Wound Healing.ppt 3n1u4l

Soft tissue Wound healing

CONTENTS  Introduction  Wound  Classification of soft tissue wounds  Healing

 Regeneration

 Repair  Healing by first intention  Healing by second intention  Factors influencing wound healing  Complications of wound healing  Conclusion

INTORDUCTION Medicine arouse out of the primary sympathy of Man with Man, out of his desire to help those in sorrow, disease and suffering. Wound, a breach in the surface of the body, can be caused by accident, assault, warfare & surgical operations. The healing of such wounds has always been central consideration in surgical practice.

So, understanding of the various mechanism of healing and factors affecting it is of Prime importance for successful practice.

IF EVERY CELL REGENERATES – NO DEATH LOST CELLS NOT REPLACED – NO LIFE ALL ORGANISMS LIFE LIES BETWEEN THESE TWO EXTREMITIES

INVERTIBRATES AND AMPHIBIANS LOBSTERS – REGROWS LOST CLAWS SALAMANDERS – DEVELOPS NEW LENS NEWTS – REPLACE LOST EXTREMETIES IN MAMMALS, GRANULATION TISSUE REPLACES LOST TISSUE

Tissue Destruction

Cell Death

Disruption of the normal continuity of structures

A) Based on Tissue integrity Open

Wound involving a break in skin Trauma by sharp object or blow (surgical incision, gunshot or mucous membranes wound) Part of body being struck by Closed Wound involving no break in blunt object (bone fracture, tear of visceral organ) skin

B) Causes of injury Intentional: Wound resulting from therapy

Surgical incision

Unintentional: Wound that occurs unexpectedly

Traumatic accident,

injury,

C) Severity of injury Superficial: Wound that involves epidermal layer of skin

only

Penetrating

Wound involving break in epidermal skin layer, as well as dermis and deeper tissues or organs

Perforating

Penetrating wound in which foreign object enters and exits an internal

abrasion, first-degree burn, shearing Foreign object or instrument entering deep into body tissues (gunshot wound, stab wound) (same as above entry)

D) Duration Acute: Short duration

Chronic: Long duration

Trauma from a sharp object

Ulcers exposed to friction, shear, moisture, pressure

E) Descriptive qualities: Laceration: Tearing of tissues with irregular wound edges

Abrasion

Severe traumatic injury (knife wound, industrial accident involving machinery, tissues cut by broken glass)

Wound often resulting from fall; Superficial wound involving scraping or wound also resulting from rubbing of skin’s surface dermatological procedure for removing scar tissue

Contusion

Bleeding in underlying tissues Closed wound caused by a blow to caused by blunt force against body by blunt object; contusion or body part bruise characterized by swelling, discoloration, and pain

F) Cleanliness Clean:(<5%

infected)

Wound containing no pathogenic organisms

Clean-contaminated

Closed surgical wound

(2-10%

infected): Wound made under aseptic conditions, but Surgical wound normally harbors microorganisms is likely Contaminated (15-20% infected) Open, traumatic, accidental wounds; surgical wound in which break in Wound existing under conditions in which• \ asepsis occurred presence of microorganisms is likely Any wound that does not properly heal Infected (>30% infected) and grows organisms, old traumatic Bacterial organisms present in wound site, wound, surgical incision into area usually above 105 organisms per gram of infected. tissue Chronic wound (vascular stasis ulcer, Colonized pressure ulcer) Wound containing multiple microorganisms (usually)

– Is the process in which body responds to injury and attempts to restore normal structure and function

• Wound healing is a symphony of biological process …….

Healing involves two process • Regeneration • Repair

REGENERATION Definition : means proliferation of the parenchymal cells resulting in complete restoration of the original tissues It requires cell proliferation which is largely regulated by micro environment that can either stimulate or inhibit cell growth

cell proliferation depends on the cell growth cycle Which consists of 4 unequal phases. 1. G1 (pre synthetic) phase 2. S (DNA synthesis) phase + 3. G2 (pre mitotic) phase 4. M (mitotic) phase quiescent or resting cells will be in a physiologic state called G0.

Cells are usually classified into three groups depending on their capacity for regeneration.

• Labile cells • Stable cells • Permanent cells

LABILE CELLS - Also called continuously dividing cells - Follow the cell cycle from one mitosis to other - Continue to proliferate throughout life, replacing tissues that are continuously destroyed ‘ - E.g.

Stable cells • Also called quiescent cells • However these cells can undergo rapid division in response to a variety of stimuli and capable of reconstituting the tissue of origin • E.g.

Permanent cells - Also called non dividing cells - Have left the cell cycle and cannot undergo mitotic division in post natal life - E.g.

Control of cell growth cell growth is controlled largely by chemical factors in the environment which either stimulate or inhibits cell proliferation. Although many chemical substances can affect cell growth the most important are polypeptide growth factors present in the serum or produced by the cells.

Growth Factors involved in Wound Healing Molecule

Source

Action

Basic Fibroblast Growth factor (FGF)

Keratinocytes, Macrophages

Stimulates angiogenesis

Salivary gland

Stimulates epidermal cell proliferation

Platelets, Endothelium

Stimulates epidermal hyperplasia in combination with EGF

Epidermal Growth Factor (EGF) Platelet-Derived Growth Factor (PDGF)

Molecular events in cell growth • Polypeptide growth factors bind to their receptors and activates them • This activation posphorylates several substrates that are involved in the generation of second messengers • These intern transmit the signal to the nucleus where activation of the transcription factors leads to the initiation of DNA synthesis and ultimately cell division

In general…… • Regeneration of parenchymal cells INVOLVES …….. 1)Proliferation of original cells from the margin of injury so as to cover the gap. 2)Proliferation of migrated cells with subsequent differentiation and maturation so as to reconstitute the original tissue.

