SM_06a: Orbit Anatomy and Development

Question 1

____ makes up roof of orbit

Answer 1

Frontal bone makes up roof of orbit

Question 2

____ and ____ make up floor of orbit

Answer 2

Maxilla (mostly) and zygomatic bone make up floor of orbit

Question 3

____ and ____ make up the lateral wall of the orbit

Answer 3

Zygomatic bone and greater wing of sphenoid make up the lateral wall of the orbit

Question 4

____, ____, and ____ make up the medial wall of the orbit

Answer 4

Maxilla, lacrimal bone, and ethmoid bone make up the medial wall of the orbit

Question 5

____ separates sphenoid wings, while the ____ traverses the lesser wing

Answer 5

Superior orbital fissure separates sphenoid wings, while the optic canal traverses the lesser wing

Question 6

Orbit is bounded medially and inferiorly by ____ and ____

Answer 6

Orbit is bounded medially and inferiorly by ethmoid and maxillary paranasal air sinuses

(these spaces have implications for fractures and the spread of infections)

Question 7

Blow-out fractures of the orbital wall are when ____

Answer 7

Blow-out fractures of the orbital wall are when orbital contents extend out of the ethmoid sinus into the maxillary sinus

(blood can also accumulate in the maxillary sinus)

Question 8

Eye develops from the ___, ___, and ___

Answer 8

Eye develops from the lens placode, optic cup, and head mesenchyme

1. Lens placode sinks under the surface as the lens vesicle is surrounded by the optic cup
2. Head mesenchyme from the neural crest begins to condense around the optic cup to form the connective tissue elements

Question 9

Coloboma is ____

Answer 9

Coloboma is retention of the ventral cleft

(may involve iris - keyhole pupil - or whole ventral sclera)

Question 10

Two layers of the optic cup form the ____, while the mesenchyme forms the ____, ____, ____, and ____

Answer 10

Two layers of the optic cup form the two layers of the retina, while the mesenchyme forms the sclera, cornea, choroid, and meninges

Question 11

____ is main artery of the eye

Answer 11

Central artery of the retina is main artery of the eye

Question 12

Optic cup is extension of the ____

Answer 12

Optic cup is extension of the neural crest

• Optic nerve (II) is a brain fiber tract surrounded by meninges and CSF unlike a typical nerve
• Two layers of optic cup form neural and epithelial layers of retina
• Two layers of optic cup never tightly fused, allowing detached retina to occur

Question 13

____ divides the aqueous humor and vitreous humor

Answer 13

Iris divides the aqueous humor and vitreous humor

(both have lots of glycosaminoglycans)

Question 14

Cornea is ____ and is nourished by ____

Answer 14

Cornea is avascular and nourished by aqueous humor

Question 15

Aqueous humor is produced in the ____ and passes through the pupil to the ____ and then to the venous ____

Answer 15

Aqueous humor is produced in the posterior chamber and passes through the pupil to the anterior chamber and then to the venous Canal of Schlemm

Question 16

Narrow angle glaucoma involves ____

Answer 16

Narrow angle glaucoma involves increased aqueous humor pressure

Question 17

____ is the optic nerve blind spot, while the ____ in the ____ is the area of most acute vision

Answer 17

Optic disc is the optic nerve blind spot, while the fovea centralis in the macula lutea is the area of most acute vision

Question 18

Dilated pupil may be indicative of ____

Answer 18

Dilated pupil may be indicative of increased intracranial pressure

(iris has circular sphincter for the pupil and a radiator dilator muscle, lens is achnored by taut suspensory ligaments, and contraction of the ciliary muscle allows the lens to round up for close-up vision)

Question 19

Describe the path of the lacrimal apparatus

Answer 19

Lacrimal apparatus

1. Lacrimal gland
2. Conjunctival sac
3. Lacrimal papillae with lacrimal puncta
4. Lacrimal canaliculi
5. Lacrimal sac
6. Nasolacrimal duct
7. Inferior meatus of nasal cavity

Question 20

____ is innervated by the oculomotor nerve, and the ____ helps raise the eyelid (sympathetic innervation)

Answer 20

Levator palpebrae superioris is innervated by the oculomotor nerve, and the superior tarsus muscle helps raise the eyelid (sympathetic innervation)

Question 21

Tarsal gland obstruction forms a ____, while ciliary gland obstruction forms a ____

Answer 21

Tarsal gland obstruction forms a chalazion, while a ciliary gland obstruction forms a sty

Question 22

Extraocular muscles from head somites include ____, ____, and ____

Answer 22

Extraocular muscles from head somites include rectus (medial, lateral, superior, inferior), levator palpebrae superioris, and obliques (superior, inferior)

(superior oblique not visible on lateral view)

Question 23

Rectus muscles originate from ____

Answer 23

Rectus muscles originate from anulus tendineus

• Fibrous ring that surrounds the optic, oculomotor, abducens, and nasociliary nerves
• Only trochlear nerve passes above the ring to the superior oblique muscle

Question 24

Elevators of the pupil include the ___ and ___, while depressors of the pupil include the ___ and ___

