Lacrimal System & Dry Eyes Anatomy Flashcards
What are the three layers of the tear film?
Lipid (superficial)
Aqueous
Mucous (deep)
What is the lacrimal gland?
A tubule-alveolar gland consisting of acini and ducts.. It consists of two parts, the orbital and the palpebral part.
What is the pathway of the lacrimal system?
Lacrimal gland -> puncta -> canaliculi -> lacrimal sac -> nasolacrimal duct -> inferior nasal meatus
What is the function of the lacrimal duct?
Forms the aqueous layer of the tear film
Where is the palpebral part of the lacrimal gland located?
Superolateral in the eyelids inferior to the Levator palpebrae muscle.
Where is the orbital part of the lacrimal gland located?
Lies in the frontal bone
What is the function of the lipid layer of the tear film and where is it produced?
Prevents the aqueous layer from evaporating, produced in the Meibomian gland.
What is the function of the aqueous layer of tear film and where is it produced?
Antibacterial activity, washing out the debris and then supplying the cornea with nutrients. Produced in the lacrimal gland and accessory lacrimal gland.
What is the function of the mucous layer and where is it produced?
Aids in spreading the tears and stabilising the tear film. Produced in the conjunctival gland cells.
What is the blood supply to the lacrimal gland?
The lacrimal branch of the ophthalmic artery.
What is the sensory supply to the lacrimal gland?
Lacrimal nerve (CNV1)
What nerve supplies the parasympathetic innervation to the lacrimal gland?
CNVII
Where does the preganglionic parasympathetic nerve for the lacrimal gland originate?
The superior salivatory nucleus in the pons
Where does the preganglionic parasympathetic nerve of the lacrimal gland travel and synapse?
It leaves the pons and travels with the greater petrosal nerve to synapse at the pterygopalatine ganglion.
What do the postganglionic parasympathetic nerves join with to reach the lacrimal gland/
The CNV1 lacrimal branch
What nerves are involved in the lacrimal reflex?
Afferent - CNV1
Efferent - CNVII
What is the function of the accessory lacrimal glands?
These glands are histologically similar to the lacrimal glands. Their role is to maintain a basal secretory level of aqueous layer.
They are called the Krause and Wolfring glands
What is the puncta?
This is a small round opening located in the medial posterior edge of the upper and lower lid margins, at the junction of the ciliated and non ciliated parts.
What are the superior and inferior canaliculi composed of?
A vertical part, the ampulla, 2mm long
A second horizontal part, 8mm long, after the vertical part.
What forms the canaliculus?
The superior and inferior canaliculi join to form this.
What is the role of the Rosenmuller valve and where is it located?
It prevents tear reflux and is located in the junction between the lacrimal sac and the canaliculus.
Where is the lacrimal sac located?
In the lacrimal fossa, which is formed y the lacrimal bone and the frontal process of the maxilla.
Where is the nasolacrimal duct?
This is a continuation of the lacrimal sac which opens into the inferior meatus of the nose.
What is found in the opening of the nasolacrimal duct and what is its purpose?
A fold of mucous called the valve of Hasner, which prevents air entering the nasolacrimal system during nose blowing.
