The lacrimal apparatus (latin: apparatus lacrimalis) is a set of connected anatomical structures located within the orbit that are responsible for the production and drainage of tears.
The lacrimal apparatus include the following structures:
- lacrimal gland,
- lacrimal canaliculi,
- lacrimal sac,
- nasolacrimal duct.
The lacrimal gland is the tear-producing organ of the lacrimal apparatus. The gland secretes the serous transparent fluid via its excretory ducts into the lateral aspect of the superior fornix, in the space between the eyeball and the eyelids. The tears wash over the eyeball and drain into the lacrimal canaliculi (superior and inferior) that open in the medial corner of the eye with puncta lacrimalia, the beginning of the tear drainage system. The lacrimal canaliculi convey the tears to the lacrimal sac, a dilated portion of the nasolacrimal duct lodged in a depression between the lacrimal bone and the frontal process of the maxilla. The fluid drains further into the nasolacrimal duct, which is the final part of the lacrimal apparatus and opens into the nasal cavity, specifically, into the inferior nasal meatus. If there is excess of tears, it drains via the nasolacrimal duct into the nasal cavity, thus causing what is called a runny nose.
The secretory functions of the lacrimal apparatus are controlled by the autonomic nervous system. The sympathetic fibers arise from the carotid plexus, while the parasympathetic fibers originate from neurons of the superior salivatory nucleus in the brainstem.