What Is the Lacrimal Gland?

The lacrimal gland is located in the lacrimal gland of the frontal bone above the outer orbit. It is approximately 20 mm long and 12 mm wide. It is fixed to the orbital periosteum by connective tissue. The lateral aponeurosis of the superior levator muscle passes through it to divide the lacrimal gland into larger orbital lacrimal glands and Smaller lacrimal glands, under normal circumstances can not touch the lacrimal glands on the eyelids. The superior levator muscle, the Lockwood ligament, and the lower supporting ligament play an important role in the fixation of the lacrimal gland. If the tension of the aforementioned ligament or superior levator muscle is weakened, lacrimal gland ptosis occurs clinically. The upper part of the lacrimal gland is closely adhered to the orbital periosteum, the posterior part is connected to the orbital fat, the lower part is adjacent to the eyeball, and the medial end lies above the superior levator muscle. At the same time, the lacrimal gland itself is dense and fragile and easily broken. Periosteum and surrounding tissues are prone to recurrence after surgery. The lacrimal gland's blood supply comes from the lacrimal gland arteries, which branch from the ophthalmic artery, and enters the center of the posterior lacrimal gland. The blood returns through the lacrimal gland vein into the superior eye vein, and finally flows into the cavernous sinus. The nerves of the lacrimal gland have three kinds of nerve components. The sensory nerves come from the branch of the eye of the trigeminal nerve. The secretory cells of the lacrimal gland and the outer branch of the excretory duct form a neural network to supply the glands. The last part passes through the glands to supply the lateral conjunctiva and eyelid skin. A considerable part of the cases of lacrimal glandular tumor type adenocarcinoma show the symptoms of sensory nerve invasion in the early stage of onset. Clinically, the eyeballs are not prominent prominently, but the affected eye pain and headache have become an important complaint. This is due to sensory nerves. The periphery is caused by cancer cell infiltration, which is very helpful for diagnosis and differential diagnosis; sympathetic nerve fibers from the internal carotid plexus and parasympathetic nerve fibers of the facial nerve control the lacrimal gland secretion. Sympathetic nerves control normal lacrimal secretion, and parasympathetic nerves control large amounts of tear secretion. If the lacrimal glands are removed, as long as the para-lacrimal glands and goblet cells are not destroyed, conjunctival desiccation does not necessarily occur clinically.

The lacrimal gland is located in the lacrimal gland of the frontal bone above the outer orbit. It is approximately 20 mm long and 12 mm wide. It is fixed to the orbital periosteum by connective tissue. Smaller lacrimal glands, under normal circumstances can not touch the lacrimal glands on the eyelids. The superior levator muscle, the Lockwood ligament, and the lower supporting ligament play an important role in the fixation of the lacrimal gland. If the tension of the aforementioned ligament or superior levator muscle is weakened, lacrimal gland ptosis occurs clinically. The upper part of the lacrimal gland is closely adhered to the orbital periosteum, the posterior part is connected to the orbital fat, the lower part is adjacent to the eyeball, and the medial end lies above the superior levator muscle. At the same time, the lacrimal gland itself is dense and fragile and easily broken. Periosteum and surrounding tissues are prone to recurrence after surgery. The lacrimal gland's blood supply comes from the lacrimal gland arteries, which branch from the ophthalmic artery, and enters the center of the posterior lacrimal gland. The blood returns through the lacrimal gland vein into the superior eye vein, and finally flows into the cavernous sinus. The nerve of the lacrimal gland has three kinds of nerve components. The sensory nerve comes from the branch of the eye of the trigeminal nerve. The secretory cells of the lacrimal gland and the outer branch of the excretory duct form a neural network to supply the glands. A considerable part of the cases of lacrimal glandular tumor type adenocarcinoma show the symptoms of sensory nerve invasion in the early stage of onset. Clinically, the eyeballs are not prominent prominently, but the affected eye pain and headache have become an important complaint. This is due to sensory nerves. The periphery is caused by cancer cell infiltration, which is very helpful for diagnosis and differential diagnosis; sympathetic nerve fibers from the internal carotid plexus and parasympathetic nerve fibers of the facial nerve control the lacrimal gland secretion. Sympathetic nerves control normal lacrimal secretion, and parasympathetic nerves control large amounts of tear secretion. If the lacrimal glands are removed, as long as the para-lacrimal glands and goblet cells are not destroyed, conjunctival dryness does not necessarily occur clinically.

