woundhealing2022-240609041126-4ebc7673.pptx

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1. WOUND HEALING Dr.Kaduyu Dennis LEARNING OBJECTIVES DEFINITION OF A WOUND CLASSIFICATIONS OF WOUNDS DEFINITION OF WOUND HEALING TYPES OF CELLS IMPORTANT IN WOUND HEALING PROCESSES OF WOUND HEALING TYPES OF WOUND HEALING PROCESS OF WOUND HEALING FACTORS AFFECTING WOUND HEALING COMPLICATIONS OF WOUND HEALING

2. INTRODUCTION TO WOUND HEALING Injury to tissue may result in cell death or tissue destruction hence tissue destruction needs repair/healing A wound is a break in the continuity of a tissue or skin often which may be associated with disruption of the structure and fuction

3. DEFINITION OF A WOUND A wound is a break in the continuity of a tissue or skin often which may be associated with disruption of the structure and fuction OR A cut or break in the continuity of any tissue caused by injury or operation .

4. CLASSIFICATION OF WOUNDS Classification based on type of wound are 4 1,Penetrating wounds is one caused by foreign object piercing the skin damaging the underlying tissues and results in an open wound 2,Incised wounds is one caused by a sharp object such as a knife , broken glass or surgeons scapels 3,Surgical wounds is a cut in the skin that is usually made by a scalpel during surgery 4, punctured wounds is a wound made by a pointed object often appear to be on the surface but may extend into deeper tissue layers.

5. Other definitions Abrasion Means that surface layer of skin(epidermis ) have been broken . occurs when the skin rubs against a rough /hard surface Bruising and contusion an injury appearing as an area of discolored skin on the body caused by a blow or impact rupturing underlying blood vessels

6. ABRASION

7. BRUISE/ CONTUSSION

8. DEFINITION OF WOUND HEALING Wound healing is the body response to injury in an attempt to restore normal structure and function. N.B By convention, the term repair is often used for parenchymal and connective tissues and healing for surface epithelia hence often we use the terms interchangeably .

9. TYPES OF CELLS IMPORTANT IN WOUND HEALING These are divided into 3 groups depending upon their capacity to divide LABILE CELLS These cells continue to multiply throughout life under normal physiologic conditions. N.B These tissues readily regenerate after injury as long as the pool of stem cells is preserved Examples Surface epithelial cells of the epidermis ,respiratory tract alimentary tract ,urinary tract ,vagina , cervix, uterine endometrium, hematopoietic cells of the bone marrow and cells of lymph nodes and spleen.

10. STABLE CELLS These are cells which are in a state of inactivity/dormant/quiescent or have only minimal proliferative activity in their normal state however are capable of dividing in response to injury or loss of tissue mass. N.B These cells enter state of inactivity or minimal proliferation after adolescence Examples ( these constitute the cells of most solid tissues) liver, pancreas, kidney ,smooth muscle cells, bone and cartilage cells, fibroblasts, vascular endothelial cells . PERMANENT CELLS These cells lose the ability to proliferate around the time of birth Examples; Neurons of nervous system ,skeletal muscle and cardiac muscle cells N.B In permanent tissues repair is typically dominated by scar formation.

11. NOTE The process of healing involves 2 distinct Processes Regeneration process Repair processs

12. PROCESSES OF WOUND HEALING REGENERATION PROCESS This is when healing takes place by proliferation of parenchymal cells and usually results in complete restoration of the original tissues. This is the goal of all surgical procedures this occurs incase of small damages involving labile cells and stable cells Regeneration process involves Proliferation of cells Cells that survive the injury (injured cells)and retain the capacity to proliferate e.g. in rapidly dividing epithelial cells of the skin ,intestines and liver .may take between 16-24 hrs Differentiation and maturation of stem cells in other cases tissue stem cells may contribute to restoration of damaged tissue incase the mature injured cells are incapable of dividing(permanent cells)

13. REPAIR PROCESS Repair is the replacement of injured tissue by fibrous tissue. This may lead to scar formation fibrosis is the extensive deposition of collagen. E.g occurs in lungs ,liver, kidney as a consequence of chronic inflammation. occurs in healing processes of permanent cells and stable cells with extensive damage e.g. myocardial infarction and extensive wounds. N.B Mammals have limited capacity to regenerate damage tissues hence damage to parenchymal cells leads to a situation where repair cannot be accomplished by parenchymal regeneration alone hence REPAIR process comes in. PROCESSES INVOLVED IN REPAIR Granulation tissue formation Contraction of wounds

