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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.