Transcript 07. Orbit 12010-10

Coats of the eyeball
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Outer fibrous coat :
1-.cornea – anterior transparent part
2-sclera--- posterior dense white part
Middle vascular coat :
1- choroid (posteriorly)– black
vascular membrane deep to sclera.
2-ciliary body (middle),contains the
ciliary muscle (accomodation).
3-Iris (anteriorly) – it has opening in
its center called the pupil + contains
circular muscle fibres called sphincter
pupillae + radial muscle fibres called
dilator pupillae.
Inner nervous coat : the retina
The Conjunctiva
It is a thin mucous membrane
that lines the inner surface of
eyelids and reflected superiorly
& inferiorly onto anterior
surface of eyeball to form
superior & inferior fornices.
Its epithelium is continuous
with that of cornea.
The upper lateral part of
superior fornix is pierced by
ducts of lacrimal gland.
Levator palpebrae superioris
Origin: roof of orbit above optic canal ,
Insertion:
1-by superior lamella (striated muscle) --anterior surface of sup. tarsal plate +skin of
upper lid.
2-by inferior lamella (smooth m.F)....
Upper margin of sup.tarsal plate.
Nerve : 1-striated ms. by oculomotor N.
Sagittal section of eyeball
Tarsal plates: Dense fibrous tissue,
lying in the eyelids and containing tarsal
glands.
2-smooth ms. by superior cervical
sympathetic F.
Action: elevation of upper eyelid.
Lesion of occulomotor or cervical
symp.trunk leads to dropping of upper lid
(Ptosis).
The eyelids
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The aponeurosis of insertion
of levator palpebrae
superioris pierces the orbital
septum to reach superior
tarsal plate & skin of upper
eyelid.
The superficial surface of
tarsal plates + orbital septum
are covered by palpebral part
of orbicularis oculi muscle.
Action :
1-closed by orbicularis oculi.
2-opened by levator P.S.
The lacrimal apparatus
Lacrimal gland :
1-main part (orbital part) lies in
lacrimal fossa in anterolateral part
of roof of orbit.
2-palpebral part lies in the lateral
part of upper eyelid.
It gives 12 ducts : open into
superior fornix of conjunctiva
carrying tears to conj.sac.– lacrimal
pucti - 2 canaliculi– lacrimal sac
(lies in lacrimal groove behind
medial palpebral ligament)–
nasolacrimal duct– inferior meatus.
The Lacrimal gland
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N.supply : Parasymp.secretomotor fibers via lacrimal N.
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Preganglionic fibers pass via N. of pterygoid canal to
the pterygopalatine ganglion.
Postganglionic fibers leave ganglion via lacrimal N.
into lacrimal gland.
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N.of pterygoid
canal
Fascial sheath of the eyeball
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It surrounds the eyeball
posteriorly from the optic nerve to
the corneoscleral junction.
It separates the eyeball from the
orbital fat and provides the eyeball
with a socket for free movement.
Posteriorly, it fuses with the dural
sheath of the optic nerve.
It is pierced by :
1-ciliary nerves & vessels.
2-tendons of orbital muscles ,
fascial sheath is reflected onto
each ms. as a tubular sheaths.
The check & suspensory
ligaments of the eyeball.
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The fascial sheaths for the tendons of the medial & lateral
recti are attached to the med.& lat. walls of the orbit by
medial & lateral check ligaments.
The lower part of fascial sheath below the eyeball is
thickened to form suspensory ligament of eye, and
connects the check ligaments, so it serves to suspend the
eyeball.
The Orbit
What is the common tendinous ring ?
 What are the structures passing through the
openings in the orbit ?
 Muscles of the orbit :
1-muscles of eyelids
(levator palpebrae superioris).
2-extrinsic muscles of eyeball.
3-intrinsic muscles of eyeball
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The Common tendinous ring
It is a fibrous ring of
thickening of the periosteum.
It surrounds the optic canal
and bridges the superior orbital
fissure.
It gives origin to the 4 recti
muscles.
The sup.R .arises from the upper
part of the ring , The inf. R. arises
from the lower part of the ring ,
The med.R. arises from the
med.part of the ring. The lat.R.
arises by 2-heads from the lateral
part of the ring.
What are the structures passing
through the openings in the orbit ?
Maxillary N.+ inf.
ophthalmic V..
The 4-Recti muscles
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Origin: common tendinous ring.
Insertion: they form a muscular cone
that encloses the optic nerve and
post.part of eyeball,/ each tendon of
the muscles pierces the fascial sheath
of the eyeball and inserted into sclera,
6 mm behind margin of cornea
(posterior to corneoscleral junction)
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N.supply: sup.,inf.,& medial recti --oculomotor N./ lateral rectus--abducent N.
Action: each ms.directs the cornea
1-Superior R.--- upward & medially.
2-Inferior R.--- downward & medially.
3-Medial R.– directs cornea medially
4-lateral R.---laterally.
The 2 oblique Muscles
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Superior O.: origin– post.wall of
orbital cavity (body of sphenoid).
Insertion--- its tendon passes
through trochlea (it is a fibrocartilagenous pully attached to
frontal bone), then inserted into sup.
surface of eyeball (sclera) beneath
sup.rectus. N.supply--- trochlear N.
Action– rotates eyeball,so that cornea
looks downward and laterally.
Inferior O.:
origin– floor of orbital cavity.
Insertion– lateral surface of eyeball
(sclera) ,deep to lateral rectus.
N.supply--- N.to inferior oblique
from oculomotor N.
Action--- rotates eyeball so that
cornea looks upwards & laterally.
