Head: Orbit Flashcards
Bones of the BASE of the Orbit
- Orbital margin (orbital opening)
Bones of the APEX of the Orbit
- At the optic canal (lesser wing of sphenoid)
Bones of the SUPERIOR part of the Orbit
- Orbital part of frontal bone
MEDIAL bones of the Orbit
- Orbital plate of ethmoid
- Lacrimal
- Frontal process of maxilla
- Lacrimal groove
- Fossa
INFERIOR bones of the Orbit
- Zygomatic
- Maxilla
LATERAL bones of the Orbit
- Frontal process of zygomatic bone
- Greater wing of sphenoid
Preorbita
- Periosteum that lines the orbit
Orbit and Orbital region content
- Obicularis oculi
- Eyelids
- Lacrimal apparatus
- Eyeball
- Extraocular muscles and their innervation
- Optic nerve
- Ophthalmic nerve (V1) branches
- Opthlamic veins
- Ciliary ganglion
- Retrobulbar fat
Eyelids (protect the eye)
- Skin on the outside
- Conjunctiva lines the inside
Content of the eyelids
- Orbicularis oculi, palpebral part (CN VII)
- Tarsal plate (tarsus)
Eyelid is the insertion of
- Levator palpebrae superioris (CN III innervation)
- Superior tarsal muscle (sympathetic innervation) onto the upper eyelid
A ptosis can result from
- Lesion of oculomotor nerve or sympathetics to the head
Cornea
- Transparent layer that covers iris and pupil
- Avascular
- Continuous with sclera (white of the eye)
Corneal reflex
- Touching elicits blink response
Sensory innervation of upper eyelid and cornea
- Ophthalmic division of trigeminal nerve
Iris
- Colored diaphragm
- Surrounds pupil
Orbital Septum
- Membranous sheet
- Attaches to orbital rim
- Separates orbit from periorbital region
Lacrimal gland
- Produces tears that are secreted through the lacrimal ducts
- Tears wash across eye and drain into the nasolacrimal duct
- Empties into inferior nasal meatus in the nasal cavity
Presynaptic parasympathetics of the Lacrimal gland originate
- In the pons
Presynaptic parasympathetics originate in the pons travel in
- Facial nerve (nervus intermedius)
- Through pterygoid canal
- Zygomatic and lacrimal nerves
Presynaptic parasympatehtics traveling in Facial nerve
- Greater petrosal nerve
- Greater petrosal joins deep petrosal forming nerve of pterygoid canal
Presynaptic parasympathetics traveling through Pterygoid canal
- Enter pterygopalatine fossa
- Synapse on postsynaptics in pterygopalatine ganglion
Presynaptic parasympathetics traveling in Zygomatic and Lacrimal nerves
- Synapse on the lacrimal gland
Sympathetic innervation of Lacrimal gland
- Travel in ICA periarterial plexus
Postysynaptic sympathetics of Lacrimal gland originate
- Originate in superior cervical ganglion
Deep Petrosal nerve (Lacrimal sympathetics) is derived from
- The ICA periarterial plexus
- Joins greater petrosal nerve to form nerve to pterygoid canal
Extra-Ocular muscles
- Muscles that move the eyeballs and eyelids
Superior Oblique innervation
- Trochlear nerve (CN IV)
Lateral Rectus innervation
- Abducens nerve (CN VI)
Extra-Ocular muscles innervated by oculomotor nerve (CN III)
- Inferior rectus
- Medial rectus
- Inferior oblique
- Superior rectus
- Levator palpebrae superioris
The 4 recti muscles originate from
- The common tendinous ring
Common Tendinous Ring
- Surrounds optic canal
- Portion of superior orbital fissure
Superior Oblique origin
- Sphenoid bone separate from ring
Superior Oblique pathway
- Passes through trochlea
- Redirects line of pull
Inferior oblique origin
- Anterior medial wall of orbit
Superior/Inferior oblique insertion
- Sclera
Muscle action based on primary position
- Based on muscle location and line of pull
- Angled line of pull in the primary position, more than one function
Vertical axis eye movements
- Abduction
