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Hannah Neuro > embryo devlopment of ear and eye > Flashcards

embryo devlopment of ear and eye Flashcards

1
Q

what controls the function of the membranous labyrinth contents

A

-from otic vesicle (surface ectoderm)
Hair cells line the labyrinth and give function
1. ampulla- acceleration
2. macula’s- gravity
3. organ of corti-sound vibration
*damage to hair cells = deafness bc does not grow back

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2
Q

which part of the ear is first to form

A

inner ear

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3
Q

what is the embryo origin of the choroidal vessels? what A. do they come from ? fun?

A
  • mesoderm
  • ciliary A.s
  • develope in 15th week, function to keep choroid vascular
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4
Q

the eye is an extension of the brain, what part of the brain gives rise to the eye

A

forebrain - prosencephalon (dicephalon branch)

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5
Q

what produces endolymph and perilymph? how do there concentrations compare?

A

endolymph

  • made by stria vascularis in membranous labyrinth.
  • high in K+ and protein, low in Na (like ICF)

perilymph

  • made from perilymphatic duct inside the boney labyrinth that is patent to the subarachnoid space; or filtration of blood from perilympatic space
  • content is high in Na, low in K and protein like CSF
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6
Q

innervation of the tympanic membrane

A

external : vagus and auriculotemporal n.

internal- glossophayrnheal N.

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7
Q

what is anotia? microtia? and how do they form ?

A

anotia= no ear
-no migration of neural crest cells from 1st and 2nd arches

microtia = malformed ear
-abnormal migration of neural crest cells from 1st and 2nd arches

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8
Q

embryo origin of the sclera (fibrous layer)

A
  • neural crest (continuous of dura matter)
  • forms stroma of cornea therefore why the cornea is neuroectoderm by stroma is NC

*dura is usually mesoderm but this is the exception

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9
Q

what is coloboma? how is it formed?

A
  • incomplete ring of the iris
  • incomplete fusion of the optic fissure to come together and form the bottom of the iris
  • related to : genetics (autosomal dominant trait) and environmental factors
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10
Q

function of the spiral ligaments

A

hold the cochlea in place

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11
Q

describe the formation of the boney labyrinth

A

the otic placode becomes the otic vesicle which will become the cochlear duct (surface ectoderm). the mesoderm from the petrous part of the temporal bone will surround the cochlear duct and form vacuoles that will become the scala tympani and scala vestibuli (space filled with perilymph surrounding the membranous cochlear duct)

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12
Q

embryo origins of the tensor tympani and stapedius M. ? innervation of both?

A

tensor tympani = 1st arch mesoderm (V3 of CN 5)

stapedius = 2nd arch mesoderm (stapedius n. from CN 7)

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13
Q

describe the formation of the iris, ciliary body, and retina of the eye

A

at week 4 the neuroectoderm begins to fold and form the optic groove (sulcus) which forms inside the optic vesicle (connected to the brain via the optic stalk) with it an opening called the optic fissure allows hyaloid A. and V. passage. during invagination of the groove the optic cup begins to form. the optic cup has 2 layers, central intra-retinal layer, and 2 rims. the rims of the cup will become the iris and ciliary bodies. the inner layer will become the neural retina. the outer layer will be the pigmented retina. these layers fuse.

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14
Q

what are the layers of the cornea and their contents ?

A
  • come from surface ectoderm
    1. anterior lens epithelium (sub capsular layer) = cuboidal cells
    2. primary lens fibers= tall columnar cells (from elongation and dissociation of nuclei to help increase transparency for light)
    3. secondary lens fibers = cuboidal cells
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15
Q

how does the membranous labyrinth of the inner ear form

A
  • surface ectoderm gives rise to the otic placode which will invaginate and form the otic sac at first and continue to form the otic vesicle which will become the membranous labyrinth (ducts in vestibulocochlear app)
  • ventral part of the otic vesicle will become the saccule and give rise to cochlear duct, ductus reunions, macula of the saccule, and organ of corti (CD dependent on PAX 6)
  • the dorsal side of the otic vesicle will give rise to the utricle (DLX 5 /6 dpdent) which will form the endolympatic duct/sac, semicircular canal/ ampulla (DLX 5/6 dpt) the lateral canal (OTX1 dep.) and the macula of the utricle
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16
Q

what is first arch syndrome

A

-malformation of the sound-conduction apparatus of middle and external ear (not internal) resulting in congenital deafness
(usually a genetic cause)

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17
Q

embryo origin of ciliary bodies

A
  • rim of optic cup
  • epithelium = neuro ectoderm
  • SMC - mesoderm

muscles = ciliary muscle

18
Q

innervation of the external ear

A
  1. auriculotemporal (V3, from CN 5)
  2. great auricular N. (C2-3)
  3. auricular branches of vagus (CN10)
  4. Facial N. (CN 7)
19
Q

what is congenital cataracts? how do they form ?

