Lecture 28

Question 1

Tissue Regeneration

Answer 1

Replacement of injured tissue with cells of the same type and function

Question 2

Tissue Repair

Answer 2

When the extent of cell injury is such that regeneration is not possible,
structure of the tissue is restored by replacement with other cells/molecules that differ from those lost through injury. This results in scarring or fibrosis

Question 3

What are the 4 stages of healing after tissue injury

Answer 3

1. homeostasis
2. inflammation
3. proliferation
4. remodeling

Question 4

Homeostasis

Answer 4

this happens within minutes and results in local vasoconstriction and activation of platelets and clotting factors to form a fibrin clot

responds rapidly to stop the loss of blood

Question 5

Inflammation

Answer 5

this occurs over hours and is driven by platelet-derived mediators, bacteria, and secreted chemoattractants.

associated with redness, swelling, and pain

Question 6

Proliferation

Answer 6

this occurs within days and is mediated by macrophage and fibroblast-derived growth factors

Question 7

Remodeling

Answer 7

this happens over weeks to months it is knowns as the transition from type 3 to type 1 collagen, restoring tensile strength of tissue

Question 8

Determinants of regeneration versus repair

Answer 8

1. nature of cells injured
2. extent of injury
3. presence or absence of ongoing inflammation
4. underlying disease

Question 9

Nature of cells injured

Answer 9

some cells don’t have the ability to do tissue regeneration

Question 10

Extent of injury

Answer 10

if the injury is too big then regeneration is not possible

Question 11

Presence or absence of inflammation

Answer 11

continuous release of inflammatory mediators may disrupt balance towards repair

Question 12

Underlying disease

Answer 12

can impair proliferation responses

diabetes

Question 13

What is the most common outcome of various signal transduction pathways of growth factors

Answer 13

change in gene expression

Question 14

Describe the two forms of ECM and their key components

Answer 14

1. interstitial matrix which includes fibrillar collagens, elastin, and proteoglycan
2. basement membrane which include type IV collagen, laminin, proteoglycan

Question 15

Identify 3 growth factors that regulate fibrosis

Answer 15

PDGF (platelet-derived growth factor): migration and proliferation of fibroblasts, smooth muscle cells, and macrophages

TGF beta (transforming growth factor): stimulates fibronectin and proteoglycan synthesis. Inhibits lymphocyte proliferation

FCF-2 (fibroblast growth factor): stimulates proliferation of endothelial cells. Promotes migration of macrophages and fibroblasts