L4 Healing and Repair

Question 1

In addition to adaptation and death, what is another possible outcome of cell injury?

Answer 1

Repair (healing)

Question 2

When is the repair of injured cells initiated?

Answer 2

When inflammation begins

Question 3

What are the two forms of healing/repair?

Answer 3

1. Regeneration

2. Scar formation

Question 4

What is regeneration?

Answer 4

The replacement of damaged cells by replicating cells of the same type

Question 5

What is scar formation?

Answer 5

Replacement of damaged cells by connective tissue

Question 6

True or false - regeneration and scar formation are mutually exclusive.

Answer 6

False - they may occur simultaneously

Question 7

In regeneration, the ___ of the tissue remains intact.

Answer 7

Extracellular matrix

Question 8

What are the three cell types with respect to division capacity?

Answer 8

1. Labile (always regenerating)
2. Stable (regenerate when stimulated)
3. Permanent (cannot regenerate)

Question 9

What is the extracellular matrix?

Answer 9

A network of interstitial proteins that comprises a significant portion of most tissues

Question 10

What are the 4 major functions of the ECM?

Answer 10

1. Mechanical support
2. Control of cell proliferation via growth factors
3. Scaffold for regeneration
4. Boundary between epithelium and underlying connective tissue

Question 11

What are the two forms of ECM?

Answer 11

1. Interstitial matrix

2. Basement membrane

Question 12

What are the 3 major components of the ECM?

Answer 12

1. Fibrous structural proteins (collagen and elastin)
2. Water hydrated gels (proteoglycans and hyaluronan)
3. Adhesive glycoproteins

Question 13

___ attach the epithelium to the basement membrane.

Answer 13

Integrins

Question 14

What are some examples of labile tissues?

Answer 14

1. HSC of bone marrow
2. Squamous epithelium of skin, oral cavity, cervix, vagina
3. Columnar epithelium of GI tract

Question 15

What is the classic example of stable tissue (and a few others)?

Answer 15

1. Liver
2. Kidney, pancreas
3. Smooth muscle cells, fibroblasts, endothelial cells

Question 16

___ cells line the blood vessel walls.

Answer 16

Endothelial

Question 17

What are three examples of permanent tissue?

Answer 17

1. Neurons (brain)
2. Myocytes (heart)
3. Skeletal muscle (mostly)

Question 18

Regeneration depends on what two major factors?

Answer 18

1. Growth factors

2. Integrity of ECM

Question 19

What is another major source of growth factors in addition to the ECM?

Answer 19

Macrophages

Question 20

What are the two main reasons scars form?

Answer 20

1. Injured tissues are incapable of regeneration

2. ECM severely damaged/stem cells lost

Question 21

What are the two major components of connective tissue?

Answer 21

1. Dense bands of collagen

2. Fibroblasts

Question 22

What are the pros and cons of scar formation?

Answer 22

Pro: scar usually provides enough structural stability for injured tissue to continue to function

Con: connective tissue cannot perform function of lost parenchymal cells

Question 23

What are the 4 steps in scar formation?

Answer 23

1. Tissue injury
2. Inflammation (macrophages)
3. Formation of granulation tissue
4. Scar formation (remodeling)

Question 24

What is angiogenesis?

Answer 24

New blood vessel development from existing vessels

Question 25

What are pericytes?

Answer 25

Cells with contractile properties

Question 26

Angiogenesis is often seen in what three situations?

Answer 26

1. Healing 2. Development of collaterals at sites of ischemia 3. Tumor growth

Question 27

What is an important mediator of angiogenesis?

Answer 27

VEGF (vascular endothelial growth factor)

Question 28

What is an important inducer of VEGF?

Answer 28

Hypoxia

Question 29

___ synthesize connective tissue proteins. Recruitment and activation of this cell is driven by what three growth factors?

Answer 29

Fibroblasts PDGF, FGF, TGF-beta

Question 30

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

Answer 30

Granulation tissue

Question 31

What are the components of granulation tissue?

Answer 31

Proliferating fibroblasts laying down type III collagen (immature connective tissue) and proliferating new blood vessels

Question 32

What is the process of transforming granulation tissue into a scar? What type of connective tissue is seen here?

Answer 32

Remodeling; type I collagen

Question 33

What type of stain makes mature collagen blue?

Answer 33

Trichrome stain

Question 34

What do myofibroblasts do?

Answer 34

Contract the wound

Question 35

What is involved in healing by first intention?

Answer 35

- Clean, uninfected surgical incision approximated by sutures - Epithelial regeneration principle mechanism of repair - Small scar - Minimal contraction of wound

Question 36

What is involved in healing by second intention?

Answer 36

- Large skin wound, extensive destruction, edges not approximated - Large clot, more intense inflammation - Wound granulates in without closing gap with sutures - Healing process is the same but takes longer - Wound contraction by myofibroblasts

Question 37

What are some factors which impair repair?

Answer 37

1. Infection 2. Nutrition deficiencies 3. Glucocorticoids 4. Poor perfusion 5. Diabetes mellitus 6. Foreign bodies 7. Type of tissue 8. Extent of injury 9. Location of injury

Question 38

What three nutritional components are important in wound healing?

Answer 38

1. Vitamin C 2. Zinc 3. Copper

Question 39

What is the function of Vitamin C in wound healing?

Answer 39

Cofactor for hydroxylation reactions (cross-linking of lysine and proline in collagen synthesis)

Question 40

What is the function of zinc in wound healing?

Answer 40

Cofactor for metalloenzymes (collagenase)

Question 41

What is the function of copper in wound healing?

Answer 41

Cofactor for lysyl oxidase (cross links lysine and hydroxylysine)

Question 42

What is an accumulation of an exuberant amount of collagen that presents with raised scars and grow beyond the wound boundaries?

Answer 42

Keloid

Question 43

What is a hypertrophic scar?

Answer 43

Excess production of scar tissue localized to the wound

Question 44

What is excessive deposition of collagen and other ECM components in a tissue/organ?

Answer 44

Fibrosis

Question 45

What is contracture?

Answer 45

Excessive myofibroblast activity in a wound causing constriction of the skin

Question 46

What is dehiscence?

Answer 46

Opening of a healing or partially healed wound with separation of its edge