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Flashcards in Tissue Repair Deck (57)
1

How is tissue repair defined?

restoration of tissue architecturally and functionally

2

Tissue repair can occur via what two mechanisms?

regeneration of the injured tissue
replacement of lost tissue
(part of each two mechanisms play vary from tissue to tissue)

3

Both mechanism require:

-cell proliferation
- interaction between cells and the presence of intact or altered extracellular matrix

4

Compare HAV to HBV.

HAV (no chronic HepA)
- hepatic necrosis
- recover or die
- not destroying hepatocyte

HBV (chronic Hep B)
- kills hepatocyte and matrix

5

Describe cell proliferation.

Continuously proliferating cells can easily regenerate after injury or being used
- contains pools of stems cells close by
- immune + for CD34, CD117, Ki67

6

What is totipotent cell?

cell can differentiate into any cell type

7

Where is the first checkpoint?

G1/S - check for DNA damage
-may undergo apoptosis if defect

8

Where is the second checkpoint?

G2/M

9

What three groups are tissues of the body divided?

Continuously dividing (labile) - skin basal, GI, hair [short G0]
Stable tissues - liver, kidney, lung alveoli, bond, breast, endocrine, adipose [ long G0]
permanent - neurons in CNS, ganglia in PNS, cardiac, skeletal muscle [cannot divide]

10

Where are the three sites of stem cells in the skin?

epidermis
sebaceous gland
hair follicle bulge

11

Haematopoietic stem cells can differentiate into ?

RBC, WBC (lymphocyte, monocyte, eosinophil, basophil, neutrophil) , platelets

12

What is the actions of growth factors?

stimulate cell division and proliferation
promote cell differentiation & survival

13

What is EGF?

epithelial growth fact
mitogenic for skin & fibroblasts

14

What is TGF?

transforming growth factor
hepatocytes & epithelials

15

What is PDGF?

platelet derived growth factor
smooth muscle mitogens
cytokines

16

Cytokines can be present in which instances?

injured tissue remnant
inflammatory cells, macrophages, vascular endothelial cells
cytokines from fibroblasts

17

Where are cytokines stored?

extracellular matrix
-basement membrane
- interstitial matrix

18

What purpose does the basement membrane and interstitial matrix serve?

-sequesters water and minerals from circulation
-stores presynthesized growth factors
-give cells a scaffolding upon which to adhere and do their assigned tasks

19

What is the consequence if the ECM is destroyed?

can't regenerate tissue
-scar forms instead

20

What does the ECM regulate?

proliferation, movement, and differentiation of the cells

21

What are the stages of tissue repair?

regeneration
scarring

22

Where does regeneration occur frequently?

labile tissues

23

Where does regeneration occur to a limited extent>

stable tissues
-kidney (if removed the other one undergoes hypertrophy and hyperplasia)
-liver (remove part of liver, some will grow back)

24

Describe the theoretical aspect of injury.

Blood clots and releases growth factors
-Inflammation
-granulation tissue
- wound contraction

25

At what point can regeneration not happen?

severe injury

26

What four components to scarring are mediated by GFs?

- new vessel formation (angiogenesis) VEGF
- fibroblast proliferation elaborating FGF, TGF
- fibroblast form an immature scar Type 1 collagen
-fibroblast remodeling with mature scar Type 4 collagen

27

What cells come in by 24 hours when an injury occurs?

PMNs
-endothelial cells are called upon to start proliferating
-fibroblasts emigrate-myofibroblasts appear wound contaction

28

With what growth factor does heeling begin with ?

PDGF

29

What happens by 3-5 days after an injury?

granulation (scab, eschar) tissue present
- new scaffolding upon which repair cells work

30

How is the scar remodeled over time?

granulation tissue changing with collagen types moving from type 1 to 4

31

Granulation tissue contains cross linked collagen. (T/F)

false; mainly blood vessels and fibrin

32

What is a trichrome stain?

stains collagen blue/green

33

Two types of wound healing

healing by first intention (a surgical incision)
healing by second intension (a third degree burn)

34

Describe scarring with 1st intention? 2nd intention?

1- small scarring
2- large scarring

35

How is healing by first intention accomplished?

epithelial regeneration predominates over fibrosis
- healing is faster with minimal scarring if no infection

36

Describe the immediate timeline of first intention.

Vasoconstriction - blood fills incision site, platelets activated
Platelets are irritated and release clotting factors.
-also release activation factors that activate edge of wound.

37

Describe the timeline changes one sees by 24 hours.

By 24 hours
-platelet aggregates
-release PDGF's
-migration of cells first neutrophils then macrophages come in
- at the cut edge of lesion, stem cells are stimulated to propogate
-chemotaxasis takes place

38

Describe the timeline changes one sees by 3-7 days.

Macrophages come in very few PMN
Granulation tissue is formed:
- new blood vessels (VGF)
- fibroblasts (fgf) & myofibroblasts (TGF)
Collagen type 1 begins to bridge incision
**very labile wound**

39

Describe timeline changes weeks later.

Granulation tissue gone, ECM back
Collagen is remodeled type IV
epidermis full thickness, mature (w/o dermal appendage)
Fibrous union

40

Scars are prone to develop cancer due to lack of?

melanin

41

Describe healing by second intention.

wounds that have large gaps
-race between epithelial cell and fibroblasts
- fibrosis predominated over epithelial regeneration
- healing is slower with MORE inflammation
-granulation tissue formation and scarring
-more wound contraction
Ex) ischemic necrosis (infarction)
large burns and ulcers

42

What is gliosis?

scar in brain

43

How can an infarct in the brain cause epilepsy?

glial cells contract leading to epilepsy

44

How do skin ulcers appear?

slide, large gap between edges
surface is hyperkeratonized

45

At the time of suture removal the tensile strength is?

only 10% of what is was before injury

46

What is the wound strength of primary intention at third month?

70-80%

47

What are examples of wounds gone bad due to aberrant cell growth of ECM?

keloid scar
proud flesh

48

Why do wounds go bad?

Extrensic factors trauma
acute and chronic infection
diabetes
steroids
ischemia - lower extremity heals slower than upper
personal care
radiation
diet

49

Why could tissue be so vulnerable to trauma?

blood supply is not adequate

50

What is a keloid scar?

hypertonic fibroblastic response
during maturation creates an overgrowth of type 1 collagen and overabundance of type IV
main proliferation below epithelium

51

What is proud flesh?

hypertonic granulation tissue
pyogenic granuloma

52

Scarring can lead to what adverse effects?

contraction --permanent dysfunction

53

What is cirrhosis?

fibrosis and regenerative nodules

54

Nephrosclerosis contains decreased what?

glomeruli

55

What is a tampanade?

blood escapes heart and fills pericardium

56

When is the heart most prone to rupture after an M.I?

1st week

57

What atypical collagen is laid down in scars caused by cancer?

type V