The lacrimal apparatus is responsible for tear formation and drainage. It includes the lacrimal gland, conjunctival sac, lacrimal puncta, lacrimal canaliculi, lacrimal sac, and nasolacrimal duct. The lacrimal gland secretes tears into the conjunctival sac. Tears are drained from the puncta through the canaliculi and lacrimal sac into the nasolacrimal duct. Blinking aids in drainage by compressing the canaliculi and lacrimal sac to push tears into the nasolacrimal duct.

1. Lacrimal apparatus
• It is concerned with the tear formation &
transport.
• Lacrimal passage includes :
Lacrimal
gland
Conjunctival
sac
Lacrimal
puncta
Lacrimal
canaliculi
Lacrimal
sac
Nasolacrimal
duct

3. ANATOMY & PHYSIOLOGY
BRIEF REVIEW
 Secretory and drainage parts.
 Lacrimal gland [orbital and palpebral parts] and accessory lac
glands of Krause and Wolfring Seven to twelve ducts open in
the supero temporal part pf bulbar conjunctiva.
 Streams running across the eye ball lead to a smaller meniscus
along upper and another along the lower lid margin.
 Eye closure is from temporal to nasal side thus pushing the
tears medially in lacus lacrimalis.
 Here starts drainage system.

5. Secretory system
• It includes lacrimal gland, accessory glands
• Lacrimal gland is above & anterolateral to globe.
• Secretes tears into superior fornix.
• Tears moisten & lubricates the : cornea , conjunctiva.
• It contributes 43D of 50D of refractive power of eye .

6. • It consists of
• Large Orbital Part
• Smaller Palpebral
part
• Lateral expansion of levator separates
the parts

7. The orbital part
• Paired almond-shaped glands.
• It is present in a fossa on the anterolateral
area of orbit
• It has 2 surfaces, 2 borders, 2 extremities
– Superior surface
• Frontal bone
– Inferior surface
• Levator palpebrae superioris & lateral rectus

8. – Anterior border
• Septum orbitale
– Posterior border
• Contact with orbital fat , level with posterior
pole.
– Lateral extremity
• Rest on lateral rectus
– Medial extremity
• On levator

9. The palpebral part
• 1/3rd size of orbital part
• Superior fornix , seen on lid eversion.
• It is situated upon the course of ducts
• Related to levator superiorly, inferiorly to
superior fornix
• Posteriorly it continues with orbital part.

10. Accessory glands
• Are small, compound, branched, tubular
glands
• Located in the middle of lid (Wolfring glands)
or superior & inferior fornices (Krause
glands).

11. Blood supply
• Artery supply : Lacrimal artery , branch of
ophthalmic artery.
• Venous drainages : Ophthalmic Vein.
• Lymphatic drainage : Joins that of conjunctiva
& drain into the preauricular lymph nodes.

12. Nerve supply
• Sensory nerve supply : lacrimal nerve , branch
of ophthalmic division of Vth nerve
• Sympathetic nerve supply : carotid plexus
• Secretomotor fibers : superior salivary nucleus

13. Excretory system
the PUNCTA
• A small, round or oval orifice on the elevation, the
papilla lacrimalis.
• At medial end of lid margin at the junction of its
ciliated and non-ciliated parts.
• Upper punctum medial to lower, from the medial
canthus being 6 and 6.5 mm.
• The upper punctum opens inferoposteriorly, the lower
superoposteriorly.

15. THE LACRIMAL CANALICULI
• First vertical and then horizontal
• Vertical part is 2 mm & turns medially at right-
angle to become horizontal 8 mm
• At angle - dilatation or ampulla.
• The canaliculi pierce the fascia (i.e. the
periorbita covering the lacrimal sac) separately,
• Uniting to enter lacrimal sac.
• Stratified squamous epithelium supported by
elastic tissue.

16. THE LACRIMAL SAC
• A fold of mucosa at the junction of common canaliculus,
forms the valve of Rosenmuller, preventing reflex tears.
• It lies in the lacrimal fossa formed by the lacrimal bone,
when distended it is about 15mm long vertically and 5-
6mm wide.
• The upper portion or the fundus extends slightly above the
level of the medial palpebral ligament and the sac itself is
surrounded by fibers of orbicularis muscle.
• The sac, closed above and open below, is continuous with
the nasolacrimal duct.

17. THE NASOLACRIMAL DUCT
• The nasolacrimal duct, continuation of
lacrimal sac to the inferior meatus.
• 12 mm.
• It descends posteriolaterally, a surface
indication a line from medial canthus to first
upper molar.

