A3 - orbit and eye Flashcards
what is the base of the orbit surrounded by?
the optic margin
describe the medial walls of the orbit
- separated by the ethmoidal sinuses and the upper parts of the nasal cavity
- lie parallel to each other
describe the lateral walls of the orbit
lie approx at a right angle
what 7 bones contribute to the orbit? (A-G)
A = frontal
B = zygomatic
C = maxilla
D = sphenoid
E = ethmoid
F = lacrimal
G = palatine
what bones contribute to the superior wall (roof) of the orbit?
frontal and sphenoid
what bones contribute to the medial wall of the orbit?
- ethmoid
- maxilla
- lacrimal
- sphenoid
what bones contribute to the inferior (floor) of the orbit?
maxilla, palatine and zygomatic
what bones contribute to the lateral wall of the orbit?
sphenoid and zygomatic
what does the superior wall of the orbit separate the orbital cavity from?
the anterior fossa
what does the inferior wall of the orbit separate the orbital cavity from?
maxillary sinus
what does the lateral wall of the orbit separate the orbital cavity from?
middle cranial fossa and the temporal fossa
what makes up the orbital margin (rim) (base)?
- supra-orbital margin : frontal bone
- medial margin : frontal process of the maxilla
- infra-orbital margin : zygomatic process of the maxilla and the zygomatic bone
- lateral margin : zygomatic process of the frontal bone and the zygomatic bone and its frontal process
what is at the apex of the orbit?
optic foramen (canal)
what does the optic canal provide passage for?
the optic nerve (CNII) and opthalmic artery to exit the skull
what is the apex of the orbit bounded by?
medially by the body of the sphenoid bone and laterally by the lesser wing of the sphenoid bone
what is the orbital apex medial to?
the superior orbital fissure
what is the depression in the roof/superior wall of the orbit?
lacrimal fossa — intended for hosting the orbital part of the lacrimal gland
describe features of the medial wall of the orbit
- the lacrimal bone and the frontal process of the maxilla build the lacrimal groove which contains the lacrimal sac
- also contains the anterior and posterior ethmoidal foramina and the trochlea
where are the ethmoidal foramina and what do they do?
- the ethmoidal foramina are found at the junction between the roof and the medial wall as a part of the frontal-ethmoidal suture
- serve as passageways for the anterior and posterior ethmoidal nerves and vessels
what is the trochlea?
- the only cartilage found in the orbit
- it is a pulley-like structure in the orbit through which the tendon of the superior oblique muscle passes
what is the most important landmark of the floor/inferior wall of the orbit?
inferior orbital fissure — separates the floor from the lateral wall, and provides passage for several neurovascular structures
what is the strongest and thickest wall of the orbit?
lateral
what does the lateral wall of the orbit contain?
superior orbital fissure, found between the greater and lesser wing of the sphenoid bone
why is there no suture between the sphenoid bone and maxilla?
they are separated by the inferior orbital fissure