Tear ducts

Tear Ducts

Tear ducts, also known as the nasolacrimal ducts, are part of the human lacrimal apparatus responsible for the drainage of tears from the eye into the nasal cavity. This system plays a crucial role in maintaining eye health by keeping the eye surface moist and free from debris.

Anatomy

The tear duct system consists of several components:

• Lacrimal Glands: These are located in the upper outer region of each orbit and are responsible for the production of tears.
• Lacrimal Puncta: Small openings located at the inner corner of the upper and lower eyelids. They serve as the entry point for tears into the tear drainage system.
• Lacrimal Canaliculi: Small channels that connect the lacrimal puncta to the lacrimal sac.
• Lacrimal Sac: A reservoir located in a groove formed by the lacrimal bone and the frontal process of the maxilla.
• Nasolacrimal Duct: A duct that extends from the lacrimal sac to the inferior meatus of the nasal cavity, allowing tears to drain into the nose.

Physiology

Tears are produced by the lacrimal glands and serve several functions, including lubrication, protection, and providing nutrients to the cornea. The tear film is composed of three layers: lipid, aqueous, and mucin. The lipid layer prevents evaporation, the aqueous layer provides moisture, and the mucin layer helps spread the tears evenly over the eye surface.

Tears flow from the lacrimal glands across the eye surface and are collected by the lacrimal puncta. They then travel through the canaliculi to the lacrimal sac and finally drain through the nasolacrimal duct into the nasal cavity. This drainage system helps prevent the overflow of tears onto the face and maintains a clear visual field.

Clinical Significance

Obstruction

Obstruction of the tear ducts can lead to conditions such as dacryocystitis, an infection of the lacrimal sac, or epiphora, excessive tearing due to improper drainage. Obstructions can be congenital or acquired due to inflammation, infection, or trauma.

Surgical Interventions

Procedures such as dacryocystorhinostomy (DCR) are performed to create a new drainage pathway for tears when the nasolacrimal duct is blocked. This surgery involves creating a direct connection between the lacrimal sac and the nasal cavity.

Also see

• Lacrimal gland
• Dacryocystitis
• Epiphora
• Nasolacrimal duct obstruction