Production of Aqueous Humor Flashcards
Aqueous humor is a ___ of blood
Filtrate
Components of aqueous humor are derived from
The blood that is traveling through the capillaries in the ciliary stroma. Can also receive contributions from the cornea, iris, and lens.
In comparison to blood, the aqueous humor has
- Less ___ in the aqueous humor vs plasma
- Less ___ in the aqueous humor vs plasma
- More ___ in the aqueous humor vs plasma
- More ___ in the aqueous humor vs plasma
- Less protein in the aqueous humor vs plasma. This minimizes light scatter.
- Less K+ in the aqueous humor vs plasma K+ is mainly found intracellularly, and since there are no cells in the aqueous, there are very low amounts of K+.
- More ascorbate in the aqueous humor vs plasma. Protects the anterior ocular structures from UV induced damage caused by free radicals.
- More lactate in the aqueous humor vs plasma. Cornea metabolizes 85% of glucose through fermentation.
Flare
proteins
What is the pathway that water, molecules and ions take to move from the capillaries to the posterior chamber?
Capillaries– stroma — pigmented epithelium — non pigmented epithelium— posterior chamber
How do water, molecules, and ions move from the capillaries into the stroma?
- Fenestrations in the endothelial cells of the capillary
- Diffusion (simple or facilitated)
- Ultrafiltration (fluid forced across a membrane by hydrostatic pressure)
How do water, molecules, and ions move from the stroma to the pigmented epithelium?
Diffusion- simple or facilitated
How do water, molecules, and ions move from the pigmented epithelium to the non pigmented epithelium
Gap junctions
How do water, molecules, and ions move from the non pigmented epithelium to the posterior chamber
- Diffusion (less often)
- Active transport (more often) by -Na+/K+ ATPases or Carbonic anhydrase
- Requires energy
- present in the non pigmented epithelium.
- Pumps Na+ into the posterior chamber, and water follows by facilitated diffusion through aquaporins.
Carbonic anhydrase:
- Requires energy
- present in the non pigmented epithelium.
- Generates bicarbonate, which then moves into the posterior chamber
- Role in aqueous production is not completely clear.
- Inhibiting carbonic anhydrase decreases the amount of aqueous humor secreted into the posterior chamber.
2 regions of the posterior chamber
- Canal of Hannover- area occupied by the zonules
2. Canal of Petit- Area from most posterior zone to virtual face
Aqueous flows where
Into the posterior chamber, between the lens and the iris, through the pupil, and into the anterior chamber.
A small amount passes into the vitreous.
How does the aqueous circulate in the anterior chamber?
Aqueous moves up along the warmer iris and down along the cooler cornea.
5 factors in controlling aqueous production
- Hydrostatic pressure in the ciliary stromal capillaries (ultrafiltration)
- Rate of diffusion
- Rate of active transport (by Na+/K+ ATPases or carbonic anhydrase)
- Circadian rhythm. IOP has a diurnal variation. At night, rate of secretion decreases.
- Neural control
Neural control of aqueous production
By alpha (alpha 2) and beta (beta 2) adrenergic receptors.
Alpha 2 adrenergic receptors:
- Where are they present?
- Stimulation results in what?
- Should you use an agonist or antagonist to lower IOP?
- Present in the ciliary epithelium
- Stimulation by NE or epi INHIBITS adenylate cyclase. which reduces CAMP production.
- You must use an AGONIST to lower the production. Agonists stimulates, resulting in decreased activity of adenylate cyclase, AKA less CAMP, AKA less production
