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

Wound Healing

wound-healing

Objective

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

Wound healing is a remarkable process that our bodies undertake whenever we suffer an injury. From minor cuts and scrapes to surgical incisions and more severe wounds, our bodies have a remarkable ability to repair damaged tissue and restore normal function.

Types of Wounds

Wounds are generally categorized into two types:

  • Acute Wounds: These are typically caused by a single, traumatic event and tend to heal quickly.
  • Chronic Wounds: Chronic wounds are more complex and can be the result of underlying health issues. They often require specialized care and a longer healing process.

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

Regeneration

       Proliferation of parenchmal cells

       Complete restoration of original tissue

       Cells are under the constant regulatory control of their cell cycle

       Involves

       Epidermal growth factor

       fibroblast growth factor, platelet derived

      growth factor, endothelial growth factor,

      transforming growth factor-β

The Stages of Wound Healing

Wound healing occurs in four distinct stages, each with its specific characteristics and requirements:

  1. Hemostasis: This is the initial stage where the bleeding is stopped. Platelets form a plug to seal the wound, and blood vessels constrict.
  2. Inflammation: Inflammation is a necessary part of the healing process. It helps remove foreign particles and prepares the wound for repair.
  3. Proliferation: In this stage, new tissue is formed to replace the damaged area. Collagen, a protein that provides strength, is synthesized.
  4. Remodeling: The final stage involves the strengthening and remodeling of the newly formed tissue, improving its durability.

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

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

       Dehydration

       Contraction of collagen

       Appearance of Myofibroblasts

Healing of wounds in the 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)

Characteristics

       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

       Organisation

       Suture tracks

Healing-by-first-intention

Healing by first intention

Healing-by-first-intention

Healing by second intention (secondary union)

Characteristics

       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

Healing-by-second-intention

Healing-by-second-intention

Factors Affecting Wound Healing

Local factors

       Infection

       Blood supply to wound area

       Mechanical factors

       Foreign bodies

       Exposure to ionising radiation

       Size, Location & type of wound

Systemic factors

       Age

       Nutrition

       Systemic infection

       Uncontrolled diabetes

       Haemetological abnormalities

Summary

       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

Frequently Asked Questions (FAQs)

  1. How long does it typically take for a wound to heal completely? The time it takes for a wound to heal depends on various factors, including the type and size of the wound, the individual’s overall health, and the quality of wound care. Generally, minor wounds may heal in a few days, while larger or more complex wounds can take several weeks.
  2. Are there any foods that can speed up the wound healing process? Yes, a balanced diet rich in essential nutrients like vitamins C and E, zinc, and protein can support the body’s healing process. Including these nutrients in your diet can help promote faster wound healing.
  3. What should I do if my wound becomes infected during the healing process? If you suspect that your wound is infected (signs include increased pain, redness, swelling, or discharge), seek medical attention promptly. Infections can delay the healing process and lead to more serious complications.
  4. Can exercise be harmful during wound healing? Exercise can be beneficial for wound healing, but it should be done under the guidance of a healthcare professional. Overexertion or engaging in inappropriate physical activity can be harmful to the healing process.
  5. Are there any new advancements in wound healing treatments on the horizon? Yes, research in the field of wound healing continues to advance. New treatments and technologies are being developed to improve the efficiency and effectiveness of wound healing, offering hope for better outcomes in the future.

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