SN7 SHORT NOTE 5M

Describe granulation tissue with its components and significance.

Pathology · 2nd Professional — Para-Clinical

Definition

Granulation tissue is the hallmark of healing: newly formed capillaries, proliferating fibroblasts and inflammatory cells within a loose oedematous matrix.

The name comes from its soft, pink, granular appearance to the naked eye, and has nothing to do with granulomas
It bleeds readily and is not painful, because it contains no nerves

Components

Component	Role
New capillaries (angiogenesis)	Supply oxygen and nutrients; driven by VEGF and FGF-2; they are leaky, which accounts for the oedema
Fibroblasts	Migrate and proliferate; synthesise collagen and matrix; driven by PDGF, TGF-beta and FGF
Myofibroblasts	Modified fibroblasts with contractile filaments; produce wound contraction
Macrophages	Clear debris and secrete the growth factors that orchestrate the whole process
Loose extracellular matrix	Fibronectin, hyaluronan and proteoglycan, later replaced by collagen

Sequence of Formation

Day 2–3 — macrophages arrive and secrete growth factors → angiogenesis — endothelial sprouting from existing venules → Fibroblast migration and proliferation → Day 5 — granulation tissue is maximal; the wound is soft, red and oedematous → Collagen is deposited progressively; type III first, later replaced by type I → Vessels regress and cells fall in number → A pale, avascular, collagenous scar remains

CLINICAL PEARL

The scar is what is left when granulation tissue is dismantled. The vessels that made the wound red regress, the fibroblasts die by apoptosis, and the collagen is remodelled from type III to type I. A red, raised scar is therefore a young one, and reassuring the patient that it will pale over months is sound advice founded on this sequence.

Granulation Tissue Compared with Granuloma

Feature	Granulation tissue	Granuloma
Nature	Reparative	Inflammatory
Chief cells	Fibroblasts and endothelial cells	Epithelioid cells and giant cells
Vascularity	Highly vascular	Poorly vascular
Purpose	To fill a defect and heal it	To wall off an indigestible agent
Seen in	Any healing wound or ulcer base	Tuberculosis, sarcoidosis, foreign body

Applied Aspects

Healthy granulation tissue is the sign a wound is ready for grafting — pink, firm, granular and bleeding on gentle contact
Unhealthy granulation tissue is pale, oedematous or covered in slough, and indicates infection, ischaemia or a foreign body; the cause must be corrected before closure
Exuberant granulation ("proud flesh") protrudes above the skin and prevents epithelium from migrating across; treated by silver nitrate cautery or curettage
Pyogenic granuloma is a misnomer twice over — it is neither pyogenic nor a granuloma, but a lobular capillary haemangioma of exuberant granulation tissue
Negative pressure wound therapy promotes granulation by removing exudate and applying mechanical stress, and has transformed the management of large wounds

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