anatomy of the lacrimal apparatus
TRANSCRIPT
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SIVATEJA
CHALLA
ANATOMY OF THE LACRIMAL
APPARATUS
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LACRIMAL APPARATUS consists of
1.Lacrimal gland
2.Lacrimal ducts3.Conjunctival sac
4.Lacrimal puncta
5.Lacrimal canaliculi
6.Lacrimal sac and
7.Naso lacrimal duct
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LACRIMAL GLAND
DEVELOPMENT
Develops from surface ectoderm
Develops as epithelial bud evaginating from basal
cells of conjunctiva in supratemporal portion of
embryonic fornix Initially solid cords formed,but by 3months central cells
vacuolte and lumina appear
Full differentiation by 3-4 yrs postnatally
Composed of ectodermal glandular units and
mesodermal myoepidermal cells and fibrous
tissue.
Functions 6wks after birth.so no tears in new born
when crying.
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ANATOMY
Located in anterolateralpart of the roof of orbit
in fossa for lacrimal
gland
Divided in to largesuperficial orbital part
and small deep
palpebral part which
are continuous witheach other around
aponeurosis of LPS
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ORBITAL PART
Almond shaped
Two surfaces (superior and inferior) two borders
(anterior and posterior and two extremities (medial
and lateral)
superior surface convex and related to orbit roof
Inferior surface concave and related to LPS
Anterior borderlimited by orbital septum
Posterior border related to orbital pad of fat
Medial extremity related to LPS
Lateral extremity rests on lateral rectus
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PALPEBRAL PART
1/3RD
size of orbital partSuperiorly related to
LPS and inferiorly to
superior fornix
When lid is everted thegland can be seen in
superior fornix of
conjunctiva
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ANCHORS
1.Above by suspensory ligament
2.Below by fibrous attachment to the zygomatic bone
3.Behind by fascial condensation around lacrimal
nerves and vessels4.Internally by fascial expansion of ocular muscles
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LACRIMAL DUCTS
10-12 ductsDucts arising from the orbital part passes through
palpebral part and opens in to superior fornix of
conjunctiva
Additional ducts from palpebral part open directly into conjunctiva
Removal or damage to palpebral part of the gland
will stop secrections reaching the fornix
So biopsy of gland always done in orbital part of
lobe
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STRUCTURE OF LACRIMAL GLAND
Lobulated tubulo acinar gland
Microscopically has Glandular tissue,Stroma andSepta-Glandular tissue consists of
acini and ducts arranged in
lobes and lobules seperated by
Septa
-acini has pyramidal cells which
secrete the tears expelled by the
contraction of myofibrils
-Stromaformed by mesodermal
tissue which has connective
tissue,lymphoid cells,plasma
cells,rich nerve terminals and
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BLOOD SUPPLY-
Internal carotid artery Angular vein
Ophthalmic artery Superior
ophthalmic vein
Lacrimal artery Lacrimal vein
Some times by infraorbital artery(Br of maxillary artery)
LYMPHATIC DRAINAGE-
Pre auricular group
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NERVE SUPPLY
Parasympathetic secretomotor fibres(efferent) from
superior salivatory nucleus
Sympathetic nerve supply from carotid plexus
Sensory supply(afferent) from lacrimal nerve Br of
ophthalmic division of fifth nerve
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CONJUNCTIVAL SAC
Conjunctiva stretches from lid margin to limbusand encloses a potential space conjunctival sac
which opens at palpebral fissure
Sac is closed only when lids are approximated
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LACRIMAL PUNCTA
Two puncta situated ineach lid margin at the
junction of ciliary and
lacrimal parts on
elevtion called lacrimalpapilla
Upper punctum 6mm
and lower 6.5 mm from
medium canthus
Surrounded by fibroustissue which keeps them
patent
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LACRIMAL CANALICULI
2 in number,Joins puncta to lacrimal sac
Two parts vertical(2mm) and horizontal(8mm) at
junction dilated to form ampulla
Pierce lacrimal fascia and unite to form common
canaliculi opens in to lacrimal sinus of maier
At opening in to sac protected by valve of
rosenmuller
Surrounded by fibres of pars lacrimalis of orbicularisoculi muscle
During blink canaliculi pulled medially,shortened and
compressed by pars lacrimalis.also helps in dilatation
of lacrimal sac
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DUCT
DEVELOPMENT
At junction of maxillary process and lateral nasal processamass of ectodermal cells submerge gets canalised to form
lacrimal sac and NLD.
The lacrimal canaliculi
are extensions from the
lacrimal sac in to the
eyelid
Non fusion of maxillary
and lateral processes
resuts in oblique facialcleft and in such cases
NLD not formed
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Fig. 6. Lacrimal drainage system embryology. A. At 5.5 weeks' gestation, an
ectodermal invagination forms between the lateral nasal process and
maxillary process,which becomes pinched off from the surface. B. At 6 weeks' gestation, a solid
cord of ectoderm is located between the primitive medial canthus and nose.
C. At 12 weeks' gestation, proliferation of the cord occurs laterally toward the
eyelid and inferiorly toward the
inferior turbinate. The isolated cavities shown appear at3 to 4 months. D. At 7
months, canalization is nearly complete, with only the puncta and valve of
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LACRIMAL SAC
Upper expanded portion of
NLD
Lodged in lacrimal fossa(medial
wall is lamina
papyracea,formed by lacrimal
bone and frontal process ofmaxilla)
Surrounded by lacrimal fascia
which results from splitting of
periorbita Between sac and fascia are
venous plexus
Part of sac above MPL is
fundus.At junction of fundus
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RELATIONS
Anter ior ly to medial palpebral ligament
Poster ior lyto posterior lacrimal crest and orbicularis
oculi
Mediallyto middle meatus and ant ethmoidal sinus
Laterallyto skin,fascia and orbicularis oculi(lacrimalpart)
ANGULAR VEIN and ANGULAR ARETRY crosses
MPL about 8mm from the medial canthus.many timesa tributary runs 3mm from medial canthus.so to avoid
profuse bleeding during sac surgery incison should
be made within 3mm medial to medial canthus
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Extends from lacrimalsac to inferior meatus ofnose
18 mm in length and
3mm diameter Upper end is the
narrowest
Runs
downward,backwardand laterally
Lined by two layers ofcoloumnar epithelium
Has intraosseus and
intra mural part
NASO LACRIMAL DUCT
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Intraosseus part lodged in naso lacrimal Canal
formed by maxilla anterolaterally,lacrimal bone
and inferior nasal concha postero medially Intramural part variable in length and lies in inferior
meatus.
NLD opens below in to anterior part of inferior
meatus. opening guarded by a fold of mucosa-valve of
hasner.prevents air from entering the sac when air
blown out of closed nose
In infants some times canalisation is delayed or do
not occur causing epiphora and cong dacrocystitis
Duct is surrounded by rich plexus of veins,forming a
erectile tissue .engorgement leads to obstruction of
NLD and epiphora
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BLOOD SUPPLY
ARTERIAL SUPPLY
Superior and inferior palpebral
A.Angular A.
Infraorbital A.
Nasal br. Of sphenopalatine A.
VENOUS DRIANAGE
Angular vein
Infraorbital vein
Nasal vein
LYMPHATICS
Sub mandibular group
Deep cervical group
NERVE SUPPLY
Infra trochlear nerve
Anterior superior alveolar N.
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