John Coutre, age 12, of Libertyville, Illinois, for his question:
How do wounds heal?
Scientists would like to know a lot more on this subject. At present, they know that the body repairs itself in well organized stages. They also know some of the biochemicals that trigger and direct the healing process. But most of the miraculous project remains a mystery. However, medical scientists know lots of ways in which we can help or hinder the body during the secretive healing of its wounds.
With some assistance the body can do a splendid job of healing torn skin, gashed muscle tissue and broken bones. Skin, muscles and bone are made from different tissues, which require different rebuilding operations. A skin scratch may be healed in a few days, wounded muscle takes several weeks and it takes several months to mend a bone fracture.
Though the rebuilding varies, the healing process always depends on four basic factors. There must be a body wide system that gives top priority to the wounded area. There must be an allocation of new raw materials for repair and rebuilding, plus a system of transportation to deliver these. materials to the wounded area. Finally, there must be a local engineering team to decide which materials go where.
Some of the signals that trigger the healing operation seem to come from steroids, a complex group of hormones secreted by the adrenal cortex. Nobody knows what alerts them, how they trigger healing or even whether other signals work with them. Meantime, the whole body is alerted by injured nerves hollering for help.
When a wound occurs, within a few seconds the body is alerted. Blood cells erupt to seal leakages, the blood and lymph systems start transporting needed materials to the damaged area. The rebuilding is directed by DNA, the blueprint chemical present in the nucleus of every cell. The DNA orders are transmitted by the messenger biochemical, RNA.
With some variations, this basic operation works to heal all wounds. The mending of a fractured bone begins when broken blood vessels form a clotted wad called a hematoma. Hard chemicals are dissolved from the jagged splinters and the two broken ends are wrapped in this rubbery pad. Later, bone building cells called osteoblasts arrive on the scene. A network of connective tissue is built through the hematoma and deposits of hard bone building chemicals are added.
Gradually, the two broken ends are joined with a bridge of new bone, but the complete healing takes several months. A gashed muscle heals much faster because fleshy tissue has more blood vessels to tote building material to the trouble spot. Skin scratches are surface wounds that begin to heal when the oozing blood clots to form a protective scab.
The body carries on most of its life processes without our advice or assistance. But usually it needs our help to heal its wounds. A broken bone must be set and sealed in a cast to keep the ragged edges in place. Badly torn flesh needs stitches, or the wound leaves a wide scar. Even a skin scratch heals faster and neater when we stick on a bandage.