14. Granulation tissue formation derives its name from the slightly granular and pink appearance of the tissue. Consists of proliferating fibroblasts in loose extracellular matrix often mixed with inflammatory cells mainly macrophages 3 phases are observed in the formation of granulation tissue Phase of inflammation following trauma there is acute inflammatory response with exudation of plasma, neutrophils and some monocytes within 24hrs leading to formation of blood clots at the site of entry. Phase of clearance Combination of proteolytic enzymes from neutrophils , autolytic enzymes from dead tissue cells and phagocytic activity of macrophages clear off the necrotic tissue and debris

15. Phase of ingrowth of granulation tissue Two main processes involved Angiogenesis/ neovasculisation fibrogenesis Contraction of wounds Movement of the edges of a wound towards the centre to close it after maturation stage of healing It starts after 2-3 days and the process is completed by the 14 th day.

16. GRANULATION TISSUE

17. TYPES OF WOUND HEALING There are 2 types of wound healing depending on the amount of tissue damage. A wound can be accidental or surgical. Healing by first intention (primary union) Healing by second intension(secondary union) HEALING BY FIRST INTENTION (PRIMARY UNION) Refers to healing of a wound in which the edges are closely re-approximated /apposed . Characteristics of such wounds clean and uninfected ,surgically incised without much loss of cells and tissue and edges of the wound are approximated by surgical sutures.

18. HEALING BY SECOND INTENTION(SECONDARY UNION) Refers to healing of wounds in which the edges are separated characteristics open with a large tissue defect ,at times infected,having extensive loss of cells and tissues and the wound is not approximated by surgical sutures but is left open

19. DIFFERENCES FEATURE PRIMARY UNION SECONDARY UNION CLEANESS OF WOUND CLEAN UNCLEAN INFECTION GENERALLY UNINFECTED MAY BE INFECTED MARGINS SURGICALLY CLEAN IRREGULARLY SUTURES USED NOT USED HEALING SCANTY GRANULATION TISSUE AT THE INCISED GAP AND ALONG SUTURE TRACKS EXUBERANT GRANULATION TISSUE TO FILL THE GAP OUTCOME NEAT LINEAR SCAR CONTRACTED IRREGULAR WOUND COMPLICATIONS INFREQUENT SUPPURATION , MAY REQUIRE DEBRIDEMENT

20. PROCESS OF WOUND HEALING Wound healing process can be divided into 4 distinct phases: Homeostasis phase The inflammatory phase Proliferative phase Remodeling phase/Maturation phase.

21. HOMEOSTASIS PHASE This process starts immediately after the injury and may continue for a few days Immediately after injury homeostasis begins with vasoconstriction Clotting/coagulation cascade is activated involving activation ,adhesion and aggregation of platelets as well as deposition and maturation of fibrin platelet dischrges ADP(Adenosine disphosphate )which promotes thrombocyte clumping forming a platelet plug (incomplete clot-a net that traps RBCS) at the wound Fibrinogen is cleaved into fibrin through the clotting cascade to complete framework for coagulation. fibrin provides structural support for cellular constituents of inflammation.

22. INFLAMMATORY PHASE This occurs within 24hrs After homeostasis is achieved ,blood vessels dilate allowing WBC (Polymorphonuclear leucocytes) , nutrients,antibiotics and other beneficial elements reach the affected are to accelerate wound healing At this stage effects of inflammation such as heat ,pain ,swelling and redness are felt polymorphonuclear leukocytes (neutrophils,eosinophils and basophils circulating in blood) “cleanse” the wound by the 3 rd day they are replaced by macrophages Macrophages continue the cleansing process and manufacture various growth factors e.g cytokines, interleukin-1, tumor necrosis factor tumor(TNF) etc.

