anatomy and physiology of lacrimal apparatus

1. Presented by
Dr Rohit Rao

2.  Wolff's Anatomy of
the Eye and Orbit.
 Adler's Physiology of the Eye .
 The Lacrimal System
Diagnosis, Management, and Surgery by Adam J.
Cohen, Michael Mercandetti & Brian G. Brazzo.
 The dry eye , a practical approach by Sudi Patel
& Kenny J Blades.
 Jack J Kanski’s clinical ophthalmology
 Clinical Anatomy of the Eye by Richard S. Snell
& Michael A. Lemp.

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

6.  The following components of
apparatus are discussed :

Embryology

Osteology

Secretory system

Excretory system

Physiology
the lacrimal

7.  Ectodermal origin
 Solid epithelial buds(first 2
 Superolateral conjunctival
months)
fornix.

8.  Lacrimal sac
and nasolacrimal duct : ectoderm
of the naso-optic furrow or nasolacrimal furrow
 The ectoderm of
the furrow buries and forms a
solid cord .
 Canalization :
begins at 4 months and may
continue after birth.

10.  The lacrimal sac
fossa is a depression in the
inferomedial orbital rim,
 Maxillary and
lacrimal bones.
 Bordered by
the anterior lacrimal crest
(maxillary bone) & posterior lacrimal crest
(lacrimal bone).

The fossa is approximately 16-mm high, 4- to 9mm wide, and 2-mm deep.

12.  The medial orbital wall :
Frontal process of
maxilla, lacrimal , ethmoid , lesser wing of
sphenoid bone.
 The frontoethmoidal suture is important in
lacrimal surgery
 It marks the roof of the ethmoid sinus.
Bony
dissection superior to this suture may expose
the dura of the cranial cavity.

13.  The nasolacrimal canal
originates at base of
lacrimal fossa.
 Formed by
the maxillary bone laterally and the
lacrimal and inferior turbinate bones medially.
 The width

of superior opening is 4–6 mm.
The duct courses posteriorly and laterally in
the bone for 12 mm to drain into the inferior
meatus of the nasal cavity.

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

15.  It consists of

Large Orbital Part

Smaller Palpebral Part
 Lateral expansion
of levator separates the parts

16.  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

17. 
Anterior border
 Septum orbitale

Posterior border
 Contact with orbital fat , level with posterior
pole.

Lateral extremity
 Rest on lateral rectus

Medial extremity
 On levator

18.  1/3rd
size of orbital part
 Superior fornix
 It is
, seen on lid eversion.
situated upon the course of ducts
 Related to
levator superiorly, inferiorly to
superior fornix
 Posteriorly it continues with
orbital part.

19.  Are small, compound, branched, tubular glands
 Located
in the middle of lid (Wolfring glands)
or superior & inferior fornices (Krause glands).
 Ectopic portions of lacrimal gland tissue.

20.  It is
with connective tissue coat and excretory
duct.
 The excretory duct splits &
form intralobular
ducts, connected to secretory glandular
epithelia.
 Secretory epithelia have
 True acini
are absent.
elongated tubules.

23.  Tubuloacinar with
short, branched tubules
 Acini
are pyramidal secretory cells with apex
towards a central lumen .
 Myoepithelial cells., contractile &
secretion
aid the

24.  In acinus,
secretory cells are joined by
junctional complexes
 Apical
microvilli extend into the lumen
 Nucleus
and rough endoplasmic reticulum are
basal in the cells.
 Abundant secretory granules, at
apex .

26.  The ducts have
two or three cell layers and
microvilli at luminal surface.
 Plasma cells of the interstitial
space are an
important source of immunoglobulins secrete
IgA(and fewer lgG, lgM, IgE)

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

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

32.  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.

34. 
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.

35.  Lacrimal fossa, formed by
lacrimal bone and
frontal process of maxilla .
 The sac,
closed above and open below, is
continuous with the nasolacrimal duct.
 The sac
is enclosed by a periorbita, splits &form
the lacrimal fascia .

36. Relations
 Medial : periorbita and bone, arc of ethmoid
sinuses.
 Lateral : skin, orbicularis oculi, and lacrimal
fascia.
 Anterior: medial palpebral ligament and
angular vein.
 Posterior : lacrimal fascia and muscle

37.  The nasolacrimal duct,
continuation of lacrimal
sac to the inferior meatus.
 15 mm.
 It lies in
a canal formed by the maxilla, lacrimal
bone and lacrimal process of inferior concha.
 It descends posterolaterally, a
surface indication
a line from medial canthus to first upper molar.

38. The valves
 They are folds of mucous
membrane with no
valvular function.
 The most constant is
the
'valve' of Hasner at the
lower end.
 It prevents sudden blast of
air (when blowing the
nose) from entenng the
lacrimal sac.

39. Structure
 Double-layered Epithelium
 The superficial layer composed of
columnar
cells, the deeper cells being flatter.
 The membranous wall
of the sac is of
fibroelastic tissue, the elastic element being
continued around the canaliculi.

40.  Around the nasolacrimal duct is
plexus of
vessels, forming erectile tissue like that on the
inferior concha.
 Engorgement of
these vessel obstruct the duct.
 The course of the lacrimal sac
and duct can be
demonstrated by dacryocystography

41. Vessels

Artery supply : palpebral branches of the
ophthalmic, angular and infraorbital arteries and nasal
branch of the sphenopalatine.

Venous drainages : Angular and infraorbital vessels
above, below into the nasal veins

Lymphatic drainage: submandibular and deep cervical
nodes.
Nerves

Infratrochlear and anterior superior alveolar nerves.

42. 
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

43.  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
evaporation.
balanced by drainage and
 Drainage is
regulated by neural reflexes ,causing
vasodilation and vasoconstriction of blood sinus.
 Evaporation depends blink
rate and
temperature, humidity, and wind speed.

44.  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
tear film hyperosmolality).
the

45.  Consists of
four layers
 Glycocalyx
 Mucous layer
 Aqueous layer.
 Lipid
layers

47. Structure

The glycocalyx is a network of polysaccharides that project
from cellular surfaces.

Mucins are classified into secreted and membrane-spanning
mucin.

Secreted mucins are either gel-forming or small soluble
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

48. 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.


49. 
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.

50.  Composed of water, with
many solutes, including
dissolved mucins, electrolyte sand 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.

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

52. 
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


53. Function
 Hydrophobic barrier to prevent tear overflow.
 The meibom 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.

55.  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,

57.  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.

58.  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.