Replacement/ fibrous tissue repair Flashcards
This type of repair occurs with severe injuries
takes place when there is damage to both parenchymal cells and extracellular matrix
repair occurs by replacement with connective tissue (involves generation of granulation tissue and formation of scars
replacement/ fibrous tissue repair
**involves generation of granulation tissue and formation of scars
What type of tissue?
> glistening red, moist connective tissue
> contains new formed capillaries, proliferating fibroblasts and residual inflammatory cells
> involves the growth of new capillary (angiogenesis), fibrogenesis, and involution to the formation of scar tissue
Granulation tissue
> involves the generation and sprouting of new blood vessels from pre-existing blood vessels, present as minute red granules from the surface of wound (granulated tissue)
eventually, portions of the new capillary bed differentiate into arterioles and venules
angiogenesis
involves the influx of activated fibroblast
> activated fibroblasts secrete extracellular matrix components including fibronectin, hyaluronic acid…
> the initiation of collagen synthesis contributes to the subsequent formation of scar tissue (or new tissue)
fibrogenesis
What type of tissue?
builds on the granulation tissue framework of new vessels and loose extracellular matrix (ECM)
process occurs 2 phases:
> emigration and proliferation of fibroblasts into site of injury
> deposition of ECM by these cells
Scar tissue
it is composed of inactive spindle-shaped fibroblasts, dense collagen fibers, fragments of elastic and other ECM components
scar
a process of repair of injured tissue
primary objective is to fill the gap created by tissue destruction and to restore the functional continuity of the injured part
wound healing
> also known as healing by first intention
it occurs at a faster rate
there is no loss of tissue
primary intention
aka healing by first intention
eg, a sutured surgical incision
> also known as second intention
larger wounds (burns and surface wounds) have greater loss of tissue and contamination heal by secondary tissue
it occurs at a slower rate (cells have to migrate across)
there is loss of tissue
large amount of scar tissue formation
secondary intention
Phases of wound healing (3)
inflammatory phase
proliferating phase
maturation/ remodelling phase
> healing begins at the time of injury
includes homeostasis, vascular and cellular phases of inflammation
this phase can last 3-4 days
inflammatory phase (acute)
> healing begins within 2-3 days of injury
may last 3-4 weeks
primary focus is to build the new tissue to fill the wound space
Characterized by: Angiogenesis Collagen synthesis Granulation tissue formation Epithelialisation Wound contracture
proliferating phase (early sub-acute)
> healing begins 3 weeks after injury
it can continue up to 6 month + depends of extent of wound
collagen is remodelled and realigned along tension lines
cells that are no longer needed are removed by aportosis
maturation/ remodelling phase
Causes of impaired wound healing (pick scab analogy) (10)
> desiccation (drying up)
malnutrition (not enough vitamin c or zinc)
maceration (urine and fecal incontinence)
necrosis
impaired blood flow and oxygen delivery
impaired inflammatory and immune responses
infection/ abnormal bacteria presence (infected wounds)
wound separation
foreign bodies (splinters, etc)
> age effects healing
cells become dehydrated and die. Healing is better in a moisture retention dressing> epidermal cell migration is enhanced > encouraging epithelisation
desiccation
