ORBIT & OCULAR ADNEXAE - Lacrimal Glands Flashcards
Where is the lacrimal gland?
Superotemporal quadrant of the orbit within the lacrimal fossa of frontal bone
What are the anatomical relations of the lacrimal gland?
superior, inferior, anterior, posterior, medial
superior - zygomatic process of frontal bone
inferior - lateral rectus
anterior - orbital septum/fat pad
posterior - orbital fat
medial - intermuscular membrane between superior and lateral recti
What are the two parts of the lacrimal gland?
orbital part and palpebral part, divided into half by levator palpebrae superioris apaneurosis.
How many lacrimal gland ducts open into the superior fornix?
How many lacrimal gland ducts open in the inferior fornix?
superior fornix - 10-12 ducts
inferior fornix - 1-2 ducts
Which lobe would you excise if you do a lacrimal gland biopsy?
Orbital lobe
as in the palepbral part an excision here would remove all secretory function of the gland as all the ducts pass through the palpebral part
What type of gland is the lacrimal gland histologically wise? Which gland is it similar to?
Compound tubuloalveolar gland similar to the parotid gland.
What are the structures within the lacrimal gland ie what is it made up of?
Lobules separated by connective tissue.
What is contained in the lacrimal gland lobules? What do they secrete?
Acini - they are composed of large serous cells which produce watery serous secretion (lacrimal fluid)
What is the pathway of lacrimal fluid ? ie. from secretion to excretion.
lacrimal fluid produced by the gland is secreted into excretory ducts, which empty into the superior conjunctival fornix.
The fluid is then ‘spread’ over the cornea by blinking
What are the accessory lacrimal glands? (2)
Where are they situated?
Gland of Krause
Gland of Wolfring
20-40 in upper fornix
6-8 in lower fornix
Contained in the stroma of the conjunctival fornix
How much do the accessory glands contribute to the lacrimal secretion?
10% - contribute to the basal tear secretion
Where is the punctum located?
Located at posterior edge of the lid margin and sits on the pars lacrimalis (avascular)
At junction of lash-bearing lateral 5/6ths (pars ciliaris) and medial non-ciliated 1/6th (pars lacrimalis)
Superior punctum are more medial than inferior punctum
What are the function of the canaliculi?
How long is the vertical part?
How long is the horizontal part?
connects punctum to lacrimal sac
vertical - 2mm
horizontal - 8mm
WHat is the 90% rule and 10% rule?
90% of people - each canaliculus unite to form the common canaliculus which opens into lacrimal sac of maier which connects to lacrimal sac.
10% of people each canaliculus opens separately into lacrimal sac.
What is angle 1?
What is angle 2?
What happens when angle 2 is increased?
1) 65 degrees
2) 60-90 degrees
if angle 2 is increased, it increases susceptibility to dacrocystitis.
What is the function of valve of rosenmuller?
prevents reflux of tears into the canaliculi
What are the 3 layers of the histology of canaliculus?
- epithelium - stratified squamous > 10 layers of cells
- corium - elastic tissue
- pars lacrimalis - fibres of orbicularis surrounding the corium
How thick is the canaliculus?
0.5mm -
What are these structures?
- anterior arm of medial canthal tendon
- lacrimal sac
- posterior arm of medial canthal tendon
How long is the lacrimal sac?
10-12mm long
What are the parts of the lacrimal sac?
Fundus: portion of sac above opening of common canaliculus
Body: middle part of sack
Neck: narrow small part that continues into naso-lacrimal duct
Where is the lacrimal sac located? It is in close association with what structure?
In the medial wall of the orbit in the lacrimal fossa, between the anterior (formed by maxillary bone) and posterior (formed by lacrimal bone) lacrimal crests.
It is in close association with ethmoid air cells
Which structure is located 8mm medially from medial canthus, anterior to lacrimal sac?
What should be avoided in DCR/lacrimal surgery?
the angular vein - crosses medial palpepbral ligament 8mm medially from medial canthus -
to be avoided in surgery by not going further than 3mm
What are the parts of the nasolacrimal duct? (2)
Intraosseous part - formed by maxilla laterally and nasal conca medially : 12.5mm
Intrameatal part - lies in mucous membrane in lateral wall of the nose: 5.5mm
What are the sensory nerves that supply the lacrimal gland?
- lacrimal nerve (smallest branch of V1) - sensory
—-> receives connection zygomatic nerve (V2) so therefore receives sympathetic and parasympathetic supply —> has all 3 nerve supplies.
What are the three nuclei of the facial nerve?
- motor nucleus
- superior salivatory nucleus
- nucleus tractus solitarius
Label this diagram of the facial nerve nucleus.
What is the course of the parasympathetic nerve fibres of the lacrimal gland?
- super salivatory nucleus –> lacrimatory nucleus
- lacrimatory nucleus –> common sheath with fibres of nucleus tractus solitatus and spinal nucleus of trigmeinal nerve –> nervus intermedius
- nervus intermedius –> internal acoustic meatus (petrous part of temporal bone) –> geniculate ganglion (no relays/synapses) –> some fibres separate to greater petrosal nerve.
- greater petrosal nerve –> foramen lacerum –> pterygoid canal –> joins with ICA sympathetic nerve (deep petrosal nerve) to form the nerve to pterygoid canal (vidian nerve - both parasympathetic and sympathetic) in the pterygoid canal
- vidian nerve –> pterygopalatine ganglion (synapses here) –> post-ganlgionic fibres –> zygomatic nerve (branch of V2) which forms connection with lacrimal nerve (branch of V1) –> lacrimal gland.
