Wound Healing and Repair

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  • 8/3/2019 Wound Healing and Repair




    Presenter: Nyangara Rajabu,


    Facilitator: Dr Mgaya

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    Types of wounds

    Regeneration and Repair Phases of wound healing

    Nature of wound healing

    Factors influencing healing Complications of wound healing


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    HISTORY The earliest accounts of wound healing date back

    to about 2000 B.C

    Galen of Pergamum emphasized the importanceof maintaining a moist environment to ensureadequate healing.

    Ambriose Par found that simply dressed gunshotwounds heal faster and are less painful than whentreated with boiling oil, the previously acceptedmethod.

    Ignaz Philipp Semmelweis advocated need forwashing hands

    Joseph Lister began soaking his instruments inphenol and spraying the operating rooms, reducingthe mortality rates from 50 to 15%.

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    The repair of tissue damage broadly separated

    into two processes, regenerationand healing Regeneration refers to growth of cells and tissues

    to replace lost structures.

    Wound healing is the effort of tissues to restorenormal function and structure after injury

    -To reform barriers to fluid loss and infection,

    -limit further entry of foreign organisms and material,-re-establish normal blood and lymphatic flow


    -restore the mechanical integrity of the injureds stem

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    TYPES OF WOUND Abrasions. Also called scrapes, they occur

    when the skin is rubbed away by friction against

    another rough surface (e.g. rope burns andskinned knees).

    Avulsions. Occur when an entire structure or

    part of it is forcibly pulled away, such as theloss of a permanent tooth or an ear lobe.Animal bites may cause avulsions.

    Contusions. Are also called bruises and arethe result of a forceful trauma that injures aninternal structure without breaking the skin.

    Blows to the chest, abdomen, or head with ablunt instrument e. . a football or a fist can

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    TYPES OF WOUND cont...

    Crush wounds. Occur when a heavy object

    falls onto a person, splitting the skin andshattering or tearing underlying structures.

    Cuts. Slicing wounds made with a sharp

    instrument, leaving even edges. They may beas minimal as a paper cut or as significant as asurgical incision.

    Incised wound: Any sharp cut in which thetissues are not severed; a clean cut caused bya keen cutting instrument. The wound mayeither be aseptic or infected, depending on the


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    TYPES OF WOUND cont...

    Lacerations. Also called tears, these are

    separating wounds that produce ragged edges.They are produced by a tremendous forceagainst the body, either from an internal sourceas in childbirth, or from an external source likea punch.

    Open wound. A contusion, in which the skin isalso broken, such as gunshot, incised or

    lacerated wound.

    Penetrating wound. A wound in which the skinis broken and the agent causing wound enters

    subcutaneous tissue or a deep lying structure

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    Healing involves two processes:

    1. Regeneration

    2. Repair

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    Definition: means proliferation of theparenchymal cells resulting incomplete restoration of the original

    tissues. It requires cell proliferation which is

    largely regulated by micro

    environment that can eitherstimulateor inhibitcell growth.

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    Regeneration cont...

    Cell proliferation depends on the cell growthcycle which consists of 4 unequal phases:

    M (mitotic) phase

    G1 (pre synthetic) phase S (DNA synthesis) phase

    G2 (pre mitotic) phase

    Quiescent or resting cells will be in aphysiologic state called G0.

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    e e yc e an eren ePopulations

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    Cells of the body are usually classifiedinto three groups depending on theircapacity for regeneration:

    1.Labile cells2.Stable cells

    3.Permanent cells

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    1. Labile cells

    Also called continuously dividing cells

    Follow the cell cycle from one mitosis toother

    Continue to proliferate throughout life,replacing tissues that are continuouslydestroyed

    These include: surface epithelial cells of

    epidermis, alimentary tract , respiratorytract, urinay tract, vagina, cervix, uterineendometrium, haematopoietic cells of bone

    marrow and cells of lymph node and

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    2. Stable cells Also called quiescent cells

    These cells lose or decrease their capacityto proliferate after adoloscene but retainthe capacity to multiply in response to

    stimuli throughout adult life These include: parenchymal cells of organs

    like liver, pancreas, kidney, adrenal and

    thyroid ; mesenchymal cells of smoothmuscle cells , fibroblasts, vascularendothelium, bone and cartilage cells.

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    3. Permanent cells

    Also called non dividing cells. Have left the cell cycle and cannot

    undergo mitotic division in post natal life.

    These include: neurons of nervoussystem, skeletal muscle and cardiacmuscle cells.

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    Is the replacement of injured tissue byfibrous tissue.

    Processes involved in repair:

    1. Granulation tissueformation

    2. Contraction of wounds

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    Normal wound healing follows a predictablepattern that can be divided into overlappingphases defined by characteristic cellularpopulations and biochemical activities:

    (a) Hemostasis & inflammation

    (b) Proliferation

    (c) Maturation and Remodeling

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    HEMOSTASIS AND INFLAMMATION In the inflammatory phase clotting takes

    place in order to obtain hemostasis, or stopblood loss, and various factors are releasedto attract cells that phagocytise debris,bacteria, and damaged tissue and release

    factors that initiate the proliferative phase ofwound healing

    The events can be divided into:

    1.Vascular events

    2.Cellular events

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    1. Vascular events Earliest manifestation is vasodilatation, it follows a transient constrictionof

    arterioles lasting a few seconds.

    Wounding disrupts tissue integrity and direct exposure of extracellular

    matrix to platelets

    Initial contact between platelets and collagen requires the von Willebrandfactor (vWF)

    Binding results in changes in platelet conformation, triggering intracellularsignal transduction pathways that result in platelet activation and the releaseof biologically active proteins.

    Platelet granules are storage organelles that contain

    -Platelet-derived growth factor (PDGF),

    -Transforming growth factor(TGF)-,

    -Insulin-like growth factor (IGF)-1,





    V l

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    Vascular events cont... The dense bodies contain the vasoactive amines, such as serotonin, which

    cause vasodilation and increased vascular permeability.

    The clotting cascade is initiated through both the intrinsic and the extrinsic

    pathways. Vasodilation is followed by increased permeability of the microvasculature,

    followed by stasis, which leads to accumulation of leucocytes along thevascular endothelium which then migrate through the vascular wall into theinterstitial tissue.

    Increased permeability is due to- formation of endothelial gaps in venules,

    - direct endothelial injury,

    - delayed prolonged leakage,

    - leucocyte mediated endothelial injury,-increased transcytosis and leakage from new vessels

    The combination of intense vasodilation and increased vascular permeabilityleads to clinical findings of inflammation,

    rubor(redness), tumor(swelling),calor(heat), and dolor(pain).

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    2. Cellular events1. Polymorphonuclear cells or Neutrophils First infiltrating cells to enter the wound site,

    peaking at 24 to 48 hours Neutrophil migration is stimulated by

    - Increased vascular permeability,- local prostaglandin release, and

    - the presence of chemotactic substances, suchas complement factors, interleukin-1 (IL-1), tumornecrosis factor alpha (TNF-), TGF , plateletfactor 4, or bacterial products.

    PMNs are also a major source of cytokinesearlyduring inflammation, especially TNF-, alsorelease proteases such as collagenases.

    Following functional activation neutrophils

    scavenge necrotic debris, foreign material, and

    PMN t

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    PMN cont. Stimulated neutrophils generate free oxygen

    radicals with electrons donated by the reduced

    form of nicotinamide

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