Tissue Injury: Inflammation and Repair

When tissue is injured, the damaged area triggers an immediate inflammatory response. Blood vessels dilate to increase blood flow, and immune cells migrate to the injury site to remove debris and pathogens. This inflammatory phase is essential for initiating the repair process and preparing the tissue for healing.

Inflammation recruits immune cells and growth factors to the injury site, clearing damaged tissue and bacteria. These inflammatory mediators stimulate fibroblasts to produce new collagen and extracellular matrix components. While inflammation causes swelling and pain, it is a critical phase that enables tissue regeneration and restoration of function.

Tissue healing occurs in three phases: inflammation, proliferation, and remodeling. The inflammatory phase removes debris and initiates repair. During proliferation, new blood vessels and collagen form to rebuild tissue structure. Remodeling strengthens and refines the repaired tissue over weeks to months.

Swelling results from increased vascular permeability during the inflammatory response. Damaged cells release chemical signals that cause blood vessel walls to become leaky, allowing fluid and immune cells to enter the tissue. This edema delivers nutrients and immune components necessary for healing while diluting harmful substances.

Different tissues repair at different rates based on their cell types and blood supply. Epithelial tissues with high cell turnover and rich vascularization heal quickly, while tissues like cartilage with limited blood flow repair slowly. Connective tissues like bone have specialized repair mechanisms involving osteoblasts that rebuild structural integrity.

Fibroblasts are connective tissue cells that synthesize collagen and other extracellular matrix proteins essential for tissue reconstruction. During the proliferation phase, they migrate to the injury site and deposit new matrix material to fill the wound. This process restores tissue strength and structural integrity.

Regenerative capacity varies by tissue type. Epithelial tissues and bone regenerate well due to active cell division and good blood supply. Nervous tissue and cardiac muscle have limited regenerative ability, often forming scar tissue instead. The extent of injury and tissue type determine whether full functional recovery occurs.