AP03: The sphenoid bone and orbit

CNV

trigeminal nerve

What are the 3 divisions of the trigeminal nerve

CNV1-ophthalmic

CNV2- maxillary

CNV3- mandibular

What are the contents of the optic canal

optic nerve CNII, ophthalmic artery

Function of the optic canal

vision- arterial supply to the orbit

Contents of the foramen rotundum

maxillary division of CNV

Function of the foramen rotundum

sensory innervation to skin over cheeks, part of oral cavity, hard palate, nasal cavity

Contents of the foramen ovale

mandibular division of CNV (trigeminal nerve)

also accessory meningeal artery, emissary vein, lesser petrosal nerve

Function of the foramen ovale

motor innervation to muscles of mastication and others;

sensory innervation to mandibular teeth, skin over mandible and lower lips

Contents of the foramen spinosum

middle meningeal artery and vein

meningeal branch of CNV3 (nervus spinosus)

Functino of the foramen spinosum

neurovascular supply to the meninges

Contents of the superior orbital fissude

CNIII- oculomotor nerve

CNIV- trochlear nerve

CNVI- abducens nerve

ophthalmic division of CNV (frontal, nasociliary and lacrimal branches)

superior ophthalmic veins

Function of the superior orbital fissure

-transmits CN III, IV, VI and V1, allowing motor control of extraocular muscles, parasympathetic control of pupil and accommodation, sensory innervation of the eye and orbit, and venous drainage via the superior ophthalmic vein

Contents of the inferior orbital fissure

infraorbital nerve (CNV2)

zygomatic nerve (CNV2)

infraorbital artery (from maxillary artery)

inferior ophthalmic vein

Function of the inferior orbital fissure

infraorbital nerve provides sensory innervation to the skin inferior to the eye

zygomatic nerve innervates skin over cheeks and temple via branches

Bones found on the roof of the orbit

-orbital plate of the frontal bone

Floor of the orbit

-orbital surface of the maxilla

-zygomatic bone

-palatine bone

Lateral wall of the orbit

-frontal process of the zygomatic bone

-greater wings of the sphenoid

Medial wall of the orbit

-frontal process of maxilla

-lesser wing of sphenoid

-orbitsl plate of ethmoid

- lacrimal bone

Which soft tissues of the orbit may be damaged if there is a blow-out fracture

eyeball

extraocular muscles

infraorbital nerve

What is a blowout fracture

break in the thin bones of the orbit (usually the floor or inner wall)

Which bony walls of the orbit are likely to be fractured in the event of a blowout fracture?

-floor of the orbit (very thin, likely to fracture)

-medial wall of the orbit (ethmoid bone) is also very thin and may fracture

Clinical symptoms of a blowout fracture

-pain, swelling, bruising (black eye)

-diplopia (double vision) due to cranial nerve palsies (paralysis of cranial nerves) specifically CN III/ oculomotor, IV/trochlear and VI/abducens

What is the optic chiasm

X-shaped structure at the base of the brain where optic nerve fibers from each eye cross over

Where is the optic chiasm located

superior to the pituitary gland and the diaphragma sellae

Label this diagram of the sphenoid bone

1- optic groove

2- optic canal

3- superior orbital fissure

4- foramen rotundum

5- foramen spinosum

6- foramen ovale

A- anterior clinoid process

B- lesser wing of sphenoid

C- greater wing of the sphenoid

D- posterior clinoid process