A
  • opaque grey / white covering over the LENS only

- caused by: genetics, maternal rubella, galactosemia(enzyme deficiency), maternal radiation

20
Q

embryo origin of the dilator and constrictor pupillae muscles of the eye

A

neuroectoderm

***only muscles in body from neuroectoderm!! all others from mesoderm

21
Q

increased retinal pressure can slow retinal venous drainage and cause fluid build up in optic disc. edema will result due to the covering of the retinal vessels by the meninges with them directly surrounded by subarachnoid space

A

papilledema (budging optic disc)

*CSF lies in subarachnoid space and is drained by arachnoid granulations into the dural venous sinuses

22
Q

how is the external auditory meatus and tympanic cavity/ eustachian tube formed

A
  • envagination of 1st pharyngeal cleft (surface ectoderm) towards the 1st pharyngeal pouch (endoderm) to make the 1st P. arch membrane (tympanic membrane of all 3 germ layers)
  • cleft fills with meatal plug cells that will undergo apoptosis at 6 months to open external canal to outside world
  • pouch become the tubotympanic recess which will proximally give rise to eustachian tube and distally give rise to the tympanic cavity
23
Q

what is the embryo origin of the extra-ocular muscles

A

-preortic myotome from preortic mesenchyme

24
Q

where does the external ear come from

A
  • 1st and 2nd pharyngeal arches
  • auricular hillocks (neural crest covered with surface ectoderm) are formed by migration of neural crest pulling surface ectoderm to form the external ear.
  • outside skin = surface ectoderm
  • cartilage = neural crest
25
Q

what is aniridia ? how is it formed?

A
  • absent or incomplete iris
  • no or improper development of the rim of optic cup
  • associated with glaucoma, cataracts, and other eye problems
  • caused by pax 6 gene mutation
26
Q

embryo origin go the choroid (vascular layer)

A
  • continous with arachnoid and pia matter
  • neural crest
  • choiroid blood vessels = mesoderm
27
Q

what is the pupillary membrane? and embryo origin of pupillary membrane ?

A
  • covering of sclera in utero
  • will degenerate when eyes unfuse in week 26
  • neural crest derived
28
Q

what happens if the pigmented layer and neural layer of the retina do not fuse

A

detachment of the retina will occur

-see it in downs syndrome and marfans syndrome

29
Q

embryonic origin of the tympanic membrane

A

external surface- ectoderm
internal surface-endoderm
blood supply-mesoderm
*all 3 layers

30
Q

how is the optic nerve formed

A

the neuroretina has two layers

  1. rods and cones
  2. ganglion cells (fibrous layer)
    - the ganglion cells axons will form the optic N. as it grows back into the optic stalk (template of optic N.)
    - hyaloid artery is incorporated into the stalk when the cavity becomes obliterated (it then turns into the CRA)
    - the optic nerve sheath is covered in all 3 meningeal layers and is continuous with the sclera and choroid
31
Q

embryo origin of the ossicles of the middle ear

A
  • malleus and incus = Neural crest of 1st P. arch
  • stapes = neural crest of 2nd P. arch
  • covering of boney ossicles is endodermal epithelium
32
Q

describe the development of the lens and cornea of the eye

A

the optic cup initiates INDUCTION of the lens formation by touching the surface ectoderm. the SE will form the lens placode, which will invaginate to for the lens pit, and then the lens vesicle when it is completely pinched from the SE. the vesicle will give rise to the lens (surface ectoderm). the SE that was left behind will reconstitute to form the corneal epithelium. the cornea stroma is neural crest derived.

33
Q

what is the critical period of ear and eye development

A

week 4-8 of embryonic development

34
Q

what is congenital glaucoma ? and how is it formed?

A
  • haziness and opaque eye (lens and cornea and whole eye)
  • caused increased intra-ocular pressure due to the malformation of canal of schlemm
  • related to : genetics, CYP1B1 mutation, rubella

*bone that houses canal of schlemm is from neural crest therefore could be NC related

35
Q

what is the innervation of the inner ear? and the embryo development of it?

A
  • CN 8 vestibulocochlear N.
  • vestibular ganglion -from surface ectoderm and neural crest supplies the vestibular apparatus
  • spiral cochlear ganglion - from surface ectoderm only will supply the cochlear apparatus
36
Q

embryo origin of parts of the iris

A
  • rim of optic cup
  • epithlium and SMC = neuro ectoderm
  • stroma = neural crest

muscles = constrictor /dilator pupil muscles

37
Q

what can happen if the pregnant mom gets rubella during weeks 7-8

A

(critical period of ear and eye )
-can cause defects of spiral organ
=congenital deafness

  • congenital cataracts
  • congenital glaucoma
38
Q

what makes aqueous humor? vitreous humor?

A

aqueous - ciliary body (drained in canal of schlemm)

vitreous - choroid (sits behind lens in the back of the eye)

39
Q

what can happen with a Pax 6 gene mutation

A
  • needed for cochlear duct development in the ventral part of the otic vesicle which makes the saccule. (congenital deafness)
  • needed for Rim of optic cup development, lead to aniridia (no iris)
40
Q

what vessels runs in the optic fissure ? whats its origin ? whats its function ?

A

hyaloid a. and v.

  • mesoderm
  • branch from ophthalmic A. that initially works to nourish the lens (supplies neural retina, lens vesicle, and optic cup mesenchyme)
  • will become the central retinal A. and nourish the retina, while the aqueous humor will continue to nourish the lens
  • if distal part persists a worm like structure will be seen in the eye and usually microopthalmmic eye will be seen (small eye)

Hannah Neuro (20 decks)

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