Ocular Embryology Flashcards
After notochord formation
Head end of embryonic disk of either side primitive streak ridges begin to appear in the ectoderm induced by notochord; adjacent neuroectodermal cells elongate become columnar rise meet and fuse dorsally forming future brain and more cuadally rest of neural tube
Squamous surface ectoderm
Will overlay columnar cells of neural tube; this will ultimately cover entire embryo
Neural tube closure
First closes in hind brain area the closure progresses rostraly; lateral dilations of hind brain midbrain and forebrain forming simultaneously
Neural crest cell at notochord closure
As neural tube is closing population of ectodermal cells between neural and surface ectoderm delaminate and disassociate from their neighbors these are neural crest cells
Flexion of embryo
Forbrain grows so fast it starts to raise up and pushes future heart, prechordal plate and septum transversum ventrally and caudally flexing embryo and placing heart oral cavity ect in correct place
First sign of eyes
Toward end of head folding, small groves appear inside bulges on surface of prosencephalon or forebrain
Eye field
Special cells that form initial small groves inside forebrain arise from anterior neural plate called eye field
Eye plate separation
Must separate or Cyclopes will occur
Optic grooves
Aka sulci; eye fields separates into two and invaginates forming optic groove
Optic cups
Optic vesicle invaginates and becomes optic cup; inner part of optic cup will begin to thicken as cells there are diferentiating and elongating to form neurosensory retina
Optic vesicles
Optic grooves (now completely enclosed by closed neural tube) balloon to form optic vesicles
Lens placode formation
Neuroectoderm of optic vessel contacts surface ectoderm inducing this formation
Inducing lens formation
Will have a neural tube with two optic stalks and an optic vesicle on far end of each stalk in contact with surface ectoderm about to induce lens formation
Lens formation
Surface epithelium thickens and becomes columnar (lens placode) then almost immediately invaginates; simultaneously surface ectodermal cells in posterior lens are elongating and filling cavity of lens vesicle
What layer is lens derives from
Ectoderm
Lens vesicle
Ectodermally derived lense pinches off of surface ectoderm forming lens vesicle; once this is pinched off the lens epithelium is encapsulated by basement membrane/ basil lamina of its epithelial cells so immune system does not recognize cells in lens protein bc immune system forms later in development
RPE differentiation
Retinal pigment epithelium differentiation is induced by neural crest cells
First ocular tissue to show significant differentiation
Primitive lens when posterior lens cells elongate to fill cavity of lens vesicle forming the primary lens fibers
Secondary lens fibers
Anterior lens epithelial cells migrate to lens equator start to elongate and eventually form secondary lens fibers; can only grow to a certain length
Sutures
When secondary lens fibers can no longer entirely surround growing lens nucleus then fibers tips meet interdigital earth precisely and form seams called sutures; become more complex y shape with age
Lens fiber clarity
These are clear in part because after elongating lens fibers lose their nucleus and intracelluar organelles
Embryonic optic fissure
Aka choroidal fissure; groove or fissure present on ventral floor of developing optic cup; it is path for developing hyaloid vessels inside eye to exit the eye
hyaloid vessels
nourish the developing lens and retina (developing from mesenchyme surrounding the cup and within the fissure)
failed closure of optic fissure
if fissure fails to close properly congenital coloboma or hole may be noted in iris or other ocular tissues
