Wound Healing by Primary Intention: Stages, Mechanism, and Modifying Factors

Wound Healing by Primary Intention: Stages, Mechanism, and Modifying Factors

Describe the process of healing in a clean incised wound and mention the factors that may modify the process of healing.
Or
Write a short note on healing by primary intention.
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Discuss in brief the mechanism of wound healing.
Or
Describe the mechanism of healing.
Or
Write a short note on wound healing.
Or
Describe the various factors affecting wound healing.
Answer:

Injury to tissue may result in cell death and tissue necrosis.

• Healing: It is body response to injury in an attempt to restore normal structure and function.
• Healing with first intention or primary union
• Healing of wounds which has the following characteristics.
• • Clean and uninfected
  • Surgically incised
  • Without much loss of cells and tissues
  • Edges of wounds are approximated by surgical sutures.

Wound healing by primary intention stages

Pathology of Actinomycosis Events in Primary Intention

• Initial hemorrhage: Immediately after injury, the space between approximated surfaces of the incised wound is filled with blood which then clots and seals the wound and prevents dehydration and infection.
• Acute inflammatory response: This occurs within 24 hours with the appearance of polymorphs from the margins of the incision. By the third day, polymorphs are replaced by macrophages which are clear of the debris.
• Epithelial changes: The basal cells of the epidermis from both cut margins start proliferating and marginating towards incisional space in the form of epithelial spurs.
  • The migrating epithelial cells separate the underlying viable dermis from overlying necrotic material and clot, forming scale which is cast off
  • The basal cells from the margins continue to divide. By 5th day a multilayered new epidermis is formed which is differentiated into superficial and deeper layer.
• Organization:
• • By third day, fibroblasts also include the wound area. By 5th-day new collagen fibrils start forming which are dominant till healing is completed.
  • In four weeks, the scar tissue with scanty cellular and vascular elements, a few inflammatory cells and an epithelial surface is formed.
• Suture tracks: Each suture track is a separate wound and incites the same phenomena as in healing of the primary wound, i.e. filing the space with hemorrhage some inflammatory cell reaction, epithelial cell proliferation along the suture track from both margins, fibroblastic proliferation and formation of young collagen.

When sutures are removed around seventh day, much of epithelialized suture track is avulsed and the remaining epithelial tissues in track is absorbed.

However, sometimes the suture track gets infected, or the epithelial cells may persist in the track (implantation or epidermal cysts).

Pathology of Actinomycosis Factors that Modify the Cause of Healing

Two types of factors influencing wound healing.

• Local factors: Those acting locally.
  • Infection: It is the most important factor acting locally which delays the process of healing.

• • Poor blood supply to wound shows delay healing–injuries to face heal quickly due to rich blood supply while injury to leg having poor blood supply heals slowly.
  • Foreign Bodies: Including suture interfere with healing and cause intense inflammation reaction and infection.
  • Movement delays wound healing.
  • Exposure to ionizing radiation delays granulation tissue formation.
  • Exposure to UV light facilitates healing.
• Primary vs secondary wound healing
  • Type, size and location of injury determine whether healing takes place by resolution or organization.
• Systemic factors: Those acting in general, these are as under:
  • Age: Wound healing is rapid in the young and somewhat slow in aged, due to poor blood supply to the injured area in later.
  • Nutrition: The deficiency of constituents like protein, vitamin C, and zinc delays the wound healing.
  • Systemic Infection: Delays wound healing.
  • The administration of glucocorticoids has anti-inflammatory effects.
  • Uncontrolled diabetes are more prone to develop infections and hence delay in healing.
  • Hematological abnormalities: Like defects of neutrophil functions, and neutropenia and bleeding disorders slow the process of wound healing.