Lacrimal Apparatus Flashcards
Define Lacrimal Apparatus.
Lacrimal Apparatus are the structures concerned with secretion and drainage of tears
What does the Lacrimal Apparatus comprise of?
Comprises of
Lacrimal Glands
- Main gland
- Accessory glands
Lacrimal passages
- Puncta
- Canaliculi
- Lacrimal sac
- Nasolacrimal duct
List the types of lacrimal apparatus.
- Main & accessory lacrimal glands
- Eyelids & their blinking action
- Lacrimal excretory system
What does each type of lacrimal apparatus do?
1.Main & accessory lacrimal glands
Secrete a tear film that protects ocular surface & helps maintain
optimal vision
2.Eyelids & their blinking action
Help distribute tears across cornea & transport tears to puncta
3.Lacrimal excretory system
Drains tears from lacus lacrimalis (Lid tear lake) into inferior
meatus
Describe the lacrimal gland.
The lacrimal gland is ‘J’ - shaped and it is a serous gland
Where is the lacrimal gland situated?
Situated = lacrimal fossa – upper eyelid (supero-lateral portion of anterior orbit)
The structures responsible for the innervation of the lacrimal gland :
- sensory: Lacrimal br. Of Va
- sympathetic & parasympathetic :
Consists of : - orbital part (large & deep)
- palpebral part (smaller & superficial)
What are orbital and palpebral parts separated by?
2 parts separated by lateral extension of levator palpebral
superioris
Describe the orbital part(of the lacrimal gland).
Paired almond - shaped glands
Where is the orbital part(of the lacrimal gland) located?
Located in a fossa on the antero-superolateral
aspect of the orbit
The orbital part has…
2 surfaces, 2 borders & 2 extremities
Where are the surfaces, borders and the extremities located?
- Superior surface – frontal bone
- Inferior surface – levator palpebrae superioris & lateral rectus
- Anterior border – septum orbitale
- Posterior border – orbital fat, level with posterior pole
- Lateral extremity – rests on lateral rectus
- Medial extremity – on levator
State the size of the palpebral part(of the lacrimal gland).
1/3rd size of the orbital part
What is the palpebral part(of the lacrimal part) continuous with?
Continuous with orbital part
posteriorly
Where is the palpebral part found?
Found beneath levator
aponeurosis
Lacrimal gland innervation - Parasympathetic :
- Preganglionic fibres are carried in the greater petrosal nerve (br.
of facial nerve) & then the nerve of pterygoid canal, before
synapsing at the pterygopalatine ganglion (sphenopalatine ganglion)
Lacrimal gland innervation - Parasympathetic :
- Postganglionic fibres leave the ganglion & travel with the
maxillary nerve & finally the zygomatic nerve
Lacrimal gland innervation - Parasympathetic :
- These nerves then reach the lacrimal gland within lacrimal
nerve - Stimulates fluid secretion from the lacrimal gland
Lacrimal gland innervation - Sympathetic :
- Fibres originate from the superior cervical ganglion & are
carried by the internal carotid plexus & deep petrosal nerve
Lacrimal gland innervation - Sympathetic :
- They join with the parasympathetic fibres in the nerve of
pterygoid canal & follow the same route to supply the gland
Lacrimal gland innervation - Sympathetic :
Inhibits fluid secretion from the lacrimal gland
Lacrimal passages - Lacrimal puncta :
: How many are found in each eye; where are is it situated?
- One in each eyelid
- Situated near the posterior border of the 6 mm from medial canthus
Lacrimal passages - Canaliculi :
How many are found in each eye; where does it commence?
- One in each eyelid
- Commences at the punctum & carries tears to lacrimal sac
Lacrimal passages - Lacrimal sac : Where does it lie? What is it covered by? What is the upper part known as? Where does the lower end narrow?
- Lies in lacrimal fossa (fossa formed by lacrimal bone & frontal process of
maxilla) - Covered by lacrimal fascia (anterior to fascia is the medial palpebral ligament)
- Upper part of the sac known as the fundus
- Lower end narrows as it opens into nasolacrimal duct
Lacrimal passages - Nasolacrimal duct :
What does it open into?
What happens to the tears secreted by the lacrimal glands?
- Opens into inferior meatus of the nose
- Tears secreted by lacrimal glands into conjunctival sac are drained by the
lacrimal passage to the nose
Tear production : Why is normal tear formation necessary?
Normal tear formation necessary to keep eye moist is provided by a continuous secretion from accessory lacrimal glands scattered throughout conjunctival sac
Tear production : What causes excessive production of tears?
Excessive production of tears i.e.
crying, is due mainly to reflex nervous
stimulation of main lacrimal gland
Tear production : Describe tear production under normal conditions.
Under normal conditions, tear
production just exceeds that lost by
evaporation; remainder passes down
nasolacrimal duct.
Pathway of lacrimal fluid :
- Lacrimal fluid(tears) is produced in the lacrimal gland
- Lacrimal fluid is dispersed across the eye surface
- Lacrimal fluid enters the lacrimal canaliculi and collects in the lacrimal sac
- Lacrimal fluid from the lacrimal sac drains through the nasolacrimal duct
- Lacrimal fluid enters the nasal cavity
