9- Corneal Repair Flashcards Preview

Ocular Physiology > 9- Corneal Repair > Flashcards

Flashcards in 9- Corneal Repair Deck (27):
1

What 3 molecules direct corneal wound healing?

Integrins
Cytokines
Growth factors

2

What is the role of corneal integrins

Facilitate interactions between cells

Matrix assembly

Cell adhesion

Sense change in extracellular environment and communicate to the cell

3

What is the role of cytokines?

Signaling

Communication between cells

Control growth of corneal cells

4

What is the role of growth factors

Promote proliferation

Induce migration

Maintain transparency

5

How many layers thick is the epithelium

5-7

6

What is the process of epithelial replacement

1. Stem cells divide
2. Become basal cells
3. Become wing cells
4. Become surface cells
5. Shed into tear film

7

What is the turnover time for epithelium

7 days

8

What process stops when there is corneal injury

Mitosis

9

What is the process of epithelium wound healing

1. Mitosis stops
2. Cytokines and growth factors released from damaged cells
3. Hemidesmosomes dissemble
4. Cytoskeleton changes and the shape of the cell changes. Cells at the edge develop extensions and migrate to cover the wound.
5. Adhesion molecules pull cells as a sheet
6. Junctions formed between cells
7. Mitosis resumes. Proliferation and apoptosis
8. Hemidesmosomes come back

10

How long does it take a small lesion of the epithelium to heal?

24-48 hours

11

What long does it take for basement membrane damage to heal

Several months

12

What is recurrent corneal erosion

When the corneal epithelium sloughs off due

13

What are the 2 causes of corneal erosion

1. Poor adhesion between epith and BM

2. Poor adhesion between BM and underlying tissue

14

When does corneal erosin occur

After I complete healing of an abrasion OR a dystrophy

15

What is the treatment for corneal erosion

Artificial tears
Oph. Ab
Bandage CL
Ant. Stromatolites micropuncture
Superficial keratectomy
PTK

16

What is bowmans layer

Acellular layer
Made of collagen
Resistant to penetration and damage

17

T/F Does Bowmans Layer regenerate?

No

18

What heals Bowmans Layer

It replaced by stomach scar tissue or by epithelium

19

What is the stroma

90% of corneal thickness

Composed of collagen fibrils, keratocytes, and ground substance

20

What is the healing process of the stroma

1. Keratocytes increase in number
2. Some become myofibroblasts
3. Wound bed contracts
4. Wound covered by epithelium

21

What are changes that occur in repaired stroma

The collagen is larger and alignment is not as precise
Increased probability of scarring

22

What happens after the stroma is healed

Myofibroblasts undergo apoptosis or revert back to keratocytes

23

How long does it take for the stroma to repair

Months

24

What is Descemets Membrane

Basement membrane of endothelium

Made of collagen fibrils

Thickens throughout life

25

How is Descemets Membrane repaired

Regenerated by stromal keratocytes and endothelium

26

What is the endothelium

Single layer
Flat cells
80% hexagonal
20% heptagonal
Little mitosis occurs

27

What is the healing process of endothelium

1. Neighboring cells enlarge and flatten to cover area of loss (decreasing cell density)
2. Cells removal into polyhedral shape
3. Ppm and barrier fxns re-established