tissue repair

Question 1

what is the purpose of an inflammatory response

Answer 1

eliminate injurious agent and set in motion repair process

Question 2

what are the cell types that proliferate during tissue repair

Answer 2

• remnants of injured tissue
• endothelial cells
• fibroblasts

Question 3

labile tissues are characterized by

Answer 3

continuous division

Question 4

stable tissues are characterized by

Answer 4

quiescent (in G0), only divide if necessary

Question 5

permanent tissues are characterized by

Answer 5

they are terminally differentiated

Question 6

cell proliferation in tissue repair is driven by signals from

Answer 6

growth factors (GFs) and within the ECM

Question 7

what is the most important source of growth factors in tissue repair

Answer 7

macrophages

Question 8

all growth factors activated signaling pathways that induce production of proteins involved in

Answer 8

•driving cells through cell cycle
or
•release block on cell cycle (checkpoints)

Question 9

what is a scar

Answer 9

replacement of parenchymal cells by collagen

Question 10

in angiogenesis, newly formed vessels are leaky because

Answer 10

•incomplete intraendothelial junctions and because VEGF increases permeability

Question 11

the leakiness of newly formed vessels leads to

Answer 11

edema

Question 12

granulation tissue is formed by

Answer 12

migration/proliferation of fibroblasts, deposition of loose CT, together with vessels and interspersed leukocytes

Question 13

the amount of granulation tissue formed depends on

Answer 13

• size of tissue deficit

* intensity of inflammation

Question 14

steps of connective tissue deposition (scarring)

Answer 14

• angiogenesis
• formation of granulation tissue
• remodeling of CT

Question 15

in angiogenesis during the formation of scar, what do matrix metalloproteinases (MMPs) do

Answer 15

degrade ECM to permit remodeling and extension of vascular tube

Question 16

what is the most important cytokine for the synthesis and deposition of connective tissue proteins

Answer 16

TGF-β

Question 17

what does TGF-β do

Answer 17

•anti-inflammatory -> limit/terminate inflammatory response by inhibiting lymphocyte activation and activity of other leukocytes

Question 18

what are myofibroblasts

Answer 18

• fibroblasts that have acquired some feature of smooth muscle
• contribute to contraction of scar over time

Question 19

what do MMPs do in remodeling of CT

Answer 19

• degrade collagen and other ECM components

* depend on zinc (or other metal ion)

Question 20

what cells produce MMPs

Answer 20

fibroblasts, macrophages, neutrophils, synovial cells, and some endothelial cells

Question 21

how can infection influence tissue repair

Answer 21

prolongs inflammation and potentially increase local tissue injury

Question 22

examples of nutritional deficits that might inhibit healing

Answer 22

vitamin c or copper deficit, which are needed for collagen synthesis

Question 23

how can glucocorticoids influence tissue repair

Answer 23

they are anti-inflammatory, but may result in scar weakness due to inhibition of TGF-β

Question 24

mechanical stress during tissue repair may result in

Answer 24

dehiscence

Question 25

important examples of poor perfusion that could inhibit tissue repair

Answer 25

* atherosclerosis * DM * obstructed venous drainage

Question 26

other factors that influence tissue repair

Answer 26

* foreign bodies * diabetes (important!) * type/extent of injury * location

Question 27

when does first intention healing/primary union occur

Answer 27

when injury involves only the epithelial layer

Question 28

what is the primary mechanism of repair in first intention/primary union

Answer 28

epithelial regeneration

Question 29

when cell loss is more extensive, second intention healing or secondary union occur. what does this process involve

Answer 29

combination of regeneration and scar formation

Question 30

what are examples of extensive cell loss that would result in second intention/ secondary union

Answer 30

large wounds, abscess, ulcer, and ischemic necrosis

Question 31

what differentiates second intention from first intention

Answer 31

* inflammation is more intense * fibrin clot is larger * more granulation tissue -> more scar tissue * type III collagen first, then type I replaces it * lots of wound contraction (myofibroblasts)

Question 32

strength in sutured wounds

Answer 32

* 70% of normal skin with sutures * when sutures removed (~1 wk) about 10% but rapidly increases over 4 wks * ~70-80% by 3 mos, usually no substantial improvement from there

Question 33

when is dehiscence of a wound most common

Answer 33

after abdominal surgery

Question 34

when would ulceration occur in tissue repair

Answer 34

inadequate vascularization

Question 35

what is a hypertrophic scar

Answer 35

raised scar from excessive collagen deposition; type I collagen dominates

Question 36

what is keloid

Answer 36

scar grows beyond the wound; type III collagen is dominates

Question 37

what is contracture

Answer 37

exaggeration of contraction of wound

Question 38

scar formation is directly proportional to ___ and indirectly proportional to ___

Answer 38

amount of stromal damage; replicative ability of damage tissue

Question 39

what does EGF do

Answer 39

epidermal growth factor | stimulates keratinocytes

Question 40

what does KGF do

Answer 40

keratinocyte growth factor | stimulate keratinocytes

Question 41

what does FGF do

Answer 41

fibroblast growth factor | stimulate fibroblasts AND promote angiogenesis

Question 42

what does VEGF do

Answer 42

vascular endothelial growth factor | promote angiogenesis

Question 43

what does PDGF do

Answer 43

platelet derived growth factor | promote granulation tissue formation (endothelium, smooth muscle, and fibroblasts)

Question 44

what does TGF-α do

Answer 44

transforming growth factor alpha | similar to EGF- stimulate keratinocytes

Question 45

what does TGF-β do

Answer 45

transforming growth factor beta | stimulates fibroblasts AND is anti-inflammatory (unique characteristic)