W3D2 tissue repair, regeneration, wound healing Flashcards
(25 cards)
repair vs. regeneration
repair: try to fix damage, but may not get complete restoration of both structure and function
regeneration: reform the structure, so hopefully get original structure and therefore restoration of function
3 proliferative behaviors for cells in adult tissue
1) post-mitotic/nondividing
2) conditionally mitotic/sometimes dividing
3) self-renewing/continuously dividing
2 examples of post-mitotic/permanent cells
neurons
cardiomyocytes
What happens in cardiac muscle when there is injury/cell death?
fibroblasts infiltrate, form scar b/c cardiomyocytes can’t replicate
may see lipofuscin, scar tissue in cardiac muscle
What happens in neural tissue when there is injury/cell death?
astrocytes proliferate and form gliosis (scar) b/c neurons can’t replicate
4 examples of conditionally active/stable cells
hepatocytes (in liver)
renal tubular cells
many parenchymal cells (cells that are key to the functional element of an organ, like hepatocytes)
many mesenchymal cells (multipotent stromal cells, like osteoblasts (bone cells), chondrocytes (cartilage cells), myocytes (muscle cells), adipocytes (fat cells))
What does it mean to be a conditionally active (aka stable) cell?
usually undergo few divisions, but can divide when activated
ex: liver can regenerate large portions of itself, b/c stable cells get activated –> get compensatory division (to replace removed part)
4 examples of self-renewing (aka labile) cells
epidermis
GI tract epithelium
GU tract epithelium
hematopoetic cells (stem cells that give rise to all other blood cells)
What types of cells allow for regeneration?
stem cells and basal cells
What do self-renewing (aka labile) cells do?
divide actively throughout life
replace lost cells (ex: skin flaking off), regenerate after injury
What 2 components do you need for regeneration?
tissue must have stem cells/basal cells in it
infrastructure must be intact, so you can build on it
What are 2 key components of tissue infrastructure, needed for regeneration?
basement membrane
extracellular matrix
What happens if you don’t have intact basement membrane and/or extracellular matrix?
can’t do regeneration
must do repair instead
Why do you get bowel obstruction in Crohn disease?
inflammation is deep (transmural) and causes chronic damage
you get scarring b/c basement membrane gets damaged (so you can’t do regeneration; must do repair)
bowel wall gets thicker/more rigid
strictures form, which cause bowel obstruction
Why is ulcerative colitis not as severe as Crohn disease?
relatively superficial injury
little or no damage below basement membrane
if basement membrane intact, can do regeneration (instead of repair)
What happens if you have intact tissue scaffold? if you have scaffold damage?
intact tissue scaffold: regeneration (form again on scaffold)
scaffold damage: repair (mend w/ fibrosis)
3 phases of cutaneous wound healing
1) inflammation
2) proliferation
3) maturation
What happens during the 1st step of cutaneous wound healing?
inflammation: clot formation, chemotaxis
What happens during the 2nd step of cutaneous wound healing?
proliferation: re-epitheliaization (reform things on top), angiogenesis (form blood vessels beneath), reform granulation tissue, make provisional matrix
What happens during the 3rd step of cutaneous wound healing?
maturation: form collagen matrix (which is stronger than the provisional matrix previously formed), wound contraction
5 main roles of macrophages in wound healing
debridement, removal of injured tissue/debris
antimicrobial activity: nitric acid, ROS
chemotaxis, proliferation of fibroblasts and keratinocytes
angiogenesis
deposition and remodeling of ECM
local factors that determine outcome of wound healing
nature of wound
size
infection
mechanical disruption
foreign bodies
systemic factors that determine outcome of wound healing
nutrition (especially protein, vitamin C)
metabolic status (ex: if have diabetes mellitus)
blood supply
hormones (especially glucocorticoids)
deficits that can cause problems in wound healing
metabolic status/diabetes mellitus
blood/nerve supply
immune/inflammatory suppression
insufficient time
