Tissue Repair Flashcards
the two types of reactions in repair are
- regeneration
- scar formation
tissue replaces damaged components and returns to a normal state is called
regeneration
damaged tissues incapable of complete restitution and/or supporting structures of tissue are severely damaged is called
scar formation
what is fibrosis
the extensive deposition of collagen in lungs, liver, kidney, and other organs due to chronic inflammation
cell types that repair injured tissue
- remnants of injured tissue
- vascular endothelial cells
- fibroblasts
function of remnants of injured tissues
attempt to restore normal structure
function of vascular endothelial cells
create new vessels that provide nutrients for the repair process
function of fibroblasts
source of fibrous tissue forming the scar to fill in defects that cannot be corrected by regeneration
key processes of cell proliferation
DNA replication and mitosis
G1 phase=
pre synthetic growth phase
S phase=
DNA synthesis phase
G2 phase=
premitotic growth phase 2
M phase=
mitotic phase
non dividing cells are either in:
- cell cycle arrest (G1) or
- they exit the cycle to enter a phase (G0)
physiologic cell proliferation is caused by:
repair
pathologic proliferation is caused by:
cancer
ability of tissue to repair themselves is influenced by their:
intrinsic proliferative capacity
3 types of tissues involved in proliferation capacity
- labile (continuously dividing) tissues
- stable tissues
- permanent tissues
examples of labile (continuously diving) cells that have a short life span
-bone marrow, skin, oral mucosa, GI tract, ducts draining exocrine glands
stable tissue quiescent cells (in G0 stage) have what kind of proliferation capacity?
have minimal replicative activity (can proliferate in response to injury and loss of tissue mass)
stable cells constitute what aspect of most solid tissues?
the parenchyma of most solid tissues (kidney, liver, pancreas, endothelial cells, fibroblasts, smooth muscle cells)
what is unique about permanent tissues?
terminally differentiated and non proliferative in postnatal life
examples of permanent tissues with long life spans
neurons, cardiac, and skeletal muscle
2 characteristic properties of stem cells
- self renewal capacity
2. asymmetric replication
what is asymmetric replication of stem cells mean?
- some differentiate to a specific cell type
- some remain undifferentiated (these maintain their self-renewal capacity
embryonic stem cell characteristics
most undifferentiated stem cells
-capacity to generate multiple cell lineages (neurons, cardiac muscle, liver cells)
adult stem cells (tissue stem cells) are:
less undifferentiated than embryonic stem cells and found among differentiated cells with an organ or tissue
what are growth factors?
proteins that stimulate the survival and proliferation of particular cells that can promote migration, differentiation, and other cellular responses
what are growth factors produced by?
by macrophages and lymphocytes, parenchymal cells or stream cells (connective tissue)
growth factors can affect cell proliferation by promoting:
- cell entry into cell cycle
- replication (mitosis)
- prevention of apoptotic death (survival)
- function of growth control genes
other things that growth factor can stimulate are:
angiogenesis, contractility, and fibrogenesis
3 types of signaling mechanisms of growth factor
- autocrine
- paracrine
- endocrine
type of signaling mechanism where a substance acts on cell that secretes it (ex: lymphocyte proliferation, liver regeneration)
autocrine
type of signaling mechanisms that affects cell in the vicinity and recruits inflammatory cells in wound healing
paracrine
type of signaling mechanisms that acts on target cells at a distance (ex: hormones)
endocrine
examples of lipid based signaling mechanisms that can affect receptors inside the cell
vitamin D, steroid, thyroid hormones
how does tissue repair depend on interactions between cells and ECM
regulates proliferation, movement, and differentiation of cells within it
what are the 2 forms of the ECM
- interstitial matrix
- basement membrane
part of ECM that is located in spaces between cells in connective tissue, and between epithelium and vascular/ smooth muscle structures
interstitial matrix
part of ECM that is a matrix of connective tissues that is highly organized around epithelial, endothelial, and smooth muscle cells (found between epithelium and mesenchymal cells)
basement membrane
components of ECM can include
- collagens and elastin
- proteoglycans and hyaluronan
- adhesive glycoproteins
collagens and elastin contribute to
tensile strength and recoil of ECM
proteoglycans and hyaluronan contribute to
water-hydrated gels for resilience and lubrication of ECM
how can ECM help control cell proliferation
signals through cellular receptors of the intern family
what is needed for renewal of structure (stroma of the parenchymal cells)
basement membrane
what cells depend on ECM to reestablish normal structure
labile and stable cells
regeneration cannot be accomplished if there is severe or chronic damage to:
parenchymal cells, stroma, or non-dividing cells
in scar formation, what begins within 24 hours of injury
fibroblasts and endothelial cells proliferate
in scar formation, what occurs in 3-5 days
granulation tissue (seen beneath a scab) with delicate capillaries
process of new blood vessel development from existing cells is called
angiogenesis
angiogenesis is primarily in
venules
3 main phases of wound healing
- inflammation
- formation of granulation tissue
- ECM deposition and remodeling
what can occur in wound healing for larger wounds
contraction (wound dimples in a little)
primary example of healing by first intention
surgical scar
in first intention healing, what regeneration predominates
epithelial regeneration predominates over fibrosis
most important cause of delayed healing
infection
