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Anatomy 2 > 3: Eye & Ear Development > Flashcards

3: Eye & Ear Development Flashcards

1
Q

when does the eye first appear

A

22 days

appears as optic grooves on sides of forebrain

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2
Q

steps to form optic cup and vesicle

A
  1. neural tube closes and grooves form the out-pocketings called OPTIC VESICLES
  2. vesicles contact surface ectoderm and LENS INDUCTION begins
  3. vesicle starts to invaginate and double-walled OPTIC CUP forms
  4. cells of surface ectoderm, in contact with optic vesicle, elongate and form LENS PLACODE
  5. placode develops into LENS VESICLE, which loses contact w/surface ectoderm and rests in mouth of optic cup
  6. layers of optic cup are initially separated by INTRARETINAL SPACE (which quickly disappears)
  7. inferior aspect of cup invaginates, forming CHOROID FISSURE allowing HYALOID A. to reach inner chamber of eye
  8. 7th week: edge of choroid fissure fuse and optic cup mouth becomes round opening –>future pupil
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3
Q

coloboma

A

key hole appearance of iris due to failure of retinal fissure to close in 7th week

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4
Q

eye at 7 weeks

A

outer layer of optic cup=retinal pigment layer

neural layer of retina is complex

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5
Q

pars optica retinae

A

posterior 4/5s of retina

rods and cones

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6
Q

mantle layer of retina

A

generates neurons & glia of outer and inner nuclear layers and ganglion layer

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7
Q

axons in retina

A

axons from neurons of deeper layers collect on retinal surface in a fiber layer

converge to form optic stalk and optic nerve

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8
Q

iris & ciliary body

A

aka pars ceca retinae

anterior 1/5 of inner layer

divides into pars iridica retinae and pars ciliaris retinae

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9
Q

pars iridica retinae

A

forms inner layer of iris

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10
Q

pars ciliaris retinae

A

helps form ciliary body

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11
Q

sphincter & dilator pupillae

A

region btwn optic cup and overlying surface epithelium

contains mesenchyme

forms sphincter & dilator pupillae mm.

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12
Q

ciliary muscle

A

formed by mesenchyme on outside of pars ciliaris retinae

controls lens curvature

connected to lens from inside, by elastic fiber network called suspensory ligament or zonula

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13
Q

suspensory ligament

A

aka zonula

elastic fiber network that connects ciliary body to lens

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14
Q

lens

A

after lens vesicle forms, cells along posterior wall elongate anteriorly and form long fibers that fill lumen of vesicle

reach anterior wall of lend by 7th week

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15
Q

choroid

A

inner layer like pia

vascularized pigmented layer

emerges from loose mesenchyme that forms around eye in 5th week

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16
Q

sclera

A

outer layer like dura

continuous with dura of optic nerve

emerges from loose mesenchyme that forms around eye in 5th week

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17
Q

cornea formation

A

anterior chamber of mesenchyme, formed by vacuolization

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18
Q

inner layer of cornea

A

in front of lens & iris

aka iridopupillary membrane (disappears)

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19
Q

outer layer of cornea

A

substantia propria

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20
Q

cornea contents

A

epithelial layer from surface ectoderm

substantial propria, aka stroma, continuous with sclera

epithelial layer that borders anterior chamber

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21
Q

anterior & posterior chambers of cornea

A

filled w/fluid, aqueous humor, produced by ciliary body

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22
Q

how do the anterior & posterior chambers of cornea communicate

A

thru pupil

fluid flows from posterior to anterior chamber, providing nutrients for avascular cornea & lens

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23
Q

where does fluid thru pass after anterior chamber

A

Canal of Schlemm at iridocorneal angle

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24
Q

what causes glaucoma

A

blockage of Canal of Schlemm

25
Q

vitreous body

A

gelatinous material that fills interstitial space in the fine network of fibers btwn lens & retina

