Summary tissue repair

Function of Stage 1

• Prepares wound for repair

• Eliminates invading microorganisms

• Removes debris and dead tissue

What triggers inflammation

• Damaged cells release inflammatory chemical

What happens to blood vessels

• Become more permeable

• Plasma, macrophages, and clotting proteins enter the area

Key components entering the wound

• Macrophages → engulf debris & microorganisms

• Clotting proteins → form a blood clot

• Stops blood loss

• Holds wound together

• Prevents further microbial invasion

Signs of inflammation

• Redness

• Pain

• Heat

• Swelling

What forms on the surface

• Scab (dried blood clot)

Function of Stage 2

• Extracellular matrix synthesis (including collagen)

• Restores blood supply

What replaces the blood clot

• Granulation tissue

Granulation tissue contains:

• Capillaries

  • Restore blood supply

  • Bring oxygen and nutrients

• Fibroblasts

  • Produce collagen fibres

  • Bridge the wound gap

• Macrophages

• Remove debris, microorganisms, and the blood clot

What do epithelial stem cells do

• Multiply

• Migrate over granulation tissue

• Begin re‑forming the epidermis

Function of Stage 3

What is the purpose of the maturation stage?

• Completes permanent skin repair through:

• Regeneration

• Fibrosis (scar formation)

What happens to collagen

Collagen remodelling

• Collagen is reorganised and tightened

• Helps pull wound edges together

What happens to granulation tissue

Replacement with scar tissue

• Existing blood vessels are compressed

• Granulation tissue is replaced by scar tissue → fibrosi

Properties of scar tissue

• Avascular

• Tough

• No elasticity or flexibility

• No hair follicles

• No sweat or oil glands

When does regeneration occur

If damage is minor OR epidermal stem cells are present

• Stem cells multiply under the scab

• Regenerate the epidermis

• Scab falls off

• Skin returns to pre‑injury appearance

When is scar tissue visible

Visible scar

• If repair occurs only by fibrosis

• Common in major wounds

Invisible or minimal scar

• If repair occurs by regeneration + fibrosis