Cornea - Functions & Regeneration (M2) Flashcards
function of cornea
refract light.
absorb and transmit light
what does the cornea allow light to do
reach the retina and allow for vision
wavelengths of light that enter cornea
290 - 2000 nm
290 - 320 nm (UV - B)
damaging to cells
90% absorbed by ozone; 10% absorbed by cornea
320 - 400 nm (UV - A)
least harmful
partially absorbed by cornea; majority absorbed by lens
400 - 700 nm (visible light)
transmitted by cornea
allows for vision
700 - 2000 nm (infrared light)
transmitted by cornea
what must cornea be for optimal light transmission
transparent
how often does epithelium regenerate
7 - 10 days
what are basal cells replaced by
limbal stem cells
what does epithelial damage result in
increased risk of infection
generally scar-free.
can result in stromal edema.
how long does it take a small epithelium injury to heal
overnight
how long does it take to heal if basement or hemidesmosomes are damaged
months.
if hemidesmosomes are malformed –> recurrent corneal erosion (RCE)
what is RCE
condition where every couple of days the corneal epithelium sloughs off continually as a result of cells not properly adhering to the layer below it
how long does it take to heal if corneal sensory nerves are damaged
wound healing is impaired.
reduced mitosis, decreased cell adhesion, impaired wound healing
does bowman’s layer regenerate
no, will be replaced by epithelial cells or stroma-like fibrous tissue.
very resistant to damage
how do new formed connective tissue components in the stroma differ slightly from original tissue
collagen fibers are larger.
alignment and organization of collagen fibers are not as precise
does the stroma scar?
yes.
opacification
does descemet’s membrane scare if injured
limited regeneration: the size of the injury plays a role… it technically can regenerate because there is an anterior and posterior section, however it does not do well.
a large area of damage will not fully heal.
plus if you damage descemet’s, you definitelyd already have a much larger issue.
what secretes and reforms descemet’s membrane
stromal keratocytes and endothelium
do endothelial cells regenerate
no
what happens to endothelial cell density with age and why
decreases with age because of cell disintegration
what happens to the shape of endothelial cells with cell loss
neighboring cells enlarge and flatten to cover the area of loss:
- enlarged endothelial cells
- irregularly shaped cells
- decrease in cell density because they are thinly spread out
what happens to water levels when you lose endothelial cells
less H2O channels are present so more water stays in the cell than is leaving the cell –> more water in stroma –> haze
