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Ch 12 part one: Bird Devo
Terms in this set (46)
vertebrates whose embryos form an amnion (water sac)
is formed early in devo and enables the embryo to float in a fluid environment and protects it from drying out
enables nutrient uptake and the development of the circulatory system
-devleops at posterior end of the embryo
-stores waste products
contain blood vessels that exchange gases with the outside environment
cleavage in birds and reptiles is...
discoidal mesoblastic (so only a small portion of the egg's volume is being used to make embryo cells)
-cleavage only occurs at the blastodisc which is at the animal pole
-cleavages create a blastoderm
fertilization of the chick occurs in the oviduct before the....
albumin and shell are secreted over it
cleavage occurs on the 1st day of devo while the egg is still...
inside the hen
the egg is telolecithal
small disk of yolk-free cytoplasm (blastodisc) sitting on top of a large mass of yolky cytoplasm
cleavages do not extend into the yolky cytoplasm, so the early cleavage cells are...
continuous with one another and the yolk at their bases
space between blastoderm and yolk
-created by blastoderm absorbing water from the albumin and secreting it btwn itself and the yolk
A 1-cell-thick area in the center of the avian blastoderm (following shedding of most of the deep cells) that forms most of the actual embryo.
the peripheral ring of avian blastoderm cells that have not shed their deep cells
Thin layer of cells between the area pellucida and area opaca
Gastrulation of the avian embryo
-the blastoderm will form...
an epiblast and hypoblast
the embryo comes entirely from the...
epiblast, the hypoblast doesn't contribute
so the area of pellucida forms the epiblast
hypoblast helps form...
portions of the extra-embryonic membranes like the yolk sac
the hypoblast also provides...
chemical signals that specify the migration of epiblast cells
a local thickening of the epiblast at the posterior edge of the area pellucida
posterior marginal zone (PMZ)
in-between Koller's sickle and the area opaca
anterior cells of epiblast delaminate and stay attached to the epiblast
hypoblast islands migrate to become ...
secondary hypoblast (endoblast)
-the complete hypoblast layer
-formed from primary hypoblast and sheet that grows anteriorly from Koller's sickle
gastrulation takes place through the...
-the equivalent of an elongated blastopore lip
primitive streak arises from...
Koller's sickle and the epiblast above it
A depression that forms within the primitive streak
-serves as an opening through which migrating cells pass into the deep layers of the embryo.
-equivalent to a blastopore
thickening area of cells at the anterior end of the primitive streak
-equivalent to the frog dorsal blastopore lip ("the organizer") and the fish embryonic shield
a depression in Henson's node through which cells can enter the embryo to form the notochord and the prechordal plate
the primitive streak defines...
the major body axes
-equivalent to dorsal-ventral axis in frogs
Henson's node gives rise too...
prechordal mesoderm, notochord, and medial parts of the somites
elongation of primitive streak
add cells to caudal end
as cells are added, cells at cranial end of streak proliferate to form circular thickening called
Formation of Endoderm and Mesoderm
-in amniote cell specification, germ layers are established before gastrulation starts, but specification of cell type is controlled by....
inductive influences during and after migration thru the primitive streak
cells migrating thru anterior end of streak...
-form endoderm, head mesoderm, and notochord
cells migrating in posterior end of streak...
-form most of the mesodermal tissues
the 1st cells to migrate through Henson's node are destined to become...
the pharyngeal endoderm of of the foregut
-region in the anterior portion of the avian and reptilian blastoderm area pellucid that contains hypoblasts displaced by migrating endodermal cells
-does not form any embryonic structures but it does contain the precursors of the germ cells, which later migrate through the blood vessels to the gonads.
prechordal plate mesoderm
cells that migrate anteriorly through Hensen's node, between the endoderm and the epiblast, and form the precursor of the head mesoderm
axial mesoderm that produces the notochord and head process
Regression of the primitive streak...
moves Henson's node from the center of the area pellucida to a more posterior portion
the regression of the streak leaves behind....
the dorsal axis of the embryo and the notochord
______ and ______- will induce the anterior parts of the brain
pharyngeal endoderm and head mesoderm
______- will induce hindbrain and spinal cord
__________ are the locomotor apparatus of the marginal cells, by which they pull other ectodermal cells around the yolk
as avian gastrulation draws to a close....
-the ectoderm has surrounded the embryo, the endoderm has replaced the hypoblast, and the mesoderm's positioned itself between these two regions
Axis specification and the "avian organizer"
-while the posterior portions of the embryo are still part of a primitive streak and entering inside and embryo, cells at the anterior end are already starting to form organs
the role of gravity and the PMZ
the conversion of
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