Definitions Flashcards
Homeosis
Where 1 structure is transformed into another homologous structure as a result of a mutation
Phylotypic stage
The stage of vertebrate embryogenesis during which embryos of different species closely resemble each other, embryo has a distinct head neural tube & somites
Involution
Cells move around the inner blastular surface to opposite the blastopore when gastrulation begins
Archenteron
A new cavity formed in the gut during embryogenesis, produced by endoderm & mesoderm invagination
Epiboly
Ectodermal cells spread to cover the outer embryo surface during gastrulation, end up covering blastula
Convergent extension
Cells converge on the dorsal side to produce an elongated “fish” shape, found in fish
Subgerminal space
Cavity formed beneath the chick embryo during early blastoderm stage
Hypoblast
Cell layer above the yolk under blastoderm, gives rise to extra-embryonic structures (yolk sac)
Epiblast
A group of cells w/in blastocyst (mouse)/blastoderm (chick), develops from the inner cell mass into the embryo proper
Chorion
Outermost extra-embryonic membrane in mammals reptiles & birds, just beneath shell (birds & reptiles), part of placenta (mammals), involved in gas exchange (all) & nutrient & waste exchange (mammals), formed from trophoblast (mammals)
Ingression
Cells individually move to the inside during gastrulation, mammals & birds: cells detach from epiblast & move through primitive streak
Amnion
Extra-embryonic membrane that forms a fluid-filled sac which encloses & protects the embryo, arises from extra-embryonic ectoderm & mesoderm, formed from inner cell mass (ICM)
Nieuwkoop center
Signalling center on dorsal side of early Xenopus embryo, forms on dorsal vegetal region b/c cortical rotation, helps specify position of Spemann organizer
Spemann organizer
Signalling center on amphibian dorsal embryo, acts as main embryonic organizer, produces signals that organize new A/P & D/V axes, cells become notochord
Trophoblast
Cells that surround the developing embryo
Tunica
Formed from L1 & L2 layers through anticlinal cell divisions, found in plants
Corpus
Formed from L3 through divisions in any direction, found in plants
Embryonic stem cell line
Pluripotent cells that can contribute to an embryo (esp germ-line) when injected into a blastocyst
Blastula
A hollow ball of cells, early stage of embryonic development
Blastoderm
Post cleavage embryo. a solid cell mass instead of a ball, found in chick, zebrafish, & fly embryos
Blastocyst
A mammalian embryo stage corresponding to the blastula stage in other animals, where embryo implants into uterine wall
Blastocoel
A fluid-filled cavity in the blastula
Blastopore
Invagination/slit on the sea urchin & amphibian embryo surface where mesoderm & endoderm move towards the center of the embryo @ gastrulation
Morpholino
Short (~25bp) oligonucleotides w/ modified bases to increase stability, can prevent translation by blocking the ribosome
Primitive streak
Site of gastrulation in avian & mammalian embryos & forerunner of A/P axis, a strip of ingressing cells that extends into epiblast from posterior margin, epiblast cells move through streak into embryo interior -> mesoderm & endoderm
Morphogenesis
How cells change shape, migrate, & recognize their positions to give an embryo its unique morphological appearance
Signalling center
A localized region of an embryo that exerts a special influence on surrounding cells usually by secreting signalling proteins that determine how the cells develop
Organizer
A signalling center that directs the organization of the entire embryo or part of the embryo (like a limb)
Rhombomere
Compartments of cell-lineage
restriction along chick & mouse embryo hindbrains
Neural tube
Ectodermally-derived tubular structure that forms along the dorsal midline of a vertebrate embryo & gives rise to the vertebrate nervous system
Commissural neuron
Neuron in vertebrate spinal column/insect ventral nerve cord where axon crosses the midline to form connections w/ neurons on the other side
