What makes up 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. About Recent Edits Go ad-free. Edit article. View revision history Report problem with Article. Citation, DOI and article data. Knipe, H. Lacrimal apparatus. Reference article, Radiopaedia. URL of Article. CT of the inferomedial orbit and the lacrimal drainage apparatus: normal and pathologic anatomy. Jinkins JR. Atlas of Neuroradiologic Embryology, Anatomy, and Variants.

Eyelids play an important role in the distribution of the tear fluid by regulating the amount of tear fluid in the eye and spreading it all over the ocular surface. Human tear film is a complex layer of fluid that covers the surface of the cornea.

Its main function is to keep the corneal epithelium moist, so that the surface epithelial cells have a medium in which to live, thus preserving the most important refractive mechanism of the eye.

A secondary function is to lubricate the front of the eye so that it moves freely beneath the eyelids. But there are two other vital components lipid and mucus , so we often refer to the tear fluid as the three-layered precorneal tear film.