WOUNDS 3

Healing 3

2.2 WOUND HEALING IN PRACTICE
Wound healing is best studied in a clean sutured surgical wound. The features of wound healing are common to all clean wounds in any tissue. The healing phases follow one another and also overlap.

2.2.1 Hemostasis Phase (Coagulation) starts immediately with release of bradykinins serotonin and histamine (Mast cells) causing Vasoconstriction and diapedesis (migration) of cells.
Fig 1.5
Platelets release clotting factors leading to production of fibrin. They also produce cytokinins the wound hormone.

2.2.2 INFLAMMATION PHASE: It is also referred to as Lag phase. This phase starts soon after injury and displays all the features described under inflammation. The exudate is partly reabsorbed and dead tissue removed by phagocytosis.

2.2.2.1 GRANULATION: This is the pink irregular surfaced tissue seen in all wounds that have no skin cover.
It is full of fibroblasts derived from cells around the wound.
Within this there is also a network of capillary endothelial growth.
These fibroblast grow into and onto the fibrin and fibronectin matrix already present as a result of the coagulation process setup during the inflamation phase.
The granulation is infiltrated with macrophages.
The fibroblasts use hyaluronidase to digest the matrix and lay down collagen.

*Granulation tissue is present in all wounds healing by secondary intention. This tissue is clinically characterized by the most like red appearance (i.e. “proud flash”) which is because of the rich bed of new capillary networks (neoangiogenesis) that have formed form endothelial cell division and migration. The directed growth of vascular endothelial cells is stimulated by platelet and activated macrophage and fibroblast products. One example is vascular endothelial growth factors, which is secreted by macrophages and acts to induce migration and proliferation of endothelial cells.

Cranulation tissue is a dense population of blood vessels, macrophages, and fiboblasts embedded within a loose provisional matrix of fibronection, hyaluronic acid and collagen.

The presence of granulation tissue is used as clinical indictor that the wound is ready for skin graft treatment. Wounds that benefit from skin grafts are of sufficient size such that the healing time would be decreased. The high degree of vascularity enables granulation tissue to readily accept and support skin grafts.*

Contraction
Open wounds partially healed by contraction this is minimal in closed surgical incioions. Open wound occurs after trauma, burns and when previously closed wounds are re-opened because of infection.

In practice wound contraction can be in excess, and can lead to contractures which results in decreased function. This is seen most often contracture near joints
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