Sandra Wagner, age 9, of Victoria, British Columbia, Canada, for her question:
What causes a bruise?
A bruise is a bodily injury that happens When you get a bang or a bump. Sometimes it takes only a slight tap that hardly hurts. You do not notice it until later when your bruised knee or arm shows a patch of purplish blue.
A hit on your hard, bony head or some other part of your body may raise a nasty bump. When the bump goes down, you can see a blotchy blue bruise. The spot may be sore, especially if you poke it or bump it again. So treat your bruise with tender care by leaving it strictly alone. Day by day the blue blotch changes to a sickly yellowish green color and finally it fades away. Your bruised patch returns to its usual skin color. The bruise was caused by an injury to your body and your body has done a lot of patient work to heal it.
When you take a tumble, you may bash a knee or an arm on the ground. When you crash into a table or drop a rock on your foot, you bash other parts of your body. These bashes may not be hard enough to break the skin.
This is what causes a bruise. Lots of tiny cells in the soft flesh are damaged and lots of tiny blood vessels are broken. Thin trickles of blood ooze out among the cells. The bruised spot swells up and turns red. Tiny nerves are also injured and they make the spot sore. The body gets busy and starts to repair the damage at once. Soothing liquids flow to the trouble spot, carrying the body's homemade healing chemi¬cals. These medicines heal the small broken blood vessels. This is important because the blood stream must circulate back to the lungs again and again. There the blood gets the fresh supplies of oxygen that keep it rosy red. The body has miles and miles of blood vessels, large and small. They form an unbroken network to keep tba ctream;_nf,, blood from escaping.
The tiny blood vessels broken by the bruise are soon mended. But the blood that trickled from them is left outside among the cells of the flesh. It cannot circulate back to the lungs for fresh oxygen. So it turns dark and darker and finally adds a purplish blue color to the bruised area. The busy body does not just leave it there.
The blood separates into tiny fragments and bit by bit, flowing liquids carry them away. The bruise turns paler and paler. The body may take a week or more to carry away all the bits of dark blood, but at last the murky mess is cleaned up.
A small bruise will heal itself in a week or so. But naturally you want to help your body to do its healing. Certainly you do not want to hinder and delay things. If you poke or bang the bruise again, the body must start its work all over and the healing takes longer. Perhaps it is wisest to cover the purple patch with a softly padded bandage. If the bash that caused the bruise was fierce enough to break the skin, you treat it with germ killing medicine and cover the wound with a friendly bandage.