Pathology
Healing and Repair
Healing and repair for MBBS and NEET-PG: labile, stable and permanent cells, granulation tissue, first and second intention healing, and factors that delay wound healing, mapped to NMC code PA5.1.
MedNext Academy | 3 min read
Healing and Repair
Healing and repair for MBBS and NEET-PG: labile, stable and permanent cells, granulation tissue, first and second intention healing, and factors that delay wound healing, mapped to NMC code PA5.1.
This chapter describes how damaged tissue is restored, by regeneration of cells or by scar formation. It covers the proliferative capacity of cell types, the phases of wound healing, granulation tissue, healing by first and second intention, and the local and systemic factors that impair repair.
High-yield: Healing and Repair
- Repair restores tissue by regeneration of parenchymal cells, by connective tissue scarring, or by a combination of the two.
- Labile cells such as epidermis and gut lining divide continuously; stable cells such as hepatocytes divide when stimulated; permanent cells such as neurons and cardiac muscle do not divide.
- Healing by first intention occurs in clean, apposed wounds and leaves a thin scar with minimal contraction.
- Healing by second intention occurs in open wounds with tissue loss and involves abundant granulation tissue and wound contraction.
- Granulation tissue is composed of new capillaries, fibroblasts and loose connective tissue and is the hallmark of healing.
- Angiogenesis, the formation of new blood vessels, is driven mainly by vascular endothelial growth factor.
- Myofibroblasts are responsible for wound contraction in healing by second intention.
- Collagen type III is laid down early and is gradually replaced by the stronger type I collagen as the scar matures.
- Wound strength reaches about 70 to 80% of normal by three months but never fully returns to that of intact skin.
- Vitamin C is essential for collagen synthesis, so its deficiency impairs wound healing.
- Zinc deficiency, infection, poor blood supply, diabetes and corticosteroids all delay wound healing.
- A keloid is exuberant scar collagen that extends beyond the original wound margin and is more common in dark-skinned people.
- Hypertrophic scar remains within the wound boundary, unlike a keloid which spreads beyond it.
- Dehiscence is wound rupture, and proud flesh is excessive granulation tissue that protrudes above the wound surface.
First versus second intention healing
- **First intention:** Clean, closed, apposed wound; thin scar; little granulation tissue or contraction.
- **Second intention:** Open wound with tissue loss; abundant granulation tissue; marked wound contraction.
- **Granulation tissue:** New capillaries plus fibroblasts; the substrate for repair.
- **Scar maturation:** Type III collagen replaced by stronger type I; strength plateaus near 80%.
NMC competencies in this chapter
- **PA5.1:** Process of repair and regeneration including wound healing and its types
Frequently Asked Questions
What is granulation tissue?
Granulation tissue is the pink, soft tissue of new capillaries and fibroblasts that fills a healing wound and forms the basis of repair.
How do first and second intention healing differ?
First intention heals a clean, closed wound with a thin scar, while second intention heals an open wound with tissue loss through abundant granulation tissue and marked contraction.
Which cell causes wound contraction?
The myofibroblast, a modified fibroblast with contractile properties, draws the edges of an open wound together.
What factors delay wound healing?
Infection, poor blood supply, diabetes, corticosteroids, and deficiencies of vitamin C, protein and zinc all slow healing.
Continue reading
MBBSAll Pathology chapters
Continue through the Pathology chapter map.
Continue studying Pathology
Explore clinician-written learning resources, structured revision and practice across the MedNext platform.
Open in the MedNext appSee plans