Tissue repair Flashcards
What are the 2 options of tissue repair?
- regeneration by proliferation of residual (uninjured) cells
- the deposition of connective tissue to form a scar
What is the cell ranking according to their ability to regenerate?
LABILE CELLS (“continuous replicators”)
- constantly replenishing their neighbors that have died or been shed.
- Examples: epithelium of skin, mucous membranes, oviducts, ducts; urothelium; endometrium; seminiferous tubules; bone marrow; lymphoid tissue.
STABLE CELLS (“discontinuous replicators”)
- can proliferate rapidly in response to need, especially when required to replace lost neighbors.
- glandular parenchymal cells, fibroblasts, endothelial cells (cuboidal, and called “angioblasts”, when they are healing), and osteoblasts.
PERMANENT CELLS (“non-replicators”)
- very limited ability to undergo mitosis or be replenished after birth.
- glia, neurons, and cardiac (non-failing heart).
Mechanisms of Tissue Regeneration
- In epithelia of the intestinal tract and skin, injured cells are rapidly replaced by proliferation of residual cells
- Tissue regeneration can occur in parenchymal organs whose cells are capable of proliferation, but with the exception of the liver, this is usually a limited process.
Mechanisms of liver Regeneration
Liver Regeneration
- From hepatocyte - after partial hepatectomy, or pvl
- From stem cells - when the hepatocyte are unable to divide
- Oval cells, intermediary hepatobiliary cells
What is the definition of healing?
The process by which the body is trying to achieve anatomical ntegrity of the injured part and restore full function
includes 2 types: primary intention and secondary intention
Describe healing by primary intention
- When does it occur
- Properties
Occurs when:
- the edges are clean and held together with ligatures
- there is a little gap to bridge healing
Healing properties (When uncomplicated)
- Occurs quickly
- Rapid ingrowth of wound healing cells (macrophages, fibroblasts, etc.)
- Restoration of the gap by a small amount of scar tissue.
Soundly united within 2 weeks
Dense scar tissue is laid down within 1 month
Describe healing by secondary Intention
- When does it occur
- Properties
Occurs when:
- The edges are separated
- The gap can not be directly bridged
- Extensive epithelial loss
- Severe contamination
- Significant subepithelial tissue damage
Healing properties
- Occurs slowly
- Granulation; healing from the bottom towards the surface
- Restoration of the gap by a small amount of scar tissue.
Scaring
Wound contracture
What are the main differences between primary and secondary healing (7)
Cleanness - Clean | Unclean
Infection - Generally uninfected | May be infected
Margins - Surgically clean | Irregular
Healing - Scanty (small) granulation tissue | Granulation tissue fill the gap
Healing period - Short | long
Healing direction - Direct healing | From the bottom to the edge
Outcome - Neat linear scar | Contracted irregular
What are the phases in the normal sequence of wound healing?
- Inflammatory phase
- Proliferative Phase
- Remodeling Phase
Describe the inflammatory phase of the normal sequence of wound healing
Starts 1st day lasts from 3-5 days
- vasoconstriction
- blood clot formation
- platelets aggregation
- platelets degranulation
- vasodilatation
-
chemotaxis
- Leucocytes
- Neutrophils
- Macrophages
Describe the proliferative phase of the normal sequence of wound healing.
Starts 3rd day lasts for 3rd week
- Angiogenesis
- fibroblasts migration
- formation of granulation tissue
- reepithelialization
Describe the remodeling phase of the normal sequence of wound healing
Starts from weeks to years
- The fibroblasts start to disappear
- Collagen type III is gradually replaced by stronger type I collagen
- The tensile strength of the scar tissue gradually increase
What are some factors affecting healing?
Local factors
- Wound sepsis
- Blood supply
- Wound tension
- Foreign bodies
- Previous irradiation
- Poor technique
Systemic factors
- Nutritional deficiencies
- Systemic diseases
- Therapeutic agents
- Age
What are dsome possible complications of wound healing?
- Infection
- Dehiscence
- Incisional Hernia
- Hypertrophic scaring
- Keloid scarring
- Contractures
This is called EXUBERANT GRANULATIONS (granulation tissue undergoes striking proliferation beyond the wound margins)
More intractable are KELOIDS, (literally “crab claws”) disfiguring scars with excessive collagen production, seen primarily in darkly-pigmented people
