Wound Healing

Regardless of size or type, all wounds follow the same path to healing. Scientific research typically refers to wound healing as a series of overlapping phases. While the body's complex healing mechanisms occur simultaneously, individual areas of a wound may respond at different rates. Often impediments or complications can slow or halt the healing process. A thorough understanding of the factors affecting wound healing is essential to achieving wound closure. The following information examines some of the elements involved in wound healing.

Under ideal conditions, all wounds follow the same healing process. Insufficient bodily resources and local or systemic impediments can alter the course of healing. The result is chronic wounds which must be redirected to the normal healing path.

Collagen's Role in Healing

Healed Wound
Injury occurs

Healed Wound

01. Inadequate resources may stagnate the healing process

02. Inadequate resources may stagnate the healing process

03. A wound that receives adequate resources can overcome impediments and progress on the normal healin path.

04. Pressure edema infection or other local factors can interrupt or stop the healing process.

05. Systemic impediments such as vascular irregularities can delay or halt wound healing.

Three Different Views of the Healing Process

Clinical View

Collagen dressing used

Theoretical view

Laboratory view

Sections taken from adult mineiswine

Day 1

Open abdominal wound, measuring
7.0 cm x 3.0 cm x 3.6 cm

Day 0-1

  1. Damaged vessels constrict to slow blood loss.
  2. Uninjured vessels permeate and release serum, proteins and platelets.
  3. Platelets aggregate to stop bleeding.
  4. Leukocytes migrate into the tissue and initiate the inflammatory process.

Leukocytes (small purple dots) infiltrate from the underlying tissue to clean up the wound.

Day 14

Reduced wound, measuring
4.0 cm x 1.2 cm x 1.5 cm

Day 0-14

  1. Neutrophils secrete chemicals that kill bacteria and mediate inflammatory activities.
  2. Monocytes emigrate to the wound and are transformed into macrophages.
  3. Macrophages engulf and digest foreign particles and necrotic debris, including cellular remains .
  4. Macrophages release angiogenic substances resulting in growth of new capillaries and granulation tissue.

New blood vessels (outlined by dark stain) grow into the wound  to  restore circulation.

Day 34

Reduced wound, measuring
1.3 cm x 0.4 cm x 0.5 cm

Day 1-35

  1. Fibroblasts proliferate in the wound and secrete glycoproteins and collagen .
  2. Epidermal cells begin to migrate from
  3. the wound edge.
  4. Granulation tissue is formed from macrophages, fibroblasts, and neovasculature.

Macrophages and fibroblasts (purple dots) are present in the wound.

Day 49

Wound closure

Day 5-90

  1. Fibroblasts secrete collagen which provides strength to the wound.
  2. Wound remodeling occurs with deposition of organized fibers.
  3. Wound contracture occurs, increasing tissue integrity.
  4. Epidermal cells grow over the connective tissue bed to close the wound.

Fibroblasts migrate into the wound from surrounding tissue (right) and deposit new collagen fibers (left). Epidermal cells (top right) close the wound.


Glossary:

  • Angiogenesis: The process by which new blood vessels are formed.
  • Chronic wounds: Wounds that take longer than normal to heal or do not heal at all because of underlying conditions.
  • Edema: The presence of an abnormally large amount of fluid in the,intercellular tissue sppces of the body.
  • Fibroblasts: A connective tis­ sue cell. They differentiate into chondroblasts, collagenoblasts, and osteoblasts, form the fibrous tissues in the body, ten­ dons, aponeuroses, supporting and binding tissues of all sorts.
  • Granulation: The process of forming granulation tissue.
  • Granulation Tissue: Small, beadlike masses of tissue formed on the surface of wounds.
  • Infection: Invasion and multipli­ cation of microorganisms in body tissues.
  • Inflammation: A localized pro­ tective response elicited by injury or destruction of tissues which serves to destroy, dilute, or wall off both the injurious agent and the injured tissue.
  • Keratinocytes: The epidermal cell which synthesizes keratin; constitutes 95 percent of the epidermal cells and with rl)elanocyte, forms the binary cell system of the epidermis.
  • Leukocytes: White blood cor­ puscles wh ich act as scav­ engers, helping to combat infec­tion.
  • Macrophages: Any of the many mononuclear phagocytes found in tissues.
  • Monocytes: A mononuclear phagocytic leukocyte. Formed in the bone marrow from promonocytes, monocytes are transported to tissues, as of the lungs and liver, where they develop into macrophages.
  • Moist Wound Healing: To maintain a moist environment at the wound bed so as to enhance epidermal cell migra­tion and encourage epithelialization.
  • Necrosis: The sum of the mor phological changes indicative of cell death and caused by the progressive degradative action of enzymes.
  • Neovascularization: New blood vessel formation in abnormal tis­ sue or in abnormal positions.
  • Neutrophils: Granular leuko­ cytes that have a nucleus with three to five lobes. They have the properties of chemotaxis, adherence to immune complex­es, and phagocytosis.
  • Occlusive Dressing: A dressing that seals a wound completely to prevent infection from with­ out and to prevent moisture from within from escaping through the dressing.
  • Platelets: A disk-shaped struc­ ture, found in the blood of all mammals and chiefly known for its role in blood coagulation.
  • Remodeling: Reorganization or rennovation of an old structure.