Which of the following structures secretes and drains tears from the eye?

The nasolacrimal apparatus is the structure responsible for both the secretion and drainage of tears from the eye. This apparatus includes the lacrimal glands, which produce tears, as well as the system of ducts that allow tears to drain into the nasal cavity. The tears are essential for keeping the eye lubricated, protecting it from irritants, and providing nutrients to the corneal surface.

When tears are produced by the lacrimal glands, they spread over the surface of the eye and eventually drain through small openings called puncta located in the inner corners of the eyelids. From there, tears are directed through the canaliculi into the lacrimal sac and finally into the nasolacrimal duct, which empties into the nasal cavity. This entire process is crucial for maintaining eye health and comfort.

In contrast, the other options mentioned refer to different anatomical structures with distinct functions. The conjunctiva is a membrane that covers the front of the eye and lines the eyelids but does not produce or drain tears. Aqueous humor is a fluid that fills the anterior chamber of the eye, contributing to intraocular pressure, but it is not involved in tear production or drainage. The Eustachian tube connects the middle ear to the