Chapter 6 : Wound Healing
Wound healing is a complex and dynamic process of restoring cellular structures and tissue layers.
One needs to be extremely careful about wound healing after a surgical procedure as an infection may create complications or render the total procedure ineffective.
It is normal to feel numb near the operated area and the patient may also experience pain.
A patient may also feel itchy near the surgery wound and this is generally normal during the wound healing duration.
The patients must ensure that the wound is kept dry and clean and the surgeon will generally give instructions that when the person can shower.
Following are the factors that determine the types of wound healing:
Topics covered in this snack-sized chapter:
- The amount of tissue loss.
Process of wound healing basically takes place in one of the three ways:
- The existence of contamination or infection.
Primary wound healing or healing by the first intention occurs within an hours of repairing a full-thickness surgical incision.
This surgical insult results in the mortality of a minimal number of cellular constituents.
Healing occurs through secondary intention when surgical wounds are characterized by tissue loss with inability to approximate wound edges.
Healing is appropriate in cases of infection, excessive trauma, tissue loss, or imprecise approximation of tissue.
The wound is left open and allowed to heal from the inside towards the outer surface.
Secondary healing results in an inflammatory response that is more intense than with primary wound healing.
A full-thickness wound is allowed to close and heal.
Secondary healing results in pronounced contraction of wounds.
This healing process takes place when approximation of wound edges is delayed by 3-5 days or more after injury or surgery.
The entire wound healing process is a complex series of events that begins at the moment of injury and can continue for months to years.
There are basically 3 phases to the healing process:
- Remodeling or Maturation Phase.
After the occurrence of a wound, a process of blood extravasation starts to fill the damaged area with plasma and cell elements, especially platelet.
Platelet aggregation and blood coagulation generate a buffer which restores hemostasis and forms a barrier against the invasion of microorganisms.
The release of factors coming from platelets, contribute for the activation of monocytes, transforming them into macrophages that are the main cell involved in the control of the repair process.
The activated macrophage is the main effector cell in the process of tissue repair, degrading and removing components from the damaged connective tissue.
The proliferative phase is the phase in which a matrix or latticework of cells forms.
Fibroblasts produce a new extracellular matrix required for cell growth.
Epithelialization is the natural act of healing dermal and epidermal tissue in which epithelium grows over a wound.
Epithelium is a membranous tissue made up of one or more layers of cells that contains very little intercellular substance.
Re-Epithelialization restoration of epithelium over a denuded area (as a burn site) by natural growth or plastic surgery.
Granulation tissue is a mixture of newly forming blood vessel buds, macrophages and fibroblasts in a collagen matrix.
Angiogenesis is an essential phase of the healing process, in which new blood vessels are formed from preexisting vessels.
New blood vessels carry oxygen and nutrients required for local cellular metabolism.
The extracellular matrix is important for the growth and normal maintenance of vessels, because they act as the support platform for the cell migration and also reservoir and modulator of the release of growth factors.
The framework (collagen) becomes more organized making the tissue stronger.
It is a phase marked by maturation of elements and affections to the extracellular matrix, leading to proteoglycan and collagen deposits.
Fibroblasts and inflammatory cells disappear from the wound site through a process of migration.
The skin forms a protective barrier between the outer environment and the body.
Various factors can lead to impaired wound healing.
The factors which influence repair are:
Wound Healing Phases
Immediate to 2-5 days
5 days to 3 weeks
Collagen forms which increases tensile strength to wounds
Bleeding stops (homeostasis)
Constriction of the blood supply
Platelets start to clot
Formation of a scab
New collagen tissue is laid down
New capillaries fills in defect
Scar tissue is only 80 percent as strong as original tissue
Opening of the blood supply
Cleansing of the wound
3 weeks to 2 years
Cells cross over the moist surface
Cell travel about 3 cm from point of origin
Local Factors are directly influence the characteristics of the wound itself.
- Oxygen is important for cell metabolism and is critical for nearly all wound-healing processes.
- Due to vascular disruption and high oxygen consumption by metabolically active cells, the microenvironment of the early wound is depleted of oxygen.
- In wounds where oxygenation is not restored, healing is impaired.
- Infection and replication status of the micro-organisms determines whether the wound is classified as having contamination, colonization, local infection/critical colonization, and/or spreading invasive infection.
- Contamination is the presence of non-replicating organisms on a wound.
- Colonization is the presence of replicating micro-organisms on the wound without tissue damage.
- Invasive infection is the presence of replicating organisms within a wound with subsequent host injury.
- Inflammation is an important step for the removal of contaminating microorganisms.
- In the absence of effective decontamination, inflammation may be prolonged.
Systemic Factors are the overall state of the person that affects his or her ability to heal.
Systemic factors that influence healing are:
- Sex hormones in aged individuals