Orbit and Eye: Embryology

Question 1

neural ectoderm

Answer 1

evaginations of forebrain neuroectoderm

• forms optic vesicles
• invaginate on themselves to form optic cup

Question 2

optic stalk

Answer 2

connection of forebrain to optic cup

Question 3

choroid fissure

Answer 3

ventral surface of optic cup

-carries hyaloid essels

Question 4

optic cup

Answer 4

forms retina - optic nerve

Question 5

surface ectoderm

Answer 5

lens placode - lens vesicle - lens

Question 6

mesenchyme

Answer 6

forms fibrous and vascular layers

Question 7

outer layer optic cup

Answer 7

pigmented layer of retina

Question 8

inner layer of optic cup

Answer 8

all neural layers of retina

Question 9

nerve fibers from retina

Answer 9

migrate through choroid fissure to form CN II

Question 10

week 7

Answer 10

choroid fissure closes

Question 11

congenital retinal detachment

Answer 11

inner and outer layer optic cup fail to fuse

separation of pigmented and neural layers

Question 12

iris and ciliary body embryo

Answer 12

outer - vascular mesenchyme surrounding optic cup

inner - optic cup (no neural)

Question 13

infants

Answer 13

born with blue-gray eyes - lack of melanin

will migrate in first 6-10 months

Question 14

congenital atresia of pupil

Answer 14

iridopupillary membrane degenerates after week 15
-failure of membrane to degenerate

abnormally closed pupil

Question 15

coloboma

Answer 15

failure of choroid fissure to fuse during 7th week development

hole in structure of eye

Question 16

sclera and cornea embryo

Answer 16

from fibrous layers of mesenchyme surrounding optic cup

Question 17

choroid embryo

Answer 17

vascular layer of mesemchyme surrounding optic cup

Question 18

aqueous and vitreous humors of eye embryo

Answer 18

form from cell deah in eyeball

Question 19

vitreous humor embryo

Answer 19

likely from neural crest cells

Question 20

lens embryo

Answer 20

lens vesicle

Question 21

congenital aphakia

Answer 21

agenesis of lens placode

absence of lens in eye

Question 22

extrinsic eye muscles embryo

Answer 22

mesoderm of myotomes

Question 23

ophthalmic artery

Answer 23

from internal carotid artery

-enters optic canal

Question 24

branches of ophthalmic artery

Answer 24

central retinal artery
short posterior ciliary a
long posterior ciliary a
anterior ciliary aa
lacrimal a
supraorbital a
posterior ethmoidal a
anterior ethmoidal a
medial palpebral a
supratrochlear a
dorsal nasal a

Question 25

blood to retina

Answer 25

central retinal artery | -runs with CN II

Question 26

blood to choroid

Answer 26

short posterior ciliary a

Question 27

blood to ciliary body/iris

Answer 27

long posterior ciliary a | anterior ciliary arteries

Question 28

venous drainage eyeball

Answer 28

central retinal vein - cavernous sinus vorticose veins - drain choroid, ciliary body, iris superior/inferior ophthalmic veins - exit superior/inferior orbital fissures > cavernous sinus and pterygoid venous plexus, respectively

Question 29

thrombophlebitis

Answer 29

of cavernous sinus may send clot to central retinal vein -vision loss

Question 30

increased intracranial pressure

Answer 30

meninges and CSF continue along CN II -may affect eye optic n, central retinal a, central retinal v - compressed