REPAIR • IS THE REPLACEMENT OF INJURED TISSUE BY FIBROUS TISSUE. • PROCESSES INVOLVED INREPAIR: 1.GRANULATION TISSUE FORMATION 2. CONTRACTION OF WOUNDS

Granulation tissue formation The term derives its name from slightly granular and pink appearance of the tissue. Each granule corresponds histologically to proliferation of new small blood vessels which are slightly lifted on the surface by thin covering of fibroblasts and young collagen. 3 phases are observed in the formation of granulation tissue 1. PHASE OF INFLAMMATION. 2. PHASE OF CLEARENCE 3. PHASE OF INGROWTH OF GRANULATIN TISSUE.

1.PHASE OF INFLAMMATION After trauma blood clot occurs at the site of injury. There is acute inflammatory response with exudation of neutrophils plasma cells and some monocytes within 24 hours.

2.PHASE OF CLEARANCE Combination of the proteolytic enzymes liberated from neutrophils, autolytic enzymes from dead tissue cells and phagocytic activity of macrophages clear off the necrotic tissue debris and red blood cells.

PHASE OF INGROWTH OF GRANULATIN TISSUE This phase consists of two main processes : 1. Angiogenesis or neovascularization 2. Formation of fibrous tissue.

Angiogenesis or neovascularization - Formation of new blood vessel at the site of injury. - Takes place by proliferation of endothelial cells from the margin of the severed blood vessel. - Newly formed blood vessels are leaky, ing for the edematous appearance of new granulation tissue. - Soon, these blood vessels differentiate in to muscular arterioles, thin walled venules and true capillaries.

1) Pre-existing vessel

2) Mobilization of EPCs from bone marrow

FACTORS INFLUENCING

FIBROUS TISSUE FORMATION Newly formed blood vessels are in amorphous ground substance or matrix The new fibroblasts originate from fibrocytes as well as by mitotic division of fibroblasts Some of the fibroblasts have morphogenic and functional characteristic of smooth muscle cells Collagen fibrils begin to appear about 6th day as maturation proceeds more and more collagen is formed while the number of active fibroblasts and new blood vessel decreases This results in formation of inactive looking scar known as cicatrisation

CONTRACTION OF WOUNDS Wound starts contracting after 2-3 days of collagen formation, and the process is completed largely by 14th day. During this period wound is reduced by approximately 70-80% of its original size. Contracted wound results in rapid healing.

MECHANISM OF WOUND CONTRACTION 1. Dehydration :as a result of removal of fluid 2. Contraction of collagen 3. Discovery of myofibroblasts

Wound healing

Skin

Primary intention

Oral soft tissue wounds

Secondary intention

Healing by first intention This is defined as healing of a wound which has the following characteristics: - clean and uninfected - surgically incised - without much loss of cells and tissue - edges of wound are approximated by surgical sutures.

• • • • •

Initial hemorrhage Acute inflammatory response Epithelial changes Organization Suture tracks A suture wound, thus, takes a little longer to heal but the scar formed is neat due to close apposition of the margins of wound. The use of adhesive tapes at the incised margins avoids this complication.

Secondary Intention [ Secondary union ] This is defined as healing of a wound having the following characteristics: • Open with a large tissue defect, at times infected • Having extensive loss of cells and tissues • The wound is not approximated by sutures but is left open.

• • • • •

Initial hemorrhage Inflammatory phase Epithelial changes Granulation tissue Wound contraction

Complications of wound healing Deficient scar formation • Dehiscence • Ulceration Excessive scar formation • Keliods • excess of fibrous tissue or Proud flesh

Excessive contraction Contracture

Miscellaneous Painful scars Pigmentary changes Implantation

Factors that influence wound healing Local Factors Infection single most important reason for delayed wound healing

Foreign bodies – suture material, bone and wood splinters ….

Mechanical factors – Early movement – Pressure

• Ionising radiation : delays granulation tissue formation • Ultra violate light : facilitates healing • Type size and location

Systemic factors • Malnutrition – Protein deficiency delays wound healing – Vitamin C deficiency (inhibition of collagen synthesis) • Metabolic status – e.g. Diabetes mellitus – Cortisone treatment • inhibits inflammation and collagen synthesis • Circulatory status – Inadequate blood supply due to arteriosclerosis – Varicose veins

• Age : Older patient at higher risk of poor wound healing • Medication : Anti-inflammatory (aspirin), cytotoxic, immunosuppressive and anticoagulant drugs all reduce healing rates by interrupting cell division or the clotting process. • Iron, required to transport oxygen.

• Minerals, zinc, copper, are important for enzyme systems and immune systems. Zinc deficiency contributes to disruption in granulation tissue formation. • Vitamins A, B complex and C, are responsible for ing epithelialisation and collagen formation. It is also important for the inflammatory phase of wound healing. • Carbohydrates and fats. These provide the energy required for cell function. When the patient does not have enough, the body breaks down protein to meet the energy needs. Fatty acids and essential for wound healing.

Conclusion • For most people, wound healing is a natural, uneventful process. For some individuals, however, it becomes a complex medical problem requiring specialized treatment and care. • Since problem of wounds are often associated with underlying medical conditions, so it is the physicians duty to understand the necessary of care level and educating people to overcome the problems

References: • Robbin’s Pathologic Basis of Disease; 7th Ed Vinay Kumar, Abbas, Fausto • Text book of Pathology; Emanuel Rubin & John C Farbar • Short Practice of Surgery; 22nd Edition: Bailey & Love. • Anderson’s Pathology; 10th Edition: James Linder • Boyd’s text book of Pathology; 3rd Edition: Ritchie. • Essentials of Pathology for Dental students; 9th Ed Harsh Mohan www.google.com