anatomy and physiology of lacrimal apparatus ppt

 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.

 It is concerned with

the tear formation &

transport.
 Lacrimal passage includes :

Lacrimal
gland

Nasolacrimal
duct

Conjunctival
sac

Lacrimal
puncta

Lacrimal
sac

Lacrimal
canaliculi

 The following components of

apparatus are discussed :


Embryology



Osteology



Secretory system



Excretory system



Physiology

the lacrimal

 Ectodermal origin
 Solid epithelial buds(first 2
 Superolateral conjunctival

months)

fornix.

 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.

 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.

 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.

 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.

 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

 It consists of


Large Orbital Part



Smaller Palpebral Part

 Lateral expansion

of levator separates the parts

 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



Anterior border
 Septum orbitale



Posterior border
 Contact with orbital fat , level with posterior
pole.



Lateral extremity
 Rest on lateral rectus



Medial extremity
 On levator

 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.

 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.

 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.

 Tubuloacinar with

short, branched tubules

 Acini

are pyramidal secretory cells with apex
towards a central lumen .

 Myoepithelial cells., contractile &

secretion

aid the

 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 .

 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)

 Artery supply :

Lacrimal artery , branch of
ophthalmic artery.

 Venous drainages

: Ophthalmic Vein.

 Lymphatic drainage

: Joins that of conjunctiva &
drain into the preauricular lymph nodes.

 Sensory nerve

supply : lacrimal nerve
, branch of ophthalmic division of Vth nerve

 Sympathetic nerve

supply : carotid plexus

 Secretomotor fibers

nucleus

: superior salivary

 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.



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.

 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 .

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

 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.

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.

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.

 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

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.



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

 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.

 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

 Consists of

four layers

 Glycocalyx
 Mucous layer
 Aqueous layer.
 Lipid

layers

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

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.




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.

 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.

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



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


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.

 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,

 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.

 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.

anatomy and physiology of lacrimal apparatus ppt

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anatomy and physiology of lacrimal apparatus ppt

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