Nasolacrimal system
Overview
The nasolacrimal system serves as a system to drain lacrimal secretions (tears) from the eye into the nose.The nasolacrimal system consists of:
- Puncta
- Canaliculi
- Lacrimal sac
- Nasolacrimal duct
The nasolacrimal system can be considered as the drainage part of the lacrimal apparatus.
Lacrimal sac
- Situated at the superior end of the nasolacrimal duct in the lacrimal groove, posterior to the medial palpebral ligament
- Not to be confused with the lacrimal gland
- Function is collection of tear fluid before passing into nasolacrimal duct
Nasolacrimal duct
- Inferior continuation of the lacrimal sac. Approximately 17mm in length in adults
- Terminates at its opening in the inferior nasal meatus
- The duct lies within the lacrimal canal and is lined by stratified columnar epithelium containing mucus-secreting goblet cells
- Course divided into two parts: Interosseeous and membranous parts
- Interosseeous part: 12mm within nasolacrimal canal of maxilla
- Membranous part: 5mm within nasal mucusa terminating at the inferior nasal meatus covered by a mucosal fold called the valve of Hasner
Images demonstrating position of nasolacrimal drainage system and nasolacrimal duct
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