Physiology: Aqueous Humor

Question 1

What is aqueous humour?

Answer 1

Specialised fluid that bathes the structures within the eye

Question 2

What are the functions of aqueous humour?

Answer 2

Provides oxygen and metabolites, and contains bicarbonate which buffers the H+ produced by the cornea and lens by anaerobic glycolysis Very high in ascorbate, which is a powerful antioxidant

Question 3

Where is aqueous humour produced?

Answer 3

Epithelial layer of the ciliary body into the posterior chamber of the eye

Question 4

Aqueous humour is an energy _________ process

Answer 4

Dependent

Question 5

Describe the flow of aqueous humour in the eye

Answer 5

Produced by the ciliary body, then flows into the anterior chamber and then drains to the scleral venous sinus through a trabecular meshwork and the canal of Schlemm

Question 6

Where is the trabecular meshwork and the canal of Schlemm located?

Answer 6

In the angle between the iris and cornea (iridocorneal angle)

Question 7

Describe the structure of the ciliary epithelium

Answer 7

The ciliary body and posterior surface of the iris are covered by two juxtaposed layers of epithelial cells - a forward continuation of the pigment epithelium of the retina (PE) overlain by an inner nonpigmented epithelial (NPE) layer

Question 8

Describe the formation of aqueous humour

Answer 8

1. CO2 hydrated into HCO3- and H+ by carbonic anhydrase
2. HCO3- and H+ transported from basolateral membranes of PE cells into the interstitial fluid in exchange for Cl- and Na+
3. Cl- and Na+ ions diffuse into NPE cells via gap junctions
4. Cl- and Na+ ions are transported out of NPE cells into the aqueous humour via the Na+/K+/2Cl- cotransporter
5. Solute movement creates an osmotic gradient and water moves into the aqueous humour

Question 9

Why can acetazolamide lead to acidosis but dorzolamide avoids systemic effects?

Answer 9

Acetazolamide is administered orally so also targets the kidneys, dorzolamide is administered as eye drops