All are single bone in the skull EXCEPT:
a- Lacrimal. ***
b- Occipital.
c- Sphenoid.
d- Parietal.
---------------------------
Tear fluid is an aqueous saline fluid that flows to the outer surface of the cornea and conjunctiva of the eye. When the flow is outside the eye, it forms tears.
It is permanently produced by the lacrimal glands and spreads evenly over the anterior surface of the eye.
Normally, it flows through the lachrymal canal to the nasal cavity where it is eliminated in the air as microscopic droplets during the breathing process.
But in some cases (pathological, or more generally emotional) the lacrimal secretion is too important and the natural pathways are saturated and no longer evacuate the excess secretion. The nasal fossae can no longer spray the excess liquid, it flows from the nose and the eye ending its course on the face in the form of tears where it is, in part, retained by the various hairs of the skin.
Composition:
Tear fluid is produced by filtration of blood from excretory cells of the lacrimal glands, however some components of this fluid (such as lysozyme) are not present in the blood and are synthesized directly by these glands.
The composition of this liquid varies slightly according to the layers of the latter:
- The superficial layer is secreted by the Meibomian glands located on the inner surface of the eyelid, this layer consists of lipids. It makes it possible to limit the natural evaporation of the tears (aqueous layer).
- The intermediate layer is aqueous, contains the different nutrients and allows the humidification of the eye, the transport of oxygen, carbon dioxide. It is secreted by the lacrimal glands called accessories.
- The deep layer is the mucinic layer: a thin film slightly viscous because containing proteins, similar to a mucus that is evenly distributed on the surface of the eye; its role is to control the regular distribution of the intermediate and superficial layers on the ocular surface. It is secreted by the mucous glands and glandular cells of the conjunctiva.
Alteration of one or more of these layers may result in dry eye.
Finally, the lacrimal fluid secreted during tearing is essentially watery (almost 99% water). It contains, among others, sodium chloride, lysozyme and lactotransferrins. It is secreted by the main lacrimal gland located behind the upper edge of the orbit.
Associated pathologies:
- Dacryocystitis: lacrimal gland infection
- Sjögren's Syndrome
- Dry syndrome, (disease with dry eye)
- Mikulik syndrome,
- Bacterial or viral conjunctivitis (lacrimal fluid infection)
- Allergic conjunctivitis (hypersecretion of liquid by irritation of the conjunctiva)
- Keratitis
- Some fractures of the facial mass can obstruct, during their consolidations, the nasolacrimal duct: thus there is a permanent excess of tear fluid on the surface of the eye and this one continually flows on the face.
a- Lacrimal. ***
b- Occipital.
c- Sphenoid.
d- Parietal.
---------------------------
Tear fluid is an aqueous saline fluid that flows to the outer surface of the cornea and conjunctiva of the eye. When the flow is outside the eye, it forms tears.
It is permanently produced by the lacrimal glands and spreads evenly over the anterior surface of the eye.
Normally, it flows through the lachrymal canal to the nasal cavity where it is eliminated in the air as microscopic droplets during the breathing process.
But in some cases (pathological, or more generally emotional) the lacrimal secretion is too important and the natural pathways are saturated and no longer evacuate the excess secretion. The nasal fossae can no longer spray the excess liquid, it flows from the nose and the eye ending its course on the face in the form of tears where it is, in part, retained by the various hairs of the skin.
Composition:
Tear fluid is produced by filtration of blood from excretory cells of the lacrimal glands, however some components of this fluid (such as lysozyme) are not present in the blood and are synthesized directly by these glands.
The composition of this liquid varies slightly according to the layers of the latter:
- The superficial layer is secreted by the Meibomian glands located on the inner surface of the eyelid, this layer consists of lipids. It makes it possible to limit the natural evaporation of the tears (aqueous layer).
- The intermediate layer is aqueous, contains the different nutrients and allows the humidification of the eye, the transport of oxygen, carbon dioxide. It is secreted by the lacrimal glands called accessories.
- The deep layer is the mucinic layer: a thin film slightly viscous because containing proteins, similar to a mucus that is evenly distributed on the surface of the eye; its role is to control the regular distribution of the intermediate and superficial layers on the ocular surface. It is secreted by the mucous glands and glandular cells of the conjunctiva.
Alteration of one or more of these layers may result in dry eye.
Finally, the lacrimal fluid secreted during tearing is essentially watery (almost 99% water). It contains, among others, sodium chloride, lysozyme and lactotransferrins. It is secreted by the main lacrimal gland located behind the upper edge of the orbit.
Associated pathologies:
- Dacryocystitis: lacrimal gland infection
- Sjögren's Syndrome
- Dry syndrome, (disease with dry eye)
- Mikulik syndrome,
- Bacterial or viral conjunctivitis (lacrimal fluid infection)
- Allergic conjunctivitis (hypersecretion of liquid by irritation of the conjunctiva)
- Keratitis
- Some fractures of the facial mass can obstruct, during their consolidations, the nasolacrimal duct: thus there is a permanent excess of tear fluid on the surface of the eye and this one continually flows on the face.
Labels
Health Specialties