ORBIT & OCULAR ADNEXAE - Lacrimal Glands Flashcards
Where is the lacrimal gland?
Superotemporal quadrant of the orbit within the lacrimal fossa
What are the anatomical relations of the lacrimal gland?
superior, inferior, anterior, posterior
superior - zygomatic process of frontal bone
inferior - lateral rectus
anterior - orbital septum
posterior - orbital fat
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)
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 surroudning 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