- Adduction
Transverse axis eye movements
- Elevation
- Depression
Anterior/Posterior axis eye movements
- Intorsion
- Extorsion
Lateral Rectus function from primary position
- Abduction
Medial Rectus function from primary position
- Adduction
Superior Rectus function from primary position
- Elevates
- Adducts
- Intorsion
Inferior Rectus function from primary position
- Depresses
- Adducts
- Extorsion
Superior Oblique function from primary position
- Intorsion
- Depresses
- Abducts
Inferior Oblique function from primary position
- Extorsion
- Elevates
- Abducts
Eye muscles have
- Resting tone
Muscle activity depends
- Eye position
Muscles work
- Synergistically with each other
Pure depression from primary position involves
- Inferior Rectus
- Superior Oblique
Coordination of both eyes requires
- The yoking of muscle actions
Eye position determines
- The primary muscle involved in producing a specific movement
Clinical use of eye position
- The eye is positioned so that one muscle dominates action
Superior Rectus and Inferior Rectus in the abducted position
- Superior rectus: elevation
- Inferior rectus: depression
Superior Oblique and Inferior Oblique in the adducted position
- Superior oblique: depression
- Inferior oblique: elevation
Oculomotor Nerve Palsy symptoms
- Ptosis
- Down and out pupil
Abducens Nerve Palsy symptoms
- Loss of abduction
- Medial deviation of eye
Trochlear Nerve Palsy symptoms
- Loss of depression while eye is adducted
- Head tilt
Branches of Ophthalmic Nerve (V1) in the orbit
- Frontal
- Lacrimal
- Nasociliary
Frontal Nerve branches of the Ophthalmic Nerve
- Supraorbital
- Supratrochlear
Nasociliary Nerve branches of the Ophthalmic Nerve
- Posterior ethmoidal
- Anterior ethmoidal
- Infratrochlear
- Long ciliary
- Sensory root to ciliary ganglia
Nerves in the Orbit
- Branches of Ophthalmic Nerve (V1)
- Trochlear nerve (CN IV)
- Optic nerve
- Abducens nerve (CN VI)
- Occulomotor nerve
- Zygomatic nerve (branch of V2)
Sensory root to ciliary ganglia
- Short ciliary connect ciliary ganglia to eyeball
Occulomotor Nerve divisions
- Superior division: SR, LP
- Inferior division: MR, IR, IO, presynaptic parasympathetic neurons
Superior division of Occulomotor nerve innervates
- Superior rectus
- Levator palpebrae
Inferior division of Occulomotor nerve innervates
- Medial rectus
- Inferior rectus
- Inferior oblique
- Presynaptic parasympathetic neruons
Ciliary ganglion
- Cell bodies of postsynaptic parasympathetic neurons to the inner eye
- Sensory and sympathetic nerve fibers pass through the ciliary ganglion
Only parasympathetic fibers synapse in the ciliary ganglion…
- Sensory and sympathetic fibers are just passing through
Parasympathetic to Intrinsic Eye Muscles
- Iris (pupil constriction)
- Ciliary muscle (increase lens convexity, near vision)
Pathway of Parasympathetic to Intrinsic Eye Muscles
- Pre-synaptic neurons travel in oculomotor nerve
- Synapse in ciliary ganglion
- Postsynaptics travel in short ciliary nerve to inner eye
Sympathetic to Intrinsic Eye Muscles
- Iris (pupil dilation)
- Ciliary muscle (decrease lens convexity, distant vision)
Pathway of Sympathetic to Intrinsic Eye Muscles
- Postsynaptics from superior cervical ganglion travel in IC perarterial plexus
- Pass through ciliary ganglion/short ciliary nerves and long ciliary nerve to inner eye
Ophthalmic Artery is a branch of
- Internal carotid artery
Branches of the Ophthalmic Artery
- Central retinal
- Lacrimal
- Posterior ciliary
- Muscular branches
- Supraorbital
- Anterior ethmoidal
- Posterior ethmoidal
- Supratrochlear
- Dorsal nasal
Veins of the Orbit
- Superior and inferior ophthalmic veins
