Tissue Repair

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.

Tissue Repair has 3 steps

1. Inflammation2. Organization3. Two possiblities:

Regeneration Fibrosis

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

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

Granulation Tissue

http://drwheatgrass.com/conditions/woundhealing/skingraft2.htm#f5

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.

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.

Scar after fibrosis

http://drwheatgrass.com/conditions/woundhealing/skingraft2.htm#f5

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.

Capability of regeneration according to tissue:

TISSUE TYPE Capacity to regenerate

Epithelial Very good

Bone Very good

Loose Connective Tissue (Areolar)

Very good

Blood Forming tissue Very good

Smooth muscle Moderate

Capability of regeneration according to tissue:

TISSUE TYPE Capacity to regenerate

Dense regular connective tissue (tendon)

Moderate to weak

Skeletal muscle Weak

Cartilage Weak

Cardiac muscle None (becomes scar tissue)

Nervous tissue in the brain None (becomes scar tissue)

Spinal cord None (becomes scar tissue)