26
Q

hyloid vessels

A

formed by mesenchyme surrounding eye primordium and invading optic eye via choroid fissure

support lens in utero and form a vascular layer on inner retina

27
Q

how is optic cup connected to brain

A

by optic stalk, with choroid fissure on ventral surface

28
Q

what does the choroid fissure contain

A

hyaloid vessels

29
Q

where do retinal nerve fibers going into the brain lie

A

along inner wall of the optic stalk

30
Q

when does optic stalk become optic nerve

A

7th week, when choroid fissure closes

hyaloid artery is now central artery of the retina

31
Q

external ear function

A

collects sound

32
Q

middle ear function

A

conducts sound

33
Q

internal ear function

A

converts sound waves to nerve impulses & detects changes in equilibrium converting them into nerve impulses

34
Q

internal ear development

A

22 days: otic placode

thickening of surface ectoderm on each side of rhombencephalon

otic placodes invaginate and form otic/auditory vesicles

35
Q

otic vesicle development

A

ventral component: saccule and cochlear duct

dorsal component: utricle, semicircular canals, endolymphatic duct

36
Q

beginning of saccule & cochlea development

A

week 6

saccule forms tubular outpocketing aka cochlear duct

cochlear duct penetrates mesenchyme while it spirals thru 2.5 turns

37
Q

ductus reuniens

A

connection btwn cochlear duct and saccule

38
Q

saccule, cochlea & Organ of Corti development (8-10 weeks)

A
  1. mesenchyme around cochlear duct –> cartilage
  2. cartilage becomes vacuolated; perilymphatic spaces arise (scala vestibuli & scala tympani)
  3. vestibular membrane separates cochlear duct & scala vestibuli. basilar membrane separates cochlear duct & scala tympani
  4. modiolus supports medial cochlear duct –> becomes axis of future bony cochlea
39
Q

2 ridges of cochlear duct epithelial cells

A

inner ridge: future spiral limbus

outer ridge: forms 1 row of inner and 3 rows of outer hair cells (sensory cells of auditory system)

40
Q

tectorial membrane

A

gelatinous material attached to spiral limbus and rests on top of hair cells

41
Q

what is the Organ of Corti made of

A

hair cells and tectorial membrane

42
Q

where are impulses from Organ of Corti sent

A

to spiral ganglion and then to brain via CN VIII

43
Q

when do semicircular canals appear

A

6th week

as outpocketings of utricle

44
Q

which end of the canals dilates

A

crus ampullare

45
Q

which end of the canals does not dilate

A

crus nonampullare

46
Q

crista ampullaris

A

crest formed by ampullae cells

important for angular acceleration (equilibrium)

47
Q

macule acusticae

A

develop in walls of utricle and saccule

important for linear acceleration

48
Q

where are impulses from cristae and maculae sent

A

to brain by CN VIII (body position)

49
Q

tympanic cavity

A

endoderm from 1st pharyngeal pouch

50
Q

tympanic cavity & auditory tube development

A

1st pharyngeal pouch expands

distal aspect = tubotympanic recess –> primitive tympanic cavity

proximal pouch = auditory (eustachian) tube

51
Q

ossicles

A

incus & malleus=cartilage of 1st pharyngeal arch

stapes=cartilage of 2nd pharyngeal arch

52
Q

ossicles development

A

embedded in mesenchyme until 8th month, after which the endodermal lining connects them to the wall of the cavity via ligaments

epithelial lining of primitive tympanic cavity extends into this new space

53
Q

development of external auditory meatus

A

dorsal portion of 1st pharygeal cleft

  1. cells at bottom of meatus proliferate and form MEATAL PLUG in 3rd month
  2. in 7th month, plug dissolves and epithelium in floor of meatus contributes to eardrum formation

sometimes plug persists and results in CONGENITAL DEAFNESS

54
Q

eardrum consists of

A

ectodermal lining at bottom of meatus

endodermal lining of tympanic cavity

intermediate layer of connective tissue (fibrous striatum)

55
Q

auricle development

A

from 6 mesenchymal proliferations at dorsal end of 1st and 2nd pharyngeal arches surrounding 1st cleft
–formed from NEURAL CREST

3 hillocks on each side of meatus fuse and form auricle

ear starts in LOWER NECK and ASCENDS as mandible develops

top of ear should be at eye level, complications are common

56
Q

anotia

A

absent external ear

57
Q

microtia

A

small ear

58
Q

preauricular appendages

A

accessory hillocks

59
Q

preauricular pit

A

abnormal hillocks

Anatomy 2 (6 decks)

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