Development 2 Flashcards
morula
humans:
After fertilization the egg divides rapidly to form morula
blastocyst
blastula stage of mammalian embryonic development, has inner cell mass, a cavity, and an outer layer (trophoblast). in humans: forms 1 week after fert.
trophoblast
Outer cells of blastocyst. Forms the fetal part of the placenta, supporting embryonic development but not forming part of the embryo proper
Inner cell mass (ICM)
inner cluster of cells at one end of mammalian blastocyst that subsequently develops into the embryo proper and some of the extraembryonic membranes
epiblast
Deep cells of ICM form epiblast.
Becomes ectoderm with fluid filled space (the amniotic cavity)
some will migrate during gastrulation to form the mesoderm]
hypoblast
ICM cells close to blastocoel form hypoblast.
become the endoderm
amnion
fluid filled membrane that protects the egg. Keep embryo from drying out.
amniotes
member of a clade of tetrapods. all have amniotic egg that has specialized membranes (fluid filled amnion) that protect the embryo. They are mammals, birds & other reptiles.
placenta
structure in uterus of pregnant eutherian mammal that nourishes the fetus with the mothers blood supply. Made from uterine lining & embryonic membranes.
chorion
Functions as gas exchange with egg shell
Made from extraembryonic ectoderm & mesoderm
yolk sac
Contains the yolk nutrients & eventually forms vessels to deliver them.
Derive from endoderm & mesoderm.
Allantois
Disposes of waste products & helps with gas exchange.
Derive from endoderm & mesoderm.
Continuous development
The newborn is smaller version of adult. Many animals.
Trees
Discontinuous development
Multiple unique stages in life cycle.
Lady bird beetle.
Egg, larvae, pupa, adult
metamorphosis
in discontinuous development, this turns animal larva into adult or adult like stage that is not yet sexually mature(instar)
