Exam 1 Remington- Aqueous Production

Question 1

What is the volume of aqueous in the anterior chamber?

Answer 1

.25 mL

Question 2

What is the volume of aqueous in the posterior chamber?

Answer 2

.06 mL

Question 3

What are the aqueous dynamics?

Answer 3

Secreted by the ciliary processes into the posterior chamber, moves through the pupil into the anterior chamber

Question 4

How does the aqueous production exit from the anterior chamber?

Answer 4

Via trabecular meshwork -> Schlemm’s canal or uveoscleral flow

Question 5

What are the 3 factors to be considered as the aqueous is produced by the processes of the ciliary body?

Answer 5

Epithelial membrane, concentration gradient, and passage mechanisms

Question 6

What are the 3 mechanisms by which substances cross the epithelial membrane?

Answer 6

Diffusion, ultrafiltration, and active transport

Question 7

Ultrafiltration

Answer 7

Flow across the epithelium, movement can be enhanced by increasing hydrostatic driving force

Question 8

What is active transport?

Answer 8

A pump mechanism, utilizes cellular energy (ATP) as solutes are moved against a concentration gradient

Question 9

What is the process of aqueous humor formation?

Answer 9

Molecules enter stroma via CB fenestrated caps, ions enter PCE via co-transporters, pumps, and exchangers from stroma, pass into NPCE via gap junctions, ions exit basolateral membrane via channels, co-transporters and pumps, aqueous is produced as these ions and fluid enter the posterior chamber

Question 10

What are the blood-aqueous barrier components?

Answer 10

Fenestrated ciliary body capillaries, ZO in non-pigmented ciliary epithelium, nonfenestrated iris capillaries, tight junctions in posterior iris epithelium

Question 11

Ascorbate is how many times higher in aqueous than plasma?

Answer 11

20

Question 12

Protein is how many times higher in plasma than aqueous?

Answer 12

200

Question 13

Why is the aqueous transparent?

Answer 13

Optically empty, little or no light scatter, no large molecules, Tyndall phenomenon

Question 14

When are cells and flare visible?

Answer 14

In aqueous in disease

Question 15

How do you maintain IOP?

Answer 15

In order to maintain IOP in a relatively small range a constant rate of production of aqueous is balanced by an equal constant rate of exit

Question 16

What 3 factors is inflow dependent on?

Answer 16

Ultrafiltration from BV’s in ciliary processes, facility of inflow C_in, and metabolic pump S

Question 17

What is ultrafiltration dependent on?

Answer 17

Hydrodynamic pressure head P_cap- IOP

Question 18

What is facility of inflow C_in dependent on?

Answer 18

Takes into accound the resistance int he tissues through which the aqueous components pass, C_in measured in microliters/min/mmHg, reciprocal relationship between facility and resistance

Question 19

What is the metabolic pump?

Answer 19

Located in ciliary epithelium, remains constant, in not affected by IOP, can be affected by drugs

Question 20

Aqueous outflow is dependent on what 3 factors?

Answer 20

Hydrodynamic pressure head, facility of outflow C_out, and uveoscleral outflow

Question 21

What is the hydrodynamic pressure head?

Answer 21

IOP- P_ev

Question 22

What is the facility of outflow?

Answer 22

Takes into account the resistance through the trabecular meshwork (TM) and juxtacanalicular tissue

Question 23

What is the uveoscleral outflow?

Answer 23

U remains constant (except at high IOP) Inflow=Outflow

Question 24

When does the aqueous production formula hold true?

Answer 24

At low and moderate levels of IOP; slight variations in the factors help to maintain homeostasis

Question 25

What does the formula represent?

Answer 25

A complex equilibrium between rate of formation of the aqueous and the rate of outflow, when the balance is disturbed, the problem is usually a decrease in outflow rather than an increase in production