Wound Healing - B. Pharma 2nd Semester Pathophysiology notes pdf

Wound Healing



       Process of Healing

       Healing by first intention

       Healing by second intention

       Contraction of wounds


At the end of this PDF, student will be able to

         Define “Healing”

        Describe the processes involved in healing

        Describe the contraction of wound

        Explain the process of healing of wound of skin

 Wound Healing


       Healing - body response to injury

       An attempt to restore normal structure and function

       Involves 2 distinct processes:

       Regeneration - healing by proliferation of parenchymal cells ; results in complete restoration

       Repair - healing by proliferation of connective tissue elements resulting in fibrosis and scar


       Proliferation of parenchmal cells

       Complete restoration of original tissue

       Cells are under the constant regulatory control of their cell cycle


       Epidermal growth factor

       fibroblast growth factor, platelet derived

      growth factor, endothelial growth factor,

      transforming growth factor-β

Cell cycle and its phases

       Period between two successive cell divisions

       M (mitosis) phase: Phase of mitosis.

       G1 (gap 1) phase: daughter cell enters G1 phase after mitosis

       S (synthesis) phase: the synthesis of nuclear DNA

       G2 (gap 2) phase

       G0 (gap 0) phase: resting phase of the cell after an M phase

Phases of cell cycle

Type of cells involved in regeneration – depending on the speed of cell division

       Labile cells - continuously dividing

       Epidermis, mucosal epithelium, GI tract epithelium etc

       Stable cells - low level of replication

       Hepatocytes, renal tubular epithelium, pancreatic acini

       Permanent cells - never divide

       Nerve cells, cardiac myocytes, skeletal muscle

Tissue Repair

       Replacement of injured tissue by fibrous tissue

Two processes are involved in repair:

1. Granulation tissue formation

2. Contraction of wounds

       Involves mesenchymal cells

       connective tissue cells

       endothelial cells, macrophages & some parenchymal cells

Granulation tissue formation

Phase of inflammation

       Acute inflammatory

       Response with exudation of plasma, neutrophils

       Monocytes within 24 hours

Phase of clearance

       Proteolytic enzymes liberated from Neutrophils

       Autolytic enzymes from dead tissues cells

       Phagocytic activity of macrophages

       Clear off the necrotic tissue, debris and RBCs

Phase of ingrowth of granulation tissue

1.       Angiogenesis

       Proliferation of endothelial cells

       Development of capillary sprout

       Vascular endothelial growth factor (VEGF)

       Platelet-derived growth factor (PDGF)

2. Fibrogenesis

          Fibroblasts originate from fibrocytes

          Collagen fibrils begin to appear by about 6th day

          Formation of inactive looking scar - cicatrisation

Contraction of wounds

       Wound starts contracting after 2-3 days

       Process is completed by the 14th day

       Reduced by approximately 80% of its original size

       Results in rapid healing


       Contraction of collagen

       Appearance of Myofibroblasts

Healing of wound in skin

       Combination of Regeneration and repair

Accomplished in one of the following two ways:

Ø  Healing by first intention (primary union)

Ø  Healing by second intention (secondary union)

Healing by first intention (primary union)


       Clean and uninfected

       Surgically incised

       Without much loss of cells and tissue

       Edges of wound are approximated by surgical sutures

Sequence of events

       Initial haemorrhage

       Acute inflammatory response

       Epithelial changes


       Suture tracks

Healing by first intention

Healing by second intention (secondary union)


       Open with a large tissue defect, at times infected

       Having extensive loss of cells and tissues

       The wound is not approximated by surgical sutures but is left open

Sequence of events

       Initial haemorrhage followed by clotting

       Inflammatory phase – neutrophills & macrophages

       Epithelial changes – epidermal cell margination & proliferation

       Granulation tissue

       Wound contraction

Factors affecting wound healing

Local factors


       Blood supply to wound area

       Mechanical factors

       Foreign bodies

       Exposure to ionising radiation

       Size, Location & type of wound

Systemic factors



       Systemic infection

       Uncontrolled diabetes

       Haemetological abnormalities


       Healing is a body response to injury it is an  attempt to restore normal structure and function

       Healing occurs by two processes- regeneration and repair

       Contraction of wound involves dehydration, contraction of collagen, appearance of myofibroblasts

       Healing of wounds of skin occurs by first intention or second intention depending on the type of infection

Post a Comment