IOS QUIZ 3/7/20

which process obtains most of the energy in the endothelial cells

corneal hydration via pumps

which process obtains most of the energy in the epithelial cells

mitosis

where does glucose come to satisfy the corneal needs?

aqueous

which metabolic process accounts for up to 80% of glucose metabolism

glycolysis

what do we call glycolysis in the prescense of oxygen?

aerobic - pyruvate further oxidizes in the Krebs or citric cycle

how many ATP is generated in the aerobic glycolysis

36

which is the intermediate where metabolism heads to in the conditions of aerobic glycolysis

pyruvate

what do we call glycolysis in the absence of oxygen

anaerobic pathway - lactate leads to epithelia and stroma edema

how much ATP is generated in anaerobic glycolysis?

2

which is the intermediate where metabolism heads to in the conditions of the absence of oxygen in glycolysis?

lactate

which enzyme is capable to shift between the 2 types of metallic processes (aerobic and anaerobic)

lactate dehydrogenase (LDHase)

where does the oxygen for the corneal epithelium needs come from?

the atmosphere

where does the oxygen for the corneal endothelium needs come from?

aqueous

at which level of oxygen does the cornea swell?

COT is 50 mmHg

COT \=

critical oxygen tension

do oxygen levels vary when the eye is open or closed?

if so, what are their values

yes!

open eye - 155 mmHg
close eye - 55 mmHg

which metabolic process generates NADPH but not ATP

hexose monophosphate shunt

which metabolic process is increased when glucose levels are in excess?

sorbitol

which enzyme catalyzes sorbitol?

aldose reductase

which enzymes are called antioxidants

catalase, gluthanione, peroxidase, superoxide, dismutase

cite 4 free radicals

1. superoxide anion O2
2. hydrogen peroxide H2O2
3. hydroxyl radical OH
4. hypocrite OCl

cite 1 oxidant enzyme

NADPH oxidase and Myeloperoxidase MPO

does corneal transparency depend on thickness?

no

does corneal transparency depend on hydration?

yes

what happens to the swelling pressure if corneal thickness increases

swelling pressure decreases

what opens to the swelling pressure if corneal thickness decreases

swelling pressure increases

how do we call the thinned areas of cornea as a result of dryness and evaporation

Dellen

name 2 factors involved in the endothelial barrier to water

1. endothelial barrier
2. endothelial to pump

which barrier is most effective in the cornea (in general), epithelial or endothelial layer?

epithelial barrier

where does the fluid come from where the cornea swells

from aqueous humor to the stroma

where does the fluid accumulate when the cornea swells

in the stroma

name the endothelial pump and its location

endothelial ion transport located in the basolateral membrane of the endothelial cell

which drug is able to block this endothelial pump

ouabain

which effects will you observe in corneal hydration with the inhibition of this endothelial pump

blocks sodium transport, produces corneal swelling, prevents temperature reversal

what does it mean? temperature reversal

the ability of the corneal to return to a normal thickness (at temperature) after being cooled causing swelling

is temperature reversal affected by the inhibition of the endothelial pump

yes, inhibition prevents temperature reversal

are corneal dystrophies present with inflammation?

not usually

what do you see in a corneal dystrophy, thinning or thickening of the cornea?

corneal thinning

what are the characteristic of stem cells? name 4

1. ulimited mitosis throughout life
2. once commented to differentiation
3. asymmetric cell division
4. cannot reverse

where are the stem cells located in the cornea

palisades of Vogt in perilimbal conjuctiva

which cells do they differentiate into

basal cell

is symmetric or asymmetric division? what does it imply?

asymmetric - 1 new cell remains as stem cell and 1 new cell differentiates (transit cell)

which corneal defects heal faster according to location

peripheral defect and large defect

10 conditions associated to delayed healing

1. diabetes mellitus
2. epithelial basement membrane to dystrophy
3. alkali burns cause damage to stem cells
4. mucin deficiency disorders
5. eyelid disorders
6. tear film disorders
7. herpetic diesases
8. drug induced
9. neurotopic disease
10. inflammation (atopic disease)

what is a corneal ulcer

a corneal ulcer is keratitis. an open sore to the cornea
-balance of callagenous
-matrix-metallo-proteinase activity and college synthesis

how are corneal ulcers formed

dry yes, delayed wound healing

in the case of loss of the stem cell population, how would this affect the healing of the cornea?

