plastic surgery - wound healing Flashcards
open wounds categories
- Laceration- Ragged tears and cuts
- Puncture- Sharp penetration
- Abrasion- Superficial layer of the skin is removed
- Avulsion- Sections of skin torn off either in part or completely
- Amputation- Nonsurgical removal of limb from the body
wounds intro
- Violation of live tissue integrity
- Largest organ in the body (skin)
- Wounding will affect normal function
- Historically wounding most primitive challenge to survival
- Thus injury eliminatd the unfit
general techniques of wound rx - primary intention
Primary Intention - all tissues closed with suture material
general techniques of wound rx - secondary intention
Secondary Intention - Wound left open and closes naturally
general techniques of wound rx - tertiary intention
Tertiary Intention - Wound left open for a number of days and then closed when clean
phases of wound healing stages
- hemostasis (sec-min)- blood clot
- inflammatory (day 3-5) - scab, fibroblast, macrophage, blood vessel
- proliferative (day 4-21) - fibroblast proliferating, subcutaneous fat
- remodelling (> day 21) - freshly healed epidermis & dermis
phases of wound healing - haemostasis
- seconds to minutes
- Immediate response to injury is vasoconstriction
- Caused by release of Thromboxane and Prostaglandins
- Platelets adhere to exposed collagen and release
contents of their granules - Tissue Factor activates both platelets and the coagulation cascades
- Results in a platelet matrix
- Controls hemorrhage, concentrates growth factors and serves as the scaffold of the wound
phases of wound healing - inflammation
- 3 to 5 days
- Begins immediately following tissue injury
- Functional priorities are removal of devitalized tissues and prevention of colonization & invasive infection by microbial pathogens
- Prostaglandins, histamine, serotonin, kinins, and bacterial products cause vasodilatation and capillary permeability, resulting in edema
- Variety of factors and cytokines attract granulocytes to the wound
- Neutrophils enter and remove dead tissue by phagocytosis & prevent infection
- Absence does not affect wound healing
- Monocytes/ Macrophages predominant cell by day 3
post wounding - Phagocyte debris and bacteria
- Also critical in production of growth factors vital for production of ECM by Fibroblasts & new blood vessel production
- Lymphocytes enter wound day 5–7, role not clear
cytokines in wound healing (inflammatory)
- epidermal growth factor
- transforming growth factor alpha and beta
- fibroblast growth factor
- keratinocyte growth factor
- tumor necrosis factor
- interleukin 1, 2, 6, 8
- platelet derived growth factor
- vascular endothelial growth factor
- endothelium derived growth factor (nitric oxide)
phases of wound healing - proliferation
- day 4 - 21
- Functional priority is balance between scar formation and tissue regeneration
- Scar formation predominates
- In foetal wound healing regeneration possible
- Phase characterized by reepithelialization
- Relies on the migration of epithelial cells from the wound margins and from any remaining adnexal structures in the dermis, such as hair follicles, sebaceous glands, and sweat glands.
- Provisional fibrin matrix replaced by granulation tissue (new platform for migration) & thinner type III collagen
Granulation tissue composed of 3 cell types
(proliferation phase)
1. Fibroblast – produce ECM that fills the healing scar &
provides scaffold for keratinocyte migration
2. Macrophages – continue to produce growth factors that induce fibroblast to proliferate, migrate & deposit ECM as well as stimulate endothelial cells
3. Endothelial cells – form new blood vessels through angiogenesis and vasculogenesis
phases of wound healing - remodelling
- Longest phase, lasts from 21 days up to a year
- Begins after wound filled in with granulation tissue and
keratinocyte migration has reepithelialized it - Characterized by wound contraction and collagen remodeling
- Wound contraction produced by wound myofibroblast (fibroblasts with intracellular actin microfilaments)
- Collagen remodeling of type III to type I collagen
- Mediated by Matrix Metalloproteinases
- Class of enzymes secreted by granulation tissue
foetal wound healing
- Scarless regenerative healing
- Dependent on size and timing (<24 weeks gestation)
foetal vs adult wound healing
- Cellular differences – foetal fibroblast secrete more type III & I V collagen, higher gene expression of MMP
- Wound repair differences – foetal faster collagen synthesis, rate of epithelialization, reduced inflammatory cellular infiltrates
- Growth factor expression – foetal upregulated VEGF
- Gene expression – foetal increased gene ass with development (e.g homeobox gene)
- Matrix composition – foetal wound matrix composed of more hyaluronic acid
factors affecting wound healing
- local
- systematic
local factors affecting wound healing
- Infection
- Foreign bodies
- Ischemia
- Edema
- Idiopathic manipulation (e.g. rough handling, tight sutures)
- Radiation therapy
systemic factors affecting wound healing
- Age
- Malnutrition
- Drugs (e.g. steroids)
- Smoking
- Chemotherapy
- Systematic conditions (e.g. DM, Obesity, CVD, COPD, renal, hepatic, endocrine, small vessel dx, Ca)
factors affecting wound healing - age
- Wound healing is the function of age
- Age affects rate of multiplication of cells
- Tensile strength and wound closure rates decrease with age
- Phases of healing are protracted
- Therefore events begin later, proceed more slowly, and often do not reach the same level