Wound healing: phases and scar !
- Process
A wound closes in four overlapping phases: stop the bleeding, clean up, rebuild with new tissue, then remodel it into a scar over months.
Updated 2026-11-01
See it in 3D: Skin
What it is
Skin repair moves through haemostasis, inflammation, proliferation and remodelling, which overlap in time. Platelets and fibrin seal the wound, neutrophils and then macrophages clean it, fibroblasts and new capillaries build granulation tissue while the epidermis grows over, and the collagen is reorganised for months. Wounds deeper than the epidermis heal with a scar, which never regains the full strength of normal skin.
Key facts
- Primary intention: clean edges brought together, little granulation tissue, thin scar.
- Secondary intention: an open gap fills with granulation tissue and contracts, giving a larger scar.
- A keloid grows beyond the wound edges and is more common in people with darker skin; a hypertrophic scar stays within them.
Step by step
- Haemostasis: vessels constrict, platelets plug the gap and a fibrin clot seals the wound and becomes the scab.
- Inflammation: neutrophils kill bacteria; macrophages remove debris and release growth factors.
- Proliferation: fibroblasts make collagen and new capillaries grow, forming red granulation tissue.
- Re-epithelialisation: basal keratinocytes from the edges and appendages migrate over the granulation bed.
- Contraction: myofibroblasts pull the edges together, more so in wounds that heal by second intention.
- Remodelling: type III collagen is replaced by type I, vessels regress and the scar flattens and pales over months.
Clinical notes
- Pressure injuries form over bony points when steady pressure cuts off blood flow; they are staged by depth, from intact red skin that does not blanch to full-thickness loss exposing bone or tendon.
- Venous ulcers sit over the inner ankle with chronic venous hypertension; diabetic foot ulcers combine neuropathy, ischaemia and infection.
- Lack of vitamin C (scurvy) weakens collagen and reopens old wounds.
Test yourself
Think of the answer, then tap the question to see it.
Which cell is considered the key orchestrator of wound repair?
The macrophage: it removes debris and releases growth factors that recruit fibroblasts and stimulate new vessels.
What does granulation tissue contain?
New capillaries, proliferating fibroblasts, loose extracellular matrix and inflammatory cells.
Which collagen type dominates early and which in a mature scar?
Type III early in granulation tissue; it is gradually replaced by the stronger type I during remodelling.
How does a keloid differ from a hypertrophic scar?
A keloid grows beyond the original wound margins and rarely regresses; a hypertrophic scar stays within them and may flatten.
Why does a pressure injury develop over the sacrum or heels?
Steady pressure between bone and surface closes the small vessels, so the tissue becomes ischaemic and dies.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Skin: epidermis layers, dermis, hypodermis
- Hair follicles, sebaceous and sweat glands, nails
- Connective tissue proper: cells and fibres
- Extracellular matrix: collagen types, elastin, ground substance
- Cell adaptations: hypertrophy, hyperplasia, atrophy, metaplasia
Related conditions
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 5.4 Diseases, Disorders, and Injuries of the Integumentary System - Anatomy and Physiology 2e | OpenStax (OpenStax, Rice University, 2022); Keloids: MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine, 2024); Pressure Sores | Bedsores | Pressure Ulcers | MedlinePlus (U.S. National Library of Medicine, 2024).
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Representative model, for educational purposes only.