The lacrimal gland: Anatomical and functional features

The lacrimal gland is an exocrine gland that is very characteristic of humans. Thanks to the presence of this gland, we are able to express our emotions. However, many people still do not know the structure and function of this gland. Then let's read through the following article to better understand this rather special exocrine gland!

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• 1. The concept of lacrimal gland - tear gland
• 2. Structure of the lacrimal gland
• 3. The path of the epidemic
• 4. Nerve distribution of tear glands
• 5. Function of lacrimal and tear glands
• 6. Common diseases of the tear gland

1. The concept of lacrimal gland - tear gland

The lacrimal gland (tear gland) is an exocrine gland located above the eyeball, in the anterior part of the upper outer surface of each lacrimal gland. This is a gland that secretes a fluid called tears — an isotonic fluid — onto the surface of the eyeball. This fluid forms the aqueous component of the laminated tear film. It lubricates, protects and provides nutrients to the conjunctiva and cornea.

Glanderous

The fluid eventually drains through a series of ducts into the nasal cavity. When overproduced, glandular secretions form tears. The tear gland consists of two connected parts: the larger orbital part and the smaller one. The lacrimal gland and its associated drainage system form the lacrimal apparatus.

2. Structure of the lacrimal gland

The tear gland has an almond-shaped structure, about 2 cm in length. It is located anteriorly, superiorly to the lacrimal canal, in the lacrimal foramen of the frontal bone. The gland is divided into two adjacent parts (lobes) by the lateral fascia fibers of the levator ciliary muscle. All form part lacrimal and part eyelid. This division is only partially due to a posterior wall of parenchyma between the lobes.

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The human lacrimal gland consists of two types, namely: the primary lacrimal gland and the minor lacrimal gland. The main gland is located between the lacrimal fossa of the eyeball and the wall of the orbital bone, consisting of two parts: One is the orbital tear gland and the other is the lacrimal gland. In case of eye irritation, the tear glands produce more tears and we get watery eyes.

The accessory glands consist of many small glands located below the conjunctiva. Secretions from the accessory tear glands wash out the front part of the eye. Then, tears flow down the tear duct into the sinuses. The secretion works to keep the cornea moist, has a slight antibacterial ability because it contains a small amount of bactericidal substance.

3. The path of the epidemic

The lacrimal gland continuously secretes fluid into the lateral aspect of the superior omentum through the lacrimal duct. The fluid is spread over the entire surface of the eye, from the side to the inside, with each blink. At the center of the corner of the eye, the fluid collects in a triangular space called the lacrimal lake.

Tear bag

The tear fluid is then drained by the action of the lacrimal ducts, which are small channels in each eyelid, through the lacrimal foramen . The lacrimal foramen is the opening of the tear duct located on the papilla of the gland at the medial ends of the upper and lower eyelids.

From the lacrimal duct, fluid drains into the lacrimal sac, which is the dilated upper portion of the tear duct. The lacrimal sac is located in a fossa formed by the lateral surface of the lacrimal bone and the anterior sinus of the maxilla. From the lacrimal sac, the fluid is drained by the lacrimal duct that opens at the anterior end of the lower nostril.

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This duct passes through a bony canal (nasal canal) made up of the lacrimal bone, the upper jaw, and the lower nasal fissure. The liquid then drains posteriorly through the nasal cavity to the nasopharynx, where it mixes with mucus and is finally swallowed. A small amount of fluid is lost by evaporation or absorption through the conjunctiva.

4. Nerve distribution of tear glands

The lacrimal gland receives sensory, afferent impulses from the sympathetic and parasympathetic nervous systems. The tear gland nerve separates from the ocular branch of the trigeminal nerve that supplies internal sensation to this gland. Parasympathetic neurons stimulate the secretion of lacrimal glands.

Diagram of the lacrimal system

Preganglionic parasympathetic fibers from the central nervous system to the palatine ganglia. Via the major petrous nerve (a branch of the facial nerve) and the sphenoid nerve. These fibers synapse with post-neuronal parasympathetic fibers in the ganglia. Then moves in the zygomatic and zygomatic branches of the maxillary nerve to supply the gland.

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The afferent sympathetic nerve originates from the superior cervical ganglia. From this ganglion, nerve fibers travel to the palatine ganglia via the internal carotid plexus and the deep stone nerve. The sympathetic fibers then travel along the same pathway as the parasympathetic fibers supplying the lacrimal gland . Afferent sympathetic impulses regulate blood flow through the lacrimal gland and its secretion.

5. Function of lacrimal and tear glands

5.1. General function of tear glands

The lacrimal gland is responsible for the secretion of tears or secretions. Tears are secreted to wash away dirt from the eyes. At the same time, tears also have an antiseptic function, so it is considered a bodyguard of the eyes. Normally, the tear glands secrete only a small amount of tears. During the day, within 16 hours of waking up, the tear glands secrete about 500-600 mg of tears. When you sleep, your eyes are closed, and the tear glands are considered to be inactive.

Tear

In the inner corner of each eye, there are small holes that collect tears and drain them down the nose. Tears will flow down to mix with the nasal discharge and flow out. When we are tired or do not breathe new air for a period of time, the body accumulates a lot of CO2. Thereby stimulating the reflex nerve causing the yawning movement.

Along with the yawning movement, a large amount of air is released from the mouth. At the same time, there is pressure in the mouth. That pressure affects the nasal cavity, temporarily blocking the exit of tears. Because of this feature, tears from the lacrimal gland overflow into the eyes causing tears when yawning. When we are sad and cry, it is because the blood rushes to the nerves affecting the tear glands, causing tears to flow.

Yawning also produces tears

5.2. Function of tears

Our tears are not a useless fluid. On the contrary, it is also very useful for the body. Besides the function of helping people express emotions, it also has a very important function. It is to help the eyes avoid the invasion of bacteria and foreign objects. It also has the effect of killing bacteria and detoxifying.

Movie tears

With each blink of the eye, the eyelids draw a little fluid from these tear glands to clean and moisten the cornea. If the cornea is not wetted and cleaned regularly, the eye will dry out. This leads to dry eyes and worse vision loss.

When wet, dirt on the surface of the eye will also be washed away. What is very meaningful here is that after each blinking movement, the liquid secreted to clean the eyes will go down the nose. Through a small tube and then vaporized to the outside environment during respiratory activity.

Dry eye disease due to lack of tears

In general, both lacrimal and lacrimal glands act as a protective barrier for the eyes. They prevent dirt and bacteria from getting deep into the eyes. At the same time maintains moisture and cleanliness at the surface of the eye, preventing dry eyes. This helps to keep our eyes healthy.

6. Common diseases of the tear gland

Some common tear gland diseases include:

• Lacrimal gland blockage .
• Inflammation of the lacrimal gland .
• Cancer of the lacrimal gland .

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Hopefully with the information that the article has provided, readers will have a better understanding of the lacrimal gland or tear gland. From there, you will know the anatomical structure and function of this gland. This is a very useful exocrine gland, which helps to protect the windows of our soul.

Dr. Nguyen Lam Giang