click below
click below
Normal Size Small Size show me how
Pathophysiology
Wound healing
Term | Definition | |||||||
---|---|---|---|---|---|---|---|---|
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 |