TISSUE TYPES
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Granulation
The wound base demonstrates healthy red granulation tissue. Granulation tissue can be noted from the healthy wound buds that protrude from the wound base. During wound healing, granulation tissue usually appears during the proliferative phase. Angiogenesis is the process by which new blood vessels form, bringing in tiny capilarry buds that appear as granular tissue. Granulation tissue sets the stage for epithelial tissue to be laid down on top of the wound bed.
Pale, unhealthy granulation tissue, as noted above, can result from lack of good blood supply and angiogenesis. Pale granulation tissue needs to be freshened up with debridement to stimulate new ingrowth of blood vessels.
Necrosis
Pictured on the left is a necrotic sacral ulcer. The necrosis can be best visualized to the left of the wound in the photograph. Necrosis is usually dark tissue, which is completely devitalized. Necrotic tissue forms as a result of tissue death from damage. For pressure ulcers, the underlying pressure causes occlusion of blood vessels blocking vital oxygen delivery to tissues. This occlusion results in tissue death and subsequent bacterial overgrowth. In order for wounds to heal, all necrotic tissue should be debrided from the wound, a process that may take multiple attempts over months to achieve the desired outcome of good healthy granulation tissue.
Slough
The sacrococcyx ulcer demonstrates significant areas of slough. Slough is defined as yellow devitalized tissue, that can be stringy or thick and adherent on the tissue bed. This wound bed has both yellow stringy slough as well as thick adherent slough. Slough on a wound bed should be surgically debrided to allow for ingrowth of healthy granulation tissue.
Eschar
Pictured left is an eschar from a pressure ulcer. Eschars result from tissue necrosis and death; they are usually black and dry. They can be firmly adherent to the wound or lifting. Eschars also result from burns; especially thermal or electric burns.
The eschar is lifting and is debrided off given the underlying infection below.
Hypergranulation
Hypergranulation or proud tissue is an overgrowth of granulation tissue above the height or border of the skin edge. It is unclear why this process actually happens in wounds. Hypergranulation tissue is usually friable and bleeds and must be dealt with. Wounds cannot heal with hypergranulation because it limits the ability for epithelial cells to migrate across the wound bed and lay down collagen and epithelium.
As shown left, application of silver nitrate to the tissue bed cauterizes the hypergranulation tissue and causes it to regress.
The picture on the left is post application of silver nitrate. Wounds may also be debrided to remove the hypergranulation tissue.
Epithelium
As wounds heal, epithelium forms on top of granulation tissue. In the wound pictured to the left, a large area of epithelium has formed where there was previously a large open sacral ulcer. You can also see epithelial islands being laid upon the granulation tissue. Chronic wounds should be classified as re-epithelialized not healed, when closed, as they may reopen.