Lacrimal Gland & Tears Flashcards
Three major components of the Lacrimal System (3)
Lacrimal and Accessory Glands
Tear Film
Lacrimal Drainage System
Location of Lacrimal Gland
Upper temporal corner of frontal bone, in lacrimal fossa
Dimension of Lacrimal Gland
20mm long and 5mm thick
What divides the lacrimal gland into two lobes
Aponeurosis of levator palpebrae superioris tendon
What is the name of the larger lobe situated above the levator
Orbital Lobe
Name of the smaller lobe below the levator
Palpebral lobe
Which lobe is attached to the conjunctiva and where (2)
Palpebral lobe
Upper temporal fornix
Number of lacrimal gland ducts
4-5 ducts
Where do Orbital and Palpebral lacrimal gland ducts open into
Upper temporal conjunctival fornix
How many Orbital lacrimal ducts are there
4-5 ducts (crosses palpebral lobe)
How many palpebral lacrimal ducts are there
8 ducts
What do the lacrimal glands consist of
Smaller lobules containing small sacs arranged into branches
What are the layers of the small sacs of the lacrimal lobules (2)
Outer layer
Inner layer
Function of the outer layer of the small sacs of the lacrimal gland
Contract for bulk expression of tears - squeezes the sac
Function of the inner layer of the small sacs of the lacrimal gland
Steadily secretes serous fluid and mucin
Features: Glands of Krause (3)
Located in the stroma of the palpebral conjunctiva
20-40 in upper fornix
8-10n in lower fornix
Features: Glands of Wolfring (2)
3-5 glands
Located in upper regions or superior tarsal conjunctiva
Blood Supply
Lacrimal Artery
Blood Drainage
Superior and inferior ophthalmic veins
Nerve Supply: Outer layer
Parasympathetic fibres from Facial Nerve
Nerve Supply: Vessels of gland
Sympathetic fibres
Nerve Supply: Sensory Innervation
Lacrimal nerve branch by Ophthalmic nerve (Trigeminal Nerve)
Tear film: Which structures provide secretions (3)
Lacrimal glands
Tarsal glands
Goblet cells
Tear film: Function
Helps maintain anterior corneal hydration and transparency
Tear film: Figures (3)
98% water
pH 7.3-7.5
Osmotic Pressure = 0.9% sodium chloride solution
Produced by: Oily Lipid Phase
Meibomian glands
Zeis glands
Produced by: Aqueous Phase
Lacrimal glands
Accessory glands
Produced by: Mucus Phase
Goblet cells
Structure: Oily Lipid Phase
0.2-0.9um
Phospholipids
Figures: Aqueous Phase
6.5-7.5um
Mostly water
Electrolytes
Salts
Immunoglobins
Figures: Mucus Phase
0.5um
Mucin
Leukocytes
Function: Oily Lipid Layer
Reduces evaporation
Prevents lids sticking
Lubricates lid margins
Stops tears falling
Barrier effect
Function: Aqueous Phase
Allows gaseous exchange
Hydrates cornea
Removes waste products
Function: Mucus Phase
Allows tears to attached to hydrophobic cornea
Adds bulk to tears
Aids protection against microbial keratitis
The formation caused by the surface tension of the tears and it’s name
Meniscus to form at each eye lid known as lacrimal river
Where are the tears drawn to
Lacrimal Puncta at the nasal lid margins
Where do the tears travel once in the puncta
Lacrimal sac through the Sinus of Mai9er
Where do the tears travel from the Lacrimal Sac
To the nasolacrimal duct through the lacrimal foramen
What prevents back flow of the tears and where is it located
Valve of Hasner and it is at the bottom of the nasolacrimal duct
What part of the conjunctive does the lacrimal gland secretions enter
Upper temporal fornix
What does the secretion of the lacrimal gland mix with to form the tear film
Secretions of the accessory lacrimal glands and goblet cells
What happens to cause movement of tears into the lac rimal sac
Contraction of orbicularis shortens canaliculi and expels tears
