A &P: Bony orbit and EOMS

Sphenoid body

Orbital plate of ethmoid bone

Largest bone of medial wall

Thinnest bone of the medial wall

Frontal process of maxilla

Lacrimal bone

Medial wall of the bony orbit consits of…

Frontal process of the maxilla

Lacrimal bone

Orbital plate of the ethmoid

Body of the sphenoid

Orbital process of the palatine bone

Orbital surface of the maxillary bone

Zygomatic bone

Floor of bony orbit

Shortest of the orbital walls

Formed by:

Orbital plate of the maxilla

Orbital surface of the zygomatic bone

Orbital process of the palatine bone

Infraorbital foramen

Transmits the infraorbital vessels and nerve

Infraborbital sulcus

Connects sphenomaxillary fissure → infraorbital canal → infraorbital foramen

Orbital surface of zygomatic bone

Greater wing of sphenoid bone

Zygomatic process of frontal bone

Lateral orbital tubercle (Of Whitnall)

Small elevation on zygomatic bone, behind lateral orbital margin

Attaches:

• Check ligament of the lateral rectus muscle

• Suspensory ligament of the eyeball

• Aponeurosis of the levator palpebrae superiori

Orbital plate of frontal bone

Lesser wing of sphenoid bone

Roof of orbit

Concave anteriorly
Flatter posteriorly

The orbital plate of the frontal bone seperates….

The orbit from the anterior cranial fossa

Lacrimal fossa of frontal bone

Where the lacrimal gland is located

_{Not the same as lacrimal fossa of the lacrimal gland, where the lacirmal sack is located}

Lacrimal fossa

Contains the lacrimal sack

Helps with draining of tears

Not the same as lacrimal fossa of frontal bone

What attaches here?

The trochlea

U-shaped piece of cartilage

Tendon of the superior oblique muscle passes through here

Orbital rim fracture

Blowout fracture

Orbital floor fracture

Optic canal

Transmits optic nerve and ophthalmic artery

Connects orbit to middle cranial fossa

Optic nerve glioma (Meningioma)

May lead to unilateral enlargement of optic canal

Superior ophthalmic vein

Lacrimal nerve

Recurrent meningeal br. of ophtalmic artery

Frontal nerve

Trochlear nerve

Superior division of oculomotor nerve

Nasocilliary nerve

Abducent nerve

Inferior division of oculomotor nerve

Inferior ophthalmic veins

Common tendinous ring

Ophthalmic atery

Optic nerve

Upper part of superior orbital fissure

Middle part of superior orbital fissure

Lower part of superior orbital fissure

Superior orbital fissure

Gap between greater and lesser wings of sphenoid

Lateral to optic canal

Divided into upper, middle, and lower parts by common tendinous ring

Inferior orbital fissure

Between floor of the orbit and the lateral wall

Structures exit through the infra orbital foramen

Zygomatic nerve

Emissary veins

Maxillary nerve

Infraorbital nerve (V2, maxillary division)

Infraorbital grooves

Infraorbital canal

Lower margin of orbit

Infraorbital foramen

Infraorbital artery + vein, maxillary and V2 nerve, and infraorbital nerve exit through here

Infraorbital artery

Infraorbital vein

Periosteum

Orbital fat

Spaces not occupied by ocular structures are filled with adipose

Thyroid ophthalmopathy cayses proliferation of orbital fat

Orbital septum

Continuous with connective tissue at orbital margins

Ends at tarsal plates

Funciton of orbital septum

Helps prevent facial infections from entering the orbit

Periorbita

Orbital periosteum

Dense connective tissue

Attachment site for muscles, tendons, and ligaments

Tenons capsule

Connective tissue

Fuses with optic nerve sheath posteriorly

Fuses with intermuscular septum anteriorly (3mm posterior to the limbus)

Periorbital sinuses

Offer route for the spread of infection

Mucoceles occasionally arise from sinuses and extend into the orbit

Four main paranasal sinuses

Maxillary sinus

Frontal sinus

Ethmoid sinus

Sphenoid sinus

Anullis of zinn

Origin of all vertical + horizontal EOM’s

Origin of superior oblique

Lesser wing of the sphenoid bone

Medial to optic canal (Near frontoethmoid suture)

Insertion of superior oblique

On top of the globe behind its equator

Origin of inferior oblique

Anterior orbit (From maxilary bone)

Only EOM to have its origin in anterior orbit

Insertion of inferior oblique

Posterior portion of the globe, laterally

Vertical + Horizontal EOM lengths

Lateral rectus > superior rectus > inferior rectus = medial rectus

Rectus EOM blood supply

Internal carotid artery → Ophthalmic artery → Muscular branches of ophthalmic artery

Muscular artery → Anterior ciliary arteries (Supply anterior part of recti)

External carotid artery → Infraorbital artery (IR and IO region)

Anterior cilliary arteries

Both vertical EOM’s contain 2 ciliary arteries

Medial rectus → 2

Lateral rectus → 1 (Exception)

Superior oblique blood supply

Superior muscular branch of ophthalmic artery

Inferior oblique

Inferior muscular branch of ophthalmic artery

External carotid artery → Infraorbital artery