1. Tissue Repair

2. Ways of Repairing Tissue
Tissue repair depends on the type of tissue damaged and the severity of the injury.
Regeneration: replacement of destroyed tissue with the same kind of tissue.
Fibrosis: involves the proliferation of fibrous connective tissue often called scar tissue.

3. Tissue Repair has 3 steps
Inflammation
Organization
Two possiblities:
Regeneration
Fibrosis

4. Step 1: Inflammation
Trauma causes injured cells to release inflammatory chemicals that cause capillaries to dilate.
Capillaries become permeable releasing antibodies and clotting proteins that stop the loss of blood and walls in the wound.
The walled in wound is isolated from other tissues
The area of the clot exposed to the air forms a scab

6. Step 2: Organization
During this phase the blood clot is replaced by granulation tissue
Granulation tissue is a delicate pink tissue composed of a network of capillaries
Capillaries are fragile and bleed freely which is demonstrated when someone picks a scab
Fibroblasts and collagen fibers bridge the gap and have contractile properties that pull the wound together.
Macrophages digest the original blood clot

7. Granulation Tissue

8. Step 3: If Regeneration…
In pure infections (a pimple or sore throat) healing = regeneration.
During organization the surface epithelium begins to regenerate growing under the scab. The scab eventually detaches.
The scar may be invisible or visible as a thin white line, depending on the severity of the wound.

9. Step 3: If Fibrosis…
Destructive/severe infections lead to scarring/fibrosis.
Granulation tissue becomes a permanent fibrous tissue patch (scar tissue) that is resistant to infection
Over months the fibrous mass becomes smaller and compact. The scar appears pale and shiny, made of collagen fibers.

10. Scar after fibrosis

11. Step 3: If Fibrosis…
It is strong but lacks flexibility and elasticity. It cannot perform the normal functions of the tissue it replaced.
Scar tissues create blockages in the heart, hampers the muscle’s ability to expand and contract.
It causes adhesions in abdominal surgery. The adhesions prevent the normal shifting of loops of the intestines causing obstructions.
They can also immobilize joints when adhesions exist in connective tissue.

12. Capability of regeneration according to tissue:
TISSUE TYPE
Capacity to regenerate
Epithelial
Very good
Bone
Loose Connective Tissue (Areolar)
Blood Forming tissue
Smooth muscle
Moderate

13. Capability of regeneration according to tissue:
TISSUE TYPE
Capacity to regenerate
Dense regular connective tissue (tendon)
Moderate to weak
Skeletal muscle
Weak
Cartilage
Cardiac muscle
None (becomes scar tissue)
Nervous tissue in the brain
Spinal cord