Lecture 18.1 Uveal Tract II (AH, transport, meshwork, channels)

Major Functions of the Ciliary Body:

1. control of _______

2. ______ and ____ of aqueous humor

accommodation, production and outflow

regarding aqueous humor production, blood flows from ______ to the ______ in the processes

ciliary stroma, epithelium

The microvasculature of the ciliary body stroma is composed of

fenestrated capillaries

the fenestrated capillaries readily leak ____, _____, and ______

fluids, ions, plasma proteins

purpose of the fenestrated capillaries readily leaking fluids, ions, plasma proteins

to provide the reservoir from which the ciliary epithelium secretes AH

direction of movement for aqueous humor: from _____ to ____

blood, posterior chamber

direction of movement for aqueous humor: which structures do they go through (3)

stroma, pigmented epithelium, non-pigmented epithelium

in aqueous humor production, _____, ______ and ____ are taken up by pigmented epithelium

nutrients, ions, water

in aqeous humor production, nutrients, ions and water are taken up by ______

pigmented epithelium

aqueous humor is transferred from _____ to _____ via _____

pigmented epithelium, non-pigmented epithelium, gap junctions channels

in aqueous humor production, non-pigmented epithelium secretes _____, _____ and ____ to ______

nutrients, ions, water, posterior chamber

in aqueous humor production, ____ secretes nutrients, ions, and water to internal limiting membrane posterior chamber

non-pigmented epithelium

Why is the blood-aqueous barrier necessary/why is fenestration capillaries important?

Proteins create ____ that ____, degrading the ____ of the eye

turbidity, scatters light, optical efficiency

Why is the blood-aqueous barrier necessary/why is fenestration capillaries important?

The ____ of ____ can bring with it unwanted or harmful growth factors

nonspecific entry, plasma-derived proteins

Why is the blood-aqueous barrier necessary/why is fenestration capillaries important?

To exclude ____ and ____ that are deleterious to the pristine environment of the eye

potential antigens, other plasma components

pigmented cells (PE) anteriorly continuous with _ _ _ _ _ and posteriorly with ____

iris anterior non-pigmented epithelial layer, RPE

nonpigmented cells (NPE) anteriorly continuous with _ _ _ _ _ and posteriorly with __

iris posterior pigment epithelial layer, retinal neural layers

pigmented and nonpigmented epithelium are joined by ____ to transport ___, ____, acting as a ______

numerous gap junctions, nutrients, ions and water, functional syncytium

non-pigmented epithelium (NPE) forms _____, preventing macromolecules passing into the _____

tight junctions, posterior chamber

breakdown of blood-aqueous barrier occurs in ____, ____, ____, ____, resulting in increased amounts of ___ and ___ in the ____

trauma, inflammation, infection vascular diseases; protein, cells, aqueous humor

breakdown of blood-aqueous barrier occurs in ____, ____, ____, ____.

trauma, inflammation, infection vascular diseases

breakdown of blood-aqueous barrier results in increased amounts of ___ and ___ in the ____

protein, cells, aqueous humor

anterior uveitis is an ____ of the middle layer of the eye, specifically affecting the ____ and the _____.

inflammation, iris, ciliary body

anterior uveitis leads to _____(“flare”) in the eye

light scattering

diffusion is substances across _____ following a ______

cell membranes, concentration gradient

what type of substances can easily penetrate biologic membrane for diffusion

lipid soluble substances

examples of lipid soluble substances in diffusion

oxygen, carbon dioxide, gases

gases can cross both the pigmented and non-pigmented ciliary epithelium into the eye via

simple passive diffusion

define diffusion

Substances across cell membranes following a concentration gradient

define ultrafiltration

Fluid and small solutes are forced through a semipermeable membrane and separated from large molecules and particles

for ultrafiltration, ____ and ____ are forced through a ____

fluod, small solutes, semipermeable membrane

for ultrafiltration, fluid and small solutes are forced through a semipermeable membrane, separating them from ____ and ____

large molecules and particles

examples of substances passing through ultrafiltration (4)

water, Na+, K+, glucose

ultrafiltration involves _____ and substances across a membrane related to ____ and ______ pressure on either side

bulk flow, hydrostatic, osmotic/oncotic

active transport happens when substances are transported against ____

concentration gradient

active transport requires ___, normally provided by ____ of _____

energy, hydrolysis, ATP (adenosine triphosphate)

examples of substances passing through active transport (5)

Na+, HCO3, HCO3-, ascorbate, amino acids

which is the most important process in the formation of aqueous humor

active transport

which process accounts for 80-90% of total aqueous humor formation

active transport

three mechanisms that contribute to the formation and composition of the aqueous humor production

diffusion, ultrafiltration, active transport

The active secretion of aqeuous humor is mediated by ____ of certain ions and substances across the ____ against a _____

elective transport, NPE, concentration gradient

which enzymes are involved in active transport in NPE

ATPase and carbonic anhydrase II and IV

ATPase is predominantly bound to the ____ of ___.

plasma membrane, NPE

ATPbase provides ___ for the ___, which transports ____ into the ____.

energy, metabolic pump, sodium, posterior chamber

carbonic anhydrase II is abundantly present in the ___ and ____ of the ___ and ___.

membranes, cytoplasm, PE, NPE

carbonic anhydrase provides ___, which is essential for secretion of ___.

HCO3-, aqueous humor

carbonic anhydrase produces ____ in ____ and transfer it to ____.