Question 31

papilledema

Answer 31

retinal edema | -occlusion of central retinal vein

Question 32

movements of eye

Answer 32

``` adduction abduction elevation depression extortion - lateral rotation intortion - medial rotation ```

Question 33

levator palpebrae superioris

Answer 33

eyelid

Question 34

medial rectus

Answer 34

common tendinous ring - medial surface eyeball adduct eye CN III

Question 35

lateral rectus

Answer 35

common tendinous ring - lateral surface of eyeball abduct eye CN VI

Question 36

superior rectus

Answer 36

common tendinous ring - superior surface eyeball elevate, adduct, intorsion CN III

Question 37

inferior rectus

Answer 37

common tendinous ring - inferior surface eyeball depress, adduct, extorsion CN III

Question 38

inferior oblique

Answer 38

anterior portion floor orbit - inferior surface eyeball elevate, abduct, extorsion CN III

Question 39

superior oblique

Answer 39

common tendinous ring - superior surface eyeball -passes through trochlea depress, abduct, intorsion CN IV

Question 40

oculomotor nerve

Answer 40

CN III GSE, GVE-P parasympathetic to ciliary ganglion

Question 41

diplopia

Answer 41

one eye positioned differently

Question 42

oculomotor nerve palsy

Answer 42

ptosis or complete closure of eye -lose levator palpebrae superioris diplopia - down and out dilated pupil loss of accomodation

Question 43

trochlear nerve

Answer 43

CN IV GSE to superior oblique muscle

Question 44

trochlear nerve palsy

Answer 44

diplopia - elevated and adducted loss of depression when eye fully adducted

Question 45

abducens nerve

Answer 45

CN VI GSE to lateral rectus muscle

Question 46

abducent nerve palsy

Answer 46

diplopia - loss of abuction

Question 47

optic nerve

Answer 47

CN II - SSA vision covered in meninges optic nerve fibers are axons of ganglion cell layer of retina which pass through optic disc and exit lamina cribrosa of sclera posterior

Question 48

CN V1

Answer 48

ophthalmic nerve GSA branches: - nasociliary - frontal - lacrimal

Question 49

nasociliary nerve

Answer 49

branch of V1 - sensory root to ciliary ganglia - short ciliary nn - long ciliary nn - posterior ethmoidal n - anterior ethmoidal n - infratrochlear n

Question 50

frontal nerve

Answer 50

branch of V1 - supratrochlear n - supraorbital n

Question 51

lacrimal nerve

Answer 51

branch of V1 - sensory to lacrimal - carry postganglionic PS and S to lacrimal gland

Question 52

ciliary ganglion

Answer 52

between lateral rectus and optic nerve -postganglionic PS cell bodies sensory - nasociliary nerve PS - motor root from oculomotor S - motor root from internal carotid plexus

Question 53

PS to intraocular eye muscles

Answer 53

preganglionic - edinger westphal -fibers with oculomotor nerve postganglionic - ciliary ganglion -fibers distrubute short ciliary nerves to sphincter pupillae muscle and ciliary muscle

Question 54

sympathetic to intraocular eye muscles

Answer 54

preganglionic - T1-2 -fibers to SCG postganglionic fibers - internal carotid plexus -ciliary ganglia without synapse distribute short and long ciliary nn - dilator pupillae and superior tarsal muscle

Question 55

parasympathetic to lacrimal gland

Answer 55

preganglinic - salivatory nucleus - fibers with greater petrosal nerve CN VII - synapse at pterygopalatine ganglion postganglionic - zygomatic nerve V2 and lacrimal nerve V1 increase secretions

Question 56

sympathetic lacrimal gland

Answer 56

preganglionic - T1-4 -synapse SCG postganglionic fibers - internal carotid nerve - deep petrosal nerve greater and deep petrosal nerve merge -nerve to pterygoid canal postganglionic distribute zygomatic V2 and lacrimal V1 nn more watery lacrimal fluid

Question 57

pupillary light reflex

Answer 57

afferent - CN II efferent - CN III (GVE-P) - sphincter pupillae m. both pupils constrict - direct ipsilateral eye light - consensual contralateral eye light

Question 58

corneal reflex

Answer 58

protect eye from foreign object afferent - CN V1 - pain sensation efferent - CN VII - orbicularis oculi puff air - stimulates CN V1 -both eyes blink - direct and consensual

Question 59

accomodation reflex

Answer 59

function - view near objects afferent CN II efferent CN III GSE and GVE-P direct and consensual response 3 events: 1. ciliary muscles contract - rounding of lens - GVE-P 2. pupils constrict - GVE-P 3. eyes adduct - GSE

Question 60

3 events of accomodation

Answer 60

1. ciliary muscles contract - rounding of lens - GVE-P 2. pupils constrict - GVE-P 3. eyes adduct - GSE