The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit.

Gross anatomy

Each lacrimal gland is divided into orbital and palpebral portions by the aponeurosis of the Levator palpebrae superioris muscle, the portions are continuous with each other.

• The orbital portion is the largest of the portions, and its convex superior surface is lodged in the lacrimal fossa of the orbit.
• For the smaller palpebral portion, its inferior surface lies close to the eye; if the upper eyelid is everted, the palpebral portion can be seen.

The orbital portion contains fine interlobular ducts that unite to form 3 - 5 main excretory ducts, joining 5 - 7 ducts in the palpebral portion before the secreted fluid may enter on the surface of the eye. Tears secreted collect in the fornix conjunctiva of the upper lid, and pass over the eye surface to the lacrimal puncta.

Microanatomy

The lacrimal gland is a compound tubuloacinar gland, it is made up of many lobules separated by connective tissue, each lobule contains many acini. The acini contain only serous cells and produce a watery serous secretion.

Each acinus consists of a grape-like mass of lacrimal gland cells with their apices pointed to a central lumen.

The central lumen of many of the units united to form intralobular ducts, and then unite to from interlobular ducts. The gland lacks striated ducts.

Innervation

The sensory innervation to the lacrimal gland is from the lacrimal nerve of the trigeminal nerve.

The parasympathetic nerve supply originates from the lacrimal nucleus of the facial nerve in the pons. Just distal to the geniculate ganglion, the facial nerve gives off the greater petrosal nerve. This nerve carries the parasympathetic secretomotor fibers through the pterygoid canal to the pterygopalatine ganglion. Here the fibers synapse and postganglionic fibers join the fibers of the Maxillary Nerve, which travels through the inferior orbital fissure. Once it has traversed this opening, the parasympathetic secretomotor fibers branch off with the zygomatic nerve and then branch off again, joining with the lacrimal branch of the ophthalmic division of CN V, which innervates the lacrimal gland.

The sympathetic postganglionic fibres originates from the superior cervical ganglion. They travel as a periarteriolar plexus with the middle meningeal artery, before they merge and form the deep petrosal nerve, which joins the greater petrosal nerve in the pterygoid canal. Together, greater petrosal and deep petrosal nerves form the nerve of the pterygoid canal (vidian nerve) and reach the pterygopalatine ganglion in the pterygopalatine fossa.In contrast to their parasympathetic counterparts, sympathetic fibers do not synapse in the pterygopalatine ganglion, having done so already in the sympathetic trunk. However, they continue to course with the parasympathetic fibers innervating the lacrimal gland.

Blood supply

The lacrimal artery, derived from the ophthalmic artery supplies the lacrimal gland. Venous blood returns via the superior ophthalmic vein.

Pathology

• Dacryoadenitis
• Sjögren's syndrome

Additional images

See also

• Lacrimal apparatus

References

External links

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