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BMES208 Human Musculoskeletal system

ORBIT AND EYEBALL

Kittikun Viwatpinyo, Ph.D.

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Orbit : Introduction

Orbit is a cone-shaped space with apex in postero-superior direction

(Drake, Wayne & Mitchell, 2005)

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Bony wall of the orbit

Major bony landmarks Trochlear

Lacrimal fossa and crests

Infraorbital fissure and canal

(Moore, Dalley & Agur, 2010)

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Bony wall of the orbit

Gateways of the orbit Optic canal

Superior orbital fissure

Inferior orbital fissure

(Drake, Wayne & Mitchell, 2005)

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Eyelids : Muscles

Orbicularis oculi Levator palpebrae superioris

Superior tarsal (smoothmuscle)

Paralysis of upper eyelidmuscle : Ptosis

(Drake, Wayne & Mitchell, 2005)

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Eyelids : Orbital septum and tarsus

Orbital septum is a membrane of periosteum fromedge of bony orbit

Orbital tarsus : a plate of dense CNT serves as a coreof eyelids

(Drake, Wayne & Mitchell, 2005)

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Eyelids : Tarsal gland

Tarsal gland is a modified sebaceous gland locatedposterior to orbital tarsus

Chalazion = Obstruction of tarsal glands

Hordeolum/Stye = Chalazion + infection(Agur & Dalley, 2008)

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Eyelids : Conjunctiva

Thin membrane covering inner surface of eyelid andreflects onto sclera

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Eyelids : Neurovascular supply

(Drake, Wayne & Mitchell, 2005)

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Fascial sheath of orbit and eyeball

Periorbital fascia (Periorbita)

Common tendinous ring : attachment for Recti muscles

(Drake, Wayne & Mitchell, 2005)

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Fascial sheath of orbit and eyeball

Suspensory ligament of eyeball : Thickening ofperiorbita on inferior half of eyeball

Check ligaments of Medial rectus and Lateral rectusmuscles

(Drake, Wayne & Mitchell, 2005)

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Extraocular muscles

7 muscles : 1 eyelid muscle : Levator palpebrae superioris

4 recti muscles : Superior, Inferior, Medial, Lateral rectus

2 oblique muscles : Superior and Inferior oblique

(Drake, Wayne & Mitchell, 2005)

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Extraocular muscles

Three axes of eyeball movements : AP, Transverseand Vertical

Two axes of eyeball orientation : Optical axis andOrbital axis

AP axis

Transverseaxis Vertical

axis

(Moore, Dalley & Agur, 2010)

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Extraocular muscles

Superior rectus (SR) Nerve : CN. III superior branch

Elevation, Adduction, Med rotation

(Agur & Dalley, 2008)

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Extraocular muscles

Inferior rectus (IR) Nerve : CN. III inferior branch

Depression, Adduction, Lat rotation

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Extraocular muscles

Medial rectus (MR) Nerve : CN. III inferior branch

Adduction

Lateral rectus (LR) Nerve : CN. VI

Abduction

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Extraocular muscles

Superior oblique (SO) Nerve : CN. IV

Depression, Abduction, Med rotation

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Extraocular muscles

Inferior oblique (IO) Nerve : CN. III inferior branch

Elevation, Abduction, Lat rotation

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Extraocular muscles

(Drake, Wayne & Mitchell, 2005)

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Blood supply of the orbit

Ophthalmic artery : a branch of internal carotid a. Lacrimal artery

Central retinal artery

Ciliary arteries

(Moore, Dalley & Agur, 2010)

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Blood supply of the orbit

Superior ophthalmic vein Inferior ophthalmic vein

(Moore, Dalley & Agur, 2010)

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Nerve supply of the orbit

Optic nerve (CN. II)

Surrounded with cranial meninges

Increased intracranial pressure can lead to papilledema

http://www.eyeatlas.com/

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Nerve supply of the orbit

Oculomotor nerve (CN. III)

Superior & Inferior branches

(Drake, Wayne & Mitchell, 2005)

(Moore, Dalley & Agur, 2010)

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Nerve supply of the orbit

Trochlear nerve (CN. IV) Abducent nerve (CN. VI)

(Drake, Wayne & Mitchell, 2005)

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Nerve supply of the orbit

Paralysis from CN. III, IV, VI injury

Oculomotor nerve palsy Trochlear nerve palsy Abducent nerve palsy

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Nerve supply of the orbit

Ophthalmic division oftrigeminal nerve (CN. V1)

Frontal nerve

Lacrimal nerve

(Drake, Wayne & Mitchell, 2005)

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Nerve supply of the orbit

Ophthalmic division oftrigeminal nerve (CN. V1)

Nasociliary nerve

(Drake, Wayne & Mitchell, 2005)

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Autonomic innervation

(Drake, Wayne & Mitchell, 2005)

(Agur & Dalley, 2008)

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Autonomic innervation

Pupil diameter : Pupillary reflexes Sympathetic : pupil dilation (responses to dim light)

Parasym : Pupil constriction (responses to bright light)

(Moore, Dalley & Agur, 2010)

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Autonomic innervation

Lens shape : Accommodation reflexes Parasym activates ciliary muscle Zonular fibers relax Lens is thicker (for near vision)

(Moore, Dalley & Agur, 2010)

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Lacrimal apparatus

(Drake, Wayne & Mitchell, 2005)

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Lacrimal apparatus

Secretomotor control : Parasym fibers

(Drake et al., 2007)

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Eyeball

Outer fibrous layer :

Sclera and Cornae

Middle vascular layer

: Choroid, Ciliary and

Iris

Inner layer :

Retina

Lens, Aqueous humor& Vitreous humor

(Moore, Dalley & Agur, 2010)

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Eyeball

Ciliary body and flow of aqueous humor

(Moore, Dalley & Agur, 2010)

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Eyeball

Glaucoma

Blockage of aqueous humorleads to increasedintraocular pressure

Cataract

Lens becomes opaque due toaging or certain diseases (e.g.Diabetes)

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