The Lacrimal System Part 1 Flashcards
The primary provider of the aqueous secretory component to the tear film is called what?
The main lacrimal gland.
Where is the main lacrimal gland located?
Lacrimal fossa.
What are the two parts of the lacrimal gland?
Orbital and palpebral lobe.
What separates the lacrimal gland into two lobes?
Lateral horn of the levator and extensions of Mueller’s muscle.
What color is the lacrimal gland when the upper lid is everted?
Pinkish gray appearance.
The main lacrimal gland is surrounded by ______________ and is made up of many ______ that drain into progressively ___________.
Connective tissue; acini; larger tubules.
What type of cells are acini?
Myoepithelial cell layer.
Why is it important that acini are myoepithelial cells?
Lacrimal gland requires muscle movement to allow contents to be drained.
When does the lacrimal gland start developing?
Near third month of fetal life but not functional until after birth.
When do newborn babies start producing tears?
2 weeks after born. (May be as long as 2 months).
What are the two accessory lacrimal glands?
Glands of Krause and Wolfring.
What is an accessory lacrimal gland?
Secondary provider of the aqueous secretory component to the tear film.
Where is the Wolfring gland located?
Tarsal plate of eyelid.
Where is the gland of Krause located?
Conjunctival fornix.
The arterial supply to the lacrimal gland comes from where?
The lacrimal branch of the ophthalmic artery, a branch of the infraorbital artery, the recurrent meningeal artery.
The lacrimal gland is innervated by which cranial nerve?
Lacrimal branch of the trigeminal nerve V.
How many layers does the tear layer have? What does the tear film consists of? What structure of the eye does the tear film cover?
- Mucous, aqueous, and oily layer. Cornea and conjunctiva.
The primary source of ________ to cornea is from the tear film.
Oxygen.
Why does cornea need oxygen?
Cornea is avascular, doesn’t have its own blood supply.
What does the tear film contain to help protect the cornea and conjunctiva from infection?
Antibacterial proteins.
The outermost lipid layer of the tear film is made and secreted by what?
Modified sebaceous glands, meibomian glands and gland of Zeiss (oil layer of fair follicle).
The middle aqueous layer of the tear film is made and secreted by what?
Lacrimal gland, gland of Krause and Wolfring.
The innermost mucous layer of the tear film is made and secreted by what?
Goblet cells, epithelial cells, and very little from the lacrimal gland.
How thick is the lipid layer?
0.1 microns.
How thick is the aqueous layer?
7 microns.
How thick is the mucous layer?
0.05 microns.
What is main contributor to the tear film?
Lacrimal gland.
How many meibomian glands are in the upper lid?
30-40 glands.
How many meibomian glands are in the lower lid?
20-30 glands.
What helps release the meibomian material from the ducts onto the tear film?
Blink.
Discharge secretion contains the entire secreting cells laden with the secretory material is known as what?
Holocrine secretion.
How is the meibomian gland regulated?
Not sure, but thought by controlling he rate of lipid synthesis in the endoplasmic reticulum and by regulating the rupture of alveolar cells.
What are some possible ways meibomian glands are regulated?
Androgen sex steroids (may regulate synthesis and secretion), neurotransmitters (from nerves surrounding the acini).
What are two possible ways the meibomian glands are neural regulated?
VIP, and NPY.
Vasoactive intestinal peptide, neuropeptide Y
Low order of tear secretion is during what?
Normal activities.
High order of tear secretion is during what?
Reflex tearing or crying.
Not only does the lacrimal gland secrete aqueous solution into the tear film, but they also secrete what?
Mixture of nutrients, growth factors, glycoproteins and immunoglobulins in an isotonic Na+-, K+-, and Cl- rich solution.
What is the predominant cell type in lacrimal glands?
Acinar cells.
The final tear aqueous fluid is a mixture of what?
NaCl-rich fluid.
Essentially, what three things make up the aqueous layer?
Proteins, electrolytes, and water.
What is included in the protein part of the aqueous layer?
Lysozyme, lactoferrin, lipocalin, immunoglobulin A, growth factors, interleukins.
Lacrimal gland dysfunction may indicate dry eye condition often termed as what?
Sjorgren’s Syndrome.
Severely dry eyes may lose what in their cornea?
Transparency.
Corneal and conjunctival epithelia are minor contributors to the aqueous humor. What do they release? What do they not release?
Electrolytes and water. Proteins.
Primary source of the mucous layer of the tear film is called what?
Goblet cells.
What is inside the mucous layer?
Mucins.
What does mucin contain?
Collection of large heterogenous glycoproteins and at least 50% carbohydrates by mass.
Mucous layer is secreted by activation of what?
Sensory nerves.
What is the secondary source of mucous layer?
Stratified squamous cells of the conjunctiva and corneal epithelia.
The opening on the medial portion of each eyelid where tears drain is called what?
Punctum.
The superior and inferior canaliculi are lined with what type of cell?
Striatified squamous epithelium.
The superior and inferior canaliculi are surrounded by which muscle?
Orbicularis oculi.
What percentage of people have the common canaliculus?
90%.
Nasolacrimal sac has a structure present at the opening of the duct into the nose. What is this structure called?
Hasner’s valve.
What percentage of tears is lost to evaporation?
10-25%.
Due to gravity, which punctum drains 4 times more tears than the contralateral punctum.
Inferior punctum.
What can be used to allow tears to remain in our eyes?
Punctal plug.
What theory states that the contraction of the pretarsal orbicularis muscle fibers during eyelid closure compresses and shortens the canaliculi to allow tear to flow towards the lacrimal sac.
Lacrimal Pump Theory.
Why does facial paralysis lead to epiphora (excessive tearing down face)?
Orbicularis muscle doesn’t do its job, lacrimal pump theory doesn’t work, shortening of the canaliculi doesn’t occur so tear never flows through the lacrimal sac.
What is the volume of tears drained per blink?
2.0 ml.
True or False: 5 blinks transports more tears than 1 min of basic secretion.
False. One blink.
The lacrimal excretory system usually functions below capacity or above capacity?
Below capacity.
What does the Doane Blink model emphasis?
Compression of the canaliculi and to lesser extend, nasolacrimal sac during eyelid closure.
When does siphoning by the lacrimal sac occur?
During relaxation of the blink.
does gravity increase or decrease lacrimal drainage?
Increase.
What three things can lead to insufficient tear layers?
Sjogren’s syndrome, increase in age, compromised innervation.
What are causes of dry eye complaints in contact lens wearers?
Insufficient tears, poor quality tears, incomplete blinking, infrequent blinking when focusing, blepharitis (inflammation of eyelid).
Why is Jones test necessary?
To see if patient has a blockage in the canaliculi. See is patients has epiphora.
What is the second part of Jones test for?
To see where obstruction occurred.
