eye and ear development Flashcards
the cornea is continuous with
the sclera
what is just deep to the sclera
the choroid(Vascular) then retina
what is deep to cornea
aqueous humor, iris, lens (with supspensory ligament)
when does the eye first appear
at 22 days
how is the eye first seen
as optic grooves on the side of the forebrain
The neural tube closes and grooves form out-pocketing known as what for the eye
optic vesicles
how does lens induction begin
when vesicles contact the surface ectoderm
when the vesicles contact the surface ectoderm, what doe they do
invaginate and the double walled optic cup forms
Cells of the surface ectoderm, in contact with the optic vesicle elongate to form what
lens placode
what does the lens placode develop into
the lens vesicle
what eventually happens to the lens placode
looses contact with the surface ectoderm and rests in the mouth of the optic cup
what separates the layers of the optic cup intially
intraretinal space
what eventually happens to the intraretinal space
quickly disappears and the two lays appose each other
what does the invagination of the inferior aspect of the optic cup form
choroid fissue
what allows the hyaloid artery to reach the inner chamber of the eye
Choroid fissure
what forms the future pupil
edges of the choroid fissure fuse and optic cup mouth becomes a round opening
failure of the retinal fissure to close in the 7th week leads to
Coloboma, key hole appearance of the iris
what later of the optic cup is the retinal pigment layer
the outer layer of the optic cup
layers of the neural layer f the retina
Pars optica retinae
Mantle layer
axons from neurons of deeper layers to collect on retinal surface in a fiber layer
what makes up the pars optica retinae
rods and cones
what makes up the mantle layer of the retina
generates neurons and glia of outer and inner nuclear layers and ganglion layer
what forms the optic stalk and optic nerve
Axons retinol ganglion cells converging
the anterior fifth of the inner layer of the eye consists of
Iris & Ciliary Body
the anterior 1/5 of inner layer divides into 2 separate parts with roles:
to form the inner layer of the iris
to help to form the ciliary body
the region betwen the optic cup and the overlying surface epithelium contains ___ that forms ____
mesenchym
sphincter and dilatory pupillae muscles
what happens to the pars ciliaris retinae
becomes infolded
what covers the outside of the pars ciliaris retinae
mesenchym that forms ciliary muscle to control lens curvature
what covers the inside of the parts ciliaris retinae to connect to the lens
elastic fibers known as suspensory ligaments or zonula
what happens to lens vesicle due to elongation of cells of the posterior wall
these cells elongate anteriorly and form long fibers that will fill the lumen of the vesicle
when do the primary lens fibers reach the anterior wall of the lens
7th week
what surrounds the eye during the 5th wek
loose mesenchyme with 2 layers
the inner layer of the loose mesenchyme that surrounds the eye
like pia, ultimately forms the choroid, that is vascular and pigmented
the outer layer of the loose mesenchym that surrounds the eye
dura, ultimately forms the sclera, that is continuous with the dura of optic nerve
what does the cornea come from
the anterior mesenchyme
the anterior chamber forms b/c
vacuolization of mesenchyme into 2 layers
the anterior portion of mesenchyme that forms the inner layer that is in front of the lens and iris
the iridopupillary membrane
what happens to the iridopupillary membran
ultimately disappears
the outer layer of the anterior mesenchyme of the eye forms
the substantia propria of the cornea
layers of the cornea
epithelial layer from surface ectoderm
stroma, continuous with eclera
epithelial layer, borders anterior chamber
what fills the anterior and posterior chambers
fluid, aqueous humor, ciliary processes of ciliary body
how do the anterior and posterior chamberes communicate with each other
through the pupil, from posterior to anterior,
why fluid flow from anterior and posterior chambers is important
provide nutrients for avascular cornea and lens
where does fluid pass after the anterior chamber
passes through canal of schlemm at iridocorneal angle
blockage at the canal of schlemm leads to
glaucoma
formation of the hyloid vessels
mesenchym surrounds the eye primordium and invades the optic cup via chroid fissure
role of th hyloid vessels
support lens in utero and forms a vascular layer on the inner retina
what forms the fine network of fibers between the lens and retina
the invading mesenchym
how the vitreous body is formed
interstitial spaces fill with gelatinous material
what connects the brain to the optic cup
