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 Inflammation Organization 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 Loose Connective Tissue (Areolar) Blood Forming tissue 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 Cardiac muscle None (becomes scar tissue) Nervous tissue in the brain Spinal cord