The nasolacrimal duct (sometimes called the tear duct) carries tears from the lacrimal sac into the nasal cavity. The opening of the nasolacrimal duct into the inferior nasal meatus is partially covered by a mucosal fold (valve of Hasner or plica lacrimalis). Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus. This is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops.
Like the lacrimal sac, the duct is lined by stratified columnar epithelium containing mucus-secreting goblet cells, and is surrounded by connective tissue.
Obstruction of the nasolacrimal duct, known as dacryostenosis, leads to the excess overflow of tears called epiphora. A congenital obstruction can cause cystic expansion of the duct and is called a dacrocystocele or Timo cyst. Persons with dry eye conditions can be fitted with punctal plugs that seal the ducts to limit the amount of fluid drainage and retain moisture.
The canal containing the nasolacrimal duct is called the nasolacrimal canal.
Other articles related to "nasolacrimal duct":
... The lacrimal sac is the upper dilated end of the nasolacrimal duct, and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla ... drain tears from the eye's surface, and the nasolacrimal duct, which conveys this fluid into the nasal cavity ... in length its upper end is closed and rounded its lower is continued into the nasolacrimal duct ...
... ectropion, punctal, canalicular or nasolacrimal duct obstruction) ... dacryocystitis), rhinitis, and in neonates or infants, failure of the nasolacrimal duct to open ... cause could be poor reconstruction of the nasolacrimal duct system after trauma to the area ...