The human body has many methods of protecting itself from injury. When tissue injury occurs, the body stimulates inflammatory and immune responses and the process of wound healing would initiate almost immediately. A wound may be described as the disruption in the continuity of cells and once it occurs, the following will result:
L – Loss of all or part of organ functioning
O – Onset of sympathetic stress response
S – Shedding of blood or hemorrhage and blood clotting
S – Subsequent bacterial contamination and death of cells
Wound healing, also termed as tissue repair, is restoration of the continuity of the cells. It occurs in two major ways namely:
- Regeneration – replacement of the destroyed tissue by the same kind of cells.
- Fibrosis – involves the repair of dense (fibrous) connective tissue, distinctively noted by the formation of scar tissue.
Some wounds undergo regeneration whilst some go through the process of fibrosis. Which occurs largely depends on the following:
- Type of tissue damaged.
- How severe the injury is.
Series of events take place when tissue injury is present. Various continuous and overlapping cellular processes contribute to the restoration of wounds which are the following:
- Increased Capillary Permeability
- Increased capillary permeability – After a tissue is injured, the capillaries become very permeable. Increased capillary permeability allows fluid abundant with clotting proteins and other substances from the bloodstream to seep into the injured area.
- Clot construction – Clotting proteins that leaked from the blood would create a clot and eventually stops the blood loss. Presence of clot would hold the edge of the wound together and wall off the injured area to prevent any bacteria and other harmful substances from spreading to surrounding tissues.
- Scab formation – Clots exposed to air quickly dries and hardens and then forms a scab.
- Cell proliferation.
- Formation of granulation tissue. – Granulation tissues are delicate pink tissues largely composed of new capillaries. These tissues would grow into the damaged area from the neighboring uninjured blood vessels. One of the characteristics of granulation tissue is its tendency to bleed freely due to the fragility of its capillaries.
- When a scab is picked away from the skin where the wound is present, bleeding is experienced because of the delicateness of the capillaries of the granulation tissue.
- Collagen Production
- Synthesis of the building blocks of collagen fibers. – Aside from capillaries, granulation tissue also contains phagocytes that in time sets the blood clot out and is replaced with connective tissue cells which are called fibroblasts. These connective tissue cells are responsible for synthesizing the building blocks of scar tissue, also called collagen fibers, to permanently restore the continuity of cells.
- Epithelium Regeneration
- Initiation of epithelium regeneration. – As the surface epithelium begins to regenerate, it makes its way to across the granulation tissue just beneath the scab.
- Full regeneration of the surface. – After the epithelium crossed the granulation tissue, the scab eventually detaches from the skin surface and the result is the presence of a fully regenerated surface epithelium that covers an underlying area of fibrosis or the scar.
- Formation of Scar. – The scar could either be visible or not. Some scars are as thin white line, depending on the severity of the wound.
- Types of tissue regenerate differently. Tissue of the skin and mucous membranes (epithelial tissue) regenerate beautifully so as the fibrous connective tissues and bones. Skeletal muscles are the type of tissues that poorly regenerates.