Pathology of Repair Overview

Study Notes

Classical types:
- Regeneration: Replacing damaged tissue with the same type of tissue
- Fibrosis (Gliosis in CNS): Formation of scar tissue, especially in the central nervous system.
Other types:
- Organization: Healing of dead or non-living material by granulation tissue, which matures into fibrous tissue

Type of damaged cells:
- Permanent cells: Do not proliferate. Repair by fibrosis (e.g., muscle, nerve).
- Stable cells: Can proliferate but have limited capacity. Repair by mixed regeneration and/or fibrosis (e.g., liver cells, kidney tubular cells, glands).
- Labile cells: Continuously dividing. Repair by regeneration (e.g., epidermis, mucous membranes, blood and lymphoid tissue).
Supporting framework:
- If the framework remains intact, healing by regeneration occurs.
- If the framework is destroyed, the proliferating cells may display a disorganized pattern mixed with fibrosis.

Definition: Replacement of damaged tissue with healthy tissue of the same kind.
Cells healing by regeneration: Labile and stable cells (with intact framework).
Example in skin: Epidermis damage only—regeneration; epithelium & sub-epithelium damage—fibrosis.
Example in liver: Intact framework—regeneration; destroyed framework—cirrhosis.

Definition: Damaged tissue replaced by granulation tissue that matures into fibrous tissue.
Mechanism:
- Capillaries (neo-vascularization).
- Fibroblasts secrete collagen.
Fate:
- Collagen fibers reorganization
- Fibroblasts change into fibrocytes.
- Formation of avascular, strong fibrous tissue (scar).
Examples: Muscle damage (e.g., myocardial infarction), nerve/neuron damage (CNS).

Definition: Healing of dead or non-living material by granulation tissue followed by fibrous tissue.
Examples: Thrombus, fibrin in sero-fibrinous inflammation.

Primary union (first intention): Clean incisional wounds; minimal tissue destruction and approximated edges. Characteristics: rapid healing, small scar, complications are rare.
Secondary union (second intention): Gaping wounds, septic wounds, or abscesses. Characteristics: slow healing, large scar, complications more frequent.

Too little repair: Ulcer, sinus, fistula, weak scar, incisional hernia, fibrous union of bone (pseudo-arthrosis).
Excessive repair: Excessive granulation tissue, excessive scar tissue, squamous cell carcinoma (rare).

Local factors: Blood supply, foreign bodies, hematoma, infection, cell type, wound size.
Systemic factors: Age, nutritional status, presence of debilitating diseases, medication.