Ocular: Aqueous Humor Dynamics

Question 1

What acid does aqueous humor transports into the anterior segment>

Answer 1

ascorbic acid

Question 2

Ascorbic acid acts as an..

Answer 2

Antioxidative agent

Question 3

During inflammation what does aqueous humor facilitate?

Answer 3

Local immune responses

Question 4

Volume of AH?

Answer 4

250-315ul

Question 5

Secretion rate of AH?

Answer 5

2.5ul/min

Question 6

Turnover rate of AH/

Answer 6

100ul/min

Question 7

What is the protein content of AH?

Answer 7

Less than one percent protein content of blood plasma
-protein causes light scattering

Question 8

What is the first step in AH formation and where does it take place?

Answer 8

-elaboration of plasma filtrate
-Ciliary body microvasculature

Question 9

What is the second step of AH formation and where does it occur?

Answer 9

-AH is formed from the plasma filtrate
-in ciliary epithelium

Question 10

Where in the ciliary body are capillaries fenestrated and why?

Answer 10

The anterior arterioles are fenestrated to allowing plasma proteins, fluids, and ions to leak into the ciliary stroma.

Question 11

What pushes the proteins, ions, and fluid into the surrounding ciliary stroma to make filtrate?

Answer 11

Hydrostatic pressure within the capillaries

Question 12

Ions from the filtration are actively transported where in the ciliary epithelium?

Answer 12

Into the pigmented ciliary epithelium

Question 13

Ions that are transported into the pigmented ciliary epithelium are moved to where? Via what type of junctions?

Answer 13

They are moved into intercellular clefts in the NPCE via GAP JUNCTIONS

Question 14

The presence of the ions in the NPCE clefts causes..

Answer 14

Water to be drawn out of the cleft and AH formation

Question 15

What type of junctions are in the NPE?

Answer 15

TIGHT JUNCTIONS

Question 16

Tight junctions in the NPE restrict flows towards what?

Answer 16

Posterior chamber

Question 17

The tight junctions the NPE create what barrier?

Answer 17

Blood aqueous barrier

Question 18

What happens if the blood aqueous barrier breaks down?

Answer 18

Secretion of proteins into the posterior chamber

Question 19

What happens if gap junctions are unable to communicate with adjacent cells?

Answer 19

Compromised and produce less AH which increase IOP

Question 20

What is carbonic anhydrase used for?

Answer 20

Decreasing AH production in glaucoma therapy, inhibits movement of h2o out of NPCE

Question 21

Na-K-ATPase and carbonic a hydrate are found along..

Answer 21

Basal enfolding of the ciliary epithelium

Question 22

The presence of Na-K-ATPase and carbonic a hydrate on the basal enfolding suggest?

Answer 22

Active metabolic pumping and moving of fluids and ions

Question 23

Explain the flow of AH?

Answer 23

-flows from posterior chamber through the pupil
-resting of iris on the anterior surface of the lens forming a one way valve
-AH enters anterior chamber and rises dues to iris vasculature(warm)
-AH falls near cooler corneal endothelium

Question 24

What percentage of AH passes through the trabecular meshwork?

Answer 24

90%

Question 25

What causes vertical orientation of Krukenburg Spindle?

Answer 25

Pigment from iris pigment epithelium deposits in a vertical line on corneal endothelium

Question 26

The BAB blocks movements of what substances?

Answer 26

-Intermediate and high molecular weight substances such as protein -toxic substances

Question 27

What are the three Locations of the BAB?

Answer 27

-tight junctions between NPCE -tight junctions between endothelial cells and the iris vasculature -tight junctions between endothelial cells of inner wall of schlemms canal

Question 28

Are tight junctions in the post iris epithelium part of the BAB?

Answer 28

NO, but important for preventing AH from ant. chamber from flowing back into post. chamber

Question 29

Trabecular pathway of aqueous flow:

Answer 29

TM -> juxtacanalicular CT -> schlemm’s canal -> collector channels and aqueous veins -> scleral and episcleral venous plexus

Question 30

What percentage of aqueous flows through the trabecular pathway?

Answer 30

90%

Question 31

Flow through the TM is _________ dependent

Answer 31

Pressure

Question 32

Where does teh bulk of the AH resistance reside? What structures contribute to it?

Answer 32

-juxtacanalicular CT -contains fibroblasts, ECM material, elastic-like fibers

Question 33

Pressure must be ______ in order to make it to the Schlemm’s canal

Answer 33

High

Question 34

What happens to the TM in the accommodated state?

Answer 34

-scleral spur moves posteriorly -flow enhances across TM by opening flow channels -increase in effective filtration area

Question 35

What happens t the TM when the ciliary muscle is relaxed?

Answer 35

-scleral spur moves forward into normal position -closing flow channels in TM which decreases flow -decreases in effective filtration area

Question 36

What percentage of AH outflow takes the uveoscleral pathway?

Answer 36

10%

Question 37

Uveoscleral pathway is pressure ___________

Answer 37

Pressure independent

Question 38

What is the uveoscleral outflow pathway?

Answer 38

-AH enters CBB and iris root -AH passes between bundles of muscle fibers of the ciliary body to enter the supraciliary space -in supraciliary space the AH is pumped through sclera to the episclera (can also exit through vortex veins)