Test 1: lecture 7 tissue repair Flashcards
4 phases of wound repair
hemostasis
acute inflammation
proliferation
remodeling
replacement by cells of the same type; requires an intact framework
regeneration
2 results of regeneration
renewing tissues such as GI can regrow
Stable tissues such as liver and kidney can undergo compensatory growth
What determines whether a tissue will undergo regeneration or healing?
Type of tissue damaged
• Damage to the ECM
• Extent of the wound
• Blood supply, nutrition
Although amphibians have the ability to regenerate limbs and some organs, regeneration in mammalian organs is ___
compensatory growth.
functional but not exact replica
name two type of cell groups that can undergo regeneration
Continuously dividing (labile) tissues - cells proliferate throughout life, replacing those that are destroyed (e.g. gut epithelium).
Quiescent (stable) tissues- low level of replication; may undergo rapid division in response to stimuli and can restore the tissue of origin. G0 stage but can be stimulated to enter G1 (e.g. parenchymal cells of liver, kidneys, and pancreas).
what type of cells can not undergo regeneration
post mitotic (terminally differentiated)
cannot undergo mitotic division
example: neurons, cardiac muscle
parenchymal cell death with intact tissue framework results in ___
regeneration of normal structure
liver, skin
parenchymal cell death with damaged tissue framework results in
repair by scar formation
heart attack
persistant tissue damage results in
fibrosis and tissue scar
cirrhosis, chronic pancreatitis
restoration of integrity to injured tissue; typically involves collagen deposition and scar formation.
healing
4 stages of wound repair
Hemostasis (vascular phase)
Acute inflammation (cellular phase)
Proliferation (proliferation phase- granulation tissue)
Remodeling (maturation phase, contraction)
inflammation phase occurs ___ to ___ hrs after injury
24-96
what cells are involved in the inflammation phase
Macrophages remove cell debris (w/neutrophils), degrade ECM, release GF (w/fibroblasts) necessary for the proliferation phase.
___ form a loose gel-like matrix to serve as the scaffold for
granulation tissue.
fibrin
how long does the proliferation phase last?
3-4 weeks depending on size of wound
Granulation tissue proliferation has connective tissue fibers that are ___ to the surface of the wound, fibroblasts, and blood vessels that are ___ to the surface of the wound
parellel
perpendicular
epithelial and mesenchymal stem cells are turned on in what stage of wound healing
proliferation (stage 3 → granulation tissue)
what starts to form in the wound during the proliferation phase
fibrous connective tissue and blood vessels
when does stage 4 of wound healing start
remodeling/maturation phase
3-4 weeks after injury after all other phases are done
when does collagen form in wound healing
remodeling/maturation phase
TGFB and ECM will help convert immature connective tissue into collagen
contraction in remodeling tissue is by ___
myofibroblasts
explain
inflammation phase 24-96 hours
1- neutrophils and macrophages come in and clean up
- lack of blood causes activation of growth factors which lead to new vessels and recruit fibroblasts, myofibrils and structural cells
- old ECM is broken down
- fibrin and serum proteins fill the wound
proliferation phase 3-4 weeks → angiogenesis and fibroplasia→ granulation tissue formation
- fibrin acts as framework for granulation tissue with connective tissue parallel and vessels perpendicular
- basement membrane reforms and re-epithelization occurs to close area
- stem cells found in hair follicles activate
remodeling phase - 3-4 weeks after injury → collagen formation and wound closure
platelets and macrophages release TFG B that stimulate the formation of collagen and myofibroblast activation
what are the white spaces
edema
picture of acute wound with fibrin and neutrophils
7 day wound
see scab and re-epithelization
cell in proliferation phase → depositing granulation tissue
7 day wound
see scab and re-epithelization- cells are stretched to cover injury
less edema- area now filled with fibrous connective tissue and congested red blood cells
cell in proliferation phase → depositing granulation tissue, vessels and fibroblast
cirrhosis
heals by fibrosis- bands of fibrosis will contract to form nodules
what are some things that disrupt repair
Bacterial infection
Poor Nutrition: protein deficiency; Vitamin C deficiency
Glucocorticoid therapy: anti-inflammatory; impairs collagen synthesis
Mechanical factors: local pressure, torsion, movement
Dehiscence
Poor perfusion
Amount of tissue injured
Tissue type: those that cannot regenerate (e.g. myocardium) lead to scarring
Aberrations of cell growth and ECM production (proud flesh)
granulation tissue
granuloma
granulation tissue-proliferative phase of tissue healing → fibroplasia and neovascularization
granuloma- chronic inflammation→ epithelioid macrophage and multinucleated giant cells
fibrin vs fibrous
fibrin part of acute/vascular phase of wound healing. leaks from endothelium that has been injured. part of the clotting cascade. acts as framework for fibroblasts to come in and deposit fibrous connective tissue/collagen
___ is when organ becomes functional due to cell hyperplasia and hypertrophy (not a replica)
compensatory growth
branch of regeneration
1st phase of wound repair
hemostasis (vascular phase)
what happens during the hemostasis phase of wound healin
first phase
stops blood flow and then starts rebuilding
injury causes vasospasm→ platelets clot and release TGF that causes vasoconstriction and thrombogenesis and angiogenesis
explain how oxygen effects wound healing
oxygen tension- lack of O2 to an area causes the production of growth factors that will activate macrophages, fibroblasts and endothelial cells
Macrophages clean up cell debris, degrade ECM and release growth factors (along with fibroblasts) to enhance proliferation of endothelial cells, fibroblasts for new ECM, ___ for contraction, and ___ cells for return to normal structure and function.
myofibroblasts
parenchymal
Degradation of the ECM occurs through physical separation or tearing, ___ from plasma proteins, infiltration by inflammatory cells, and degradation by ___ produced by macrophages, fibroblasts, mast cells, and most leukocytes.
dilution
MMPs
what three processes occur during proliferation
granulation tissue phase
angiogenesis, epithelialization, and fibroplasia.
Excessive/exuberant granulation can lead to a type of hypertrophic scar called ____
proud flesh.
Contraction of healing tissue is mediated by ____
myofibroblasts (specialized fibroblasts with contractile activity).
Secretion of TGF-β by platelets and macrophages
Function is to contract the wound and thus bring together injured tissue separated by edema and inflammation.
Scirrhous Reaction
when too much connective tissue/collagen is put down
causes damage to original tissue
cirrhosis (bands of fibrous tissue that contract to form nodules)