Chinese name

Lacrimal gland

Make up

Made of thin tubular glands and ducts

lie in

In the lacrimal gland above the orbit

Upper part

Orbital

Lower part

Eyelid

Structure

Lacrimal gland

Lacrimal gland I. Overview:

The lacrimal gland consists of secretory acinars that secrete tears and ducts that drain them. The acinar consists of two layers of cells, the cylindrical cells are the real lacrimal gland secreting cells, and they form a round cavity. In addition to the cylindrical cells, there is a flat muscle epithelium, which is contractile, and outside is the basement membrane. The catheter has two layers of cells, the inner cells are columnar or cubic, and the outer layers are flat. The stroma is derived from mesoderm tissue deep in the conjunctiva. The secretion of the acinar enters the collection tube between the lobules, starting with the intralobular glandular tube, moving backward into the extralobular glandular tube, and finally opening in the draining tube. The lacrimal gland has 10 to 20 excretory tubes. The excretory tubes open in the temporal superior fornix conjunctiva. The lacrimal gland is an exocrine gland that produces serous fluid. The tear fluid is discharged into the conjunctival sac through the excretory tube, which acts as a lubricating and protecting eyeball. Lacrimal fluid originates from the basal and reflex secretions of the lacrimal glands. Basal secretions are produced by glands and tissues that secrete mucus, watery fluids, and lipids. During sleep, the basal secretion process still exists, and its secretion gradually decreases with age. Basal secretion is not eternally innervated. Reflex secretions are produced by the lacrimal glands, which are innervated. Reflex secretion can be divided into: peripheral sensory reflex secretion, which occurs in any stimulus such as conjunctiva, cornea, pigmented membrane, nasal mucosa and surrounding skin; retinal reflex secretion, which is the reverse secretion of light that stimulates the retina into the eye It provides tears at the same time as the basal secretion, which constitutes normal tear flow. The retina adapts to light and keeps the tear flow constant. When the light stimulation is enhanced, the tear flow often changes. In complete darkness or closed eyes, the reverse Secretion stops; reverse spiritual secretion, any emotional stimulus can cause reflex tear secretion. Generally, the basic secretion of tears can meet the needs of lubricating the eyes, and the reflexive secretion of lacrimal glands can provide a large amount of tears for emergency needs. After the tears are secreted, the eyelids are used to lubricate the surface of the eyeballs by the instantaneous action of the eyelids, and most of them are evaporated. Because the lipid secreted by the meibomian glands is on the edge of the eyelids, the remaining small amount of tears does not overflow and stays in the conjunctival sac. The contraction of the orbicularis oris muscles moves from the outside of the conjunctival sac through the tear river to the tear lake of the medial condyle, enters the upper and lower punctum, lacrimal canaliculus, lacrimal duct, lacrimal sac, and nasolacrimal duct, and drains into the nasal cavity on the outer wall of the lower nasal passage.

In addition, there are para-lacrimal glands located in the fornix conjunctiva, including Krause, Wolfring, and Ciaccio glands, which secrete serous fluid. The tissue structure of the para-lacrimal gland is very similar to that of the lacrimal gland, but its location is different from that of the lacrimal gland. The Krause gland is located near the fornix of the upper and lower conjunctiva. There are 20 on the upper eyelid and 8 on the lower eyelid. Their drainage ducts have a small lumen, a gland connected to a separate catheter, and an opening in the upper vault. The upper edge of the meibomian has the same serous glands, called Wolfring glands. There is also a para-lacrimal gland with the same structure on the half-moon pupa and lacrimal fu. In theory, any lesion that can occur in the lacrimal gland can also occur in the para- lacrimal gland. However, in clinical practice, the lesions of the lacrimal gland are far more than those of the para- lacrimal gland.

Lacrimal gland , tearing:

Tears refer to the excessive secretion of tears, which can not be discharged normally but flow out from the cleft lip.

Common diseases

1. Inflammatory stimulation: conjunctivitis, keratitis, iridocyclitis, scleritis, blepharitis, electro-optic ophthalmia, etc.

2.Exogenous stimuli: irritation of wind, sand, dust, light, poisonous gas, etc., foreign bodies and abrasions and lacerations in the cornea and conjunctiva, epitheliitis and epithelial detachment, trichiasis, inversion of the eyelids, and incomplete closure of the eyelids cause corneal and conjunctival exposure.

3. Systemic factors: pain irritation and mental factors.

Patients often complain of constant tears or "tears" in their eyes. Excessive tear secretion or obstruction of lacrimal passage can cause tears to flow out of the conjunctival sac. Seen at:

1. Environmental irritation, inflammation of the anterior segment of the eye, trauma, or foreign matter retention, etc., can cause tears to affect the reflex arc of the tear secretion nerve. In particular, corneal lesions, due to the dense distribution of corneal nerves, mild irritation can cause a large amount of tear secretion, often accompanied by pain, photophobia, blepharospasm and other irritation symptoms, and tears are mostly secondary symptoms. When a corneal penetrating injury occurs, the patient can consciously "tear" because of the outflow of aqueous humor.

2. Punctal occlusion, abnormal eyelid position, or facial nerve paralysis caused by lacrimal ectropion, lacrimal duct obstruction, etc. can cause frequent tears, the course of which can be months or years, more common in the elderly.

3. Infants with tears are mostly nasolacrimal duct obstruction and congenital glaucoma.