets a little
red. Maybe it feels hot and itchy.
That's because the cells of
your immune system have arrived on the scene. They're squirting their
chemical weapons on the invading bacteria! These
chemicals are kill bacteria. But the chemicals are so strong,
they're also making you feel a little itchy and uncomfortable.
