Granulation tissue

Its histological appearance is characterized by proliferation of fibroblasts and thin-walled, delicate capillaries (angiogenesis), and infiltrated inflammatory cells in a loose extracellular matrix.

This is necessary both to aid the healing process and to protect against invading pathogens, as the wound often does not have an effective skin barrier to act as a first line of defense.

It is necessary for a network of blood vessels to be established as soon as possible to provide the growing tissue with nutrients, to take away cellular wastes, and transport new leukocytes to the area.

Fibroblasts, the main cells that deposit granulation tissue, depend on oxygen to proliferate and lay down the new extracellular matrix.

[7] In vascularisation, also called angiogenesis, endothelial cells quickly grow into the tissue from older, intact blood vessels.

Example of hypergranulation tissue from a cut on a finger.
Histopathology of granulation tissue at 11 days after injury, showing fibroblasts, hemorrhage and lymphocytes.
Approximate times of the different phases of wound healing , with substantial variation depending on wound size and healing conditions. Granulation tissue formation is seen in green box at days to weeks.