THE ORBIT Flashcards
Name the seven bones of the boney orbit?
ethmoid, sphenoid, zygomatic, frontal, maxillary, palatine, and lacrimal
what bones are common to both orbits?
sphenoid, frontal, and ethmoid
the orbital rim is the strongest where?
on the sides, laterally (zygomatic bone, and zygomatic processes of the frontal bone).
The lateral rim is displaced, allowing for 100 degree depth view but making eye vulnerable. true or false
true
the orbit gets its widest diameter how many cm behind the orbital rim?
1cm
The orbital roof is what shape? Name the bones that make it up.
Triangular.
frontal bone
lesser wing of sphenoid
lacrimal fossa
The orbital floor is the strongest wall of the eye and extends to the apex. True or False.
False. It is the weakest and doesn’t extend to the apex. it stops abruptly. Is 35-40mm long.
what bone makes up orbital floor?
maxillary bone. very thin
what does orbital floor do?
support the eye and adnexal connective tissues. separate it from maxillary sinus.
Describe a Blow Out Fracture and the Symptoms.
blunt trauma to the orbital floor and damage to maxillary bone into maxillary sinus. symptoms: diplopia numb cheek loss of vision enophthalmos
what is enophthalmus?
displacement of eye in to orbit.
what shape is the lateral wall and what bones make it up?
triangular.
zygomatic (anteriorly)
greater wing sphenoid (posteriorly)
What bone makes up medial wall? Describe its significance.
Lamina Papyrcea of the Ethmoid bone. Very thin. located behind lacrimal crest. However, uniformly protected by honeycomb shaped ethmoid sinus bony lamina. smallest bone of eye.
which gets fracture more often….lamina papyrcea or orbital floor?
orbital floor
what is the anteroposterior diameter of the globe as infant and adult?
infant= 16mm
adult= 24mm
baby reaches 90% of adult size eye by 20 months.
what are the volume measurements and anteroposterior and verticle and horizontal diameters of eye?
the volume of the globe is 7 cm3 the volume of the orbit is 30 cm3. the anteroposterior diameter is ≈24 mm the vertical diameter is ≈23 mm the horizontal diameter is ≈23.5 mm
eye not perfect sphere.
define exophthalmos
forward displacement of the eye.
define proptosis
forward movement of any object, not specific to eye.
what disease is the most common cause of exophthalmos?
Thyroid eye disease. This is when glycosaminoglycans accumulate in the extraocular muscles, connective tissues, and fat around the eye. Lead to swelling.
what are other causes of exophthalmos?
hemangiomas, benign or malignant tumors, severe myopia and buphthalmos (elongated globe) inflammatory pseudotumors, and craniostenoses and the craniofacial dysostosis
what is a Hertel exophthalometer used for?
Eye protrusion. You measure from lateral orbital rim to corneal apex.
what does orbital connective tissue consist of?
fibroblasts, collagen 1, 3 and 4 and endothelial cells.
what is collagen type 1, 3 and 4 function?
collagen 1:
structural integrity
collagen 3:
adhesive between connective tissue and adipocytes cells
collagen 4:
basement membranes of connective tissue to vessels.
The orbital vasculature comes from where?
ophthalmic artery.
Do the arterial and venous blood supply in eye run parallel to one another?
No. they travel two different routes.
except for lacrimal and ethmoidal veins.
orbital veins possess valves. True or False.
False. they have no valves.
