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Lacrimal sac

Lacrimal sac

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The lacrimal sac is the upper dilated end of the nasolacrimal duct
Nasolacrimal duct
The nasolacrimal duct carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus...

, and is lodged in a deep groove formed by the lacrimal bone
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...

 and frontal process
Frontal process
Frontal process can refer to:* Frontal process of maxilla* Frontal process of zygomatic bone...

 of the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

. It connects the lacrimal canaliculi
Lacrimal canaliculi
The lacrimal canaliculi, also known as the lacrimal canals or lacrimal ducts, are the small channels in each eyelid that commence at minute orifices, termed puncta lacrimalia, on the summits of the papillae lacrimales, seen on the margins of the lids at the lateral extremity of the lacus...

, which drain tears from the eye's surface, and the nasolacrimal duct
Nasolacrimal duct
The nasolacrimal duct carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus...

, which conveys this fluid into the nasal cavity.

This is mainly for high amounts of tears, in which the lacrimal sac pumps inward and outward driven by the orbicularis muscle during blinking.

It is oval in form and measures from 12 to 15 mm. in length; its upper end is closed and rounded; its lower is continued into the nasolacrimal duct.

Its superficial surface is covered by a fibrous expansion derived from the medial palpebral ligament
Medial palpebral ligament
The medial palpebral ligament , about 4 mm. in length and 2 mm. in breadth, is attached to the frontal process of the maxilla in front of the lacrimal groove....

, and its deep surface is crossed by the lacrimal part of the Orbicularis oculi, which is attached to the crest on the lacrimal bone.

Like the nasolacrimal duct, the sac is lined by stratified columnar epithelium
Stratified columnar epithelium
Stratified columnar epithelia is a rare type of epithelial tissue composed of column shaped cells arranged in multiple layers.Stratified columnar epithelia are found in the ocular conjunctiva of the eye, in parts of the pharynx and anus, the female's uterus, the male urethra and vas deferens...

 with mucus-secreting goblet cells, with surrounding connective tissue. The Lacrimal Sac also drains the eye of any debris, bacteria, dirt, etc.