orbital blood supply
TRANSCRIPT
Orbital Blood Supply
Othman Al-Abbadi, M.D
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Ophthalmic artery
The first main branch of the internal carotid
artery.
Course:
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Relation to the optic
nerve
Relation to the
meninges
Pre-optic canal Inferolateral Subarachnoid
Optic canal Inferolateral Dural-Arachnoid sheath
Orbital cavity Lateral Extra-dural
Superior 85%
Inferior 15%
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Branches
1. Central artery of the retina2. Lacrimal artery3. Muscular branches4. Ciliary arteries5. Supraorbital artery6. Posterior ethmoidal artery7. Anterior ethmoidal artery8. Meningeal artery9. Medial palpebral arteries10. Supratrochlear arteries11. Dorsal nasal artery
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Central retinal artery
First branch from the ophthalmic artery.
End arteries.
Course:
◦ Runs beneath optic nerve, then at about 1.25cm behind eyeball it pierces the dural & arachnoid sheaths of optic n, enters eyeball through lamina cribrosa
Divides into equal superior & inferior branches, then another division (nasal & temporal).
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Branches:◦ Small meningeal branches supply the pial
sheath
◦ Central collateral branches which pass with the CRA to the lamina cribrosa & a branch goes posteiorly to supply the macular nerve fibers
Circle of Zinn occurs between the pialvessels & the small vessels in the sclera around the nerve head.
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Lacrimal artery
Runs on upper border of the LR, passes through lacrimal gland & sends terminal branches to the eyelids & conjunctiva.
Branches: ◦ Lateral palpebral to the U & L eyelids &
anastomose with the medial palpebral
◦ Zygomatic which pass through the zygomaticofacial & zygomaticotemporalforaminae
◦ Muscular branch to the LR
◦ Recurrent meningeal anastomoses with the middle meningeal artery.
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Muscular branches
Most of these branches accompany
the branches of the oculomotor nerve.
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Ciliary arteries
1. Long posterior ciliary artery
◦ 2 in no.
◦ Pierce the sclera & run in the epichoroidal space
to the ciliary body where they divide into upper &
lower branches & encircle iris
◦ Anastomose with the anterior ciliary arteries to
form the major arterial circle of iris..
◦ recurrent branches supply the choroid posteriorly to
the equator & anastomose with the short posterior
ciliary arteries
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2. Short posterior ciliary arteries:
◦ 7 in no.
◦ divide into 10-20 branches
◦ run around the optic nerve before piercing the sclera to
supply the choroid as far as the equator where they
anastomose with recurrent branches of the LPCA, ACA &
the major arterial circle of the iris
A number of small branches form an anastomotic
ring(ring of Zinn) around optic disc with the pial
arteries
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Cilioretinal artery
◦ ~15-20% of the population
◦ Enters the retina at the lateral border of the
optic nerve & supplies the retina between the
disc & the macula
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3. Anterior ciliary arteries
◦ 7 in no.
◦ originate from the muscular branches
◦ Join the LPCA to form the major arterial
circle of iris.
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Supraorbital artery
Runs at the medial border of the SR & LPS then
with the supraorbital nerve between the LPS &
orbital roof,
leaves orbit through the supraorbital foramen &
ascends to the scalp deep to the frontalis
Anastomose with supratrochlear & superficial
temporal arteries
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Posterior ethmoidal artery
Passes between the upper border of the MR &
SO muscles to enter the posterior ethmoidal
canal
Supplies posterior ethmoidal air sinuses, dura of
anterior cranial fossa & upper part of nasal
mucosa.
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Anterior ethmoidal artery
Larger
Enters anterior ethmoidal canal then
anterior cranial fossa & passes into the
nose through cribriform plate down in a
groove in the nasal bone to enter face
between the nasal bone & upper cartilage
supplies ant. & middle ethmoidal air cells,
frontal air sinus, meninges, ant. nasal
mucosa & skin of nose.
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Meningeal artery
Runs posteriorly through the superior
orbital fissure to supply meninges of
middle cranial fossa.
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Medial palbebral atery
Arise below the pulley for the SO
Descend behind the lacrimal sac
pierce the orbital septum above & below the
medial palpebral ligament
form peripheral & marginal arterial arches
Run between the orbicularis oculi & the tarsal
plate
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Supratrochlear artery
Terminal branch
Pierces the orbital septum above pulley for the
SO
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Dorsal nasal artery
Terminal branch
Pierces the orbital septum
Passes above medial palpebral ligament &
descends to nose, gives branches to lacrimal sac
& anastomoses with the facial artery
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Arterial Supply of Eyeball
Outer 1/3rd (up to the outer nuclear layer)
is avascular & supplied by the choroidal
vessels
Inner 2/3rd by the CRA
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Veins of the Orbit
Tortuous & freely anastomose with one
another
No valves
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Superior ophthalmic vein
Larger
formed by union of supraorbital & facial
veins
communicates with CRV, then recieves
IOV & 2 vorticose veins from the upper
part of the eyeball
Leaves the orbit through superior orbital
fissure to join the cavernous sinus.
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Inferior Ophthalmic vein
Arises from venous plexus in orbital floor,
Communicates with facial v & pterygoid venous
plexus,
Receives muscular branches & 2 inferior
vorticose v,
Drains into the cavernous sinus or the pterygoid
venous plexus.
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Central retinal vein
Leaves the eyeball by piercing lamina cribrosa
with the CRA
Drains into cavernous sinus or SOV.
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