there would be a slow healing of the conjcutival cell trans-differentiation it is similar to the corneal epithelium

which elements comprise the fibrous tunic of the eyeball? which position does it have in the eyeball?

sclera and cornea

external surface

which elects comprise of the vascular tunic of the eyeball? which position does it have in the eyeball?

uvea - iris, ciliary body (ciliary muscle and process)

choroid - middle layer

what other name receives the vascular tunic of the eyeball

middle coat

which elements comprise of the nervous tunic of the eyeball? what position does it have in the eyeball?

the retina

the innermost layer of the eye

describe the limits of the anterior chamber

between the inner surface of the corona to the anterior surface of the iris

describe the limits of the posterior chamber

between the posterior surface of the iris and in front of the ciliary body

describe the limits of the anterior segment

front - most section of the eye

cornea, iris, lens

describe the limits of the posterior segment

posterior 2/3 of the eye - vitreous humor, retina, choroid, optic nerve

what are the components of the ciliary body and where are they located?

ciliary muscle
ciliary process
ciliary zonules

all are located behind the iris

ciliary process

folds posterior surface of ciliary bodies

ciliary zonules

fibers that bridge between the ciliary muscle and the lens of the eye

Where is aqueous humor produced?

between the posterior surface of the cornea and the anterior surface of the lens

what is the composition of the aqueous humor

carbohydrates, glutathione, urea, amino acids and proteins, oxygen, carbon dioxide and water

what is the function of the aqueous humor

provides nutrients to corneal endothelium and stoma lens and iris

maintains pressure

what do we call "the angle"

the angle between the cornea and the iris

what is the ora serrata?

which 2 structures meet to form the ora serrata?

the circular structure attached to the ciliary body and retina.

non-pigmented layer of ciliary epithelium and the multilayered retina

what is the anterior and posterior part of the ciliary body?

anterior - pars plicate
posterior - pars plana

how is the endothelium in the ciliary body, leaky or a tight barrier

very porous and without tight junctions, permeable to macromolecules

which are the limits of the trabecular meshwork

lies within the angle of the anterior chamber

between scleral spur and Schwalbe's line (end of Descemet's membrane)

what is Schwalbe's line

line found on the interior of the cornea's outer limit

end of Descemet's membrane

where does the ciliary muscle attach in the vicinity of the trabecular meshwork

scleral spur

what is the function of the trabecular meshwork

drains aqueous, regulates IOP, compliant and responds to functional change, filters inflammatory cells, pigment and red blood cells

is the trabecular meshwork rigid or elastic

elastic

does it contain pores

series of pores in each lamina are not lined up

where is the endothelial layer of the trabecular meshwork located

Juxtacanalicular tissue

which structure in the trabecular meshwork acts as a filter ingesting melanin granules

TM endothelium

what is the most internal layer of the trabecular meshwork

uveal meshwork

what is the most external layer of the trabecular meshwork

Juxtacanalicular tissue

which trabecular meshwork layer exerts the major resistance to aqueous outflow

Juxtacanalicular tissue

which trabecular meshwork layer exhibits the biggest pores

uveal meshwork

are these pores lined up

no. they are irregularly spaced

where is the Scheme's canal and where does it drain? explain the path up until the ophthalmic vein

1. located, ring-like structure encircles the cornea, directly against the Juxtacanalicular tissue
2. from collectors to deep scleral plexus
3. intrascleral plexus
4. episcleral veins to vortex (from choroid)
5. to the ophthalmic vein

which processes that contribute to aqueous formation are active or require energy

active secretion

does it move down concentration gradient or against concentration gradient

against concentration gradient

which processs contribute to aqueous formation are passive or do not require energy?

diffusion dan ultrafiltration

does it move down [M] gradient or against [M] gradient

down the [M] gradient

which passive process is highly dependent of pressure

filtration

which of the previous processes accounts for up to 90% of aqueous production

active secretion

describe the conventional and the uncoventhational or uveoscleral outflow of the aqueous

convention - aqueous leaves the anterior chamber angle through the TM across the inner wall of the Schlemm's canal into its lumen, into the collector channels, into the aqueous veins into the episcleral venous cicrulation

unconventional - leaves across the iris root, the uveal meshwork and the anterior face of the muscle, through the connective tissue between the muscle bundles, through the suprachoroid space, through the sclera

which is the function of the ciliary muscle

accommodation