Download Anatomy Lecture 7 – The Orbit

Anatomy Lecture 7- The Orbit










The eye is surrounded by three “spaces”
o Ethmoidal Air Cells
o Fat around the orbit
o Maxillary Sinus
Enophthalmos: eyeball sinking into the orbit once fat is gone.
Blowout Fracture: the orbit becomes continuous with the maxillary sinus
Hephema: a less forceful blow to the eye where blood accumulates in the
anterior chamber
Bones of the Orbit:
o Sphenoid Bone
o Palatine Bone
o Frontal Bone
o Ethmoid Bone
o Lacrimal Bone
o Maxillary Bone
o Zygomatic Bone
Supraorbital Foramen:
o Supraorbital Nerve – Ophthalmic Division (V1) of Trigeminal Nerve
(CN V)
o Supraorbital Artery
Infraorbital Foramen:
o Infraorbital Nerve – Maxillary Division (V2) of Trigeminal Nerve (CN
V)
Superior Orbital Fissure:
o Ophthalmic Vein
o CN III – Oculomotor
o CN IV – Trochlear
o CN VI – Abducens
o Ophthalmic Division (V1) or Trigeminal Nerve (CN V)
Orbitalis Muscle of Muller:
o Largely covers the Superior Orbital Fissure
o Contraction is caused by sympathetic stimulation
o Results in exophthalmos: protrusion of the eyes forward
Parts of the Eye:
o Sclera: white, fibrous outer coat
o Cornea: the central, clear area
o Iris: pigmented
o Pupillary Aperture: the pupil
o Lacrimal Lake: medial corner that collects the tears and send them to
the nasolacrimal duct
o Eyelids: protect the eye
 Tarsal Plate: dense connective tissue that gives the lid its shape






 Glands
 Conjunctival lining
o Palpebral Fissure: opening between the upper and lower lids
o Medial and Lateral Canthi: where the upper and lower eyelids meet
on each side of the eye
Glands of the Eye:
o Meibonian Glands: Oily component of tears
 Chalazion: when the gland is blocked and causes a cyst
o Sebaceous Glands of Zeiss: Sebaceous gland at the base of hair follicles
 Causes external sty
The Conjunctiva:
o Palpebral Conjunctiva: membranous tissue that lines inner surface of
eyelids (pink)
o Bulbar Conjunctiva: membranous tissue over eyeball (transparent)
o Conjunctivitis: Pink eye, irritation
o Jaundice: Yellow conjunctiva
Muscles of the Eye:
o Levator Palpebrae Superioris: draws the eyelid upward
 Innervated by: Oculomotor Nerve (CN III)
 Paralysis of Muscle: Ptosis: drooping of eyelid
o Superior Rectus
 Elevation + Adduction + Intorsion
 Innervated by: Oculomotor Nerve (CN III)
o Inferior Rectus
 Depression + Adduction + Extorsion
 Innervated by: Oculomotor Nerve (CN III)
o Lateral Rectus
 Laterally
 Innervated by: Abducens Nerve (CN VI)
o Medial Rectus
 Medially
 Innervated by: Oculomotor Nerve (CN III)
o Superior Oblique
 Depression + Abduction + Intorsion
 Innvervated by: Trochlear Nerve (CN IV)
o Inferior Oblique
 Depression + Abduction + Extorsion
 Innervated by: Oculomotor Nerve (CN III)
What muscles are used for a vertical downward gaze?
o Inferior Rectus + Superior Oblique
What muscles are used for a vertical upward gaze?
o Superior Rectus + Inferior Oblique
Which nerves pass through the Cavernous Sinus?
o CN III
o CN IV
o CN VI
o CN V – V1 (Opthalmic)


The Bulbar Fascia: Tenon’s Capsule
o Sheath (lateral and medial check ligaments) that form the suspensory
ligament of the eyeball.
Lesions and Conditions
o Oculomotor Nerve Paralysis
 Presentation: Affected eye is down and out
 Down – Superior Oblique is active
 Out – Lateral Rectus is active
o Abducent Nerve Paralysis
 Presentation: When asked to gaze right, right eye does not
abduct.
 Medial rectus is not opposed (crossed eyes)
o Trochlear Paralysis
 Presentation: Eye deviates inward, but not downward.
 Diploplia when looking down (double vision from Med.
& Lat. Rectus)
o Congenital Strabismus
 Presentation: Crossed eyes
o Nystagmus
 Abnormal movements or uncontrollable rhythmical and jerky
eye movements
Arteries:
 Ophthalmic Artery: branch off of Internal Carotid that enters through the
Optic Canal with the Optic Nerve
o Lesion causes blindness
 Ciliary arteries
Veins
 Opthalmic Veins: connect to the Angular Vein, the Cavernous Sinus
o An aneurism in the Cavernous Sinus causes dilation in these veins,
which leads to exophthalmos in the eyeball.

Retinal Vein Occlusion (RVO): second most common cause of vision loss due
to a thrombus within the retinal vein

Sympathetic Nervous System Targets:
o Blood Vessels
o Sweat Glands
o Dilator Muscle
o Superior Tarsal Muscle of Muller – opens palpebral fissure
 Paralysis: Pseudo-ptosis
o Orbitalis Muscle – sling
 Paralysis: Enopthalmos
o Lacrimal Gland
Horner’s Syndrome:
o Pesudo-ptosis: Inactive Superior Tarsal Muscle
o Miosis: Inactive dilator muscle (constricted pupil)
o Enopthalmos: Inactive Orbitalis Muscle
o Flushed Face – Reduced sweat production
Parasympathetic Targets:
o Lacrimal Gland (tear production)
Autonomic Innervation of Lacrimal Gland:
o Pre-Ganglionic: Superior Salivatory Nucleus
o Exit: CN VII (as Greater Petrosal Nerve)
o Joined by Deep Petrosal Nerve
o Go through Vidian Canal
o Post-Ganglionic: Pterygopalatine Ganglion
o Axons course (with zygomatic nerve of V2)
o Go to Lacrimal Branch of V1
o Lacrimal Gland
Consensual Blink Reflex:
o If both eyes blink when the right eye is touched, but not when the left
eye is touched, the problem is with the left trigeminal innervation.
o If only the right eye blinks when either eye is touched, the problem is
with the left facial nerve.



