The lacrimal sac or lachrymal sac is the upper dilated end of the

nasolacrimal duct The nasolacrimal duct (also called the tear duct) carries tears from the lacrimal sac of the eye into the nasal cavity. The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards. The ...

, and is lodged in a deep groove formed by the

lacrimal bone The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of ...

and

frontal process of the maxilla The frontal process of maxilla is a strong plate, which projects upward, medialward, and backward from the maxilla, forming part of the lateral boundary of the nose. Its ''lateral surface'' is smooth, continuous with the anterior surface of the b ...

. It connects the

lacrimal canaliculi The lacrimal canaliculi, (sing. canaliculus), are the small channels in each eyelid that drain lacrimal fluid, from the lacrimal puncta to the lacrimal sac. This forms part of the lacrimal apparatus that drains lacrimal fluid from the surface of ...

, which drain tears from the eye's surface, and the

, which conveys this fluid into the nasal cavity. Lacrimal sac occlusion leads to

dacryocystitis Dacryocystitis is an infection of the lacrimal sac, secondary to obstruction of the nasolacrimal duct at the junction of lacrimal sac. The term derives from the Greek ''dákryon'' ( tear), ''cysta'' (sac), and ''-itis'' (inflammation). It causes ...

Structure

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 The medial palpebral ligament (medial canthal tendon) is a ligament of the face. It attaches to the Frontal process of maxilla, frontal process of the maxilla, the lacrimal groove, and the Tarsus (eyelids), tarsus of each eyelid. It has a superfic ...

, and its deep surface is crossed by the lacrimal part of the

orbicularis oculi The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short ...

, which is attached to the crest on the lacrimal bone.

Histology

Like the nasolacrimal duct, the sac is lined by

stratified columnar epithelium Stratified columnar epithelium is a rare type of epithelial tissue composed of column-shaped cells arranged in multiple layers. It is found in the conjunctiva, pharynx, anus, and male urethra. It also occurs in embryo. Location Stratified col ...

with mucus-secreting

goblet cells Goblet cells are simple columnar epithelial cells that secrete gel-forming mucins, like mucin 5AC. The goblet cells mainly use the merocrine method of secretion, secreting vesicles into a duct, but may use apocrine methods, budding off their secre ...

, with surrounding connective tissue. The Lacrimal Sac also drains the eye of debris and microbes.

Function

It serves as a reservoir for overflow of tears, in which the lacrimal sac pumps inward and outward driven by the orbicularis muscle during blinking.

Imaging

The lacrimal sac can be imaged by ''dacrocystography'', in which

radiocontrast Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography (contrast CT), projectional radiography, and fluoroscopy. Radiocontrast agents are typically io ...

is injected, followed by

X-ray imaging Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

Additional images

File:Gray192.png, Medial wall of left orbit. File:Gray379.png, Left orbicularis oculi, seen from behind. File:Gray896.png, The

lacrimal apparatus The lacrimal apparatus is the physiological system containing the Orbit (anatomy), orbital structures for tears, tear production and drainage.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Com ...

. Right side. (Lacrimal sac visible at upper right.) File:Gray894.png, The tarsi and their ligaments. Right eye; front view. (Lacrimal sac visible at middle right.)

References