Granulation tissue

Granulation tissue is a kind of tissue generated in a healing wound to both support the healing process and lay the groundwork for the growth of new tissue. It is typically characterized by its pink or red appearance and its granular surface.

Formation

The formation of granulation tissue is usually the first step in the healing process. This occurs after the initial (inflammatory) phase of wound healing, which is characterized by swelling, redness, heat, and pain. The formation of granulation tissue involves the proliferation of fibroblasts and endothelial cells, which are stimulated by various growth factors such as platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and fibroblast growth factor (FGF).

Characteristics

Granulation tissue is composed of a matrix of collagen and proteoglycans that is highly vascularized and often edematous (swollen due to fluid buildup). It also contains a large number of macrophages, which are cells that help to clean the wound and fight infection. The tissue is typically pink or red in color due to the presence of newly formed capillaries.

Role in Wound Healing

The primary role of granulation tissue is to fill the wound space and provide a supportive structure for the growth of new tissue. It also helps to protect the wound from infection and further injury. Once the wound is filled with granulation tissue, the process of epithelialization (the growth of new skin) can begin.

Clinical Significance

In some cases, the formation of granulation tissue can be excessive, leading to a condition known as hypergranulation or "proud flesh". This can delay wound healing and may require treatment. On the other hand, insufficient formation of granulation tissue can also impede wound healing.

See Also

• Wound healing
• Fibroblast
• Endothelial cell
• Macrophage
• Collagen
• Proteoglycan
• Capillary
• Epithelialization
• Hypergranulation

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  Granulation tissue on a finger

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  Histopathology of biopsy site at 11 days, high magnification

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  Phases of wound healing