Answer 24

Elevators of the pupil include the superior rectus and inferior oblique, while depressors of the pupil include the superior oblique and inferior rectus

Question 25

Adductors of the pupil include the ____, ____, and ____, while abductors of the pupil include the ____, ____, and ____

Answer 25

Adductors of the pupil include the superior rectus, medial rectus, and inferior rectus, while abductors of the pupil include the superior oblique, inferior oblique, and lateral rectus

Question 26

Align visual axis with ____ to test a muscle

Answer 26

Align visual axis with line of pull of the muscle to test a muscle

(brings muscle to its most efficient position for elevation/depression with its synergist in its most inefficient position)

Question 27

Describe testing the oculomotor nerve

Answer 27

Testing the oculomotor nerve

• No levator palpebrae superioris function
• Pupil dilated (no parasympathetics)
• Pupil stays in the down and out quadrant because lateral rectus / superior oblique are still working

Question 28

Abducens palsy is ___

Answer 28

Abducens palsy is inability to abduct the pupil

(VI has a long intracranial course and is often damaged as it gets stretched over the petrous part of the temporal bone)

Question 29

CN VI goes to the ____

Answer 29

CN VI goes to the lateral rectus

Question 30

CN IV goes to the ____

Answer 30

CN IV goes to the superior oblique

Question 31

CN III goes to ____

Answer 31

CN III goes to all other muscles of the eye

Question 32

V1 (general sensory) turns into the ___, ___, and ___

Answer 32

V1 (general sensory) turns into the frontal, lacrimal, and nasociliary nerves

(frontal becomes supraorbital/supratrochlear)

Question 33

____ and ____ are on the left, while ____ and ____ are on the right when looking ventrally at the eye apparatus

Answer 33

Nasociliary nerve and ciliary ganglion are on the left, while motor nerves and lacrimal nerve are on the right when looking ventrally at the eye apparatus

Question 34

Describe motor nerves and the parasympathetic pathway for the eye

Answer 34

Motor nerves and the parasympathetic pathway for the eye

• Ciliary ganglion connected to oculomotor nerve
• Parasympathetics exit the brain with III -> synapse in ciliary ganglion -> follow short ciliary branches of V1 to ciliary muscle and pupil constrictor
• Short ciliary nerves (V1) and ciliary ganglion receive sensory fibers from the nasociliary nerve and presynaptic parasympathetics from III
• Postsynaptics and sensory fibers follow short ciliary nerves to the eye

Question 35

Parasympathetics for lacrimal secretion exit the brain with the ___, NOT the ___

Answer 35

Parasympathetics for lacrimal secretion exit the brain with the facial nerve (CN VII), not the lacrimal nerve

(synapse in pterygopalatine ganglion -> follow V2 branches to the lacrimal gland)

Question 36

Special sensory nerve related to eye function is ___

Answer 36

Special sensory nerve related to eye function is optic nerve (II) for vision

Question 37

General sensory nerve related to eye function is ___

Answer 37

General sensory nerve related to eye function is ophthalmic division (V1) of trigeminal nerve

(lacrimal nerve, frontal nerve - supraorbital and supratrochlear, nasociliary - long and short ciliary, anterior and posterior ethmoidal)

Question 38

Branchiomotor nerve related to eye function is ___

Answer 38

Branchiomotor nerve related to eye function is facial nerve (VII) to orbicularis oculi for closing eyelids (and origin of parasympathetics to lacrimal gland)

Question 39

Somatomotor nerves related to eye function include ___, ___, and ___

Answer 39

Somatomotor nerves related to eye function include

• Trochlear nerve (IV) to superior oblique (eye down and out)
• Abducens nerve (VI) to lateral rectus for pupil abduction
• Oculomotor nerve (III) to all other muscles including levator palpebrae superioris for opening eyelids)

Question 40

Sympathetic nerves related to eye function originate from the ____, travel up the ____, synapse, then follow arteries to the ____ and ____

Answer 40

Sympathetic nerves related to eye function originate from the thoracolumbar outflow, travel up the sympathetic trunk, synpase, then follow arteries to the dilator of the pupil and superior tarsus muscle

Question 41

Parasympathetics for eye function include ____, ____, and ____

Answer 41

Parasympathetics for eye function include

• Pupil constrictor (III to ciliary ganglion to short ciliary nerve)
• Ciliary muscle for close-up vision (accomodation)
• Lacrimal gland (VII to V2 to terminal lacrimal branches)

Question 42

Arteries of the orbit mostly follow ____, while the ____ travels with the optic nerve through the optic canal and the ____ travels within the optic nerve to retina

Answer 42

Arteries of the orbit mostly follow trigeminal nerve branches, while the ophthalmic artery travels with the optic nerve through the optic canal and the central artery of the retina travels within the optic nerve to retina

Question 43

Describe the pathway of venous blood from the opthalmic veins

Answer 43

Patbway of venous blood

1. Ophthalmic veins and veins from deep in the brain
2. Cavernous sinus
3. Superior and inferior petrosal sinuses
4. Beginning and end of the sigmoid sinuses