18. • The most constant is the 'valve' of Hasner at
the lower end.
• It prevents sudden blast of air (when blowing
the nose) from entering the lacrimal sac.

19. physiology
• The tear film overlays corneal and conjunctival
epithelia.
• Tears produced by the ocular surface epithelia
and adnexa.
• Thickness of up to 40 µm,
• Volume of tears covering the ocular surface
range from 2.74 ± 2.0µL to 7 µL

20. • For mucous and aqueous layers, secretion is
regulated by neural reflexes.
• For the lipid layer, the blink itself regulates release
of pre-secreted meibomian gland .
• Tear secretion is balanced by drainage and
evaporation.
• Drainage is regulated by neural reflexes ,causing
vasodilation and vasoconstriction of blood sinus.
• Evaporation depends blink rate and temperature,
humidity, and wind speed.

21. The roles of the precorneal tear film
• To protect the cornea from drying;
• To maintain the refractive power of the cornea;
• To defend against eye infection;
• To allow gas to move between the air and the avascular
cornea;
• To support corneal dehydration (assisted by the tear
film hyperosmolality).

22. • Consists of four layers
– Glycocalyx
– Mucous layer
– Aqueous layer.
– Lipid layers

23. Glycocalyx
Function
• The membrane-spanning mucins function to
hydrate the ocular surface and serve as a
barrier to pathogens.
• Membrane-spanning mucins appear to be
altered in dry eye

24. Mucous layer
Structure
• The mucous layer backbone is the gel-forming mucin ,
synthesized and secreted by conjunctival goblet cells.
Function
• To resistance of the eye to infection by providing protection
against microorganisms.
• Mucins serve as wetting agents that keep the apical
epithelia hydrated.

25. Aqueous layer
• Lacrimal gland produce aqueous layer.
• Other ocular surface epithelia also contribute to the
aqueous layer, eg. conjunctiva, accessory lacrimal glands
• 7µm thick.
• Without the lubrication , the shearing forces produced on
blinking will cause accumulative ocular surface damage.

26. • Composed of water, with many solutes,
including dissolved mucins, electrolytes and
proteins.
• The osmotic pressure : concentrations of
sodium, potassium and chloride ions.
• The tear film’s osmotic pressure is important
in the control of cornea–tear film water flux.
• Bicarbonate and carbonate : pH buffering,
maintaining the pH at 7.3–7.6 when the eyes
open & 6.8 eyes closed.

27. Aqueous layer function
• Aqueous deficiency dry eye.
• Protection from bacterial infection
• Reflex secretion washes away noxious
substances.
• Protects against changes in pH.

28. Lipid layer
• Meibomian glands, modified sebaceous glands, that
line the upper and lower eyelids.
• Meibomian gland lipids are stored in vesicles.
• The secretory product contains a complex mixture of
lipids and proteins and is termed meibum.
• Meibum is released on to the ocular surface in small
amounts with each blink.
• 0.1m in thickness

29. Function
• Hydrophobic barrier to prevent tear
overflow.
• The meibum forms a water-tight seal of the
apposed lid margins during sleep.
• Reduce tear evaporation .
• Lipids enhance the stability of the tear
film and provide a smooth optical.

31. DISTRIBUTION OF THE TEARS
• Conjunctival fornices, preocular tear film, and
marginal tear strips.
• Marginal tear strips are wedge shaped tear
menisci, borders of upper and lower lids.
• Apposed lacrimal puncta dip into marginal
strip of tears
• Anterior limit of the marginal strip is the
mucocutaneous junction of the lid,

33. CONDUCTION OF THE TEARS
LACRIMAL PUMP MECHANISM:
• Tears are lost from the conjunctiva sac by
absorption, evaporation, and nasolacrimal
system.
• This is related to the size of the palpebral
aperture, the blink rate, ambient temperature
and humidity.

34. • Tears flow
– the upper and lower marginal strips → upper
and lower canaliculi (capillarity + suction)
• Eyes close
– Pretarsal orbicularis oculi compresses the
ampullae + shortens and compresses canaliculi
+ puncta medially.
– Lacrimal part of the orbicularis oculi, contracts
→ compresses the sac,(positive pressure)
tears → nasolacrimal duct → nose.
• Eyes open
– Muscles relax → canaliculi and sac
expand(negative pressure) + capillarity= tears
into sac.