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Ocular Phys Block 9 > Corneal Repair > Flashcards

Corneal Repair Flashcards

1
Q

What does corneal initiate

A

A cascade of mechanisms to repair damaged tissue, a process directed by various biomolecules

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2
Q

Integral membrane glycoproteins

A

Corneal integrins

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3
Q

Roles of corneal integrins

A
  • facilitate interactions between cells and ECM
  • matrix assembly
  • impact cell adhesion and formation of intercellular junctions
  • sense change in the extra cellular environment and communicate to the cell nucleus by an alteration in the cytoskeleton
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4
Q

Signaling molecules that are expressed in the normal and inflammatory cornea after infections, burns, etc

A

Cytokines

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5
Q

Roles of cytokines

A
  • facilitate cellular communication between cells and surrounding tissues
  • control the growth of the corneal cells
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6
Q

Roles of growth factors

A
  • promote proliferation of corneal cells
  • induce migration of corneal cells
  • maintenance of corneal transparency
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7
Q

Which epithelial layer can cells divide

A

Basal layer

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8
Q

How many layers thick is the epithelium,

A

5-7 cells thick

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9
Q

What are the different cell layers in the epithelium and how thick is each layer

A
  • surface layer: 2 cells thick
  • wing layer: 2-3 cells thick
  • basal layer: 1 cell thick
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10
Q

Epithelial replacement

A
  • stems cells in peripheral cornea divide (mitosis)
  • new cells move towards the center of the cornea to become basal cells
  • basal cells move up to become wing cells
  • wing cells move up to become surface cells
  • surface cells shed into tear film
  • 7 day turnover
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11
Q

Epithelial injury

A
  • Mitosis stops, biomolecules get signaled
  • growth factors and cytokines are released from damaged cells
  • hemidesmosomes dissemble along wound edge
  • changes in cytoskeleton (cell changes shape, cells at wound edges develop membrane extensions, cells migrate to cover wound)
  • defect covered by a single layer of cells (cell-to-cell junctions formed between neighboring cells)
  • mitosis resumed (proliferation continues until normal cell density is reached, apoptosis prevents epithelial hyperplasia)
  • heidesmosomes replace biochemical bonds holding basal cells
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12
Q

During corneal epithelial injury, cell migration requires control of

A
  • hemidesmosomes
  • cytoskeleton structure
  • cell-to-matrix adhesion

This preserves the structural integrity of epithelial sheet

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13
Q

Adhesion molecules in epithelium wound healing

A
  • allows for epithelial sheet to adhere to basement membrane
  • pulls cells forward as sheet covers wound area
  • growth factors stimulate production of matrix components to enhance adhesion
  • proliferation suppressed until migration occurs
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14
Q

Healing time frame of small lesion to epithelium

A

24–48 hours

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15
Q

Healing time frame for basement membrane damage of epithelium

A

Several months for normal hemidesmosomes adhesions

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16
Q

Is there a scar in epithelial wound healing

A

No

17
Q

Corneal epithelium sloughs off either continually or periodically

A

Recurrent cornel erosion

18
Q

Cause of recurrent corneal erosion

A
  • poor adhesion between epithelium and basement membrane

- poor adhesion between basement membrane and underlying tissue

19
Q

When does recurrent corneal erosion occur

A

After incomplete healing of an abrasion OR by epithelial basement membrane dystrophy

20
Q

Treatment for recurrent corneal erosion

A
  • artificial tears
  • Abx
  • bandage CLs
  • anterior strongly micropuncture
  • superficial keratectomey
  • phototherapeutic keratectomy
21
Q

Bowman’s layer

A

A cellular layer

  • composed of collagen
  • highly resistant to penetration or damage
22
Q

Does bowmans layer regenerate?

A

No

Only one cell layer thick and does not regenerate

23
Q

What is bowmans replaced by if it gets damaged

A

Storm all scar tissue or by the epithelium

24
Q

90% of total corneal thickness

A

Stroma

25
Q

What is the stroma composed of

A
  • collagen fibrils (form lamellae)
  • keratocytes (corneal fibroblasts)
  • extracellular ground substance (fills between fibrils, lamellae, and cells)
26
Q

Stroma wound healing: upon injury

A

Keratocytes increase in number; some stimulated to become myofibroblasts, cause wound bed to contract, wound coverage by epithelium

27
Q

Regenerated stroma collagen

A

Is larger than the original fibrils and alignment and organization are not as precise, increasing probability of scarring

28
Q

Stroma wound healing: after healing complete

A

Myofibroblasts undergo apoptosis or revert back to keratocytes

29
Q

Healing time frame for stromal wouldn’t healing

A

Months

30
Q

New collagen fibrils in stromal wound healing

A

Have diminished strength, months to reach typical strength

31
Q

Basement membrane of endothelium

A

Descemet’s membrnae

32
Q

Composed of collagen fibrils and produced constantly, thickens throughout life

A

Descemet’s membrane

33
Q

What is the descemet’s membrane is regenerated by what

A

Stromal keratocytes and the endothelium

34
Q

Layers of cells in endothelium

A

Single layer of flattened cells

35
Q

Endothelium cell shape

A

Polyhedral

  • 70-80% hex (5)
  • 20-30% hept (7)
36
Q

Cell orientation in the endothelium

A
  • basal part rests on descemet’s membrane

- apical surface lines the anterior chamber

37
Q

Mitosis and endothelial wound healing

A

Little mitosis occurs

38
Q

Endothelial wound healing

A
  • neighboring cells enlarge and flatten to cover area of cell loss, decrease in endothelial like cell density
  • cells remodel into polyhedral shape
  • pump and barrier functions are re established (increase in ion pumps to compensate for loss of pumps from cell loss)

Ocular Phys Block 9 (5 decks)

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