the optic stalk
where is the choroid fissure found
on the ventral surface of the optic stalk
the choroid fissure contains
hyaloid vessels
where do retinal nerve fibers going into the brain lie in the optic stalk
along the inner wall
when does the choroid fissure close
7th week
closing of the choroid fissure leads to
formation of a tunnel in the optic stalk
nerve fibers add in
outer walls of stalk fuse
the optic stalk becomes
the optic nerve
the central artery of the retina
hyaloid artery
3 parts of the ear
external=collect sound
middle= conduct sound
inner= converts sound waves and detects changes in equilibrium to convert them to nerve impulses
organ of corti
found in the cochlea to determine sound
cristae
found in the semicircular ducts to detect angular acceleration
maculae
found in the utricle and Saccule to detect linear acceleration
when does the otic placode appear
22 days
thickening of surface ectoderm on each side of the rhombencephalon
Otic placode
how is the internal ear formed
the otic placode invaginates to form otic or auditory vesicles
what does each otic vesicle develop into
Ventral component
Dorsal component
the ventral component of the otic Vesicle develops into
the saccule and cochlear duct
the dorsal component of the otic Vesicle develops into
the Utricle, semicircular canals, endolymphatic duct
when does the saccule form a tubular outpocketing to make the cochlear duct
week 6
travel of the cochlear duct
penetrates mesenchym and spirals 2.5 turns, still connected to the saccule by the ductus reuniens
the mesenchyme that surrounds the cochlear duct differentiates into
cartilage
what happens to the cartilage of the inner ear
becomes vacuolated and perilymphatic spaces arise, forming the scala vestibuli and scala tympani
what separates the cochlear duct and scala vestibuli
Vestibular membrane
what separates the cochlear duct and scala tympani
basilar membrane
what supports medial cochlear duct
modiolus
the modiolus the supports the medial cochlear duct becomes
the axis of the future bony cochlea
epithelial cells of the cochlear ducts are what initially and change into water later
uniform initially, 2 ridges later
the outer ridge of the cochlear duct forms
1 row of inner and 3 rows of outer hair cells
what covers the hair cells
tectorial membrane
gelatinous material attached to spiral limbus and rests on top of hair cells
tectorial membrane
what are hair cells and tectorial membrane together known as
organ of corti
how are impulses from the organ of corti sent out
to sprial ganglion and then brain via CNVIII
what do the semicircular cancals appear out of
out pocketing of the utricle
when do semicircular canals appear
week 6
what happens to the ends of each semicircular canal
one end dialates (crus ampullare) , the other does not (Crus nonampullare)0
ampullae cells form a crest called for angular acceleration
the crista ampullaris
what develops in the walls of the utricle and saccule for linear acceleration
Macule acusticae
how are impulse in cristae and maculae, body position carried to brain
CNVIII
what does the tympanic cavity come from
endoderm from 1st pharyngeal pouch
how is the primitive tympanic cavity formed
pouch expands
distal aspect becomes tubotympanic recess, which widens
the proximal pouch of 1st pharyngeal pouch becomes
the auditory tube
incus and malleus form from
cartilage of 1st pharyngeal arch
the stapes is derived from
cartilage of 2nd pharyngeal arch
when do the ossicles no longer become embedded in mesenchyme
end of 8th month, when surrounding tissue involutes
what extends into the space left by the surronding tissues of the ossicles involution
endodermal epithelial lining of the primitive tympanic cavity extends into said space
how are the ossicles connected to the wall once completely free of surrounding mesenchyme
endodermal lining connects them to wall of cavity via ligaments
the external auditory meatus forms from
dorsal portion of 1st pharyngeal cleft
how is the external auditory meatus formed
cells at bottom of meatus proliferation, forming a solid epithelial plate and meatal plug
how is the eardrum formed
the meatal plug dissolves and the epithelium in floor of meatus add to it
what happens if meatal plug persists
cogenital deafness
the external ear develops from
6 mesenchymal proliferations at the dorsal end of the 1st and 2nd pharyngeal arches, surrounding 1st clept
the auricle is formed from
neural crest
what fuses to form the auricle
3 hilocks on each side of the meatus
are auricle abnormalities common
yes, b/c complication
travel of ear
starts in lower neck, ascends as mandible develops, top of ear should be at eye level
absent external ear
anotia
small ear
microtia
