#4 healing/repair Flashcards
regeneration
repair process in which injured or dead cells are replaced by replicating cells of the same type. Connective tissue/extracellular matrix of the organ is intact
replacement
connective tissue replaced the injured or dead cells replacing it with fibrous tissue (scar). Happens if either the connective tissue framework was destroyed or the parenchymal cells cannot regenerate.
labile cells
continuously divide. Lost cells replaced by
maturation from stem cells or proliferation of mature cells. (epithelium of skin and mucous membranes, and hematopoietic cells)
stable cells
low level of replication but divide rapidly when stimulated. In G0 (quinescence phase) of cell cycle. Examples- liver, kidney, pancreas, smooth muscle cells, fibroblasts.
permanent cells
non-dividing, terminally differentiated. brain and heart and sort of skeletal muscle
process of replacement by connective tissue
- angiogenesis- VEGF (vascular endothelial growth factor)
- migration and proliferation of fibroblasts- TGF-B, PDGF(platelet derived GF), and FGF (fibroblast GF)
- formation and deposition of extracellular matrix (by fibroblasts)
- maturation and organization of the fibrous tissue elements.
granulation tissue
the tissue that fills in defects when non-regenerative cells and/or connective tissue framework is destroyed. It consist of proliferating fibroblasts and new blood vessels. It appears red and edematous to the naked eye. It is only present during healing
organization
the process of transforming granulation tissue into dense scar tissue. connective tissue elements mature and blood vessels become less prominent.
healing by first intention (primary union)
using sutures to speed up heeling. Wound is usually clean, limited in the amount of destroyed tissue. Epithelial regeneration principle mechanism of repair.
healing by second intention (secondary union)
Same process as internal organ healing.
Large skin wound
Extensive destruction, contaminated, infected
Edges are not approximated
Larger clot, more intense inflammation
Wound granulates in without closing gap with sutures
Process of healing same but takes longer because of the size of the defect
Wound contraction by myofibroblasts
hypertrophic scar
excess production of scar tissue localized to the wound (may regress)
keloid
exuberant amount of collagen, grows beyond wound boundaries. May be hereditary more common in african americans.
what initiates the repair process?
inflammation
2 requirements for regeneration
- connective tissue intact
2. cells are capable of dividing
composition of ECM
fibrous structural proteins (collagens, elastins)
water hydrated gels (proteoglycans, hyaluronan)
Adhesive glycoproteins
ECM
network of interstitital proteins
2 forms: interstitial matrix and basment membrane
pros and cons of scar tissue
Con- Fibrous tissue cannot perform function of lost parenchymal cells
Pro- Scar usually provides enough structural stability for injured tissue to continue function
VEGF
Family of growth factors
Promote angiogenesis
Increase vascular permeability
Stimulate endothelial cell migration, proliferation
Expressed at low levels in most adult tissues
Expressed at higher levels in a few sites
(Podocytes in glomerulus, pigment epithelium of retina)
Hypoxia = important inducer
Mutations = defective angiogenesis and vasculogenesis
Fibrosis
excessive deposition of collagen and other ECM components in a tissue
important nutrients for wound healing
vitamin C, Zinc, Copper
Dehiscence
wound breaks open
contracture
get lots of myofibroblast to pull it together and shrink the size of the injury
