Lacrimal

Lacrimal apparatus

The lacrimal apparatus is the physiological system containing the orbital structures for tear production and drainage. It consists of the lacrimal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the human eye; the lacrimal canaliculi, the lacrimal sac, and the nasolacrimal duct, by which the fluid is conveyed into the cavity of the nose; and the lacrimal puncta, two minute orifices, one of which is seen on the margin of each eyelid, at the lateral extremity of the lacrimal lake.

Structure

The lacrimal apparatus is made up of a secretory system, which produces tears, and an excretory system, which drains the tears. The lacrimal gland is primarily responsible for producing emotional or reflexive tears. As tears are produced, some fluid evaporates between blinks, and some is drained through the lacrimal punctum. The rest of the fluid that is drained through the punctum, will eventually be drained through the nose.

Function

The lacrimal apparatus produces and drains tears. Tears are essential for the health of the eye. They keep the eye moist, help wounds heal, and protect against eye infection. In humans, the tear film coating the eye, known as the precorneal film, has three distinct layers, from the most outer surface:

1. Lipid layer
2. Aqueous layer
3. Mucous layer

Clinical significance

Diseases can affect the lacrimal apparatus, including dacryoadenitis, an inflammation of the lacrimal gland, and dacryocystitis, an inflammation of the lacrimal sac. Inflammation of the lacrimal ducts is known as dacryocystitis. Other diseases are rare, but include lacrimal duct obstruction, lacrimal duct cyst, and lacrimal duct tumor.

See also

• Tears
• Lacrimal gland
• Lacrimal canaliculi
• Lacrimal sac
• Nasolacrimal duct
• Lacrimal puncta
• Lacrimal lake

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