Granulation tissue is a temporary, yet necessary, structure produced by the body when repairing an open wound. It serves as the initial, soft filler material that bridges the gap created by an injury. Many people who notice this reddish, bumpy substance wonder if it will persist. Its formation is a sign of healthy healing, and its eventual disappearance is a natural, expected outcome of wound maturation.
Defining Granulation Tissue and Its Appearance
Granulation tissue is new connective tissue and microscopic blood vessels that form on the surface of a wound. It is composed primarily of proliferating fibroblasts, which generate the extracellular matrix, and new, thin-walled capillaries (angiogenesis). These new blood vessel loops give the tissue a distinct and easily recognizable look.
Healthy granulation tissue appears light red or dark pink due to the extensive new vascular network. Its texture is moist and bumpy, or granular, which is why it receives its name. This characteristic appearance is sometimes described as resembling cobblestones or ground beef.
The Essential Role in Wound Healing
The purpose of granulation tissue is to fill the defect left by the injury, a process known as healing by secondary intention. It grows from the base of the wound upward, creating a temporary scaffold for eventual replacement tissue. Fibroblasts rapidly deposit a provisional matrix, initially consisting of Type III collagen.
The dense network of new capillaries restores blood flow to the site, delivering oxygen and nutrients to the growing cells. This vascularization also removes cellular waste and transports immune cells to protect the wound surface from microbial invasion.
How Granulation Tissue Transforms into Scar Tissue
Granulation tissue is temporary and is progressively remodeled and replaced as the wound matures. This transformation marks the transition from the proliferative phase to the remodeling phase of healing. The change involves a significant shift in the tissue’s cellular composition and structure over a period that can last months to years.
A key event is the replacement of the initial Type III collagen with the stronger, more organized Type I collagen. As the matrix strengthens, the dense network of blood vessels begins to regress, driven by the death of vascular cells. This reduction in vascularity causes the tissue to lose its prominent red color, eventually becoming the paler tissue known as a scar.
Some fibroblasts differentiate into myofibroblasts, specialized cells with contractile properties. These cells pull the wound edges inward to reduce the size of the defect, a process called wound contraction. As the wound matures, the majority of these myofibroblasts and excess vascular cells undergo apoptosis (programmed cell death), completing the resolution of the granulation tissue.
Understanding and Treating Hypergranulation
In some cases, the normal process of resolution is disrupted, leading to a condition called hypergranulation, informally known as “proud flesh.” This occurs when an excessive amount of granulation tissue forms, rising above the level of the surrounding skin. The overgrowth acts as a physical barrier that prevents the epithelial cells from migrating across the surface to close the wound, thereby hindering healing.
Common causes include prolonged exposure to excessive moisture, such as from poor wound drainage or occlusive dressings, and the presence of infection or foreign bodies. These factors can trigger a prolonged inflammatory response that stimulates the excessive growth of new capillaries and connective tissue.
Management focuses on addressing the underlying cause and promoting a balanced wound environment. This often involves controlling moisture with appropriate dressings and treating any underlying infection. For persistent overgrowth, clinicians may use chemical agents like silver nitrate to cauterize the excess tissue, or apply short-term topical steroids to dampen the inflammatory response.