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Flashcards in Development Deck (47)

we all start out as what?

single cells


what are the three cellular events in development?

1. proliferation
2. migration
3. differentiation


what is the order of structures formed once we start from a single cell?

zygote, morula, blastula, gastrula, neurula


when the first sperm enters the egg what occurs?

we get depolarization causing the release of Ca2+ ions which causes changes in the zona pellucida to prevent entry of other sperms.


what is the blastocyst made up of?

outer layer of cells called trophoblast, inner cell mass and a fluid filled cavity called the blastocele.


what forms the fetal portion of the placenta?

trophoblast and part of inner cell mass (parts of blastocyst, rest of inner mass forms embryo)


morphogenesis occurs by what?

polarity and tubular organization (gastrula)
neural tube formation (neurula)
neural crest cells


organogensis occurs by what?

developmental fields and stem cells/progenitors.


morphogenesis and organogenesis involves the control of what? which is determined by the combination of?

phenotypic expression
determined by environmental and genetic factors.


Control mechanisms for phenotypic expression (altering the genome which produces changes in phenotype) are?

1. epigenetics
2. transcription factors
3. Growth factors


which HOX gene defines the eye?

PAX i.e. this the pax gene was put on the leg, an eye would develop on the leg.


which ocular structures grow from the surface ectoderm?

1. epithelium of conjunctiva and lids
2. corneal epithelium
3. lens


which ocular structures arise from the neuroectoderm?

ciliary epithelium
iris epithelium and dilator muscle
nerves (i.e. ciliary and choroidal nerves)


what ocular structures arise from the neural crest?

corneal keratocytes (stroma) and conreal endothelium
iris stroma, melanocytes, sphincter muscle
ciliary body (muscle and connective tissue)
most of choroid and sclera


Which ocular structures arise from the mesoderm?

endothelium of BV and schelmms canal
caudal ventral part of the sclera
extraocular muscles


where does the blastocyst implant?

uterine wall


the inner mass of the blastocyst forms what two cavities? and what are their functions?

yolk sac (in humans produces blood cells and future sex cells and gut) and amniotic cavity (cavity in which embryo floats).


of the three primary germ layers, the bulk of the eye is made from which layer?



what are the three primary germ layers and generally what do they produce?

ectoderm: skin, nerves, most of eye
mesoderm: eye muscles, heart, kidney, other muscles
endoderm: lungs, gut (all exposed to the outside, blind ended system)


after implantation the blastocyst becomes what?

embryo (at week 8 it becomes a fetus)


by day 35, what is unique about the embryo?

eye starts to form (at 4 weeks)


does retinal development continue after birth?



humans have notochords (becomes spinal cord/CNS) therefore we are part of what family?



what is non sensory retina?

RPE (develops from primitive nerve tissue)


What are the eight phases in embryonic and fetal development at the cellular level?

1. mitosis/prolifertaion
2. migration (according to signals)
3. differentiation (occurs during migration, post mitosis they are fixed and develop normal structures i.e. dendrites, axons etc)
4. aggregation (like neurons move together and form layers)
5. synaptogenesis (axons form synapses with other neurons or tissues)
6. neuron death (40-75% of neurons from birth do not survive, they fail to make synapses, neurons are broken NOT made)
7. synapse rearrangement (happens all the time, allows us to store info)
8. myelination


is the nervous system a fixed system?

NO, plastic. changing all the time.


how do neurons know where to go during the migration stage?

1. extrinsic signals
2. different sources of extrinsic signals
3. generic signal transduction pathway
4. intrinsic determinants


muscles of the head are made from which germ layer? individual units of mesoderm are called? head somites are divided into which two sets?

pre otic (3 somites) and post otic (5 somites)


which set of somites forms the muscles that move the eyes?

pre otic.


the first somite in the pre otic set is innervated by which cranial nerve? second somite? third somite?

oculomotor (CN3)
trochlear (CN4)
abducent (CN6)


the first gill arch is innervated by? second? third? fourth? fifth?

1= trigeminal (V1 opthalamic branch, V2 maxillary branch and V3 mandibular branch)
2= facial nerve
3= glossopharyngeal nerve
4= vagus nerve
5= spinal accessory nerve


placodes are for what type of nerves? placode one is for what sense? 2? 3?

special sensory
placode 1: nose (olfactory nerve)
placode 2: eye (optic nerve)
placode 3: hear (vestibulocochlear nerve)


which of the three germ layers continuously divides? which tissue in the eye continuously divides and is the only one?

lens (because it is derived from surface ectoderm)


which artery supplies the lens during development? after development what supplies the lens?

hyaloid artery
aqueous humor


eyes develop from what?

developing brain


what is the first thing to occur during eye development?

optic vesicle is formed by an outpocking of the ectoderm. ectodermal tissue (eventually the lens) grows and pushes into this vesicle and collapses it therefore becoming the optic cup. We then get formation of the lens vesicle, the inner layer becomes the retina and outer becomes RPE.


at six o clock in the lens vesicle what is unique?

there is a cleavage, this is where a coloboma can occur (birth defect)


primary vitreous does what? secondary? tertiary?

promotes angiogenesis (vasculature present for supplying lens)
inihibits angiogenesis (vascular supply now lost and is supplied by aqueous)
zonules form (made of collagen)


what is sineresis?

the vitreous humor in our eye is normally gel like, however as we age it becomes more sol (fluid like) which is otherwise known as sineresis.


why can there be no vasculature present in the vitreous in adults?

because it would interfere with optical pathway, would cause scattering of light.


in the fovea, is there vasculature present?

NO, it would disrupt our visual acuity.


any material near the optic nerve that appears out of focus is usually what?

remaining glial tissue


what is mittendorf's dot? epicapsular stars? bergmeisters papilla? persistent pupillary membrane?

1. remaining embryonic tissue on posterior surface of the lens
2. remaining embryonic tissue on anterior surface of lens
3. remains around optic nerve
4. embryonic remains on pupil


is the corneal epithelium continuously growing?

YES due to stem cells located at the limbus, centripetal formation (XYZ hypothesis)


how many cell types form the retina?

ONE (stem cells). all other cells in retain originate from stem cells.


how does the macula form? what is unique about the macula with respect to humans?

macula forms due to stretching of the retina between 2 blood vessels. ONLY primates have a macula (gives us high resolution)


bulk of tissue in our orbit is formed from which of the three germ layers?

surface ectodermal tissue