2.5 Wound healing

Question 1

What are the two general mechanisms of healing?

Answer 1

Regeneration or repair

Question 2

What, generally, is regeneration? What is it dependent on?

Answer 2

Replacing damaged tissue with the native tissue

Dependent on the regenerative capacity of the tissue

Question 3

What are labile tissues? Examples?

Answer 3

Tissues that continuously cycle to regenerate tissue

Small/ large bowel
Skin
Bone marrow

Question 4

Where are the stem cells in the small and large bowel?

Answer 4

Crypts

Question 5

Where are the stem cells in the skin?

Answer 5

Stratum basale of epidermis

Question 6

What are the stem cells in the bone marrow?

Answer 6

Hematopoietic stem cells

Question 7

What is the CD marker for hematopoietic stem cells?

Answer 7

CD34

Question 8

What are the stem cells of the lung?

Answer 8

Type II pneumocytes

Question 9

What are stable tissues?

Answer 9

Tissues that are quiescent, but can reenter cell cycle PRN

Question 10

What are some examples of stable tissues?

Answer 10

Hepatocytes–compensatory hyperplasia

Question 11

What are the three permanent tissues in the body?

Answer 11

Myocardium
Skeletal muscle
Neurons

Question 12

When does repair occur, as opposed to regeneration?

Answer 12

If a tissues lacks regenerative capacity, or if the regenerative stem cells are lost

Question 13

What material is initially deposited in tissues that lack regenerative capacity? What are the three major components of this?

Answer 13

Granulation tissue:

• Fibroblasts
• Capillaries
• Myofibroblasts

Question 14

What type of collagen is laid down by fibroblasts with granulation tissue? What is this later replaced with?

Answer 14

Collagen type III initially, followed by type I after collagenases remove type III

Question 15

What is the role of myofibroblasts in wound repair?

Answer 15

Contract wound edges

Question 16

What are the enzymes that remove type III collagen in scar to allow for type I collagen to be depositied? What is the cofactor that is needed for these to work?

Answer 16

Collagenases

Zn is the cofactor

Question 17

What type of signalling is used in regeneration and repair?

Answer 17

Paracrine signalling via growth factors

Question 18

What is the role of TGF-alpha in the tissue repair process? (2)

Answer 18

Epithelial and fibroblast growth factor

Question 19

What is the role of TGF-beta in the tissue repair process? (2)

Answer 19

Fibroblast growth factor and inhibits inflammation

Question 20

What is the role of PDGF in the tissue repair process? (3)

Answer 20

Endothelium repair, smooth muscle repair, and fibroblast growth factor

Question 21

What is the role of FGF in the tissue repair process? (2)

Answer 21

Angiogenesis and skeletal development

Question 22

What is the role of VEGF in the tissue repair process?

Answer 22

Angiogenesis

Question 23

What is primary intention wound healing?

Answer 23

Wound edges are brought together with minimal scar formation

Question 24

What is healing by secondary intention?

Answer 24

Edges are not approximated–granulation tissue fills the defect

Question 25

What causes wound to reduce in size?

Answer 25

Myofibroblasts

Question 26

What is the most common cause of delayed wound healing?

Answer 26

Infection

Question 27

What vitamin deficiency can cause delayed wound healing? Minerals?

Answer 27

- Vit C - Cu - Zn

Question 28

What is procollagen?

Answer 28

Alpha chains of Gly-X-Y wrapped around each other, prior to crosslinking

Question 29

What is the usual primary structure of collagen?

Answer 29

{Gly-X-Y | X=proline, Y=lysine}

Question 30

What is the role of vitamin C in the formation of collagen?

Answer 30

Hydroxylation of proline / K

Question 31

What is the role of Cu in collagen formation?

Answer 31

Lysl oxidase, an enzyme responsible for cross linking collagen chain, requires Cu as a cofactor

Question 32

What, generally, is dehiscence?

Answer 32

Rupture of wound, commonly seen after abdominal surgery

Question 33

What is a hypertrophic scar? What type of collagen is this made of?

Answer 33

Excess production of scar tissue that is localized to the wound Type I collagen

Question 34

What is a Keloid? What type of collagen is this comprised of?

Answer 34

Excess production of scar tissue that is out of proportion to the wound Excessive type III collagen