Lacrimal gland

The lacrimal gland (Latin lacrimal gland ) is a gland in the production of most of the tear fluid. The lacrimal gland is located within the orbit of the eye laterally on top. It produces electrolytes, and a large number of protein compounds. My secretion is ( conjunctival fornix ) 6-12 excretory ducts into the vault of the conjunctival sac directed and spread over the eyelid over the cornea. The tear fluid keeps the cornea moist and nourished them.

The lacrimal gland, together with the additional lacrimal gland the producing portion of the lacrimal system. The tears formed liquid is passed through the lacrimal duct into the nasal cavity.

Histology

The lacrimal gland of man is a pure serous gland with tubuloazinösen end pieces, and differential diagnosis to distinguish as such in the light microscopic preparation of the parotid and the pancreas: A switching and strip piece system is not formed in contrast to the parotid gland, islets of Langerhans and centroacinar cells exist only in the pancreas. Fat cells in varying numbers but can occur in both parotid and in the lacrimal gland.

The acinar cells secrete a day about 500 milliliters of NaCl-containing secretions, which also includes factors for defense against pathogens such as lysozyme or immunoglobulin A.

Innervation

The lacrimal gland is innervated by sympathetic, parasympathetic and somatosensory nerve fibers.

The proportion of the parasympathetic nervous system stimulates the production of secretions of the lacrimal gland. The post-ganglionic ( second neuron ) fibers come from the pterygopalatine ganglion, originating from the facial nerve, the seventh cranial nerve. The parasympathetic fibers of the facial nerve originate in the superior salivatory nucleus and drag to the geniculate ganglion through which they pass through it but Not interconnected. This arises from the greater petrosal nerve, which the deep petrosal nerve (from the internal carotid plexus ) applies. Both move in together as the pterygopalatine nerve of the pterygoid canal through the pterygoid canal ( in the root of the pterygoid processes of the sphenoid bone ) to the ganglion. Here, the ( presynaptic ) fibers can be switched to the lacrimal gland to the second neuron.

The fibers for the lacrimal gland emerge from the ganglion in the pterygopalatine and put the nerve zygomatic ( a branch of the maxillary nerve, which originates from the trigeminal nerve ) as it passes through the foramen rotundum into the cranial cavity to follow him through the orbital fissure the inferior orbital and leave him there for a communicating branch. You lie down on the lacrimal nerve ( a branch of the ophthalmic nerve of the trigeminal nerve ) and get together with it to its destination, the lacrimal gland.

The sensory innervation of the lacrimal gland is done by the lacrimal nerve (V1 ), which is the parasympathetic fibers last anneal.

The sympathetic nervous system has an inhibitory effect on the production of secretions, presumably where it causes vasoconstriction. Sympathetic fibers are from the superior cervical ganglion and form the internal carotid plexus. They converge to the deep petrosal nerve, contact the internal carotid artery through the carotid canal, lie down ( as described above ) the greater petrosal nerve and eventually reach the pterygopalatine ganglion. You leave this without switching, lie the zygomatic nerve and the lacrimal nerve and thus reach the area of the lacrimal gland.

Vascular supply

The arterial supply via the lacrimal artery, a branch of the ophthalmic artery. The blood outflow via the jugular lacrimal, which then empties into the superior ophthalmic vein.

Diseases of the lacrimal gland

With an increased production of tears it comes to Augenträufeln ( epiphora ). Such overproduction is mostly a reflex response to irritation of sensitive nerve endings of the eye, particularly the cornea. It therefore represents no disease "in itself" is, rather than a normal (physiological ) protection response to a pathological condition (eg foreign body, pathogens, physical or chemical stimuli). Overproduction can also be caused by emotional stimuli ( crying). A drainage of the lacrimal drainage system can also at normal tear production lead to epiphora. Decreased tear production by a decreased expression of lacritin is the cause of keratoconjunctivitis sicca ( ​​" dry eye ").

Inflammation of the lacrimal gland are called Dacryoadenitis and are rare. When Heerfordt syndrome is a chronic inflammation of the lacrimal gland is combined with inflammation of the parotid gland. Sjogren's syndrome is an autoimmune disease of the body, which also relates to the lacrimal and salivary gland, among other things. Also in Mikulicz 's syndrome, a reactive swelling of the lacrimal and salivary glands in various general and systemic diseases - for example, in Hodgkin and non -Hodgkin's lymphoma, leukemia, and sarcoidosis, also in some tuberculosis, syphilis, Sialadenosis and hyperthyroidism - a lacrimal gland inflammation can be observed.

An incident of the lacrimal gland in humans is occasionally before, but also in animals ( guinea pigs, pea eye ). This is where the lacrimal gland pushes under the conjunctiva in the upper part of the eye and is visible here as a whitish- yellow mass. The lacrimal gland prolapse is harmless and requires no treatment at other freedom from symptoms.

Other lacrimal glands

Besides the actual lacrimal gland found in the eyelids, meibomian glands, which produce a liquid fatty substance that stabilizes the tear film. Its function is depending on hormonal fluctuations. Be found on the eyelashes, the openings of the minor glands, which produce substances that are effective against disease-causing germs.

In the conjunctival sac of the accessory (additional) lacrimal glands found ( lacrimal glands accessoriae ). It is here in the mucous glands embedded packages. Such accessory glands are located in the wall of the conjunctiva ( Glandulae conjunctivales, Krause 's glands, Wolf Ring glands ), the nictitating membrane ( Glandulae tertiae palpebrae, Harderian gland ) and the dog in the Tränenkarunkel ( parotid carunculae lacrimal ). These are similar to the fine structure of the actual lacrimal gland and contribute to the production of the aqueous component of the tear film in liquid. The additional lacrimal glands are parasympathetic fibers run in the vagus infratrochlearis supplied.

Swell

• Exocrine gland
• Anatomy of the eye
• Facial
• Glandular tissue