Repair and Healing

Question 1

possible outcomes of acute inflammation

Answer 1

1. resolution (back to NORMAL fxn)
2. progression to chronic inflammation
3. healing to fibrosis (LOSS of function; activation of fibroblasts)

Question 2

outcome of chronic inflammation

Answer 2

ALWAYS fibrosis (loss of function)

Question 3

regeneration

Answer 3

replacement of damaged tissue with native tissue
*driven by growth factors

Question 4

regeneration & labile tissues

Answer 4

*tissues in which cells are continuously lost and replaced by maturation from stem cells and by proliferation of mature cells
*CONTINUOUSLY DIVIDING CELLS (good at regeneration)
*skin, small/large bowel, bone marrow

Question 5

regeneration & stable tissues

Answer 5

*quiescent cells (G0) that can re-enter the cell cycle to regenerate cells if necessary
*minimal proliferative activity in normal state but can be induced to regenerate
*liver & kidney parenchyma, blood vessels, smooth muscle cells

Question 6

regeneration & permanent tissues

Answer 6

*LACK regenerative potential
*REPAIR replaces damaged tissue with a FIBROUS SCAR
*myocardium, neurons, skeletal muscle

Question 7

repair

Answer 7

replacement of damaged tissue with a fibrous scar
*always involves inflammation

Question 8

5 steps of repair by scar

Answer 8

1. inflammation
2. angiogenesis
3. migration and proliferation of fibroblasts
4. scar formation
5. connective tissue remodeling

Question 9

repair by scar: 1) inflammation

Answer 9

*MACROPHAGES play a central role
-clear debris, dead tissue, and pathogens
-provide antimicrobial activity
-provide growth factors
-secrete cytokines

Question 10

repair by scar: 2) angiogenesis

Answer 10

*new blood vessel development from existing vessels
*critical in healing (need oxygen and nutrients; need to remove wastes)
*induced by macrophages

Question 11

repair by scar: 3) formation of granulation tissue

Answer 11

*migration and proliferation of fibroblasts, blood vessels, and deposition of loose connective tissue
*pink, soft, granular appearance (e.g. beneath the scab of a wound)
*fibroblasts make collagen 3

Question 12

repair by scar: 4) deposition of connective tissue

Answer 12

*deposition of ECM proteins produced by fibroblasts (replacing collagen 3 with collagen 1)

Question 13

repair by scar: 5) remodeling of connective tissue

Answer 13

*maturation and reorganization of the connective tissue to produce the stable fibrous scar
*myofibroblasts contract the scar (pull it tighter)

Question 14

healing by first intention

Answer 14

*only a FOCAL DISRUPTION (e.g. incisions) of epithelial basement membrane and death of relatively few epithelial and connective tissue cells

Question 15

3 processes of healing by first intention

Answer 15

1. inflammation
2. cell proliferation
3. connective tissue maturation & scar

Question 16

healing by second intention

Answer 16

*when cell or tissue loss is more extensive (eg. large, ulcerative processes)
*healing from the base up to the surface

Question 17

processes of healing by second intention

Answer 17

*combination of regeneration and scarring
1. inflammation
2. development of granulation tissue
3. accumulation of ECM and formation of large scar
4. wound contraction by myofibroblasts

Question 18

parenchymal (visceral) repair by scar

Answer 18

*basic mechanisms are the same as skin repair
*could lead to fibrosis (excess collagen deposition) that leads to loss of function

Question 19

local issues that can cause delayed healing

Answer 19

*infection
*extent/size/type of injury
*mechanical factors (pressure, torsion)
*foreign bodies (sutures, etc)
*location of wound

Question 20

systemic issues that can cause delayed healing

Answer 20

*nutrition (vitamin or cofactor deficiencies)
*metabolic status (diabetes)
*circulatory status (atherosclerosis)
*hormones/steroids (anti-inflammatory effects)

Question 21

dehiscence (pathologic tissue repair)

Answer 21

*rupture of wounds due to insufficient collagen deposition
*ex. abdominal wounds - due to increased abdominal pressure or mechanical stress on the wound

Question 22

ulceration (pathologic tissue repair)

Answer 22

*inadequate vascularization
*common in lower extremity wounds in people with atherosclerosis

Question 23

hypertrophic scar (pathologic tissue repair)

Answer 23

excessive collagen confined to wound (localized, raised scar)

Question 24

keloid (pathologic tissue repair)

Answer 24

scar tissue grows beyond boundaries of original wound (collagen type 3)

Question 25

exuberant granulation tissue (pathologic tissue repair)

Answer 25

*protrudes above the level of the surrounding skin re-epithelialization (due to too much vascular supply)
*“pyogenic granuloma”