orbit and contents · 2019-07-15 · levator palpebrae superioris skin ... a dry eye or reduced...
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Orbit and Contents
Mikel Snow, Ph.D.Professor
Dept. Integrative Anatomical [email protected]
July 15, 2019
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• Extraocular muscles (actions & innervations)
Lecture Outline
• Relationships of orbits to paranasal sinuses
• Arrangement of orbital contents (fascial structures)
• Structure of eyelids & lacrimal apparatus
• Cranial nerves of the orbit (CN II, III, IV, V1, VI )
• Autonomics of the orbit (parasympathetic & sympathetic)
• Blood supply to the orbit and retina
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ORBIT
Maxillary sinus
Nasal cavity
Frontal Section through Orbit
Frontal sinusEthmoid
air cells
F
E
MN
ORBIT
Anteroposterior Radiograph
Relationships of the Orbit
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• Relationships of the orbit• Arrangement of orbital contents (fascial structures)• Structure of eyelids & lacrimal apparatus• Blood supply to the orbit and retina• Cranial nerves of the orbit (CN II, III, IV, V1, VI )• Autonomics of the orbit (parasympathetics & sympathetics• Extraocular muscles (actions & innervations)
Lecture Outline
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Skull
Dura mater lining the cranial cavity has two layers:
DuraPeriostealMeningeal
Cranial Dura
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Fat
Fat
Fat
Fat
Orbital septum
Tarsal plates
Periosteum
Orbital septum
Superior tarsal plate
Inferiortarsal plate
Bilaminarintracranial
dura
General Arrangement of Orbital Fascia & Fat
Optic sheath:
Periorbita (periosteum)
Optic canal
Orbital septum
DuraArachnoidPia
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Levator palpebrae superioris
Skin
Orbital septum
Orbicularis oculi
Tarsal plateTarsal plate
Conjunctival vessels
Bulbar conjunctiva
Superior tarsal muscleSuperior tarsal muscle
Palpebral conjunctiva
Anatomy of the Eyelids
Cilia
(skeletal)
(skeletal muscle innervated by CN III)
(smooth muscle innervated by sympathetics)
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Lacrimal Apparatus
The lacrimal gland produces tears that wash across the eye from lateral to medial to moisten and aerate the cornea.
Lacrimal lake
Lacrimal gland
A dry eye or reduced tears can lead to corneal edema.
Lacrimal gland is innervated by parasympathetics from facial nerve.
Nasolacrimal duct
Excess tears drain to nasal cavity
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• Relationships of the orbit• Arrangement of orbital contents (fascial structures)• Structure of eyelids & lacrimal apparatus• Blood supply to the orbit and retina• Cranial nerves of the orbit (CN II, III, IV, V1, VI )• Autonomics of the orbit (parasympathetics & sympathetics)• Extraocular muscles (actions & innervations)
Lecture Outline
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Optic nerve ICA
The blood supply to the orbit and eye is via the ophthalmic artery, which is first branch of internal carotid.
Ophthalmic artery
Internal carotid in cavernous sinus
Ophthalmic artery
Central artery of
retina
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Internal carotid artery
Central artery of the retina
Ophthalmic artery
CNII
Optic canal
Normal retina, right eye
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CSF
Normal
CSF
Intracranial pressure
Clinical Correlation
Papilledema
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Venous drainage from the orbit communicates with facial vein anteriorly & cavernous sinus posteriorly.
Facial veinCavernous sinus
Superior ophthalmic
vein
These veins have no valves!
Danger area
Cavernous sinus thrombosis
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• Relationships of the orbit• Arrangement of orbital contents (fascial structures)• Structure of eyelids & lacrimal apparatus• Blood supply to the orbit and retina• Cranial nerves of the orbit (CN II, III, IV, V1, VI )
• Autonomics of the orbit (parasympathetics & sympathetics)• Extraocular muscles (actions & innervations)
Lecture Outline
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Optic (II)Oculomotor (III)
Trochlear (IV)
Trigeminal (V)Ophthalmic (V1)
Abducent (VI)
Cranial Nerves Related to the Orbit
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CN II
CN V2
CN V3
3 Cranial nerves innervate extraocular muscles:
Oculomotor (III)
Trochlear (IV)
Abducent(VI)
Abducent(VI)
CN V1
Superior oblique
Lateral rectus
All others
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Handy mnemonic:LR6SO4AO3
(Lateral Rectus CN VI, Superior Oblique CN IV, All Others CN III)
Summary of Extraocular Muscle Innervation
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CN V
Trigeminal ganglion
Ophthalmic (V1)
Nasociliary
Lacrimal
Frontal
Sensory Nerves in the Orbit
NFL
Long ciliary n.
Short ciliary n.
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Ciliary ganglionCN III
Cornea
Long ciliary nerves
V1
Short ciliary nerves
Somatosensory pathways for blink reflex:• Pass thru short & long ciliary nerves.
• Cell bodies in trigeminal ganglion.
• Pass thru ophthalmic nerve.
