Question

Production and outflow of aqueous humour.

Hint:

Impaired outflow of aqueous humour can lead to increased intraocular pressure, a major risk factor for glaucoma.

Answer 1

Step 1: Production of Aqueous Humour.
Aqueous humour is produced by the ciliary body, specifically by the pars plicata of the ciliary processes. The production occurs through a process of ultrafiltration of plasma, as well as active secretion by the epithelial cells of the ciliary body. The total volume of aqueous humour in the anterior chamber is about 250 to 300 µL, and it is produced at a rate of about 2.5 µL/min.

Step 2: Outflow of Aqueous Humour.
The aqueous humour flows from the posterior chamber through the pupil into the anterior chamber, where it nourishes the avascular structures such as the lens and cornea. It then exits the eye through two primary pathways:
1. Trabecular Meshwork (Conventional Pathway): The majority of the aqueous humour drains through the trabecular meshwork into Schlemm's canal, and then into the episcleral veins. This is the main outflow route.
2. Uveoscleral Pathway (Unconventional Pathway): A smaller amount of aqueous humour flows through the uveoscleral route, where it passes through the ciliary body and sclera into the venous system.

Step 3: Conclusion.
Aqueous humour plays a critical role in maintaining intraocular pressure and providing nutrients to the avascular ocular structures. Disruptions in its production or outflow can lead to glaucoma.