Exam 1 Remington- Aqueous Production Flashcards
What is the volume of aqueous in the anterior chamber?
.25 mL
What is the volume of aqueous in the posterior chamber?
.06 mL
What are the aqueous dynamics?
Secreted by the ciliary processes into the posterior chamber, moves through the pupil into the anterior chamber
How does the aqueous production exit from the anterior chamber?
Via trabecular meshwork -> Schlemm’s canal or uveoscleral flow
What are the 3 factors to be considered as the aqueous is produced by the processes of the ciliary body?
Epithelial membrane, concentration gradient, and passage mechanisms
What are the 3 mechanisms by which substances cross the epithelial membrane?
Diffusion, ultrafiltration, and active transport
Ultrafiltration
Flow across the epithelium, movement can be enhanced by increasing hydrostatic driving force
What is active transport?
A pump mechanism, utilizes cellular energy (ATP) as solutes are moved against a concentration gradient
What is the process of aqueous humor formation?
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
What are the blood-aqueous barrier components?
Fenestrated ciliary body capillaries, ZO in non-pigmented ciliary epithelium, nonfenestrated iris capillaries, tight junctions in posterior iris epithelium
Ascorbate is how many times higher in aqueous than plasma?
20
Protein is how many times higher in plasma than aqueous?
200
Why is the aqueous transparent?
Optically empty, little or no light scatter, no large molecules, Tyndall phenomenon
When are cells and flare visible?
In aqueous in disease
How do you maintain IOP?
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
What 3 factors is inflow dependent on?
Ultrafiltration from BV’s in ciliary processes, facility of inflow C_in, and metabolic pump S
What is ultrafiltration dependent on?
Hydrodynamic pressure head P_cap- IOP
What is facility of inflow C_in dependent on?
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
What is the metabolic pump?
Located in ciliary epithelium, remains constant, in not affected by IOP, can be affected by drugs
Aqueous outflow is dependent on what 3 factors?
Hydrodynamic pressure head, facility of outflow C_out, and uveoscleral outflow
What is the hydrodynamic pressure head?
IOP- P_ev
What is the facility of outflow?
Takes into account the resistance through the trabecular meshwork (TM) and juxtacanalicular tissue
What is the uveoscleral outflow?
U remains constant (except at high IOP) Inflow=Outflow
When does the aqueous production formula hold true?
At low and moderate levels of IOP; slight variations in the factors help to maintain homeostasis
