Healing/repair

Question 1

Irreversible injury to the myocardial fibers will have occurred when which of the following cellular changes occurs? 
A. Blebs on cell membranes
B. Cytoplasmic sodium increases
C. Glycogen stores are depleted
D. Intracellular pH diminishes
E. Nuclei undergo karyorrhexis

Answer 1

E. Nuclei undergo karyorrhexis - all the other processes are part of the injury process, but they are all reversible. When the nucleus disintegrates (karyorrhexis), it is beyond repair.

Question 2

Possible outcomes of injured cells

Answer 2

Adaptation
Repair
Death

Question 3

When does repair of injured cells begin?

Answer 3

Initiated when inflammation begins

Question 4

What are the two parts of the healing process?

Answer 4

• Regeneration (replacement of damaged cells by replicating cells of the same type)
• Scar formation (replacement by connective tissue)

Both occur simultaneously

Question 5

When can regeneration occur?

Answer 5

Connective tissue framework of tissue remains intact and cells must have capacity to divide

Question 6

Two forms of interstitial protein network in the extracellular matrix

Answer 6

Interstitial matrix and basement membrane

Question 7

Protein composition in the extracellular matrix

Answer 7

• Fibrous structural proteins (Collagens, elastins)
• Water hydrated gels (proteoglycans, hyaluronan)
• Adhesive glycoproteins

Question 8

Define labile tissues

Answer 8

Continuously dividing cells that can be replaced by maturation from stem cells or proliferation of mature cells

Question 9

Examples of labile tissues

Answer 9

• Hematopoietic cells of bone marrow
• Squamous epithelium of skin, oral cavity, cervix, vagina
• Columnar epithelium of GI tract

Question 10

Define stable tissues

Answer 10

Low/no level of replication; locked in G0 of the cell cycle. However, they can rapidly divide upon stimulation.

Question 11

Examples of stable tissues

Answer 11

Liver, kidney, pancreas, smooth muscle cells, fibroblasts

Question 12

Define permanent tissues

Answer 12

Terminally differentiated; non-proliferative in postnatal life

Question 13

Examples of permanent tissues

Answer 13

Neurons and myocytes

Question 14

Where does scar formation not occur?

Answer 14

In the brain

Question 15

Pro to scar formation

Answer 15

Scar usually provides enough structural stability for the injured tissue to continue function

Question 16

Con of scar formation

Answer 16

Fibrous tissue cannot perform the original function of the lost parenchymal cells

Question 17

Components of scar formation

Answer 17

• Angiogenesis
• Migration/proliferation of fibroblasts
• Formation/deposition of ECM by fibroblasts
• Maturation/organization of fibrous tissue elements

Question 18

Important mediators of angiogenesis

Answer 18

VEGF, FGF, PDGF, and TGF-beta

Question 19

What does VEGF do?

Answer 19

Promotes angiogenesis, increases vascular permeability, and stimulates endothelial cell migration/proliferation

Question 20

What are the normal levels of VEGF in an adult tissue?

Answer 20

Low levels usually, but higher in podocytes of glomerulus and pigment epithelium of the retina

Question 21

Inducer of VEGF

Answer 21

Hypoxia

Question 22

In what pathology is VEGF indicated?

Answer 22

Kidney cancer

Question 23

What do fibroblasts do?

Answer 23

Synthesize connective tissue proteins

Question 24

Define granulation tissue

Answer 24

Specialized tissue that fills in defects in organs when non-regenerative cells and/or connective tissue framework is destroyed

Question 25

Components of granulation tissue

Answer 25

Proliferating fibroblasts that lay down immature connective tissue (type III collagen) and new blood vessels

Question 26

When is granulation tissue present?

Answer 26

Only during healing or attempt to heal destroyed tissue

Question 27

Definition of organization

Answer 27

Process of transforming granulation tissue into a dense scar

Question 28

What happens during organization?

Answer 28

With time, blood vessels become less prominent, collagen matures to type I collagen

Question 29

What type of staining is used to determine the difference between mature scar and granulation tissue?

Answer 29

Trichrome stain that stains mature collagen blue

Question 30

Myofibroblasts

Answer 30

Modified fibroblasts with functional features of contractile smooth muscle cells that will contract the wound

Question 31

Healing by first intention

Answer 31

Clean, uninfected surgical incision that is approximated by surgical sutures; leaves a small scar, minimal contraction of wound

Question 32

Healing by second intention

Answer 32

Large skin wound with extensive destruction, contamination, infection with unapproximated edges

Question 33

Wound strength after 1 week

Answer 33

10% of normal; collagen is still being synthesized and modified

Question 34

Wound strength after 3 months

Answer 34

70-80%

Question 35

Fibrosis definition

Answer 35

Excessive deposition of collagen and other ECM components in a tissue

Question 36

Eight factors influencing repair

Answer 36

``` Infection Nutrition Glucocorticoids Poor perfusion Diabetes mellitus Foreign bodies Stable/labile vs permanent cells Location of injury ```

Question 37

``` Supplementation of which dietary deficiencies would be most appropriate for wound healing? A. Copper and vit D B. Folate and zinc C. Iodine and vit E D. Vit C and E E. Vit C and zinc ```

Answer 37

E. Vitamin C and zinc: vitamin C helps in collagen synthesis and zinc is a cofactor in collagenase

Question 38

Keloid

Answer 38

Accumulation of exuberant amount of collagen, forming raised scars that grow beyond wound boundaries

Question 39

In which population are keloids more common?

Answer 39

African-Americans

Question 40

Aberrations

Answer 40

Hypertrophic scar; excess production of scar tissue localized to the wound that may regress