Wound Repair

Question 1

definition of a wound

Answer 1

an acquired defect in the structural and functional integrity of tissue caused by physical or chemical insults

Question 2

two subtypes of wound healing

Answer 2

regeneration & replacement

Question 3

wound regeneration

Answer 3

restoration of lost tissue structures via cell division and growth of new parenchymal cells

Question 4

wound replacement/repair

Answer 4

filling of the wound with less specialized connective tissue, principally collagen resulting in a scar

Question 5

three types of regeneration

Answer 5

1) division of parenchymal cells in intact stroma
2) division of parenchymal cells in remaining structure
3) stem cell division and differentiation

Question 6

labile cells

Answer 6

cells that can undergo high regeneration due to highly proliferative tissues (GI epithelium, epidermis, bone marrow)

Question 7

stable cells

Answer 7

tissues that undergo limited regeneration bc they divide at low rates. (liver, kidney, vascular endothelium)

Question 8

permanent cells

Answer 8

post-mitotic tissue (neurons, cardiac muscle)

Question 9

chronic inflammation and wound repair

Answer 9

inhibits regeneration and therefore leads to replacement

Question 10

milder injury & regeneration

Answer 10

when accompanied with persistence of underlying stromal framework, enables regeneration

Question 11

severe injury & regeneration

Answer 11

destroys stromal framework precluding regeneration or triggering abnormal regeneration

Question 12

characteristics of replacement of a wound with a scar

Answer 12

destruction of tissue stromal architecture, limited proliferation of tissue stem cells, chronic inflammation

Question 13

primary union

Answer 13

straight wound, well apposed edges, clean. minimal scar formation. minimized formation of granulation tissue and scar formation.

Question 14

secondary union

Answer 14

irregular wound, unappeased edges, dirty/infected, significant scar formation. extensive inflammation and granulation tissue, wound contraction. attempts to close via primary union can prevent infection from clearing.

Question 15

tertiary union

Answer 15

wound that is allowed to begin healing by secondary union and is sutured after resolution of infection to allow further healing by primary union

Question 16

5 steps in wound healing

Answer 16

1. clot formation
2. inflammatory cell recruitment
3. proliferation/migration of parenchymal/stromal cells
4. synthesis of ECM proteins
5. remodeling

Question 17

PDGF (platelet derived GF)

Answer 17

released by activated platelets and macrophages, stimulates proliferation of fibroblasts and vascular endothelial cells

Question 18

FGF (fibroblast GF)

Answer 18

produced by macrophages and fibroblasts. potent activator of angiogenesis via stimulation of proliferation of endothelial cells and via directing their formation into tubular vessels

Question 19

KGF (keratinocyte GF)

Answer 19

produced by fibroblasts, stimulates growth of keratinocytes during reepithelialization of the wound

Question 20

VEGF (vascular endothelial GF)**

Answer 20

synthesis is stimulated by hypoxia, released from many cells including endothelial cells, fibroblasts, macrophages. stimulates endothelial cell proliferation and angiogenesis. also increases permeability of vessels

Question 21

TGF-beta (transforming GF-beta)

Answer 21

produced by many cells including platelets, macrophages, fibroblasts, keratinocytes. regulates multiple target cells and all stages of wound healing

Question 22

wound healing steps (simple version)

Answer 22

clot, inflammation, epithelialization, granulation, collagenization, maturation

Question 23

clot phase of wound healing

Answer 23

initial coverage of the wound via clot, entry of acute inflammatory cells (PMNs) via leaky/damaged vessels, which release chemokines and GFs that attract cellular components of epithelialization

Question 24

first line of defense against wound

Answer 24

clot

Question 25

scab

Answer 25

superficial aspect of a clot that has become dehydrated

Question 26

epithelialization phase of wound healing

Answer 26

keratinocytes migrate under the clot

Question 27

granulation tissue phase of wound healing

Answer 27

epithelial regrowth has reached surface. underneath there is ingrowth of fibroblasts, new/leaky endothelial bus (create edema), macrophages

Question 28

functions of fibroblasts in a wound

Answer 28

secrete ECM (collagen, glycoproteins, etc), secrete growth factors, contract to reduce size of wound

Question 29

functions of endothelial cells in wound

Answer 29

migration and angiogenesis=leaky vasculature

Question 30

collagenization phase of wound healing

Answer 30

replacement of granulation tissue with disorganized collagen (type 3)

Question 31

maturation phase of wound healing

Answer 31

collagen deposition stops and it is reorganized into tensile bundles. vascularity and cellularity decrease, production of GF ceases

Question 32

matrix metalloproteinases (MMPs)

Answer 32

key regulators of wound healing. set of 24 proteins that help keratinocyte migration, modulate chemokine activities, help remodel ECM,

Question 33

principle components of granulation tissue

Answer 33

leaky capillaries and macrophages

Question 34

examples of pathologic scarring

Answer 34

nodule formation in cirrhosis, contractures, keloids, strictures

Question 35

keloids

Answer 35

growth of the scar beyond the boundaries of the original wound. over exuberant deposition of collagen and ECM