23. PROLIFERATIVE PHASE This phase is characterized by formation of granulation tissue in the wound . ( Granulation tissue it is a fragile structure composed of an extracellular matrix of fibrin,fibronectin,gylycosaminoglycans,proliferating endothelial cells , new capillaries and fibroblasts mixed with inflammatory macrophages and lymphocytes.) Two key cells are present in this phase ; fibroblasts and endothelial cells. This phase consists of different subphases. Fibroplasia , matrix deposition, angiogenesis and re-epithelialization FIBROPLASIA- Growth of fibrous tissue A combination of action of cytokines produced initially by platelets and subsequently by macrophages and lymphocytes stimulate fibroplasia which involves formation of fibroblasts which migrate into the wound site laying down new collagen of subtypes I and II . N.B fibrolast production starts on 3 rd day achieves their peak number on 7 th day.

24. MATRIX DEPOSITION The wound is suffused with GAGS( Glycosaminoglycans ) and fibronectin that are bonded covalently to protein core and contribute to matrix deposition. (a large network of proteins and other molecules that surround, support, and give structure to cells and tissues in the body. ANGIOGENESIS Formation of new blood vessels at the site of injury takes place by proliferation of endothelial cells from margins of severed blood vessels Newly formed blood vessels are more leaky accounting for the more edematous appearance of new granulation tissue.

25. RE-EPITHELISATION Re- epithelization occurs with the migration of cells from the periphery of the wound and adnexal structures. This process commences with the spreading of cells within 24 hours. Division of peripheral cells occurs in hours 48-72, resulting in a thin epithelial cell layer, which bridges the wound. This succession of subphases can last up to 4 weeks in the clean and uncontaminated wound.

26. RE-MODELING PHASE After 3 week the wound undergoes constant alterations known as remodeling . This is the final phase of the wound healing process occurs concurrently with granulation tissue formation leading to formation of new epithelium and scar tissue .

27. The basic events in secondary union are similar to primary union but differ in having a larger tissue defect which has to be bridged . The healing by secondary union is slow and results in a large at times ugly scar compared to rapidly healing and neat scar of primary union. N.B Compare the sequential process of wound healing in primary union and secondary union

28. FACTORS THAT AFFECT WOUND HEALING LOCAL FACTORS Type, size and location of the wound vascular supply Infection Movement

29. SYSTEMIC FACTORS Circulatory status cardiovascular status determines the blood supply to injured area. Poor healing in old age is often largely attributed to impaired circulation Infection systemic infection delay wound healing Metabolic status poorly controlled diabetes is associated long term complication of Atherosclerosis which is associated with delayed wound healing. Nutritional deficiencies protein deficiency ;proteins are important in granulation tissue and collagen formation

30. Vitamin deficiency ;is required in collagen synthesis and and secretion important in wound healing Hormones corticosteroids impair wound healing due to inhibition of collagen synthesis, anti-inflammatory actions .corticosteroids inhibit fibroplasia and neovascularization. Thyroid hormones , Androgens,and growth hormones also influence healing may be due to their regulation in metabolism Anti-inflammatory drugs These do not interfere with wound healing when administered at the usual daily dosages.

31. COMPLICATIONS OF WOUND HEALING INFECTION A wound may provide a portal for entry for many organisms. DEFICIENT SCAR FORMATION Usually due to inadequate formation of granulation tissue INCISIONAL HERNIA A weak scar especially after laparotomy may result into wound dehiscence(bursting of a wound ) or an incisional hernia . EXCESSSIVE SCAR FORMATION Excessive formation of collagen in healing may result into; Keloid, scar margin not confined to the borders of initial wound hypertrophied scar , scar margins confined to borders of initial wound

32. Hypertrophied scar

33. KELOID SCAR

34. ULCERATION Wounds ulcerate because of inadequate intrinsic blood supply or insufficient vascularization during healing ( when does a wound become an ulcer) EXCESSIVE CONTRACTION Exaggeration of wound contraction may result into formation of contractures(permanent tightening of muscles, tendons ,skin and near by tissue causing the joints to shorten and become stiff.) NEOPLASM Rarely chronic wounds or scars develop in carcinoma of the skin e.g squamous cell carcinoma in marjolins ulcer ( is a cutaneous malignancy that arises from chronic wounds, long standing scars)

35. CLINICAL ASPECTS Wound vs ulcer Marjolins ulcer Contractures Incisional hernia Keloids and hypertrophied scars

36. Questions 1Compare and contrast wound healing by primary and secondary union 2Discuss the complications of wound healing 3What are the two basic processes of healing ? What factors determine which of these occurs. 4Understand fracture healing 5 Define the following classification of surgical wounds clean surgical wound, clean contaminated surgical wound, contaminated wound and dirty infected wound