Chapter 14: Wound Healing Flashcards Preview

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Flashcards in Chapter 14: Wound Healing Deck (62):
1

Wound healing: days 1-10

Inflammation: PMNs, macrophages

2

Rate of epithelialization during wound healing

1-2 mm/day

3

Wound healing: 5 days - 3 weeks

Proliferation: fibroblasts, collagen deposition, neovascularizaiton, granulation tissue formation; type 3 collagen replaced with type 1

4

Wound healing: 3 weeks - 1 year

Decreased vascularity

5

What happens during the remodeling phase of wound healing?

Net amount of collagen does not change with remodeling, although significant production and degradation occur. Collagen cross-linking occurs.

6

Rate of regeneration of peripheral nerves

1 mm/day

7

Order of cell arrival in wound

Platelets, PMNs, Macrophages, Lymphocytes, (recent research shows arrival before fibroblasts), fibroblasts

8

Essential for wound healing (release of growth factors, cytokines, etc)

Macrophages

9

Chemotactic for macrophages; anchors fibroblasts

Fibronectin

10

Replace fibronectin-fibrin with collagen

Fibroblasts

11

Predominant cell type by day:
- Days 0-2
- Days 3-4
- Days 5 and on

- Days 0-2: PMNs
- Days 3-4: Macrophages
- Days 5 and on: fibroblasts

12

What comprises platelet plug?

Platelets and fibrin

13

What comprises the provisional matrix?

Platelets, fibrin, fibronectin

14

Definition: accelerated wound healing

Reopening a wound results in quicker healing the 2nd time (as healing cells are already present there)

15

Most important factor in healing open wounds (secondary intention)

Epithelial integrity

16

What does secondary intention wound healing depend on?

- Epithelial integrity.
- Migration from hair follicles (#1 site), wound edges, sweat glands. Dependent on granulation tissue in wound.

17

Unepithelialized wounds leak...

Serum and protein, promote bacteria.

18

Most important factor in healing closed incisions (primary intention)

Tensile strength

19

What does tensile strength / primary intention depend on?

Depends on collagen deposition and cross-linking of collagen

20

Strength layer of bowel

Submucosa

21

Weakest time point for small bowel anastomosis

3 - 5 days

22

- Smooth muscle cell-fibroblast; communicate by gap junctions
- Involved in wound contraction and healing by secondary intention
- Perineum has better wound contraction than leg

Myofibroblasts

23

Collagen: MC type of collagen; skin, bone, tendons. Primary collagen in a healed wound.

Type 1

24

Collagen: Cartilage

Type 2

25

Collagen: increased in healing wound, also in blood vessels and skin

Type 3

26

Collagen: Basement membrane

Type 4

27

Collagen: widespread, particularly found in the cornea

Type 5

28

Required for hydroxylation (prolyl hydroxylase) and subsequent cross-linking of proline residues in collagen

Alpha-ketoglutarate, vitamin C, oxygen, and iron

29

Collagen: every third amino acid

Proline

30

What does proline cross-linking do?

Improves wound tensile strength

31

Vitamin C deficiency

Scurvy

32

% tensile strength to pre-wound strength

80%

33

Predominant collagen type synthesized for days 1-2

Type 3 collagen

34

Predominant collagen type synthesized by days 3-4

Type 1 collagen

35

When is type 3 collagen replaced with type 1 collagen?

By 3 weeks

36

When does the wound reach maximum tensile strength?

At 8 weeks.

37

When is maximum collagen accumulation?

2-3 weeks. After that the amount of collagen stays the same, but continued cross-linking improves strength.

38

Inhibits collagen cross-linking

d-Penicillamine

39

Essentials for wound healing

- Moist environment (avoid desiccation)
- Oxygen delivery
- Avoid edema
- Remove necrotic tissue

40

How do you optimize oxygen delivery for wound healing?

Optimize fluids, no smoking, pain control, arterial revascularlization, supplemental oxygen.

41

What do you want transcutaneous oxygen to measure for wound healing?

Want transcutaneous oxygen measurement (TCOM) > 25 mm Hg

42

Impediments to wound healing

Bacteria > 10^5, devitalized tissue and foreign bodies, cytotoxic drugs, diabetes, albumin

43

How does bacteria 10^5 impede wound healing?

Decreased oxygen content, collagen lysis, prolonged inflammation

44

How does devitalized tissue and foreign bodies impede wound healing?

Retards granulation tissue formation and wound healing.

45

How do cytotoxic drugs impede wound healing?

5FU, methotrexate, cyclosporine, FK-506, etc can impair wound healing in first 14 days after injury

46

How can diabetes impede wound healing?

Can contribute to poor wound healing by impeding the early-phase inflammation response (hyperglycemia causes poor leukocyte chemotaxis)

47

How do steroids impede wound healing?

Inhibit macrophages, PMNs, and collagen synthesis by fibroblasts; decreases wound tensile strength as well

48

Counteracts effects of steroids on wound healing

Vitamin A (25,000 IU qd)

49

What can cause wound ischemia (hypoxia)?

Fibrosis, pressure (sacral decubitus ulcer, pressure sores), poor arterial inflow (atherosclerosis), poor venous outflow (venous stasis), smoking, radiation, edema, vasculitis

50

Diseases associated with abnormal wound healing

Osteogenesis imperfecta, Ehlers-Danlos syndrome, Marfan's, Epidermyolsis bullosa, Scurvy, Pyoderma Gangrenosum

51

Common location of diabetic foot ulcer

Charcot's joint (2nd MTP joint) secondary to neuropathy

52

90% due to venous insufficiency.
- Tx: Unna boot

Leg ulcers

53

What do scars contain?

A lot of proteoglycans, hyaluronic acid and water.

54

When can you revise a scar?

Wait for 1 year to allow maturation; may improve with age.
- Infants heal with little to no scarring.

55

Contains no blood vessels (get nutrients and oxygen by diffusion)

Cartilage

56

Has no effect on wound healing

Denervation

57

Has no effect on wound healing after 14 days

Chemotherapy

58

Autosomal dominant, dark skinned
- Collaged goes beyond original scar
- Tx: intra-lesion steroid injection; silicone, pressure garments, XRT

Keloids

59

Dark skinned; flexor surfaces of upper torso
- Collagen stays within confines of original scar
- Often occurs in burns or wounds that take a long time to heal
- Tx: steroid injection, silicone, pressure garments

Hypertrophic scar tissue

60

What are contained in alpha granules of platelets?

- Platelet factor 4: aggregation
- Beta-thrombomodulin: binds thrombin
- Platelet-derived growth factor (PDGF): chemoattractant
- Transforming growth factor beta (TGF-beta): modulates above responses

61

What do dense granules of platelets contained?

Contain adenosine, serotonin, and calcium

62

Platelet aggregation factors

TXA2, thrombin, platelet factor 4