Exam 1: Ch 4 Flashcards
proliferation
increase in cell number by mitotic division
endothelial cells & fibroblasts proliferate during tissue repair
driven by growth factos
differentiation
when stem cells specialize in structure & function
multiple orderly steps driven by expression of a tissue-specific set of genes
many tissues retain ______ cells that are….
progenitor cells
able to replace cells for that tissue only
interphase
G1: RNA & protein synthesis
S: DNA replication
G2: protein synthesis
mitosis
2 cells form from 1
cell cycle checkpoints
allow opportunity for repair
no progression from G1 –> S if DNA is damaged
no progression from G2 —> M if DNA wasn’t duplicated
cell cycle regulation
cyclins control cell cycle by activating protein kinases (CDK)
CDKs phosphorylate target proteins to activate them
causes progression through cell cycle
progression through specific checkpoints controlled by specific cyclins
proliferative capacity
labile cells like intestinal endothelium cycle continuously
other cells become stable and stop cycling
stable cells and G0
stop cycling = G0
stable cells can re-enter cycle with proper stimulation
some stable cells stop cycling permanently – nerve, skeletal/cardiac muscle
stem cells
cells that remain incompletely differentiated throughout life
divide to: replace cells that died from apoptosis, or to produce another stem cell
properties of stem cells
self renewal: one cell form each mitotic division remains a stem cell (undifferentiated)
asymmetric replication: 2 cells from mitotic division are not identical – one differentiates, the other does not
types of stem cell potency
stem cells have different differentiation potential
totipotent
pleuripotent
multipotent
unipotent
totipotent stem cells
can produce all tissue types and placenta
cells generated by the first few divisions of fertilized ovum
pleuripotent stem cells
can produce all embryonic tissue types
multipotent stem cells
can produce a few related cell types
ex. hemocytoblasts
unipotent stem cells
can produce 1 cell type only
embryonic vs. adult (somatic) stem cells
embryonic are pleuripotent
adult may have less capacity
growth factos
small hormone-like proteins that are chemical triggers for cellular proliferation
contribute to tissue regeneration & wound healing
how are growth factors named
for tissue of origin
EGF: epidermal growth factor
TGF: transforming growth factor
VEGF: vascular endothelial cell growth factor
mechanism of growth factors
bind to surface receptors, activate 2nd messenger systems, increase expression of specific genes –> cellular division
ECM includes
basement membrane (borders epithelial tissue)
interstitial matrix (between cells of connective tissue)
ECM contains
protein fibers: collagen & elastin
water-hydrated gels: proteoglycans & hyaluronic acid
adhesion glycoproteins: fibronectin & laminin
cells have integrins that…
bind to adhesion molecules
fibroblasts produce…
collagen fibers
functions of ECM
provides turgor to soft tissue (structure of proteins is different between old/young skin b/c of H2O loss)
regulates cell movement & differentiation
scaffold for tissue renewal after injury
primary goal of healing by conn. tissue repair
fill gap created by injury and restore structure of neighboring tissues
regeneration
restoration of injured tissue to a normal state
scar formation
replacement of injured tissue with fibrous connective tissue
phases of tissue repair
angiogenesis & ingrowth of granulation tissue
emigration of fibroblasts and deposition of ECM
maturation and remodeling of fibrous tissue
angiogenesis
phase 1 of tissue repair
growth of new blood vessels stimulated by VEGF & FGF
new vessels are initially leaky –> wound edema persisting after inflammation
ingrowth of granulation tissue
phase 1 of tissue repair
granulation tissue: conn. tissue that fills injured area while necrotic debris is removed
requires new blood vessels
emigration of fibroblasts and deposition of ECM
fibroblasts migrate to wound and proliferate
deposit ECM including collagen
stimulated by FGF & TGF-beta
maturation and remodeling of fibrous tissue
transition from granulation tissue to scar tissue
ECM remodeled by metaloproteases
healing of skin wounds
involves both epithelium & conn. tissue
primary intent
secondary intent
primary intent
sutured surgical incision – only for clean wounds
secondary intent
wound left open and irrigated
for larger wounds with tissue loss & contaminated wounds
phases of wound healing
inflammatory
proliferative
remodeling
inflammatory phase (phase 1 of wound healing)
starts at time of injury
blood clotting and vasoconstriction stop bleeding
vessels dilate to bring inflammatory cells to the wound
neutrophils/macrophages phagocitize bacteria and release growth factors
GF stimulate angiogenesis & attract fibroblasts
proliferative phase (phase 2 of wound healing)
starts 2-3 days post-injury
fibroblasts secrete collagen and produce GF
endothelial cells proliferate and migrate to close wound edges
granulation tissue forms
collagen synthesis continues
remodeling phase (phase 3 of wound healing)
starts at ~3 weeks post-injury
collagen is remodeled and epithelium reestablished
the wound contracts – limits scar size but can also limit joint movement
keloid
excess scar tissue production
factors affecting wound healing
nutritional status
blood flow
impaired inflammatory response
infection, wound separation, foreign bodies
nutritional status
wound healing requires adquate protein, carbohydrates, & vitamins
blood flow for wound healing
O2 needed for collagen synthesis and phagocytosis
ischemic tissue heals slowly
impaired inflammatory response
disorders that impair action of phagocytes slow wound healing
infection, wound separation, foreign bodies
uncontaminated wounds with no foreign bodies and approximated edges heal the fastest