Intrinsic muscles of eyeball
(smooth muscles): Smooth ,involuntary muscles of circular F
(sphincter pupillae) & radiating F.
(dilator pupillae).... lying in the iris.
Sphincter Pupillae N.supply : by parasymp.F.
from oculomotor N. via N.to inferior oblique
after relay in ciliary ganglion, postganglionic
fibres pass to eyeball via short ciliary nerves.
Action : constricts pupil in bright light & during
accommodation.
Dilator Pupillae : N.supply : by symp.F,
which pass to eyeball via long ciliary Ns.
Action : dilates pupil in low intensity light & in
excessive symp. activity as in fright.
Ciliary muscle– smooth muscle in the ciliary
body. N.supply– parasymp.F. of 3rd N. as
sphincter pupillae muscle. Action : accomodation
by making lens more biconvex and increasing the
refractive power of lens.
The End
Sensory Nerves :
1-optic 2-(lacrimal)
3-frontal. 4-(nasociliary)
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Optic Nerve : It
is the sensory
nerve of vision.
Arise from the retina,and peirces the
posterior surface of sclera.
It passes through the optic canal
,accompanied by the ophthalmic artery
(below & lateral to N.) into the middle
cranial fossa, where it joins the optic
chiasma.
It is surrounded by ciliary nerves
& vessels and 4 recti muscles. It is
surrounded also by meninges,
which fuse with the posterior part of
sclera.
Lacrimal N :+parasymp.
It arises from ophthalmic
division of trigeminal N. in lateral
wall of cavernous sinus.
It enters orbit through S.O.F,
outside tendinous ring.
It passes forward above lateral
rectus muscle to enter lacrimal
gland (parasymp.secretomotor N.).
It ends by supplying skin of
lateral part of upper lid.
Frontal N. :
As above in orgin and enters orbit
through S.O.F, outside tendinous ring.
It passes forward above L.P.S muscle
and ends by dividing into
supraorbital & supratrochlear
nerves to supply skin of forehead.
Nasociliary Nerve
Origin : from ophthalmic N. of trigeminal
N. in the lateral wall of cavernous sinus.
It enters orbit through sup. Orbital fissure
inside the tendinous ring.
It passes medially, crossing above optic N.
with ophthalmic artery to reach medial wall of
orbit., along upper margin of medial rectus to
end by dividing into 2 terminal branches.
Branches :
1-sensory root to ciliary ganglion : to
supply eyeball through short ciliary Ns.
2-2 long ciliary Ns. : contains sympathetic
Fs. To dilator pupillae.
3-posterior ethmoidal N. : to supply
ethmoid air sinuses.
4-anterior ethmoidal N. : one of the
terminal branches.
5- infratrochlear N. : its 2nd terminal
branch.
Motor nerves: 1-Oculomotor
2-Trochlear
3-Abducent
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Oculomotor N.:
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Sup.division leaves lat.wall of
cavernus sinus and enters the
orbit through sup.orbital
fissure,inside tendinous ring.It
supplies sup.rectus & levator
P.S.
Inf.division--- as above ,and
supplies inf.rectus ,med.rectus
,and inf.oblique. The nerve to
inf.oblique gives off
preganglionic Fs. to ciliary
ganglion and carries
parasympathetic fibers to the
sphincter pupillae & ciliary
muscles, via short ciliary nerves
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Trochlear & abducent nerves
Trochlear N. leaves
lat.wall of cavernus S. To
enter orbit through S.O.F,
outside tendinous ring ---to supply sup.oblique
muscle.(SO4).
Abducent N. leaves
cavernus sinus to enter
orbit through S.O.F, within
tendinous ring---- to
supply lateral rectus (LR6)
The ciliary ganglion
It is parasympathetic
ganglion, situated in the
posterior part of the orbit
lateral to optic nerve.
It receives preganglionic
parasymp.f. from nerve to
inf.oblique of oculomotor N.
It sends postganglionic Fs.
via short ciliary nerves to
the eyeball to supply--sphincter pupillae & ciliary
muscle.
Few sympathetic Fs. pass
from internal carotid plexus
into orbit without relay in the
ganglion.
Ophthalmic artery
It is a branch of the
int.carotid artery after it
emerges from the cavernous
sinus.
It passes through the optic
canal below & lateral to the
optic nerve, then crosses
above it to reach medial wall
of orbit. It is now gives off
numerous branches.
Branches : ….
Branches of Ophthalmic artery
Centeral artery of retina :
it pierces meningeal sheaths of
optic N. to enter inside
substance of optic N. to reach
eyeball (optic disc) and divides
into terminal end arteries.
Muscular branches.
Ciliary arteries : anterior group
which enter eye at corneoscleral
junction & posterior group,
which enters near optic N.
Lacrimal artery : to lac.gland.
Supratrochlear & supraorbital
arteries to skin of forehead.
Ophthalmic veins
Sup.oph.V.communicates in front with the facial V.
 Inf.oph.V.communicates throuth the inf.orbital fissure with
the pterygoid venous plexus.
 Both veins pass
backward through
sup.orbital fissure
to drain into the
cavernous sinus.
 No lymph vessels
or nodes are present
in orbital cavity.
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Medial rectus.
Lateral rectus.
Superior rectus.
Inferior rectus.
Superior oblique.
Inferior oblique.
The optic disc
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It is the site where the optic N. leaves the retina.
It is the site where it is pierced by the centeral
artery of the retina ,and there is complete absence
of rods & cones, so that it is insensitive to light and
is referred to as * Blind Spot.