Quick Facts
The lacrimal gland is either of a pair of glands, one at the superior lateral angle of each orbit, secreting the tears; they are divided into two portions, the orbital and palpebral, by the levator palpebrae superioris muscle (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Feature(s)
The lacrimal gland is a lobulated exocrine gland. It is located in the superior lateral corner of the orbit (orbital part) extending out into the upper eyelid (palpebral part), continuous with each other posterolaterally around the levator palpebrae superioris muscle. The gland itself contains the secretory unit, the acini, that discharge their aqueous product into a central lumen. Numerous lumens converge on an intercalated duct that opens into the conjunctival sac and is how tears are expelled from the gland. Myoepithelium surrounds the acini and ducts, and these provide mechanical force to expel tears. There are as many as twelve ducts for each gland.
The lacrimal gland is supplied by the lacrimal branch of the ophthalmic artery, with contributions from the infraorbital artery. Blood is drained by the superior ophthalmic vein.
Sensory innervation of the lacrimal gland is provided by the ophthalmic nerve (CN V1). Secretomotor preganglionic parasympathetic innervation of the lacrimal gland is carried by the greater petrosal nerve, a branch of the facial nerve (CN VII). Preganglionic fibers terminate in the pterygopalatine ganglion. Postganglionic fibers reach the gland by following the zygomatic and lacrimal branches of the maxillary nerve (CN V2) or directly from the ganglion. The superior cervical ganglion provides sympathetic fibers to the lacrimal gland.
Anatomical Relations
The larger orbital part of the lacrimal gland (about the size and shape of an almond) is contained within a shallow fossa on the lateral aspect of the frontal bone. It lies above the levator palpebrae superioris and the lateral rectus muscles. Its inferior surface is attached to the fascia of levator palpebrae superioris; its posterior border is attached to the dense orbital fat; its anterior border is in contact with the orbital septum (palpebral fascia). The smaller palpebral part of the lacrimal gland extends inferior to the levator palpebrae superioris and to the lateral part of the upper eyelid. It is attached to the superior conjunctival fornix.
Function
The lacrimal gland is responsible for producing the aqueous component of tears. This watery secretion contains several proteins, such as lysozymes and immunoglobulin A, which protect the surface of the eye from infection, while maintaining the hydration of the epithelial surface of the eye.
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
