Anatomy of Lacrimal Apparatus, parts of lacrimal system, Mechanism of tear drainage

1. Lacrimal Apparatus
Pukar K.C
Kathmandu University School of
Medical Sciences

2. Parts
• Lacrimal glands
(exocrine gland)
– Main
– Accessory
• Lacrimal passages
– Puncta
– Canaliculi
– Lacrimal sac
– Nasolacrimal duct (NLD)

3. Main Lacrimal Glands
1. Orbital part
– Located in fossa of lacrimal gland at outer part of orbital
plate of frontal bone
– Size and shape of small almod
– Surfaces:
• Superior: convex and lies in contact with bone
• Inferior : concave and lies on levator palpebrae superioris muscle
2. Palpebral part
– Small and contains one or two lobules
– Located in course of duct of orbital part
and is separated by LPS muscle
– Posteriorly continuous with orbital part

4. Main Lacrimal Glands
• Serous acini and ducts

5. Accessory Lacrimal Glands
• Glands of Krause
– Microscopic glands
beneath palpebral
conjunctiva between fornix
and edge of tarsus
– 42 in upper fornix and 6-8
in lower fornix
• Glands of Wolfring
– Present near the upper
border of superior tarsal
plate and along the lower
border of inferior tarsus

6. Ducts of Lacrimal Gland
• 10-12 ducts passes downwards from main
gland to open in lateral part of superior fornix
• 1-2 ducts open in lateral part of inferior fornix

7. • Blood supply
– Lacrimal artery, a branch of ophthalmic artery
– Also from infraorbital artery
– Venous drainage into the superior ophthalmic
vein
• Nerve supply
– Sensory: Lacrimal nerve, branch of ophthalmic
division of trigeminal nerve
– Sympathetic: Carotid plexus of cervical
sympathetic chain
– Secretomotor: Parasympathetic pathway

8. Secretomotor Pathway
• Superior salivatory nucleus
(pons)
Greater petrosal nerve
Synapse at pterygopalatine
ganglion
Zygomatic nerve
Lacrimal nerve
Lacrimal gland

9. Lacrimal Passage

10. Lacrimal Puncta
• Two small rounded or oval openings at upper
and lower eye lids 6 and 6.5 mm, respectively,
temporal to the inner canthus
• Situated upon a slight elevation called lacrimal
papilla
• Pucta dips in lacus lacrimalis (collection of tear
fluid in inner canthus)

11. Lacrimal Canaliculi
• Superior and inferior canaliculi
• Two parts that lie perpendicular to each other
– Vertical part (1-2 mm)
– Horizontal part (6-8 mm)
• Connects the puncta to lacrimal sac
• Horizontal part opens into sac
• Two canaliculi may open separately or joins to form
common canaliculi which opens to lacrimal sac
• A fold of mucosa at the opening in sac forms valve of
Rosenmuller, prevents the reflux of tears

12. Lacrimal Sac
• Location
– lacrimal fossa at anterior part of medial orbital wall
– Lacrimal fossa formed by: lacrimal bone and frontal
process of maxilla and bounded by anterior and
posterior lacrimal crest
– Lacrimal fascia encloses the lacrimal sac
– Alveolar tissue and venous plexus lies in between
lacrimal fascia and lacrimal sac
• Size: 12-15 mm length, 5-6 mmn breadth
volume: 2 cc

13. Parts of Lacrimal Sac
• Fundus
– Portion above opening
of canaliculi
• Body
– Middle part
• Neck
– Narrow lower part that
is continuous with
nasolacrimal duct

14. Nasolacrimal Duct
• Location:
– Lies in the bony canal formed by maxilla and
inferior turbinate
– Extends form neck of lacrimal sac to inferior
meatus of the nose
• Dimensions: 15-18 mm long, 5-6 mm wide
• Parts: Intaosseous part
Meatal part

15. Nasolacrimal Duct
• Direction
– Downwards, backwards and laterally
– Externaly represented by line joining inner
canthus to ala of nose
• Numerous memranous valves are present
– Valve of Hasner, present at the lower end of duct
and prevents reflux from the nose

16. Lining Epithelium
• Canaliculi
– nonkeratinized, stratified squamous epithelium
• Lacrimal sac
– pseudostratified columnar epithelium
• Nasolacrimal duct
– columnar epithelium

17. Secretion of Tear
• Continuously secreted throughout the day,
Basal Secretion, by accessory lacrimal gland
• Reflex secretion by main lacrimal gland
– Stimuli: Ocular surface irritation
– Afferent: ophthalmic branch of the trigeminal
nerve
– Efferent: Parasympathetic pathway

18. Elimination of Tear
• Flow of tear: downward and medially across
the ocular surface
• Some amount of tear lost by evaporation
• Remainder collects as lacus lacrimalis in the
inner canthus drained by lacrimal passage
into the nasal cavity
• Lacrimal pump drains the tear
– 70% from inferior canaliculus
– 30% from superior canaliculus

19. Lacrimal Pump
• Occurs with each blinking of eye
• Orbicularis oculi muscle involved
• Events
– Eyelids close
– Eyelids open

20. Eyelid Close
Propels the tear fluid present in
ampulla and canaliculii towards
lacrimal sac
Compresses the Ampulla
Shortens the Canaliculi
Contraction of pre tarsal orbicularis
oculi
Draws tear fluid from canaliculi into
lacrimal sac
Distends the lacrimal sac
Creates the negative pressure
Contraction of pre septal orbicularis
oculi

21. Eyelid opens
Draws tear fluid from Lacus
lacrimalis and marginal tear strip
Expansion and reopening of
canaliculi and ampulla
Relaxation of pretarsal orbicularis
oculi
Forces the tear down the
nasolacrimal duct, Gravity also helps
downward flow of tear
Positive pressure is created
Collapse of lacrimal sac
Relaxation of preseptal orbicularis
oculi

22. Rosengren-doane Mechanism