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• Relationships of the orbit• Arrangement of orbital contents (fascial structures)• Structure of eyelids & lacrimal apparatus• Blood supply to the orbit and retina• Cranial nerves of the orbit (CN II, III, IV, V1, VI )
• Autonomics of the orbit (parasympathetics & sympathetics)• Extraocular muscles (actions & innervations)
Lecture Outline
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Netter Plate 133
Trigeminal ganglion
CN III
Brainstem
Superior cervical sympathetic ganglion
Thoracic Spinal cordThoracic sympathetic trunk
Internal carotid artery
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Smooth Muscles of the Eye
Ciliary muscle (parasymp) – adjusts
thickness of lens (accommodation/focus)
Sphincter pupillae m. (parasympathetic) –
constricts pupil
Dilator pupillae m.(sympathetic) – dilates pupil
Dilator pupillae m.(sympathetic) – dilates pupil
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Ciliary ganglionCN III
V1
Autonomic Innervation to the Eye:Parasympathetics to ciliary & sphincter pupillae mm.
Sphincter pupillae m.
Ciliary muscle
Dilator pupillae m.
Short ciliary nerves
Sympathetics to dilator pupillae muscle
• Short ciliary nerves: para/post, symp/post & SS.• Long ciliary nerves: symp/post & SS.
Long ciliary nerves
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Pupillary light reflex*
*Pupillary (light) reflex (constriction of pupil in response to light shone in pupil):afferent limb = CN II from stimulation of retinal ganglion cellsefferent limb = CN III (para) via ciliary nerves to pupillary sphincter
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1. Ptosis (droopy upper eyelid) paralysis of superior tarsal muscle
Patient with right‐side Horner’s syndrome
4. Anhydrosis (dry skin due to lack of perspiration) sweat glands denervated
3. Vasodilation (flushed, warm skin) paralysis of smooth muscle in walls of facial vessels
2. Miosis (constricted pupil) paralysis of dilator pupillae muscle because no resistance to parasympathetically controlled pupillary sphincter
What are the signs in this patient that there is an interruption of sympathetic innervation to the head?
Clinical correlate: Horner’s Syndrome
“Sahara dessert syndrome”
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• Relationships of the orbit• Arrangement of orbital contents (fascial structures)• Structure of eyelids & lacrimal apparatus• Blood supply to the orbit and retina• Cranial nerves of the orbit (CN II, III, IV, V1, VI )• Autonomics of the orbit (parasympathetics & sympathetics)• Extraocular muscles (actions & innervations)
Lecture Outline
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Med
ial orbita
l wallM
edial orbital wall
Anatomical arrangement, innervation, & function of extraocular muscles
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Extraocular Muscles
The key to learning and retaining knowledge of how the 6 extraocular muscles move the eyeball is to knowvisualize each muscle’s anatomical position relative to the eyeball’s axes.
Vertical AxisHorizontal Axis
ABduction / ADduction
Anterior/Posterior Axis
Elevation / Depression Extorsion / Intorsion
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LR
MR
SO
IO
IR
SR
IO = inferior obliqueIR = inferior rectusLR = lateral rectusMR = medial rectusSO = superior obliqueSR = superior rectus
Right orbit seen from above
The position of each extraocular muscle can be represented by a simple line of contraction for visualizing each muscle’s action relative to an axis:
Visual gaze
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Horizontal axisVertical axis
When SR contracts relative to horizontal axis, cornea moves upward (ELEVATION).
When SR contracts relative to vertical axis, the cornea moves medially (ADUCTION).
Superior Rectus Muscle: Anatomical Actions
Horizontal axis
SR passes medial to vertical axis.M
edia
l wal
l
Lateral ViewSuperior View
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Horizontal axis
Vertical axis
Horizontal axis
Med
ial w
all
Superior Oblique: Anatomical Actions
When SO contracts relative to horizontal axis, it rotates back of eye forward making cornea rotate downward (DEPRESSION).
When SO contracts relative to vertical axis, it rotates back of the eye medially causing cornea to rotate outward (ABDUCTION).
Inferior oblique & Inferior rectus schematized at end of this PPT.
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Horizontal axisVertical axis
Horizontal axis
Inferior Rectus: Anatomical Actions
Med
ial w
all
When IR contracts relative to horizontal axis, it rotates cornea downward (DEPRESSION).
When IR rectus contracts relative to vertical axis, it rotates cornea medially (ADDUCTION).
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Horizontal axisVertical axis
Med
ial w
all
Inferior Oblique: Anatomical Actions
When IO contracts relative to horizontal axis, it rotates back half of eyeball down causing cornea to rotate upward (ELEVATION).
Horizontal axis
When IO contracts relative to vertical axis, it rotates back of eyeball medially causing cornea to rotate laterally (ABDUCTION).
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Summary Movements Relative to Vertical Axis
ADDUCTORS:Superior rectusInferior rectusMedial rectus
SR
MR
IR
ABDUCTORS:Superior obliqueInferior obliqueLateral rectus
SO
IO
LR
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Summary Movements Relative to Horizontal Axis
ELEVATORS:Superior rectusInferior oblique
DEPRESSORS:Superior oblique
Inferior rectus
SR
IO
SO
IR
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Walled City of Dubrovnik
Questions?