Granulation tissue

Granulation tissue is characterized by proliferation of fibroblasts and new thin-walled, delicate capillaries in a loose extracellular matrix, often with admixed inflammatory cells, mainly macrophages. This tissue progressively invades the site of injury; the amount of granulation tissue that is formed depends on the size of the tissue deficit created by the wound and the intensity of inflammation.

What is repair by scar formation? What are the steps?

If repair cannot be accomplished by regeneration alone, it occurs by replacement of the injured cells with connective tissue, leading to the formation of a scar, or by a combination of regeneration of some residual cells and scar formation.

Steps involved in repair in scar formation:

• Clot formation
• Inflammation
• Angiogenesis and formation of granulation tissue, 
• Migration and proliferation of fibroblasts, 
• Collagen synthesis, 
• Connective tissue remodeling.
  

Repair by regeneration

• Different tissues consist of continuously dividing cells (epithelia, hematopoietic tissues), normally quiescent cells that are capable of proliferation (most parenchymal organs), and nondividing cells (neurons, skeletal and cardiac muscle). The regenerative capacity of a tissue depends on the proliferative
  potential of its constituent cells.
• Cell proliferation is controlled by the cell cycle, and is stimulated by growth factors and interactions of cells with the extracellular matrix.
• Regeneration of the liver is a classic example of repair by regeneration. It is triggered by cytokines and growth factors produced in response to loss of liver mass and inflammation. In different situations, regeneration may occur by proliferation of surviving hepatocytes or repopulation from progenitor cells.

What is Tissue repair? Steps involved in tissue repair.

 Tissue Repair:

Critical to the survival of an organism is the ability to repair the damage caused by toxic insults and inflammation. In fact, the inflammatory response to microbes and injured tissues not only serves to eliminate these dangers but also sets into motion the process of repair.

Repair of damaged tissues occurs by two types of reactions: regeneration by proliferation of residual (uninjured) cells and maturation of tissue stem cells, and the deposition of connective tissue to form a scar.

 1. Regeneration:  Some tissues are able to replace the damaged components and essentially return to a normal state; this process is called regeneration. Regeneration occurs by proliferation of cells that survive the injury and retain the capacity to proliferate, for example, in the rapidly dividing epithelia of the skin and intestines, and in some parenchymal organs, notably the liver.

2. Connective tissue deposition (scar formation):  If the injured tissues are incapable of complete restitution, or if the supporting structures of the tissue are severely damaged, repair occurs by the laying down of connective (fibrous) tissue, a process that may result in formation of a scar.