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Lec 24- embryology
| Question | Answer |
|---|---|
| 2 major points on embryology | 1. the eye is formed from ectoderm (neural and surface) and mesenchyme 2. induction is responsible for the dev of many ocular structures |
| 3 germ layer of emybryonic dev | ectoderm, mesoderm, endoderm |
| how is the neural plate formed? | formed from the thicken ectoderm on the dorsal surface |
| what will the neural plate give rise to? | CNS and eye |
| longitudinal groove that forms down the neural plate | neural groove |
| the lateral edges of the neural groove are brought together to form?/ | neural folds |
| the neural folds will fuse to form? | neural tube of neural ectoderm |
| what is surrounded by mesoderm, in which is covered by surface ectoderm on the dorsal surface? | neural tube |
| where are neural crest cells found? | b/w the neural tube and the surface ectoderm situated within the mesoderm |
| what is mesenchyme? | a collective term that includes mesoderm and neural crest cells |
| what small depressions forms on both sides of the forebrain as the neural tube is closing? | optic pits |
| what do the optic pits form on the lateral aspect of the forebrain? | optic vesicles |
| briefly, what is the optic vesicles touching during their lateral expansion? | surface ectoderm |
| the proximal portion of the optic vesicle near the forebrain begins to constrict to form | optic stalk |
| what is continuous with the third ventricle of the brain? | the cavity inside the optic vesicle and optic stalk |
| what is formed from the inferior aspect of the optic stalk and the inferior aspect of the optic vesicle? | inferior optic fissure |
| invagination of the portion of the inferior optic fissure in the optic stalk pulls the anterior portion of the optic vesicle posterioly forming what double layered structure? | optic cup |
| the inferior optic fissure closes and zips itself shut to form the? | optic canal |
| in what arrangment are the inner layer and outer layer of the optic cup? | apex-to-apex |
| what structures cells with the PR? | ep of CB, iris pigment ep, apice of RPE cells |
| the space that separates the nner and outer layers of the optic cup is called? | intraretinal space |
| what does the intraretinal space become? | subretinal space |
| what forms from the inner layer of the optic cup? | neural retina, NPE, iris posterior pigmented ep |
| what forms from the outer layer of the optic cup? | RPE, PE, iris anterior pigmented ep |
| what is induction? | the influence that one structure has on another |
| when the optic vesicle was in contact with the surface ectoderm, the surface ectoderm thickens to form what? | lens plate or lens placode |
| when the lens placode elongates and the center invaginates, what is it forming? | the lens pit |
| when the lens pit invaginates, what hollow circular structure does it form? | lens vesicle |
| the lens vesicle is in the position of what future structure? | vitreous chamber |
| describe the appearance of the lens vesicle | hollow; composed of a single layer of cells; surrounded by basal lamina |
| why is there no posterior epithlium in the adult lens? | b/c the posterior lens fiber (aka primarylens fiber) forms the embryonic lens |
| nuclei of the primary lens fiber moves anteriorly to form what? | lens bow |
| what gives rise to the secondary lens fibers? | the anterior ep in the germantive zones at the equator |
| the region that contains the Y-sutures continues to develop until birth is called? | fetal nucleus |
| what is the adult nucleus? | secondary fibers laid down b/w birth and sexual maturity |
| what is the lens cortex? | newly formed fibers surrounding the adult nucleus that contain nuclei |
| the hyaloids vasculature and other vascular mesenchyme enters the optic stalk and optic vesicle via what? | inferior optic fissure |
| what is the posterior surface of the lens called that the hyaloid basculature forms a plexus around? | posterior vascular tunic of the lens |
| what annular vessel does the posterior vascular tunic of the lens communicate with to form the anterior vascular tunic of the lens? | rim of the optic cup |
| True or false: hyaloid vasculature is usually completely resorbed by birth | true |
| what remnants of the hyaloid arterial system often remains on the lens and optic nerve? | Bergmeisters papilla on the optic nerve head; Mittendorf's dot on the posterior surface of the lens |
| what does the hyaloid vasculature give rise to? | the central retinal artery and vein |
| what induces the choriocapillaris to form from mesenchyme? | RPE |
| what also forms after the choriocapillaris is formed from mesenchyme? | sattler's and haller's layers, vortex veins, short posterior ciliary arteries, and the arterial circle of zinn |
