HOW WOUNDS HEAL

EQUUS - - Eq Case Report -

The process of grow­ing new tis­sue to close a wound oc­curs in two dis­tinct stages: gran­u­la­tion, a mix­ture of tiny blood ves­sels, con­nec­tive tis­sue cells (fi­brob­lasts) and col­la­gen that fills in the gap; and ep­ithe­lial­iza­tion, the growth of new skin cells across the sur­face of the wound to close it.

If su­tures are used to bring the edges of a wound to­gether, the gap be­tween the two sides is nar­row, and both stages hap­pen more or less si­mul­ta­ne­ously. This is called “first in­ten­tion” heal­ing of a wound.

If a wound is wide, and too much tis­sue has been lost, it may be im­pos­si­ble to bring the edges to­gether with su­tures. In this case, the wound will be left open to heal. This is called “sec­ond in­ten­tion” heal­ing, and gran­u­la­tion and ep­ithe­lial­iza­tion oc­cur at dif­fer­ent rates:

• First, as soon as the wound oc­curs, blood and lymph flu­ids rush to the scene; blood platelets are stim­u­lated to form long, sticky pro­tein threads that dry into a clot to seal off the wound and pro­tect it from con­tam­i­nants. White blood cells also ar­rive to help fight in­fec­tion. The platelets and other agents also re­lease other fac­tors that stim­u­late the next stages of heal­ing.

• Next, gran­u­la­tion tis­sue be­gins to form over the ex­posed sur­faces within the wound. Be­cause most wounds are nar­row­est at their deep­est part, the gap usu­ally closes from the in­side out­ward.

As heal­ing pro­gresses, the gran­u­la­tion tis­sue pulls the edges of the wound to­gether. Mean­while, the wound con­tin­u­ously cleans it­self, slough­ing off flu­ids filled with dead cells and other wastes.

• Fi­nally, ep­ithe­lial cells mul­ti­ply along the edges of the wound, grow­ing out­ward from the edge of the skin, to cover and ad­here to the bed of gran­u­la­tion tis­sue. If all goes well, ep­ithe­lial­iza­tion and gran­u­la­tion con­tinue un­til the wound closes and heal­ing is com­plete.

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