Eye and Ear Development (Exam 3) Flashcards
What causes congenital deafness?
abnormal development of the inner or middle ear
How long does the ear take to develop
weeks 3-24
What allows the middle ear to be continuous with the pharynx
eustachian tube (pharyngotympanic tube)
What bone is the inner ear found within
temporal bone
How is the otic vesicle formed
thickening of the ectoderm into an otic placode, that invaginates into an otic pit and vaginates into a vesicle
What will the otic vesicle form
inner ear
How is the vestibulocochlear ganglion formed
cells of the otic placode and neural crest cells
What is the vestibulocochlear ganglion a ganglion for
cranial nerve 8
What will the 1st and 2nd pharygeal arches contribute to the ear
first pouch and cleft–> external ear and internal ear cavity down to the eustachian tube
What does the first pharyngeal pouch contribute to the ear
tube and tympanic cavity
What layers are the typanic membrane composed of
ectoderm
mesoderm (mesenchyme)
endoderm
What are the ossicles of the ear derived from
mesenchyme of 1st and 2nd arches
What does the mesenchyme of the 1st arch give rise to
malleus and incus
What does the mesenchyme of the 2nd arch give rise to
stapes
What muscle attaches to the stapes
stapedius
What muscle attaches to the malleus
tensor tympani
What is the tensor tympani innervated by
CN V
What is the stapedius innervated by
CN VII
What will mesoderm contribute to the ear
bones of the ear: malleus, incus, and stapes
What are mastoid air cells
after birth, tympanic cavity invades the mastoid process
Posterior wall of the middle ear communicates with what
mastoid air cells fo the mastoid process of the temporal bone
What does the auricle of the ear develop from
First and Second pharyngeal arches
What germ layer derives the auricle of the ear
ectoderm
What will auricular hillocks form
cartilaginous parts of the external ear
What auricular hillocks come from the first arch
hillocks 1-2-3
What auricular hillocks come from the second arch
hillocks 4-5-6
What is the sin of the ear innervated by
CNV CNVII greater auricular nerve (cervical plexus) CNIX CNX
What can occur to auricular sinus
infected or get an abscess
What is the result of auricular appendages
usually just cosmetic
What parts of the eye will the neuroectoderm contribute to
retina, posterior lens, and optic nerve
What parts of the eye will the surface ectoderm contribute to
lens
corneal epithelium
What parts of the eye will the mesoderm contribute to
vascular and fibrous coats
What parts of the eye will the neural crest cells contribute to
Sclera, Choroid, corneal endothelium
What is papilledema
increase in intracranial pressure which causes elevated optic disk with blurred margins; bigger blind spot
When do the eyes start to form
4th week
How do the eyes start to form
optic vessicles grow out of the forebrain and lens placodes form
What will form the retina
ends of the optic cups
How many layers does the retina have
2 layers
What provides arterial supply to the lens during development
hyaloid artery
What does the hyaloid artery form in the eye
cleft in the optic stalk
What eventually occurs to the hyaloid artery
degenerates from lens and will persist as the artery of the retina
What does the hyaloid artery supply during development
lens
The artery of the retina is a branch from what artery
opthalmic
What is found within the choroid fissure during development
hyaloid artery
What will the outer and inner layers of the optic cup develop into
outer: pigmental layer
inner: neural layer
What is the ciliary body derived from
choroid mesenchyme and optic cup
What is the iris formed from
edge of the optic cup
What is the gap that remains between the optic cups form
pupil
How is the lens of the eye formed
surface ectoderm invaginates and pinches into a vesicle
What do the posterior cells of the lens vesicle do
elongate and form a rounded surface
What do the posterior cells of the lens vesicle cause when elongating
obliterating cavity
Where are lens fibers created
at the equator
What is the arterial supply to the lens
hyaloid artery
What is the cornea derived from
surface ectoderm
mesoderm
neural crest cells
What induces formation of the cornea
lens vesicle formation
