Orbital cavity Flashcards
Which is the strongest part of the orbital margin
lateral wall - formed by the frontal process of the zygomatic bone below and teh zygomatic process of the frontal bone above
how many bones form the orbit
Seven:
- frontal
- lacrimal
- ethmoid
- sphenoid
- zygomatic
- maxilla and palatine
What forms the roof of the orbital canal
- orbital plate of the frontal bone
- lesser wing of sphenoid
What forms the floor of the orbital canal
- orbital plate of maxillae
- orbital process of palatine bone
- orbital zurface of zygomatic
what forms to lateral wall of the orbit
- zygomatic bone
- greater wing of the sphenoid
what forms the medial wall of the orbit
anterior to posterior
- frontal process of the maxilla
- lacrimal
- orbital plate of ethmoid
- body of the sphenoid
Where is the optic canal located
lesser wing of sphenoid
What structures pass outside the common tendinous ring
superiorly:
- lacrimal nerve
- frontal nerve
- trochlea nerve
- superior ophthalmic vein
- x2 muscles: superior oblique and levator palpabrae superioris
inferiorly:
- inferior ophthalmic vein
What structures pass within the common tendinous ring
Laterally, superior to inferior:
- superior branch of oculomotor nerve
- nasocillary nerve
- abducent nerve
- inferior banch of oculomotor nerve
Medially
- optic canal containing the optic nerve and ophthalmic artery
Where is the inferior orbital fissure located and what does it transmit
- between the greater wing of sphenoid and the maxilla.
- transmits the maxillary nerve (becomes infraorbital nerve), the zygomatic nerve and the inferior ophthalmic vein (drains to pterygoid venous sinuses)
- usually covered by periorbita and müllers muscle
What is the approximate length of the orbital canal
4-10mm
What is the periorbita
orbital fascia/periosteum of bones that form the walls of the orbit.
- it is continuous with the dura at the optic canal, superior orbital fissure and anterior ethmoidal canal
- at orbital margin, continuous with skull periosteum and gives rise to orbital septum of eyelids
- posteriorly, it forms the common tendinous ring
- innervated by the trigeminal nerve
Where is the supera orbital notch found, why is this important
- medial one third and lateral two thirds along the orbital rim. The supraorbital nerve (branch of frontal which is a branch of CNV1) curves round the notch
- need to infiltrate here with local anaesthetic if removing lesions e.g. dermoid cyst, around this area of the face as this nerve provides the sensation
How can sinusitis be related to diplopia
chronic sinusitis can cause inflammation and secondary hypertrophy of mucous membranes. If this happens i can block off the draining of mucus from the sinuses and cause a cystic lesion (mucocele ) to form
In fractures involving the bones of the walls of the orbit, whre dos the blood ususally accumulate
blood and pus can accumulate between the periorbita and bone, bulging into the orbital cavity, causing proptosis