| the pigmented layer of the CB will form ridges that the NPE layer will follow, giving rise to? | the ciliary processes of the pars plicata |
| the CB stromal elements originate from what? | neural crest cells |
| the ciliary muscle is derived from what? | mesenchyme |
| what are the iris dilator and iris sphincter derived from? | neural ectoderm |
| what iris stromal connective tissue and blood vessels form from what? | mesenchyme |
| what does the papillary membrane form between? | the lens ep and the corneal ep |
| what is the papillary membrane derived from? | mesenchyme |
| what 2 structures is usually resorb by birth? | papillary membrane and hyaloid vasculature |
| what accumulates near the ciliary body and iris root at the iridocorneal angle? | neural crest cells and mesenchyme |
| what is the trabecular meshwork derived from? | mesenchyme |
| what is the schlemm's canal derived from? | deep scleral plexus |
| what is referred to as the primary vitreous? | the mass of fibrillar material that fills the vitreous cavity |
| what begins to develop from the neural retina and degenerating hyaloids basculature in vitreous development? | secondary vitreous |
| cloquet's canal spans what anteriorly and posteriorly? | anteriorly from the retrolental space to the posterior area of martegani |
| what gives rise to the attachments at the vitreous base and ligamentum gyaloidea capsulare? | secondary vitreous |
| what is referred to as the tertiary vitreous? | the len zonules develop from fibrillar material secreted by NPE |
| what is the precursor of the optic nerve? | optic stalk |
| invagination of the inferior optic fissure gives rise to what? | optic stalk |
| the outer layer of the optic stalk gives rise to? | neuroglial sheath that surrounds the optic nerve |
| the inner layer of the optic stalk is destroyed by apoptosis to create what? | a passageway for axons of the retinal ganglion cells |
| what is the RPE formed from? | outer layer of the optic cup |
| which is the first layer of the retina to differentiate? | RPE |
| which is the first pigmentation to be visible to the embryo? | RPE |
| what basal surface of the RPE faces what? | Brunch's membrane |
| the apex of the RPE faces what? | PR |
| what is the retina formed from? | inner layer of the optic cup |
| for a short time, what is the thickest region of the retina? | the macula |
| what causes the shallow depression otherwise known as the fovea centralis? | the displacement of ganglion cells and inner retinal elements |
| what needs to happen in order to increase the packing density of the cones within the fovea? | inner segments of cones decrease their width; outer segments of cones elongate |
| how is Henle's fiber layer formed? | the synapse of the oblique orientation of the axons (inner fibers) of the cones with the interneurons |
| what is the last portion of the retina to fully develop? | fovea |
| what induces the formation of the cornea? | lens vesicles |
| what is corneal ep derived from? | surface ectoderm |
| what is corneal endothelium derived from? | neural crest cells |
| the corneal stroma is derived from what? | mesenchyme |
| the scleral originates from condensation of what? | mesenchyme |
| what is located just posterior to the developing eyelinds | cornea |
| what does the secretion of meibomian glands breakdown allowing the separate of eyelids? | desmosomes |
| what parts of the eyelid forms from surface ectoderm? | epithelium of the skin; epithelium of conj.; hair follicles and cilia of the eyelid; meibomian glands; glands of zeiss; glands of moll |
| what parts of the eyelid forms from mesenchyme? | tarsal plates; orbicularis oculi muscle; levator palpebrae superioris muscle; superior tarsal muscle of Muller; orbital septum |
| epithelial buds arise of the lateral superior forniceal conj. and develops what? | lacrimal gland |
| what forms the secretory part of the lacrimal gland? | the mesenchymal condensation around the epithelial buds |
| what does the nasolacrimal drainage system develop from? | a cord of surface ectodermal cells |
| a cord of surface ectodermal cells becomes canalized to give rise to what structures of the nasolacrimal drainage system? | nasolacrimal canaliculi, nasolacrimal sac, and lasolacrimal duct |
| EOMs are derived from? | mesenchyme |
| adipose tissue and connective tissue in the orbit is from? | neural crest cells |
| bones of the orbit are formed from what? | mesenchyme surrounding the optic vesicle |
| in early embryonic dev, the angle b/w the orbit is 180 degress and gradually reduces to what? | 90 degrees |
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babytigger131
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