HCO3, PE, NPE

equation for carbonic acid to bicarbondate

CO2 + H2O —> H2CO3 —> H+ + HCO3-

main function of carbonic anhydrase II: breakdown ____ and produces ____ and ____

H2CO3 (carbonic acid), HCO3- (bicarbonate), H+

main function of carbonic anhydrase II: breakdown H2CO3 (carbonic acid) and produces HCO3- (bicarbonate) and H+ needed for _____ and ____.

ion exchange, fluid secretion

what type of isoenzyme is CA II

cytosolic

what type of isoenzyme is CA IV

membrane-bound

main function of carbonic anhydrase IV: facilitate ___ movement across the ____ and works with the ___

HCO3-, epithelium, CA II

main location of CA II

Cytoplasm of pigmented ciliary epithelium

sub-location of CA II

NPE and stroma

location of CA IV

Basolateral membrane of non-pigmented ciliary epithelium

key proteins in aqueous humor (9)

Transthyretin, Cystatin C, Clusterin, Transferrin, Vitamin D-binding protein, alpha-Crystallins, Carbonic Anhydrase II, Interleukins (IL-6, IL-8), and Serpins

Stages/pathways of active aqueous humor secretion across the ciliary epithelium.

NaCI uptake by PE, intracellular transfer via gap junctions, NaCl secretion by NPE

gap junctions of ciliary processes connects ___ and ___ at ____.

PE, NPE, apical ends

NaCl uptake by PE is affected by ____

CA II

NaCl secretion by NPE is affected by ___

CA IV

volume of anterior chamber

250 ul

volume of posterior chamber

60 ul

structures in anterior border of the anterior chamber

the cornea

structures in posterior border of the anterior chamber

iris surface and pupillary portion of the lens

structures in lateral recess of the anterior chamber

the iridocorneal angle occupied by the trabecular meshwork

Aqueous humor is initially secreted directly into the ____ of the eye, and it then transports and flows into the ____.

posterior chamber, anterior chamber

what are the two primary outflow pathways through which aqueous humor drains from the anterior chamber of the eye to regulate intraocular pressure (IOP)

uveoscleral outflow and trabecular outflow

Aqueous humor is produced by the ___

ciliary processes

aqueous humor enter the _____, flows through the pupil into the _____, and exits at the _____.

posterior chamber, anterior chamber, chamber angle

aqueous humor exits at the chamber angle via the ____, ____, and ____

trabecular outflow, uveoscleral outflow, iris outflow

trabecular outflow accounts for ___ of the aqueous flow pathways

70-90%

uveoscleral outflow accounts for ___ of the aqueous flow pathways

10-30%

aqueous humor exits through the trabecular outflow via the ____ and ____.

trabecular meshwork, Schlemm’s canal

aqueous humor exits through the uveoscleral outflow via the ____ between ___ and ____ of the ____ .

intercellular spaces, ciliary muscle fibers, loose connective tissues, suprachoroidal space

conventional outflow pathway of aqueous humor

trabecular outflow

unconventional outflow pathway of aqueous humor

uveoscleral outflow

ciliary processes —> ___ —> ___ —>

aqueous in the posterior chamber through pupil, anterior chamber, trabecular meshwork or ciliary body

for the trabecular outflow pathway: trabecular meshwork —> ___ —> ___

Schlemm’s canal, collector channels

for the uveoscleral outflow pathway: ciliary body —> ____ —> ___

suprachoroidal space, venous circulation of ciliary body, choroid, and sclera

key zones of the trabecular meshwork

uveal meshwork, corneoscleral meshwork, cribriform meshwork

uveal meshwork has pore size up to ____, and it is a ____ trabeculae

70 um, cord-like

corneoscleral meshwork has pore size up to ____, and it is a _ _ trabeculae

30 um, flattened sheet-like

cribriform meshwork is a ____ tissue facing the ____ by a monolayer of ____.

juxtacanalicular, schlemm’s canal, endothelial cells

cribriform meshwork has pore size of ____

4-7 um

cribriform meshwork consists of ____ cells enmeshed in _ _ _ _ _, ____ fibers, and ___.

trabecular, loose extracellular matrix of collagen, elastic-like, proteoglycans

cribriform meshwork is the main site of _____

resistance of outflow

Schlemm’s canal connects to the _____ by _____

venous system, 30 collector channels

Schlemm’s canal is lined by a _ _ _ _ _.

single layer of endothelial cells

Schlemm’s canal is characeterized by ___ or _____, with both ___ and ____ openings

transcellular channels, giant vacuoles, basal, apical

Schlemm’s canal is connected to ____and ____ by a complex system of ____ channels call_.

episcleral veins, conjunctival veins, intrascleral, collector channel

two systems of intrascleral channels

direct system of large caliber vessels and indirect system of numerous (15-20) finer channels

the direct intrascleral channels has ___ vessels, which run a short ____, and drain directly into the _ __.

large caliber, intrascleral course, episcleral venous system

the direct system of intrascleral channels are about ____ in number and are also called the ____

6-8, aqueous vessels

the indirect system of intrascleral channels form an _____ before eventually draining into the ____ system.

intrascleral plexus, episcleral venous

most aqueous vessels are directed ____, with most of these draining into ____, whereas a few cross the _____ and drain into the _____.

posteriorly, episcleral veins, subconjunctival tissue, conjunctival veins

the episcleral veins drain into the ____ via the ____ and _____.

cavernous sinus, anterior ciliary, superior ophthalmic veins

the conjunctival veins drain into the ____ or ____ via the ___ and ___

superior ophthalmic veins, facial veins, palpebral veins, angular veins

Episcleral and conjunctival veins ultimately drain into the ___.

cavernous sinus