The conjunctiva are kept moist by fluid produced by the:
A. corneal duct.
B. posterior orbit.
C. optic chiasma.
D. lacrimal gland.
The Correct Answer and Explanation is :
The correct answer is D. lacrimal gland.
Explanation:
The conjunctiva is a thin, transparent membrane that lines the inner surface of the eyelids and covers the white part of the eyeball (sclera). Its primary function is to protect and lubricate the surface of the eye, ensuring smooth and comfortable eye movement. To achieve this, it requires a constant supply of moisture, which is provided by tears.
Tears are produced by the lacrimal gland, which is located in the upper outer part of the orbit (the bony cavity surrounding the eye). The lacrimal gland produces a watery secretion known as lacrimal fluid or tear film. This fluid helps keep the conjunctiva moist, preventing it from drying out and offering several additional benefits:
- Lubrication: The tear film spreads across the eye each time the eyelid blinks, providing essential lubrication for the eye and reducing the risk of irritation.
- Nutrient supply: Tears provide nutrients to the corneal cells, which lack a blood supply.
- Protection: Tears contain enzymes and antibodies that help flush out debris and microorganisms, protecting the eye from infections.
Tears are distributed over the conjunctiva and the cornea by blinking. Excess tear fluid drains into the nasolacrimal duct, which leads to the nose.
The other options listed are not directly involved in moisture production for the conjunctiva:
- A. Corneal duct: This is not a structure associated with tear production; it is involved in the drainage of tears.
- B. Posterior orbit: This refers to the rear part of the bony cavity of the eye, which does not produce moisture for the conjunctiva.
- C. Optic chiasma: This is a part of the brain involved in the crossing of optic nerves, unrelated to tear production.
Thus, the lacrimal gland plays the crucial role in keeping the conjunctiva moist through the production of tears.