Lacrimal gland

Lacrimal gland
Lacrimal apparatus of the right eye. The lacrimal gland is to the upper left. The right side of the picture is towards the nose.
Tear system. a = lacrimal gland b = superior lacrimal punctum c = superior lacrimal canal d = lacrimal sac e = inferior lacrimal punctum f = inferior lacrimal canal g = nasolacrimal canal
Latin	glandula lacrimalis
Gray's	subject #227 1028
Artery	lacrimal artery
Nerve	lacrimal nerve, Zygomatic nerve via Communicating branch

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. Inflamation of the lacrimal glands is called lacrimitis.

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 formed by the frontal bone.
• 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. ^[1]

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 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 supplies sensory innervation to the eye lid and conjunctiva.

The sympathetic postganglionic fibres originate 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

The ophthalmic artery and its branches.	Nerves of the orbit. Seen from above.	Sympathetic connections of the sphenopalatine and superior cervical ganglia.	The tarsal glands, etc., seen from the inner surface of the eyelids.
Alveoli of lacrimal gland.

See also

• Lacrimal apparatus

References

1. ^ "eye, human."Encyclopædia Britannica. 2008. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 5 Apr. 2008

External links

• Lacrimal+gland at eMedicine Dictionary
• lesson3 at The Anatomy Lesson by Wesley Norman (Georgetown University) (orbit2)

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