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Pathophysiology

Wound healing

TermDefinition
Phases of normal wound healing Hemostasis (1) - stop bleeding (day 1-3) Inflammation (2) - new frame work for blood vessel growth (day 3-20) proliferation phase (3)- pulls the wound closed granulation tissue formation, epithelialization week 1-6) Remodeling or Maturation (phase 4) wound contraction and remodeling, final proper tissue
Proliferation and remodeling phases Granulation tissue forms 24-48 hours after injury Fibroblast Synthesizes collagen, key ECM in wound healing Produce collagen for days, weeks, or months, depending on wound Granulation tissue secretes growth factors Endothelium, platelets, fibroblasts, tissue, Interleukin-1, TGF-beta Epithelial cells migrate and proliferate From new surface and fill in gap between wound edges Lasts about 3 weeks – shaped by fibroblasts and myofibroblasts
Fibroblast proliferation and remodeling phase of healing Synthesizes collagen, key ECM in wound healing Produce collagen for days, weeks, or months, depending on wound
Primary intention least complicated wound healing -surgical wound Requires mostly resurfacing with new epithelium and shoring up edges of wound to former strength/integrity 5 days for granulation tissue to fill gap and angiogenesis to occur 2 weeks collagen and fibroblasts in scar 1 mo:inflammation down and CT covered by intact epidermis
Secondary intention more complex would healing -extensive loss of tissue -Regeneration of same cells to replace lost tissue is not possible -longer process needing extensive support wound contraction: Myofibroblasts (CT cells with muscle characteristics) Cause edges to contract Substantial scarring and highly likely to become infected, have complications, or result in deformity I.e. Pressure ulcers
Factors Affecting wound healing Nutrition – esp. lack of protein; positive nitrogen balance Dehydration – water needed by all cells for life Oxygenation – neutrophils and collagen synthesis (hyperbaric) Circulation – no blood, no oxygen; gangrene results Immune strength – immunocompromise = infection Contamination – foreign bodies (bacteria, sutures) = infection Obesity – adipose does not heal efficiently; bad suture site Age – fetal wounds heal without fibrosis/scarring; elders don’t
Wound rupture Undue tension on wound can inhibit edge approximation and epithelialization of surface Dehiscence, wound eviceration Abdominal wall wounds : Especially high tension due to coughing, vomiting, sneezing, Valsalva
Keloid Formation Hyperplastic epithelialization and collagen formation Hypertrophic scar -etiology unknown -african american genetic predisposition Can be reduced by cosmetic surgery but may cause return of worsening hypertrophy
Contractures strictures: Narrowing or closure of normally open area of body Ex: esophagus stricture reducing tubular passage after injury Last step of second intention wound healing -may become exaggerated inflexible shrinkage of wound tissue pulls center BURN WOUNDS limited mobility if contracture occurs
Fistula Abnormal connection between two different areas of tissue or organs Can form with abnormal wound healing; complications result Ex: tracheoesophageal fistula b/w trachea and esophagus = aspiration
Adhesions Invasive post-surgical outcome of abnormal bands of internal scar tissue -limits mobility -causes pain and inflammation (body may attack) may cause obstruction -re requires surgical excision Ex: endometriosis excision and hysterectomy cause extensive scarring, possibly adhering bowel portions together or causing a stricture of a ureter
Wound dehiscence when previously closed wound edges open and rupture
wound evisceration internal orans and tissues protrude from dihiscent wound = abdomen
Cell Cycle of wound healing tissue healing depends on type of cells that were injured 1. Labile 2. stable 3.permanent Synthesis: S phase DNA replicated between G1 and G2 phase precise and accurate DNA replication is necessary to prevent genetic abnormalities which often lead to cell death or disease G1 phase: the first growth period of the cell cycle, during interphase, in which the cell grows and cytoplasmic organelles are replicated. G2 phase: the second growth period of the cell cycle, following DNA replication and preceding prophase, during which the cell forms the materials that make up the spindle. Mitosis: a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. Makes exact copy of original to replace scar tissue
Labile cells (busy cells) Cells that continually proceed through cell cycle Divide and replicate entire life, replacing worn out cells (i.e. skin/mouth cells) Skin, oral mucosal cells, GI mucosal lining cells, urogenital mucosal cells, bone marrow Cancer cells (because they constantly divide)
Stable cells Remain in resting stage until stimulated, then enter cell cycle Bone cells Post fracture, must regenerate and repair with osteoid Hepatocytes Surgery, trauma, chemical injury to liver Undergo mitosis to regenerate and repair liver lobules
Permanent cells Cannot regenerate and therefore do not enter cell cycle have lost ability to proliferate i.e. centeral nervous system neurons Cardiac myocytes (MacLellan) primitive state not good at contracting-vital for heart function -humans need optimum blood pressure and circulation
Mitosis phases Prophase: 1st stage the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells complex of DNA and proteins contained in the nucleus, known as chromatin, condenses. Metaphase: 3rd stage he process that separates duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells the cell's chromosomes align themselves in the middle of the cell through a type of cellular "tug of war Anaphase: is the stage of mitosis after the metaphase when replicated chromosomes are split and the daughter chromatids are moved to opposite poles of the cell Telophase: end stage the sister chromatids reach opposite poles. The small nuclear vesicles in the cell begin to re-form around the group of chromosomes at each end. Cytokinesis: physical process of cell division divides cytoplasm of a parental cell into two daughter cells separates cell in half with each nucleus created into each Daughter cells
Tertiary infention Most complex wound healing process -missing large amount of tissue and is CONTAMINATED -Deep gouge, tissue missing; SKIN GRAFT may be REQUIRED or Temporary packing with extensive drainage prominent scarring with healing 5th day WBCs have phagocytosed contaminated tissue and resurfacing of epithelium, new collagen deposit takes place Macrophages wall off foreign substances Leukocytes form granulomas I.e. severe burns
Post Intention Wounds Not strong, none of three types result in new skin with same strength as original skin due to weakened integrity and tensile strength careful support necessary first few weeks post op -sutures removed = skin vulnerable MAX TENSILE STRENGTH 70-80% after 3 months
Created by: meagangraf