Lacrimal gland

Lacrimal Gland

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Lacrimal gland

The lacrimal glands are paired almond-shaped glands, one for each eye

Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
, that secrete the aqueous layer of the tear

Tears

Tears are the liquid product of a process of lacrimation to clean and lubricate the eyes. The word lacrimation may also be used in a medical or literary sense to refer to crying....
film. They are situated in the upper, outer portion of each orbit

Orbit (anatomy)

In anatomy, the orbital bone is the cavity or socket of the skull in which the eye and its adnexa are situated.It can also mean the skin which surrounds the eye of a bird....
. Inflamation of the lacrimal glands is called lacrimitis.

lacrimal gland is divided into orbital and palpebral portions by the aponeurosis

Aponeurosis

Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, and are histologically similar to tendons, but are very sparingly supplied with blood vessels and nerves....
of the Levator palpebrae superioris muscle

Levator palpebrae superioris muscle

The levator palpebrae superioris is the muscle in the orbit that elevates the superior eyelid....
, the portions are continuous with each other.

The orbital portion contains fine interlobular duct

Interlobular duct

A Interlobular duct is a gland duct which connects more than one lobule. It is smaller than an interlobar duct.Examples of where it can be found include...
s 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.

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Gross anatomy

Each lacrimal gland is divided into orbital and palpebral portions by the aponeurosis

Aponeurosis

Levator palpebrae superioris muscle

The levator palpebrae superioris is the muscle in the orbit that elevates the superior eyelid....
, 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
Lacrimal fossa

The inferior surface of each orbital plate of the frontal bone is smooth and concave, and presents, laterally, under cover of the zygomatic process, a shallow depression, the lacrimal fossa , for the lacrimal gland....
of the orbit.
For the smaller palpebral portion, its inferior surface lies close to the eye; if the upper eyelid
Eyelid

An eyelid is a thin fold of skin that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body....
is everted, the palpebral portion can be seen.

The orbital portion contains fine interlobular duct

Interlobular duct

Fornix

The fornix is a C-shaped bundle of fibres in the brain, and carries signals from the hippocampus to the mammillary bodies and septal nuclei....
conjunctiva of the upper lid, and pass over the eye surface to the lacrimal puncta

Lacrimal punctum

The lacrimal canaliculi, one in each eyelid, commence at minute orifices, termed puncta lacrimalia , on the summits of the papillae lacrimales, seen on the margins of the lids at the lateral extremity of the lacus lacrimalis....
.

Microanatomy

The lacrimal gland is a compound tubuloacinar gland, it is made up of many lobules separated by connective tissue

Connective tissue

Connective tissue is a form of fibrous biological tissue.It is one of the four types of tissue in traditional classifications .Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% of the total protein content....
, 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

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine. By extension, a lumen can also be the inside space of a cellular component or structure, such as the endoplasmic reticulum....
.

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

Facial nerve

The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla oblongata, and controls the muscles of facial expression, and taste to the anterior two-thirds of the tongue....
in the pons

Pons

The pons is a structure located on the brain stem. It is cranial to the medulla oblongata, caudal to the midbrain, and ventral to the cerebellum....
. Just distal to the geniculate ganglion

Geniculate ganglion

The geniculate ganglion is an L-shaped collection of fibers and sensory neurons of the facial nerve located in the facial canal of the head. It receives fibers from the motor, sensory, and parasympathetic nervous system components of the facial nerve and sends fibers that will innervate the lacrimal glands, submandibular glands, sublingual g...
, the facial nerve gives off the greater petrosal nerve. This nerve carries the parasympathetic secretomotor fibers through the pterygoid canal

Pterygoid canal

The pterygoid canal is a passage in the skull leading from just anterior to the foramen lacerum in the middle cranial fossa to the pterygopalatine fossa....
to the pterygopalatine ganglion

Pterygopalatine ganglion

The pterygopalatine ganglion is a parasympathetic ganglion found in the pterygopalatine fossa. It is one of four parasympathetic ganglia of the head and neck....
. Here the fibers synapse and postganglionic fibers join the fibers of the Maxillary Nerve, which travels through the inferior orbital fissure

Inferior orbital fissure

The lateral wall and the floor of the Orbit are separated posteriorly by the inferior orbital fissure which transmits the maxillary nerve and its zygomatic branch, and the ascending branches from the sphenopalatine ganglion....
. Once it has traversed this opening, the parasympathetic secretomotor fibers branch off with the zygomatic nerve

Zygomatic nerve

The zygomatic nerve is a branch of the maxillary nerve that enters the orbit and helps to supply the skin over the zygomatic bone and temporal bones....
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
Sympathetic

The word sympathetic means different things in different contexts.* In neurology and neuroscience, the sympathetic nervous system is a part of the autonomic nervous system....
postganglionic fibres originate from the superior cervical ganglion

Superior cervical ganglion

The superior cervical ganglion , the largest of the cervical ganglia, is placed opposite the second and third cervical vertebr?. It contains neurons that supply sympathetic nervous system innervation to the face....
. 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

Lacrimal artery

The lacrimal artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic artery: not infrequently it is given off before the artery enters the Orbit ....
, derived from the ophthalmic artery

Ophthalmic artery

The ophthalmic artery is a branch of the internal carotid artery which supplies branches to supply the eye and other structures in the orbit . It enters the orbit together with the Optic nerve through the Optic canal....
supplies the lacrimal gland. Venous blood returns via the superior ophthalmic vein

Superior ophthalmic vein

The superior ophthalmic vein begins at the inner angle of the orbit in a vein named the nasofrontal which communicates anteriorly with the angular vein; it pursues the same course as the ophthalmic artery, and receives tributaries corresponding to the branches of that vessel....
.

Pathology

Dacryoadenitis
Dacryoadenitis

Dacryoadenitis is inflammation of the lacrimal glands . Also described as a blocked tear duct....
Sjögren's syndrome
Sjögren's syndrome

Sj?gren's syndrome is an autoimmunity in which immune cells attack and destroy the exocrine glands that produce tears and saliva.It is named after Swedish ophthalmology Henrik Sj?gren , who first described it....

Lacrimal gland

Gross anatomy

Microanatomy

Innervation

Blood supply

Pathology

Additional images

See also

External links