The lacrimal apparatus is involved in the production, movement, and drainage of fluid from the surface of the eyeball. The lacrimal apparatus consists of the following parts:

Lacrimal gland and excretory ducts of lacrimal gland
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct

The lacrimal gland lies anteriorly in the superolateral region of the orbit and is divided into two parts by the levator palpebrae superioris muscle (Read more!) - orbital and palpebral. The larger orbital part lies in a depression - the lacrimal fossa - in the frontal bone. The smaller palpebral part is situated inferior to the levator palpebrae superioris in the superolateral part of the eyelid.

Numerous excretory ducts empty the glandular secretions into the lateral part of the superior fornix of the conjunctiva. Fluid is continually being secreted by the lacrimal gland and moved across the surface of the eyeball from lateral to medial as the eyelids blink. The fluid accumulates medially in the lacrimal lake and is drained from the lake by the lacrimal canaliculi (superior canaliculus and inferior canaliculus), one canaliculus being associated with each eyelid. The lacrimal punctum (superior lacrimal punctum and inferior lacrimal punctum) is the opening through which fluid enters each canaliculus.

Passing medially, the lacrimal canaliculi eventually join the lacrimal sac between the anterior lacrimal crest and posterior lacrimal crest posterior to the medial palpebral ligament and anterior to the lacrimal part of the orbicularis oculi muscle. When the orbicularis oculi muscle contracts during blinking, the small lacrimal part of the muscle may dilate the lacrimal sac and draw tears into it through the canaliculi from the conjunctival sac.

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Lacrimal apparatus