Repair and Regeneration

Question 1

What are the 3 categories of tissue types based on the regenerative capacity?

Answer 1

Labile tissues (with stem cells that continuously cycle to regenerate tissue), stable tissues (can reenter cell cycle to regenerate tissue), permanent tissues without significant ability to regenerate.

Question 2

What is the name of continuously dividing tissues, and what are 3 examples?

Answer 2

Epidermis (stem cells in basal layer), gastrointestinal mucosa (stem cells in crypts) and bone marrow (stem cells in hematopoietic system)

Question 3

What is the name of tissue that are quiescent but can reenter the cell cycle to regenerate tissue when necessary, and what is an example?

Answer 3

Stable tissues. Classic example is liver regeneration after partial resection by compensatory hyperplasia.

Question 4

What is the name of non-dividing tissues and what are 3 examples?

Answer 4

These are permanant tissues and lack signficiant regenerative potential. 3 examples are neurons, myocardium, skeletal muscle.

Question 5

During tissue repair, what growth factor mediator is an epithelial and fibroblast growth factor?

Answer 5

TGF-alpha (also happens to be an attractant for macrophages)

Question 6

During tissue repair, what growth factor is the most important fibroblast growth factor which also inhibits inflammation?

Answer 6

TGF-beta, released by macrophages. It stimulates fibroblasts to lay down collagen (recall that macrophages release TGF-beta and IL-10 to shut down inflammatory response).

Question 7

During tissue repair, what is the important growth factor for angiogenesis?

Answer 7

Vascular endothelial growth factor (VEGF) (also FGF, fibroblast growth factor, promotes angiogenesis and skeletal development)

Question 8

During tissue repair, what is the growth factor for endothelium, smooth muscle, and fibroblasts, which helps to seal the blood vessel?

Answer 8

Platelet derived growth factor

Question 9

What is the difference between fibrosis and scarring?

Answer 9

Fibrosis is the 1. active process that occurs with persistent injury in 2. internal organs in response to chronic injury which 3 involves abnormal deposition of collagen and ECM).
Scarring is the 1. end result of wound healing when 2. inciting agent has been removed or walled off that results in 3. less collagen deposition due to fibroblast quiescence.

Question 10

What growth factors promote fibroblast migration and proliferation?

Answer 10

PDGF, TGF-beta, and FGF are examples.

Question 11

In wound healing, what is the order of collagen deposition? What removes the first type of collagen, and what is its required cofactor?

Answer 11

Collagen III is laid down first, followed by collagen I. Collagenase removes the type III collagen and requires zinc as a cofactor

Question 12

What tissue type is the initial phase of repair? What does this tissue type contain?

Answer 12

Granulation tissue, which contains fibroblasts, capillaries, and myofibroblasts.

Question 13

After repair, what mediate wound contracture?

Answer 13

Myofibroblasts

Question 14

What is the difference between first intention and second intention?

Answer 14

First intention is the wound healing where the wound edges are brought together, leading to minimal scar formation.
Second intention is wound healing where edges are not approximated, so myofibroblasts contract the wound and granulation tissue fills in the defect and forms a large scar.

Question 15

What are the two major contributors to scarless wound healing in the fetus?

Answer 15

Absence of fibrosis and reduced inflammation (fetal TGF-beta receptors in fetus seem to signal less robustly thus reducing fibrosis and fetal IL-10 is increased thus reducing inflammation)

Question 16

What enzymes are key enzymes that breakdown extracellular matrix and thus keep scarring in check?

Answer 16

Metalloproteinases and collagenases

Question 17

What is dehiscence?

Answer 17

Separation of tissue edges normally apposed in a surgical incision or repair; involves rupture of the wound

Question 18

What is the difference between a hypertrophic scar and keloid?

Answer 18

Both involve an excessive deposition of collagen which results in a raised scar. Hypertrophic scar is characterized by excessive production of type ___ collagen; keloid is excessive production of type ___ collagen (conflicting info from pathoma and first aid)

Question 19

What are adhesions that occur especially in bowel loops?

Answer 19

Happens after surgery or infection, abnormal bridging of tissues together via fibrous bands; glues tissues together

Question 20

Why does a vitamin C deficiency lead to impaired wound healing?

Answer 20

Vitamin C is required for hydroxylation of proline and lysine procollagen residues, which is required for cross-linking of collagen

Question 21

Why does zinc deficiency lead to impaired wound healing?

Answer 21

Zinc is a required cofactor for collagenase which replaces type III collagen with type 1 collagen

Question 22

Why does copper deficiency lead to impaired wound healing?

Answer 22

Copper is required cofactor for lysyl oxidase which cross-links lysine and hydroxylysine to form stable collagen

Question 23

What is it called when large wounds contract excessively, and what can this lead to?

Answer 23

Called contracture; can lead to joint immobility

Question 24

What are the two types of pathologic calcification?

Answer 24

They both result from an abnormal deposit of calcium:

Dystrophic calcification and metastatic calcification

Question 25

What are the expected serum calcium levels in patients with dystrophic calcification and metastatic calcification?

Answer 25

Dystrophic calcification is when patients have normal calcium metabolism. Metastatic calcification is when patients have abnormal calcium metabolism and are not normocalcemic (usually secondary to hypercalcemia)

Question 26

In what tissue types does dystrophic and metastatic calcification deposit in?

Answer 26

Dystrophic deposits in necrosis or other areas of tissue damage. Metastatic calcification deposits in normal interstitial organs such as gastric mucosa, kidney, or lungs.

Question 27

Would calcification of the arteries due to atherosclerosis be an example of dystrophic calcification or metastatic calcification?

Answer 27

Dystrophic calcification

Question 28

What is the abnormality in exuberant granulation (proud flesh)?

Answer 28

excess granulation tissue in response to injury which prevents re-epithelialization.