Granulation tissue represents a fundamental step in the body’s ability to repair itself after an injury extending beyond the skin’s top layer. Its formation signifies the transition from the initial cleanup phase into the active rebuilding stage. This specialized tissue is the body’s temporary construction material, filling the defect from the wound bed upward. Its presence is generally a positive indicator that the wound environment is healthy and regeneration is actively underway.
Appearance and Composition of Granulation Tissue
Healthy granulation tissue has a distinct appearance that signals active and successful healing. It is typically “beefy red” or dark pink due to a dense network of newly formed microscopic blood vessels. The surface often looks moist, soft, and slightly bumpy, giving it a characteristic “cobblestone” or granular texture. This granular appearance is why the tissue received its name.
This delicate tissue is structurally composed of an extracellular matrix, which acts as a scaffold, and various cell types. The most prominent cellular components are fibroblasts, which produce structural proteins, and endothelial cells, which form the walls of the new capillaries. The high concentration of these new, thin-walled blood vessels causes the tissue’s color and fragility. Although easily bleeding with minimal contact, healthy granulation tissue is usually painless to the touch.
The Essential Role in Rebuilding Tissue
The primary function of granulation tissue is to provide a temporary bridge and foundation to replace lost dermal tissue. It fills the wound space from the bottom up, ensuring the cavity is properly closed before the surface can be sealed. This process begins with angiogenesis, the formation of a new blood supply from existing, intact blood vessels near the wound periphery. This vascularization delivers the oxygen, nutrients, and immune cells required for sustained tissue growth and metabolism at the injury site.
Fibroblasts migrate into the wound, stimulated by growth factors released by immune cells. They immediately begin synthesizing the extracellular matrix, initially depositing a softer, temporary Type III collagen. This initial matrix provides the structural integrity needed for the tissue to grow and withstand mechanical stresses. The coordinated activity of these cells transforms the initial blood clot into living, vascularized tissue ready for the final stages of closure.
Identifying Issues in Granulation Development
While granulation tissue is a positive sign, deviations from the healthy red color and cobblestone texture indicate underlying problems. Unhealthy tissue may appear darker red or dusky purple, often accompanied by increased pain and excessive bleeding. If the tissue looks pale, smooth, or very thin, it suggests delayed or hypotrophic granulation, potentially due to poor blood flow, inadequate oxygen supply, or nutritional deficiencies.
A common problem is hypergranulation, sometimes called “proud flesh,” which is an excessive overgrowth of the tissue. This condition causes the tissue to rise above the surrounding skin, forming a raised mound. When the tissue protrudes, it creates a physical barrier that prevents epithelial cells from migrating across the wound surface to complete closure. Hypergranulation is often triggered by prolonged excessive moisture, the presence of a foreign body, or an underlying infection.
Any signs of pus, a foul odor, increased warmth around the wound edge, or a sudden change in the color of the granulation tissue may signal a localized infection. If the tissue remains pale, fails to progress, or if hypergranulation persists despite basic care, consulting a healthcare professional is advisable. The wound cannot fully close until these underlying complications are addressed and the environment is optimized for epithelial cell migration.
Maturation into Scar Tissue
Granulation tissue is a temporary structure that must transition into a permanent scar. This final stage is the remodeling phase, which can last for many months or even years after the initial injury. During this period, the dense network of new blood vessels begins to regress, reducing the blood supply. This reduction in vascularity causes the tissue to gradually fade from red to a paler, less noticeable color.
The softer Type III collagen that initially provided the scaffolding is progressively broken down and replaced by stronger, more organized Type I collagen. Specialized myofibroblasts, differentiated from the original fibroblasts, play a major role in wound contraction by pulling the wound edges together. As the collagen fibers reorganize and align, the temporary granulation tissue converts into the denser, less cellular tissue recognized as a mature scar. The scar tissue, however, only achieves about 80% of the tensile strength of the original, uninjured skin.