Tissue Injury Flashcards
what are the two main processes that resolve cell injury
regeneration
repair
what are the mechanisms of cell injury
ischemia
infectious agents
immune reactions
genetic alterations
what are the two infectious agents
bacteria
viruses
what is ischemia
blood flow below the minimum necessary to maintain cell homeostasis and cell homeostasis
and metabolic function
what can ischemia result in
hypoxia or anoxia in tissue
decreased nutritional delivery
decreased removal of waste
how do bacterial agents affect cells
invade tissue
release exotoxins and endotoxins
cause cell lysis and degradation of ECM that aids in the spread of infection
what are two ways a virus may get into a host
indirect or direct
what is direct virus effect
usually found with RNA
kill by disturbing various cellular processes or disrupting the integrity of the cell nucleus/plasma membrane
what is indirect virus effect
integrate themselves into the cellular genome
encode production of foreign proteins that are not recognized by body’s immune system
what are the inflammatory cells
neutrophils
macrophages
T/B lymphocytes
mast cells
basophils
hallmarks of irreversible cell injury
alternations in the cell nucleus
mitochondria
lysosomes
rupture of cell membrane
2 mechanisms of tissue healing
regeneration and repair
what are regeneration / repair
regeneration - regrowth of original tissue
repair - formation of a connective tissue scar
what cells are involved in tissue healing
fibronectin
proteoglycans
elastin
collagen
function of fibronectin
“glue” for substances and cells
attracts fibroblasts and macrophages
what do proteoglycans and elastin do
bind to fibronectin and collagen to stabilize tissue undergoing repair
water retention
function of collagen
most important protein to provide structural support and tensile strength
how does collagen change during the maturation process
moves from type 3 to 1
3 being most immature, 1 being most mature
tell me about type 1 collagen
main component of mature scars
predominant in strong tissues such as tendons and bones
tell me about type 2 collagen
assembled thin supporting filaments
predominant type of collagen found in cartilage
tell me about type 3 collagen
assembled into thin filaments
makes tissue strong but supple and elastic
prevalent in newborns
what are two current theories proposed to explain collagen realignment
tension vs induction
what is the tension theory
as collagen gets laid, stress on the tissue will regulate how much collagen is laid down
what is the induction theory of scar formation
the body knows what to do/has its own blueprint and lays down collagen according to that
4 phases of healing
hemostasis and degeneration
inflammation
proliferation and migration
remodeling and maturation
when does hemostasis and degeneration occur?
immediately after an acute injury to help the body try to stop bleeding and initiate coagulation
characteristics of degeneration/hemostasis
formation of hematoma
necrosis of dead cell
start of inflammatory cell response
when does inflammatory phase begin
once blood clot forms
what occurs in the inflammation stage
vasodilation and increased capillary permeability to activate movement of cells to the wound site
what coordinated reaction of body tissues involved in inflammation
vascular
humoral
neurologic
cellular responses
functions of the inflammatory reactions
inactivate the injurious agent
break down and remove dead cells
initiate the healing of tissue
tell me about the clinical manifestations of acute inflammation
redness, swelling, increased temperature, pain, decreased function
primary outcomes of acute inflammation
complete resolution of normal tissue structure
healing of scar formation
chronic fibrosis
vascular changes of acute inflammation
leakage of protein poor fluid (transudate) into interstitial spaces
leakage vessels become engorged with blood cells causing a slowing of blood flow
leukocytes accumulate and adhere to endothelial cells
adhesion of glycoproteins
what are the predominant leukocytes present in acute inflammation
neutorphils
chemical mediators of inflammation
histamine
platelet-activating factor
prostaglandins
leukotrienes
cytokines
what is the purpose phagocytosis
inactivation and remove inflammatory stimulus in order to begin healing
explain phagocytosis
what are the most important phagocytes
ingestion of microorganisms, other foreign substances, necrotic cells and connective tissue
monocytes and macrophages
what are the hallmark signs of acute inflammation
pallor - pain
calor - heat
rumbor - redness
tumor - swelling
loss of function
what is proliferation and migration
revascularization and rebuilding of tissue
fibroblasts drawn to the matrix and synthesis of new collagen/elastin/and proteogylcans
what is the time frame of proliferation and migration
within 2 days of wound or injury
what is neovascularization / angiogenesis? when does it occur?
establishment of a network that can transport oxygen and nutrients to support metabolism and healing
proliferation and migration
tell me about remodeling and maturation
balance between tissue synthesis and degradation
how long can remodeling and maturation take
years as initial collagen strands are broken down and rearranged due to stress
tell me about the scar tissue changes during maturation phase
reduced and remodeled - smoother and stronger
less red due to decreased concentrations of blood vessels
what are myofibroblasts
abundant contractile proteins to contribute to shrinkage of healing tissue
scar formation process
initial collagen (type3)
remodeling (3 to 1)
consolidation
maturation
hypertrophic scars
elevated collagen that is laid down within the borders
keloid scars
outside of OG borders, laid in circular fashion
what is the expected regeneration of peripheral nerves
undergoes myelin degeneration and axonal fragmentation
within 24 hours axonal sprouts occur
regeneration of 1 inch per month