What does surface ectoderm contribute to the cornea
corneal epithelium
What does mesoderm contribute to the cornea
CT
What does NCC contribute to the cornea
corneal endothelium
What is the conjunctiva composed of
surface ectoderm
What will the mesenchyme that surrounds the optic cup form
inner vascular layer
outer fibrous layers
What is the inner vascular layer of the eye ultimately
choroid
What is the outer fibrous layer of the eye ultimately
sclera
How is the lacrimal gland formed
invagination of ectoderm from the eyelinds
What is the orbicularis oculi derived from
second pharyngeal arch
What are the precursors to the eye muscles
preotic somtites
What order do the eye muscles form
Lateral rectus and Superior rectus and levator papillae
Superior oblique
Inferior oblique, inferior rectus, medial rectus
When will nerves of the extrinsic eye muscles reach the orbit
Oculomotor: 5th week
Trochlear and Abducens: end of 5th week
What nerve innervates lateral rectus
Trochlear
What nerve innervates Superior oblique
Abducen
What nerve innervates inferior oblique, superior rectus, inferior rectus, and medial rectus
Oculomotor
What is the cause of cyclopedia
not enough facial mesoderm
What do babies with cyclopedia often have instead of a nose
proboscis
What is syncopthalmia
incomplete fusion of the eyes in cyclopia
What causes a tear drop shaped pupil
gap in the iris; remnant of the choroid fissure that can extend to the sclera
What causes a spider web pupil
persisten pupillary membrane
What is anoridia
no iris, all pupil
What causes anoridia
mesoderm and neural crest cell malfunction
What is retinoblastoma
congenital tumor that involves the retina; lens is clear, cloudiness is caused by tumor in the retina
What are the most common signs/symptoms of retinoblastoma
white reflex strabismus pain glaucoma poor eye sight
WHat causes congenital glaucoma
defect in the draining system
What is congenital glaucoma
increased intraocular pressure
When will the otic placode start developing
Week 4
What are the two parts of the otic vesicle
utricle
saccule
What does the utricle form
utricle, semicircular canals, endolymphatic tube
What does the saccule form
saccule and cochlear duct
What are the specialized hair cells that will develop within the membranous labryinth
Cristae ampularis
Macula
Cochlear
Where do the cochlear hair cells form
cochlear duct
Where do the cristae ampularis hair cells form
semicircular canal ampullas
Where do the macula hair cells form
utricle and saccule
What is the function of the spiral ganglion
related to cochlear duct and involved in hearing
What is the function of the vestibular ganglion
related to remaining hair cells and involved in detection of head movement
What will the otic capsule contribute to
formation of the petrous part of the temporal bone
Where is the perilymphatic space found
within the otic capsule; related to the cochlea duct
What is the perilymphatic space filled with
perilymph
Where is the perilymphatic space found in relationship to the cochlea duct
above: scala tympani
below: scala vestibuli
What is tensor tympani attached to
malleus
What is stapedius attached to
stapes
What is anotia
absence of an ear
What is microtia
small ear
What causes auricular appendeges
persistence of extra auricular hillock
What causes preauricular sinus
failure of first cleft to close
What is atresia of the external auditory meatus
failure of canalizatiion of the external ear canal
What is congenital cholesteatoma
epidermoid tissue within the tympanic membrane
What are the eyelids composed of
surface ectoderm with a core of mesenchyme
When will the eyelids separate
during 5-7 months of development
What gives rise to preotic somites
prechordal plate mesoderm
What happens in congenital retinal detachment
two layers of the retina are separated
What is colobama
improper closure of the choroid fissure resulting in a gap in the iris or iris and retina
What is cyclopia
fusion of the eyes in the midline
What causes cyclopia
defect involving midline structures
What is microphtlamia
small, normal appearing eye or an eye that was arrested at some point during normal development
What is anophthalmia
congenital absence of eye tissue
What is aniridia
absence of iris
What is congenital aphakia
absence of lens
