ORBIT & OCULAR ADNEXAE - Lacrimal Glands Flashcards

1
Q

Where is the lacrimal gland?

A

Superotemporal quadrant of the orbit within the lacrimal fossa

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2
Q

What are the anatomical relations of the lacrimal gland?
superior, inferior, anterior, posterior

A

superior - zygomatic process of frontal bone
inferior - lateral rectus
anterior - orbital septum
posterior - orbital fat

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3
Q

What are the two parts of the lacrimal gland?

A

orbital part and palpebral part, divided into half by levator palpebrae superioris apaneurosis.

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4
Q

How many lacrimal gland ducts open into the superior fornix?

How many lacrimal gland ducts open in the inferior fornix?

A

superior fornix - 10-12 ducts
inferior fornix - 1-2 ducts

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5
Q

Which lobe would you excise if you do a lacrimal gland biopsy?

A

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

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6
Q

What type of gland is the lacrimal gland histologically wise? Which gland is it similar to?

A

Compound tubuloalveolar gland similar to the parotid gland.

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7
Q

What are the structures within the lacrimal gland ie what is it made up of?

A

Lobules separated by connective tissue.

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8
Q

What is contained in the lacrimal gland lobules? What do they secrete?

A

Acini - they are composed of large serous cells which produce watery serous secretion (lacrimal fluid)

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9
Q

What is the pathway of lacrimal fluid ? ie. from secretion to excretion.

A

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

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10
Q

What are the accessory lacrimal glands? (2)
Where are they situated?

A

Gland of Krause
Gland of Wolfring

20-40 in upper fornix
6-8 in lower fornix
Contained in the stroma of the conjunctival fornix

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11
Q

How much do the accessory glands contribute to the lacrimal secretion?

A

10% - contribute to the basal tear secretion

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12
Q

Where is the punctum located?

A

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)

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13
Q

What are the function of the canaliculi?

How long is the vertical part?
How long is the horizontal part?

A

connects punctum to lacrimal sac

vertical - 2mm
horizontal - 8mm

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14
Q

WHat is the 90% rule and 10% rule?

A

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.

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15
Q

What is angle 1?
What is angle 2?

What happens when angle 2 is increased?

A

1) 65 degrees
2) 60-90 degrees

if angle 2 is increased, it increases susceptibility to dacrocystitis.

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16
Q

What is the function of valve of rosenmuller?

A

prevents reflux of tears into the canaliculi

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17
Q

What are the 3 layers of the histology of canaliculus?

A
  1. epithelium - stratified squamous > 10 layers of cells
  2. corium - elastic tissue
  3. pars lacrimalis - fibres of orbicularis surroudning the corium
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18
Q

How thick is the canaliculus?

A

0.5mm -

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19
Q

What are these structures?

A
  1. anterior arm of medial canthal tendon
  2. lacrimal sac
  3. posterior arm of medial canthal tendon
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20
Q

How long is the lacrimal sac?

A

10-12mm long

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21
Q

What are the parts of the lacrimal sac?

A

Fundus: portion of sac above opening of common canaliculus
Body: middle part of sack
Neck: narrow small part that continues into naso-lacrimal duct

22
Q

Where is the lacrimal sac located? It is in close association with what structure?

A

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

23
Q

Which structure is located 8mm medially from medial canthus?
What should be avoided in DCR/lacrimal surgery?

A

the angular vein - crosses medial palpepbral ligament 8mm medially from medial canthus -

to be avoided in surgery by not going further than 3mm

24
Q

what is the course of the nasolacrimal duct?

A

it is the inferior continuation of the lacrimal sac, goes downwards, backwards and laterally (DBL) and opens into the INFERIOR nasal meatus, guarded by valve of Hasner.

25
Q

What are the parts of the nasolacrimal duct? (2)

A

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

26
Q

How long is the nasolacrimal duct?

A

18mm

27
Q

What is the function of the valve of hasner?

A

prevents entry of air into lacrimal sac when air is blown out of a closed nose

28
Q

Who has a narrower NLD, males or females?

A

Females, therefore more likely to develop nasolacrimal duct obstruction

29
Q

Which foramina do the trigeminal nerve branches enter?

A

V1 - SOF
V2 - rotundum
V3 - ovale

30
Q

What is the basal tear secretion stimulated by?

A

Light, temperature stimulation and proprioceptors in the lids.

31
Q

What is the lacrimal gland derived from embryologically?

A

Surface ectoderm

32
Q

What are the sensory nerves that supply the lacrimal gland?

A
  1. lacrimal nerve (smallest branch of V1) - sensory
    —-> receives connection zygomatic nerve (V2) so therefore receives sympathetic and parasympathetic supply —> has all 3 nerve supplies.
33
Q

What clinical sign is associated with enlargement of the lacrimal gland?

A

inferomedial dystopia

34
Q

Is basal tear flow contributed by main or accessory lacrimal glands?

A

both.

35
Q

Is reflex tear secretion contributed by main or accessory lacrimal glands?

A

main lacrimal gland.

36
Q

What is the mechanism of lacrimal pump failure?

A

abnormal lid tone or lid position

37
Q

Where does the 6th and 7th cranial nerve arise from?

A

The pons of the brainstem.

38
Q

What are the three nuclei of the facial nerve?

A
  1. motor nucleus
  2. superior salivatory nucleus
  3. nucleus tractus solitarius
39
Q

Label this diagram of the facial nerve nucleus.

A
40
Q

What is the function of the superior salivatory nucleus?

A

Provides secretory/parasympathetic supply to lacrimal gland, submandibular gland, sublingual glands, palatine glands and nasal glands.

GVE - General visceral efferents.

41
Q

What is the function of the nucleus tractos solitaris?

A

Special sensory –> sensation from anterior 2/3rd of the tongue and palate

SVA - Special visceral afferents

42
Q

What is the function of the motor nucleus?

A

Provides motor supply to the muscles of facial expression
(and elevation of hyoid bone)

43
Q

What are the two subparts / subnuclei of the superior salivatory nucleus

A

upper part - supplies parasympathetic supply to the lacrimal gland –> LACRIMATORY NUCLEUS.

inferior part - supplies parasympathetic supply to other salivatory glands

44
Q

What is the course of the parasympathetic nerve fibres of the lacrimal gland?

A
  1. super salivatory nucleus –> lacrimatory nucleus
  2. lacrimatory nucleus –> common sheath with fibres of nucleus tractus solitatus and spinal nucleus of trigmeinal nerve –> nervus intermedius
  3. nervus intermedius –> internal acoustic meatus (petrous part of temporal bone) –> geniculate ganglion (no relays/synapses) –> some fibres separate to greater petrosal nerve.
  4. 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
  5. 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.
45
Q

Which canaliculus is longer? Upper or lower canaliculus?

A

lower (10mm vs 8mm)

46
Q

Where is the most common site for acquired nasolacrimal duct obstruction?

Where is the most common site for congenital nasolacrimal duct obstruction?

A

acquired: osseuous nasolacrimal canal
congenital: valve of Hasner (into inferior meatus)

47
Q

What is the epithelium lining in the..
(1) canaliculus
(2) lacrimal sac

A

canaliculus - stratified squamous
lacrimal sac - double layer of columnar epithelium

48
Q

What are the main types of cells found in the lacrimal gland? (3)

A
  1. acinar (80%)
  2. ductal (around duct of gland)
  3. myoepithelial (around acinar cells)
49
Q

What percentage of tears are reabsorbed through the nasolacrimal duct mucosa?

What percentage of tears are drained into the floor of nasal cavity?

A
  1. reabsorbed - 90%
  2. drained - 10%
50
Q
A