Embryology Flashcards
what fibers are included in the fetal nucleus
contains all fibers before birth
what type of fibers are in the fetal nucleus
secondary fibers
how does the embryonic nucleus form?
posterior epi elongates to fill the lumen
formation of the lens bow
what type of fibers are in the embryonic nucleus?
primary lens fibers
when do the eyelids fuse and separate?
fuse: month 3
separate: month 5-6
lacrimal system: surface ectoderm
nasolacrimal drainage system
what is a coloboma?
incomplete closure of fetal fissure in the inferior and nasal aspect
when does the optic cup elongates between the lens + cornea
month 3
what structures can be involved in an coloboma
optic disc, iris, retina, cb, optic nerve
what structures in the iris are formed from neural ectoderm
anterior + posterior iris epi
dilator + sphincter muscle
bergmeister papilla
glial tissue persists at ONH
- posterior remnant on lens
- remnants of the fetal hyaloid system
- posterior remnant of the hyaloid system
what structure is the retina formed from?
optic cup
Mittendorf dot
small, circular opacity on the posterior lens capsule, classically nasal in location, which represents the anterior attachment of the hyaloid artery
what is the GCL + INL like at birth?
still thin layer across fovea
when are the GCL + INL completely displaced from fovea
4 months post birth
what is corneal curvature
- circular + steep (55D) @ birth
- decreases to 40D 6mo after birth
what is the first step in corneal development and when does it happen
day 33- corneal epi from surface ectoderm
aniridia
absence of iris- altered depth of focus
iris: neural crest cells
iris stroma
when does myelination reach the chiasm? lamina cribosa?
chiasm: 6 mo
what is the horizontal raphe
wraps around mac bundles to get back to optic disc –> brain
-horizontal raphe is temporary
when does myelination reach lamina cribosa?
LC: 1-3 mo after birth
-visual implications, foveal displacement, cone development, myelination
where does myelination travel from and to
from brain –> eye
LGN –> lamina cribosa
horizontal raphe fibers
inferior and superior fibers dont cross
if damage to NFL - VD respects midline
inferior damage in horizontal raphe
superior VFD
where does maturation of PR occur
fovea + macula
what is in hollow eye ball
empty space filled w/ CSF
continuous w/ 3rd V
mesenchyme iris
anterior border layer
how long can iris darken
6 mo after birth
bc –> blood to cornea
hyaloid artery system process
hyaloid artery (ICA branch) enters optic cup through fetal fissure, filling the vitreous cavity, supplies nutrients to lens
neural plate- what happens at week 3
thickening of ectoderm on the dorsal side
when do cones migrate towards center
4-5 yrs after birth
20/20 at age 5
what does neural plate gives rise to
CNS + ocular structures
what gives rise to hyaloid artery system
mesenchyme ( CT of globe)- neural crest and/or mesoderm
hyaloid artery system: 4th month
atrophy- totally reabsorbed by birth- to supply to nutrients to lens
eyelids: surface ectoderm
- skin + conj epi
- hair follicles + cilia
- meibomian glands
- zeis glands
- glands of moll
when/where does CRA develop from?
month 4 from HAR
when does CRA fully develop?
3mo after birth
what happens to RPE in week 3-4
RPE pigmentation seen in outer later of optic cup
when does optic pit form into the optic cup
day 25
neural crest cells do what
tissue that differentiates
what are optic pits
indentations form on the surface of the neural tube
when do INL and GCL begin to move to peripheral macula
month 7
when does pupillary membrane form between lens + cornea and why
month 3
when does pupillary membrane completely break off
month 8.5
when do the optic pits form
day 22
coloboma: key hole pupil
bilateral- light sensitive
orbit: neural crest cells
orbit fat + CT
when does neural retinal cells differentiate
month 3
what is the potential space between the neural retina + RPE
site of retinal detachment
NR + retina separated
what is micropthalmos
small globe; incomplete development of optic cup + lens (lack of induction)
likely a blind eye
when does the lens placode form and how
day 27
induction: formation of some structures depends on interactions among other tissues
what week is the embryonic plate formed by
week 3
what does the lens vesicle form and how
day 33
forms once it separates form surface ectoderm
persistent pupillary membrane
remains attached to lens or free floating
very common 17-32%
what is primary vitreous
degenerating tissue from hyaloid system + fibers ret + lens
when does myelination begin and why
months 5 - when axons reach the LGN
what is secondary vitreous
encloses primary vitreous forming cloquets canals
forms attachment at vitreous base + hyaloid capsular ligament
when does the fetal fissure begin to fuse
week 5 (goes anteriorly –> posteriorly)
when does fetal fissure close
week 7
what gives rise to the lens capsule
BM
what type of cell gives rise to sclera
neural crest cells
goes around optic cup until reaches ON
retina coloboma
no RPE can see straight through sclera
unilateral
can have no light perception
continuous
outer –> ? –> CB –> inner
anterior epithelium w/ dilator + sphincter muscle –> CB –> posterior epi
continuous
outer –> ? –> IRIS –> inner
anterior pigmented epi –> CB –> inner non-pig epi
continuous
outer –> ? –> RETINA –> inner
RPE –> retina –> neural retina
how is the optic stalk made
tissue joining the vesicle to the neural tube constricts
what structures are needed for the lens placode to develop
optic vesicle and surface ectoderm
y suture cataract
allows lines of suture, very common
can see around- not visually important
can use location for timeline of development
retinopathy of prematurity
baby born early- put in 02 chamber
retinal bv dont develop bc no need
after taken out - you get neovascularization- ret detach
now they gradually take out to complete growth
what happens in neural retina at week 7
migration of the proliferative zone
rpe –> outer neuroblastic layer (2 cells) –> transient later chievits –> inner neuroblastic layer (2 cells) –> marginal zone of His –> vitreous
eyelids mesenchyme
tarsal plate, obicularis, tarsal plate muller
- rare for muscles to be formed by neural cells
- sphincter + dilator is an exception
day 22- neural
neural folds fuse to form neural tube –> brain + spinal cord
brain = neural ectoderm
ocular albinism
reduced pigmentation of ocular structure, no foveal depression, BVA: 20/30
-underdeveloped macula from lack of signals from RPE
what 2 zones does the neural retina form
proliferative (germinative) zone: outer closest to RPE, has cell bodies ( 4 cells)
marginal zone of His (inner, anuclear)
CB: neural crest
ciliary muscle, ciliary stroma
CB: neural ectoderm
outer pigment epi, inner non-pig epi
what gives rise to choroid and what structures needed
neural crest cells
needs RPE contact or proper development
when does hyaloid artery system begin
week 5
neural crest cells: cornea
cornea stroma + endo
when does development of neural retina
week 4-6 cells of inner layer of optic cup form 2 zones
congenital cataract
embryonic cataract
formation in embryonic nucleus
devasting to vision, surgery to avoid amblyopia
when do neural retinal cells differential
month 3
when does the neural groove and neural folds form
day 18-21
lacrimal gland development
not fully formed at birth
not developed until 3-4yo
when/where first place to see pigment in body and when
RPE at week 3-4
when does optic pit turn into optic cup
day 25
optic stalk –>
optic nerve
fetal nucleus
anterior: upright y
posterior: inverted y
cells go posteriorly + anteriorly until they come together at midline
when does folds of surface ectoderm + mesenchyme grow together
month 2
