Vert. Anatomy 3 Flashcards
Amniotes
Vertebrates that lay eggs on land and their descendants
Macrolecithal
extremely large amount of yolk that remains outside of the body; can develop musculoskeleton & respiratory system before hatching
-reptiles, birds, monotremes
Secondarily microlecithal
egg that reverts to the microlecithal condition from ancestors that were macrolecithal
Eutheria
“placental” mammals
Metatheria
marsupial mammals
Cleavage
a period of rapid cell division during which the cell cycles are abbreaviated; G1 & G2 are essentially skipped
Maternal effect genes
mRNA from the mother used to synthesize proteins during cleavage
Blastula
Result of cleavage in microlecithal and mesolecithal embryos consisting of a hollow ball of cells surrounding a cavity
Blastocoele
cavity of a blasula
Macromeres
Develop from the vegetal hemisphere of mesolecithal embryos
Micromeres
Develop from the animal hemisphere of mesolecithal embryos
Cleavage of macrolecithal embryos
only occurs at the animal pole
Blastoderm
single layer of cells covering the blastocoele
Blastodisc
the thin, flat disc of tissue covering the blastocoele; as seen from above
Posterior Marginal Zone (PMZ)
the edge of the blastoderm, along the rim of the blastocoele; homologous to the gray crescent
Chorion
a thin membrane that covers the entire outer surface of the yolk
Extraembryonic ectoderm
The chorion and other ectoderm
Extraembryonic endoderm
the inner surface of the blastoderm, continuous endoderm of the gut
Hypoblast
A sheet of cells from the posterior marginal zone that spreads across the center of the blastocoele, dividing it into upper and lower cavities.
Subgerminal cavity
cavity below the hypoblast; will form the gut and a couple of extraembryonic cavities; precursor to the endoderm
Epiblast
the upper layer of tissue overlying the subgerminal cavity formed by the original blastoderm
bilaminar stage
two-layered body stage of development of macrolecithal amniotes
Syncytiotrophoblast
the outer layer of the trophoblast; a continuous mass of cytoplasm formed by cells fusing together (in therian mammals)
Morula
undifferentiated clump of cells formed during the early rounds of mitosis
Blastocyst
In therian mammals, the stage in which a cavity forms within a morula
Unlike a blastula, the cells surrounding the cavity do not form the body of the embryo
Inner cell mass
cluster of cells located within the cavity that the body will develop from
Trophoblast
the layer of cells surrounding the blastocyst, involved in implantation and formation of the placenta
Syncytiotrophoblast
outer layer of the trophoblast
-produces enzymes that digest the wall of the uterus at whatever location the blastocyst comes into contact with it, causing implantation
Endometrium
the surface of the uterine wall
