Lacrimal gland

The lacrimal gland (latin: glandula lacrimalis) is a paired lobular gland located at the upper lateral corner of the orbit that is responsible for the production of tears.

The lacrimal gland consists of orbital and palpebral parts that are continuous posterolaterally around the concave lateral edge of the aponeurosis of the levator palpebrae superioris muscle. The orbital part of the lacrimal gland is located in a shallow fossa on the medial aspect of the zygomatic process of the frontal bone within the orbital margin. The palpebral part of the lacrimal gland is subdivided into two or three lobules and extends below the aponeurosis of the superior palpebral levator muscle into the lateral part of the upper eyelid, where it is attached to the superior conjunctival fornix. The palpebral part of the lacrimal gland is visible through the conjunctiva when the lid is everted.

The lacrimal gland receives both autonomic and sensory innervation. The lacrimal gland receives sensory nerve supply from the lacrimal nerve, a branch of the ophthalmic nerve (CN V1), via the communicating branch and the zygomatic nerve, a branch of the maxillary nerve (CN V2). The greater petrosal nerve, a branch of the facial nerve (CN VII), conveys the parasympathetic and sympathetic fibers to the lacrimal gland. The preganglionic parasympathetic fibers originate from a nucleus in the brainstem, synapse in the pterygopalatine ganglion, and the postganglionic parasympathetic fibers that join branches of the maxillary nerve to reach the lacrimal gland. The postganglionic sympathetic arise from the superior cervical ganglion of the sympathetic trunk and travel along with the parasympathetic fibers (without synapsing in the pterygopalatine ganglion) to innervate the lacrimal gland.

The blood supply to the lacrimal gland is provided by the ophthalmic artery with its branch - the lacrimal artery, while the venous blood is drained from this region via the superior ophthalmic vein.

There are three main types of tears produced by the lacrimal gland. These are basal tears that are responsible for keeping the eye moist and nourished, reflex tears that are produced as an answer to an irritation for lubrication and cleansing of the eyes, and psychic tears that are secreted during a process that is called crying most oftenly in response to strong emotions, stress or pain. The composition of tears can vary based on their type and functions, but the main components are water, salts, antibodies, as well as antibacterial enzymes.