The orbit and peri orbital structures Flashcards
Shape of orbit
Pyramidal
Orientation of orbit
Slight lateral and slightly outwards
Does the orbit and peri orbital have gender and racial variations
Yes
Inferior wall of the orbit
Zygomatic bone and maxilla
What is the peri- orbital rim
A thick buttress of bone continuous with the facial buttresses
What is the orbit filled with
Fluid
Full of soft tissue.
Not compressible
Shape of medial wall
Rectangular
Boundaries of medial wall
From anterior lacrimal crest (maxilla) to the apex
Lacrimal fossa - anterior
Lamina papyracea - posterior (paper thin plate of bone overlying the ethmoid sinus)
What suture is at the margin of the medial wall and the roof of the orbit
Fronto- ethmoidal suture
Anterior and posterior ethmoid foramina
What shape is the floor of the orbit
Triangular
Slopes upwards to merge with the medial wall at the maxilla - ethmoidal suture
What separates the floor and the lateral wall
Inferior orbital fissure
Significance of thin orbital floor
Protective mechanism - area of weakness - if the eye takes a blow there is a way pressure can be dissipated
Boundaries of the floor of the orbit
Maxillary bone medially
Zygomatic bone laterally
Palatine bone posteriorly
Separates orbit from middle cranial fossa and temporal fossa
Boundaries of the lateral wall
Zygomatic bone anteriorly and greater wing of sphenoid posteriorly
Where are the zygomatic- temporal and zygomatic- facial nerves
Lateral wall
They pass through their respective foraminas
What bone is the roof of the orbit formed from
Almost entirely frontal bone
What is the roof formed from
Frontal bone and lesser wing of sphenoid
What is housed in the infra temporal fossa
Temporalis muscle, maxillary artery and vein, buccal and temporals fat pads, communicates with the anterior part of IOF
What is housed in the pterygopalatine fossa
Pterygopalatine ganglion, maxillary nerve and its branches, infra- orbital branch of the maxillary artery, communicates with the posterior part of the IOF
Are the infra temporal fossa and pterygopalatine fossa intra or extra cranial
Extra cranial
Function of orbital apex
Route of communication between the intra- cranial cavity and the orbit
Contains the optic canal and part of the SOF
Orbital apex syndrome
Function of the annulus of Zinn
Divides the SOF into intra coronal and extra coronal spaces
Superior orbital fissure
Gives origin to 4 rectus muscles
Transmits lacrimal nerve, frontal nerve, trochlear nerve, superior ophthalmic, abducens, nasociliary, inferior ophthalmic vein
Which structures are not inside the annulus of zinc
Lacrimal, frontal and trochlear
Fascial sheath
Eyeball lies in the orbit surrounded by a fascial sheath separating it from the orbital muscles and fat
Eye is suspended in place by check ligaments and suspensory ligament of Lockwood
Muscles of the eye
Superior rectus
Inferior rectus
Lateral rectus (VI)
Medial rectus
Ocular muscles
Superior rectus (III) Inferior rectus (III) Lateral rectus (VI) Medial rectus (III) Superior oblique (IV) - Down and lateral Inferior oblique (III) - NOT IN ANNULUS OF ZINN - Up and lateral
Dacryoadenitis
Inflammation of the lacrimal glands
Function of lacrimal gland
Produces tears which flow into canals leading to the lacrimal sac
Tears drain through the nano- lacrimal duct into the inferior meatus of the nose
