noun, plural: nasolacrimal ducts
Tears are produced by the lacrimal apparatus and the process of tear production and secretion is lacrimation. Tears produced through this process are due to emotions, injuries, or irritations. They are in the form of drops of limpid, saline, slightly alkaline fluid. They diffuse between the eye and the eyelids.
In humans, the lacrimal apparatus is comprised of two major parts, i.e. those associated with tear production and those involved in tear drainage system. The role of tear production is primarily carried out by the lacrimal glands. These glands are the paired almond-shaped glands that produce and secrete the aqueous part of the tear film. As for the tear drainage system, it includes the lacrimal sac, nasolacrimal duct, and the lacrimal canaliculi. The lacrimal sac is a reservoir when there is an excess secretion of tears. The lacrimal sac is the dilated part of the nasolacrimal duct. Its upper end though is closed. The nasolacrimal duct is about 18 mm in length and serves as a passageway through which the tears are conducted into the nasal cavity. The duct commences in the eye socket between the maxillary and the lacrimal bones. Tears that flow from the nasolacrimal duct drain into the inferior nasal meatus. When this happens, the nose starts to run while crying.
- tear duct
- ductus nasolacrimalis
- nasal duct