Lecture 45 4/30/24 Flashcards

1
Q

What are the characteristics of the uvea?

A

-vascular tunic of eye
-supplies blood and its nutrients to the eye and its constituent parts

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2
Q

How does the uvea work around not being able to directly supply the avascular components of the eye?

A

-relies on the creation of aqueous humor
-aqueous humor bathes the cornea and lens and provides them with nourishment

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3
Q

What are the characteristics of aqueous humor production?

A

-continuously created and drained
-results in a constant flow of fluid within the eye
-involves both passive and active transport
-active transport is most important
-occurs at the non-pigmented epithelium of the ciliary processes

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4
Q

Which two enzymes drive the production of aqueous humor?

A

-Na+/K+ ATPase
-carbonic anhydrase

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5
Q

What are the steps of ultrafiltration that lead to the production of aqueous humor?

A

-Na+/K+ ATPase exchanges sodium for potassium, creating an osmotic and electric gradient across cell membrane
-carbonic anhydrase catalyzes conversion of H2O and CO2 to HCO3- and H+ to maintain a neutral electrochemical gradient
-the two processes work together to create a concentration gradient that favors diffusion of water from the plasma within the stroma into the aqueous humor

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6
Q

How does passive transport contribute to aqueous humor production?

A

by creating a reservoir of fluid within the ciliary process stroma that will become aqueous humor via the active transport mechanism

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7
Q

How does conventional outflow of aqueous humor differ from unconventional outflow?

A

-conventional outflow involves a specific drainage mechanism
-unconventional outflow occurs from natural absorption of fluid into and around the uveal tissue

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8
Q

What are the anatomic components of the aqueous humor drainage system?

A

-iridocorneal angle
-pectinate ligaments
-trabecular meshwork
-angular aqueous plexus

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9
Q

What is the iridocorneal angle?

A

region within the anterior chamber that is comprised of the intersection of the iris and cornea at the periphery

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10
Q

What is the pectinate ligament?

A

-beginning of the aqueous drainage structure
-comprised of beams of iris tissue crossing from the iris to the cornea/sclera

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11
Q

What is the trabecular meshwork?

A

-second set of collagenous beams
-thinner, with collagenous material, elastin, and extracellular matrix protein components
-lined by endothelial cells that respond to pressure and outflow changes; also have phagocytic activity

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12
Q

What is the main function of the trabecular meshwork?

A

controlling the pressure within the eye

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13
Q

What is the angular aqueous plexus?

A

set of vessels where the aqueous humor begins its journey outside the eye

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14
Q

In which species is unconventional flow significant?

A

horses

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15
Q

Why is unconventional outflow important in inflamed eyes?

A

it allows for outflow in case inflammation and/or debris prevents drainage through the conventional pathway

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16
Q

What are the physiological differences between plasma and aqueous humor?

A

aqueous humor has:
-decreased protein
-increased ascorbate

17
Q

Why is it important that the aqueous humor has low protein?

A

allows for a clear ocular media

18
Q

What is the role of ascorbate in the aqueous humor?

A

prevents oxidative damage from light

19
Q

What is the function of the blood-ocular barrier?

A

prevents optically dense material within the blood from entering the eye and causing opacity/decreased vision

20
Q

What is the epithelial component of the blood-aqueous barrier?

A

tight junctions in the NPE of the ciliary body; prevent movement of molecules/cells into anterior chamber

21
Q

What is the endothelial component of the blood-aqueous barrier?

A

tight junctions in the iris endothelial ells

22
Q

What is the epithelial component of the blood-retinal barrier?

A

RPE that regulates diffusion of material from choroid to the retina

23
Q

What is the endothelial component of the blood-retinal barrier?

A

retinal vessel capillary tight junctions and lack of fenestrations

24
Q

What regulates constriction of the pupil?

A

-iris sphincter muscle
-parasympathetic system

25
Q

What mediates the degree of constriction?

A

parasympathetic nucleus of CN3, based on the amount of light present

26
Q

What regulates dilation of the pupil?

A

-dilator muscle
-sympathetic system
-inactivation of sphincter muscle