vertebrate development Flashcards
stages of embryotic development
cleavage, blastula formation, gastrulation, neurulation
cleavage (frog)
rapid division of the zygote into a MORULA (solid ball of cells)
*** more rapid in animal pole
animal vs vegetal pole
more yolk in vegetal, slower division
blastula (frog)
hollow ball of cells
blastula formation (frog)
continued division to form blastula (with blastocoel inside)
gastrulation (frog)
cells from outer surface migrate in through blastopore, displacing the blastocoel and forming the archanteron.
3 embryonic germ layers are established - eventually outside lined by ectoderm, archanteron lined with endoderm, and other is mesoderm
medial region of the mesoderm gives rise to the notochord, on the dorsal midline of the embryo
mesoderm generally gives rise to
many regions of the skeleton, most muscles, notochord, circulatory system
endoderm generally gives rise to
lining of the digestive tract as well as liver, pancreas, gall bladder, digetive glands, lungs, swim bladder, and urinary bladder
ectoderm generally gives rise to
epidermis and many skin glands, as well as nervous system and many sensory organs
neural plate formation (frog)
notochord signals for ectoderm dorsal to notochord to differentiate into neural plate ectoderm
neurulation (frog)
neural plate ectoderm bends, forming neural groove surrounded by neural folds
folds fuse into hollow neural tube (inside is neurocoel), gives rise to central nervous system
neural crest cells from dorsal region of tube (what was connecting to neural plate ectoderm) separate, become mesenchymal
differentiation of mesoderm
AFTER gastrulation, meso diff into EPIMERE, MESOMERE, HYPOMERE
epimere mesoderm forms___ and differentiates into ____
somites
dermatome (most dorsal), myotome (my how far from midline), sclerotome (sneakily close to notochord)
hypomere mesoderm is located where in the embryo (frog)
to the right and left of the archanteron
coelom - how does it form and what is it?
two spaces which give rise to the major body cavities in adults
the hypomere mesoderm to the right and left of the archanteron differentiate into somatic on the outside, splanchnic on the inside and the space between them is the coelom
microlecithal eggs
little yolk
mesolecithal eggs
medium yolk
macrolecithal eggs
large yolk
early development in birds
cleavage at small region of animal pole, forming a BLASTODISC
cells in disc differentiate into top - EPIBLAST, and bottom - HYPOBLAST, with blastocoel between
blastodisc
flat disc of cells
epiblast
top part of differentiated blastodisc
hypoblast
bottom part of differentiated blastodisc
gastrulation in birds
epiblast (top) cells migrate towards the primitive streak , 3 germ layers are derived from the epiblast
mesodermal cells to middle, endodermal cells displace the hypoblast (hypoblast guides)
neurulation in birds
now embryo w/ three layers, ectoderm on top, mesoderm in middle split by notochord, endoderm on bottom on yolk surface
noto signals diff of ecto into neural plate ectoderm, folds into neural groove w/ neural folds on each side, fuse to form neural tube
neural crest cells separate from the dorsal region of the neural tube
development of the central nervous system
anterior of neural tube swells into brane, posterior to head gives rise to spinal cord
differentiation of mesoderm into 3 regions
epimere (SUPER CLOSE TO NOTO, mesomere(mid close to noto), hypomere (super far from noto)
differentiation of epimere mesoderm
forms somites in trunk region which differentiate into myotome, dermatome, and sclerotome
formation of the coelom
hypomere mesoderm differentiates into somatic (top) and splanchnic (bottom) mesoderm, space in between is the coelom
digestive system formation in chicks
***** in frogs gastrulation ends, then neurulation vs in chicks, gastrulation is still happening during neurulation
endoderm invaginates to form early gut
what are the 4 extra embryonic membranes
what do amniotes have?
amnion, chorion, allantois, yolk sac
only amniotes have an amnion, chorion, and allantois
many INCLUDING amniotes produce a yolk sac
what are amnion and chorion from
somatopleure - ectoderm and somatic hypomere mesoderm (top layer of embryo , not aroud the neural tube etc
what are the yolk sac and allantois from?
splanchnopleure - endoderm and splanchnic hypomere mesoderm (bottom of embryo by yolk)
allantois function
sequesters nitrogenous metabolic wastes
yolk sac function
surrounds the yolk and forms vitelline vessels
vessels generally formed by splanchnic hypomere mesoderm
amnion function
waterproof, and surrounds the embryo with amniotic fluid
chorion function
outermost membrane
fuses with outer section of the allantois to form chorioallantoic membrane
this contains allantoic vessals from splanchnic hypomere mesoderm
used to exchange gases w/ environment through shell, transport calcium from shell to embryo
specific roles of extra-embryonic membranes in mammals
choreoallantoic membrane and/or yolk sac prod the umbilical cord and embryonic region of the placenta
amnion surrounds embryo in a fluid filled capsule
benefits of amniotic sac
control of proteins reaching embryo
protection from pathogens
cusioning from mechanical impact
temperature regulation
room for embryo to grow and move
prevents dessication (drying out)
provides support by letting embryo float as skeletal system develops
