• Illustration by Christine Gralapp.
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    Oculoplastics/Orbit

    Lacrimal pump. A, In the relaxed state, the puncta lie in the tear lake. B, With eyelid closure, the orbicularis oculi muscle contracts. The pretarsal orbicularis squeezes and closes the puncta and canaliculi. The preseptal orbicularis, which inserts into the lacrimal sac, pulls the lacrimal sac open, creating a negative pressure that draws the tears into the sac. C, With eyelid opening, the orbicularis relaxes, the puncta open, and the lacrimal sac collapses, propelling tears down the duct. Simultaneously, with the puncta opened, the canaliculi refill, completing the cycle.