embryogenesis 8 Flashcards
describe briefly the event of eye formation
Lens-forming competence
Formation of lens placode
Outgrowth of optic stalk from diencephalon
Lens / neural retinal interactions
Lens differentiation
Retinal differentiation
what does the neural segment of the eye develop from
an outgrowth of the diencephalon
what does the lens and cornea develop from
ectoderm
describe how the lens is formed
The lens pit -> lens vesicle -> 1 lens fiber cell or len epithelial -> 2 lens fibers
descrbie the genes involved in lens formation
The head surface ectoderm acts on the optic vesicle through FGFs. that vesicle then acts on the Pax6, Sox2, Sox3, L-Maf through BMP4, BMP7 which then forms the lens placode
th head surface ecto derm forms:
lens placode
cornea
the optic cup diffentiates into:
Neural retina, iris/ ciliary body and the retinal pigment epithelium.
what cells form the cornea
mesenchymal cells which migrate to the front, condensing.
from the lens vesicle how do the fibres form sight
Initially you have the lens vesicle, then the fibres align. The interaction between the neural tissue and lens allows the shape change (focus), this is control by the ciliary body and ciliary muscle
describe the segments of the lens
Anterior lens cell- germinal zone, continued division
Equatorial lens cells – elongating lens fibres
Posterior lens cells - synthesis of crystallins
what is the gene crucial for the eye development and lens competence
Pax 6
the retinal is laminar, list the ten structures
pigment epithelium
receptor layer
external limiting membrane
outer nuclear layer
outer plesiform layer
inner nuclear layer
inner plexiform layer
gangion cell layer
optic fiber layer
inner limiting membrane
what is the order of which the retina mature cells are developed
ganglion, horizontal, cones, amacrine, rods, bipolar, moller glia
what is the precursor to the inner ear
otic vesicle
where does the inner ear form
lateral to the rhombencephalon
describe the formation of the
Otic placode invaginates to form the otic pit
Otic pit separates from the surface ectoderm to form the otic vesicle
The cavity of the otic vesicle is filled with fluid and an outgrowth forms the ganglia of the auditory nerve
The mesenchyme of the membranous labyrinth becomes cartilage and later ossifies to become the osseous labyrinth within the temporal bone.
the inner ear has two segments, what are they
dorsal (utricle)
ventral (saccule)
what is the inner ear dorsal segment
semicircular ducts form from the utricle (balance organs)
what is the inner ear ventral segment
cochlear ducts form from the saccule (auditory system)
the middle ear forms between:
the first and second pharyngeal arches
what is the tympanic cavity
dorsal blind end of the first pharyngeal pouch
how does the middle ear form
Middle ear forms as an endodermal outpouching between the first and second pharyngeal arches
Mesenchymal growth between the outer endodermal and the inner ectodermal walls fuses the three layers together to give rise to the tympanic membrane. (seperating structure of the inner and middle ear)
then the ossicles form
how do the ossicles form int the middle ear
Formed from mesoderm of first and second pharyngeal arches
What is the embryonic origin of the neuro- and adenohypophysis of the pituitary.
Derived from two embryonic origins
1 - Oral ectodermal component becomes the Rathke’s pouch (adenohypophysis)
Form the glandular component of the pituitary
2 - Neural component becomes the neurohypophysis (infundibulum of the diencephalon)
Forms neural component of the pituitary
