Orbital Anatomy

Question 1

What bones make up the orbital rim?

Answer 1

Zygomatic, frontal, and maxillary

Question 2

What passes through the optic canal?

Answer 2

optic nerve, ophthalmic artery, and sympathetic nerves

Question 3

What is the arcus marginalis?

Answer 3

Anterior fusion of periorbita with orbital septum and periosteum of facial bones

Question 4

Length and diameter of intraorbital optic nerve?

Answer 4

25-30 mm, 4 mm

Question 5

Which muscles originate at the orbital apex, and which originate at the annulus of Zinn?

Answer 5

All except inferior oblique

S/I/M/L rectus muscles

Question 6

Where does the levator palperbae superioris muscle originate?

Answer 6

above the annulus of Zinn on the lesser wing of the sphenoid

Question 7

What separates the intraconal and extraconal fat?

Answer 7

the intermuscular septum

Question 8

Innervation for EOMs?

Answer 8

Superior rectus and levator: superior division of CN III (oculomotor)
I/M recti and inferior oblique: inferior division of CN III
Superior oblique: CN IV (trochlear)
Lateral rectus: CN VI (abducens)

Question 9

What separates the two portions of the superior orbital fissure, and what structures pass through each portion?

Answer 9

The superior origin of the lateral rectus muscle. Inferomedially is the oculomotor foramen, through which the sup and inf divisions of CN III, the nasociliary branch of V1, and CN VI pass. Superolaterally, CN IV, the sup ophthalmic vein, and the lacrimal and frontal branches of V1.

Question 10

What structures pass through the annulus of Zinn?

Answer 10

Optic nerve, ophthalmic artery, and structres of oculomotor foramen (sup and inf divisions of CN III, the nasociliary branch of V1, and CN VI)

Question 11

Origin and branches of ophthalmic artery?

Answer 11

Internal carotid artery; branches to EOMs, posterior ciliary arteries (long to anterior segment, short to choroid), and central retinal artery (to optic nerve and retina). Terminal branches anastomose anteriorly with branches of external carotid in the face and periorbital region.

Question 12

What functions does parasympathetic innervation in the orbit control?

Answer 12

Accommodation, pupillary constriction, and lacrimal gland stimulation

Question 13

What functions does sympathetic innervation in the orbit control?

Answer 13

Pupillary dilation, vasoconstriction, smooth muscle function of eyelids and orbits, and hidrosis

Question 14

What bone is the lacrimal fossa situated in?

Answer 14

frontal bone