Post on 13-Aug-2020
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The Orbit, Orbital Contents and Cranial Nerves III, IV and VI
Lecture Objectives• Describe the location of the orbit.• Make a list of structures making the orbit starting from
orbital margin.• Define each component. • Describe openings into orbital cavity.• Define the orbital fascia.• Describe muscles of the orbit, their cone arrangement,
origin, insertion, nerve supply and their function.• Describe the nerves of the orbit, their courses,
important relations and their targets• Describe blood supply and lymph drainage of the orbit.
The Orbit: Orbital Margin
The Orbit: Orbital Cavity
• Shape ..• Orientation ..• Walls ..
Openings into Orbital Cavity• Supraorbital notch (foramen)• Infraorbital groove, canal, & foramen• Nasolacrimal canal• Inferior & superior orbital fissures• Anterior & posterior ethmoidal foramina
Orbit: Content
• Eyelid • Lacrimal apparatus• Eyeball• Fascia • Extraocular muscles• Nerves• Blood vessels• Fatty tissue
Eye: Fascia
• Covers the eye• Separate the eye from
surrounding orbital fat• Facilitates movement of
eye• Pierced by orbital muscles
– Tubular sheath• Attaches to orbital walls
– Medial & lateral check ligaments
• Suspensory ligament of the eye
Eye: Muscles• Extrinsic muscles
– Superior rectus– Inferior rectus– Medial rectus– Lateral rectus – Superior oblique
• trochlea– Inferior oblique
• Intrinsic muscles– Ciliary m. ‐ parasympathetic– Constrictor pupillae of the iris
‐ parasympathetic– Dilator pupillae of the iris ‐
sympathetic
Axes of Eyeball movements
Movements around transverse axis
Movements around vertical and A-P axes
Movements of Eyeball
Nerves of the Orbit
Nerves that Moves the Eyeball
• Oculomotor (III)• Trochlear (IV)• Abducens (VI)
Oculomotor Nerve (III)• Mixed nerve; principally
motor (GSE, GVE) (with proprioseptive)
• Midbrain (anteriorly)
• Cavernous sinus
• Superior and inferior branches
• Superior orbital fissure
Oculomotor Nerve Nuclei
• Main motor nucleus (GSE)– Location– Relations
• PAG, superior colliculus– Connections
• Cortex, superior colliculus– Fibers course
• Accessory parasympathetic nucleus (Edinger‐Westphalnucleus)(GVE)– Location– Relations
• Main motor nucleus– Connections
• Pretectal nucleus– Fibers course
Pupillary Light Reflex
Oculomotor Nerve (III)• The superior branch
– Superior rectus and levator palpebraesuperioris mm.
• The inferior branch – Medial rectus, inferior rectus, and
inferior oblique mm.– Parasympathetic innervation via the
ciliary ganglion to the intrinsic eye muscles
• Major functions – Regulating movements of upper eyelid
and eyeball– Adjustment of lens for near vision, and
constriction of pupil
Oculomotor Nerve (III): Lesion
• Ptosis (denervation of levatorpalpebrae)
• External ophthalmoplegia: Eye look down & out (denervation of extraocular muscles)– Diplopia
• Internal ophthalmoplegia: Dilated, fixed pupil & Paralysis of accommodation
• Test – Asked to move the eye
• Unable to move up, down, or medial
– At rest looks down & lateral
Trochlear Nerve (IV)• Mixed nerve; primarily motor (GSE)
(with proprioceptive)• Smallest of the cranial nerves
• Midbrain*
• Cavernous sinus
• Superior orbital fissure
• Innervate the superior oblique muscle
*Only one to arise from the posterior aspect of the brain stem ‐ Decussate and rotate around the brainstem
Trochlear Nerve (IV): Lesion
• Difficulty to turn eye downward & laterally
• Diplopia in looking downward
Trochlear Nerve Nucleus• Trochlear nerve
nucleus (GSE)– Location– Relations
• PAG, inferior colliculus, main oculomotor nerve nucleus
– Connections• Cortex, superior colliculus
– Fibers course
Abducens Nerve (VI)• Mixed nerve; primarily motor
(GSE) (with proprioceptive)• Pons (anteriorly)
• Cavernous sinus
• Superior orbital fissure
• Called abducens because it causes abduction of the eyeball (lateral rotation)
• Innervates the lateral rectus muscle
Abducens Nerve (VI): Lesion
• Nerve lesion causes internal strabismus& diplopia
• Unable to turn eyeball laterally
Abducens Nerve Nucleus
• Abducent nerve nucleus (GSE)– Location– Relations
• 4th ventricle• Colliculus facialis
– Connections• Cortex, superior colliculus
– Fibers course
Nerves of the Orbit Branches of ophthalmic nerve (V1) Superior orbital fissure
• Frontal nerve Scalp – Branches:
• Supraorbital & Supratochlearnn.
• Lacrimal nerve Lateral part of upper eyelid– Carry parasympathetic fibers to lacrimal gland via zygomaticotemporal nerve
Nerves of the Orbit Branches of ophthalmic
nerve (V1)• Nasociliary nerve‐ Branches:
– Comunicating branch to ciliaryganglion‐ sensory fibers from short ciliary nn.
– Long ciliary nn.‐ carry sympathetic fibers (dilator pupillae m.)
– Posterior ethmoidal n. (ethmoid & sphenoid sinuses)
– Anterior ethmoidal n.• External nasal branch (tip of nose)
– Infratrochlear n. (medial part of upper eyelid & part of nose)
Nerves of the Orbit
Orbit: Ophthalmic Artery
Optic canal• Branches of ophthalmic artery– Supraorbital a.– Supratrochlear a.– Central retinal a.– Ciliary aa. (short & long)– Ethmoidal aa. (anterior & posterior)
– Lacrimal a.– Dorsal nasal a.
Orbit: Ophthalmic Veins
** No lymphatic vessels or nodes in orbit