The role of vasoconstriction in the wound healing process is to curtail hemorrhaging. But after about 10 to15 minutes, that process reverses and vasodilatation occurs along with increased vascular permeability. (See previous issue)
As a result of vascular permeability andchemotaxis, plasma, leukocytes, and other cells necessary to woundhealing pour from the intravascular space to the extracellular compartment in a process called diapedesis. (Image expandsto 48K JPEG).
The wound responds with a flourish of acute symptoms of inflammation,which we like to think of as the 4 "ors" -- rubor, tumor, calor,and dolor (sounds like an R & B group but of course they refer to redness, swelling, heat, and pain).
The first cells to arrive at thewound site are the polymorphonuclear leukocytes(PMNs). They have a limited scavenging role, eating and digesting foreign materialthrough acid hydrolytic enzymes (image expands to 84K JPEG).
Monocytes, mostly lymphocytes, then push their way in butfunction mainly as immunoreactants. As they enter the connectivetissue they differentiate into free and fixed macrophages. Themighty macrophage is the key player. These white cells have bothscavenger and nonscavenger functions. With no slight intended to theother inflammatory cells, without macrophages there is no healing orwhat healing occurs is poor.
It takes 3 to 5 days for macrophage products to cause thedifferentiation of fibroblasts from resting mesenchymal cells inconnective tissue. You guessed it -- that 3 to 5 days is called the Lag Phase. Fibroblasts are responsible for synthesizingcollagen, and collagen makes up about 50% of the scartissue.
Too much of agood thing is . . . well, too much. The acute phases of inflammationare essential to wound healing, but the hydrolytic activity andrelease of enzymes can cause devascularization of surrounding tissueand even abscess formation. The presence of bacteria or foreignmaterial keeps the acute phase going and results in chronicinflammation and poor or even disastrous wound healing(image expands to 86K JPEG).
|Go back to Basic Science Introduction||Move to NEW TISSUE FORMATION|
Home |Welcome |Clinical Update |Managing Your Residency |Board Review |Opportunities |Links | Contributors | Contact Us