Development Flashcards
Stages of development
cleavage, blastula formation, gastrulation, neuralation
cleavage ID
rapid division to form a morula - SOLID BALL OF CELLS
look @ differences btwn animal and vegetal pole, slower division so larger cells in the vegetal pole
blastula formation ID
continued cell division, undifferentiated cells with a hollow space in the center - the BLASTOCOEL
gastrulation ID
*DIFFERENTIATION of cells into the 3 embryonic germ layers: mesoderm, ectoderm, endoderm
***before migration, ectoderm forms in the animal pole before migrating to surround the embryo
- cells from outer surface migrate inwards through BLASTOPORE (endoderm from the veg pole to the interior)
*the space they form is the ARCHENTERON
*displace the blastocoel
*in vertebrates, blastopore forms in the posterior of the embryo
neurulation ID/steps
- Notochord releases proteins signal to ectoderm dorsal to noto to differentiate into NEURAL PLATE ECTODERM
- neural plate ecto bends along midline, NEURAL GROOVE w/ NEURAL FOLD on either side
- neural folds fuse to form NEURAL TUBE, neural plate cells diff from neural tube, forming NEURAL CREST CELLS (mesenchymal) which eventually form the peripheral nervous system
- Mesoderm differentiates into MESOMERE, HYPOMERE, EPIMERE
- Hypomere mesoderm diff into SPLANCHNIC (inside), SOMATIC (exterior) w COELOM in the middle!!!
Memo embryonic germ layer fates - in lab deck!!!!!
single fertilized egg
zygote
animal v vegetal pole
high yolk concentration at the vegetal pole, slowing division
morula
solid ball of cells
blastula
hollow ball of cells (space in middle is blastocoel)
yolk plug
region of slow endodermal cells during gastrulation , next to the blastopore
archenteron
gives rise to the digestive tract
coelom
forms during neurulation from differentiation of hypomere mesoderm
becomes the body’s main cavities
differentiation of mesoderm during neurulation
* see summary for diagram*
EPIMERE - SOMITES in trunk region, big chunk right next to notochord/neural tube
**further diff into DERMATOME, SCLEROTOME, MYOTOME - if u drew a triangle on the somite dermatome is the upper point, sclerotome is the medial point, myotome is the lateral point
HYPOMERE - lateral regions of embryo, next to archenteron and endoderm. Differentiates into splanchnic and somatic hypomere mesoderm
MESOMERE - little bulge between epimere and hypomere
little vs med vs lots of yolk - what taxa?
microlecithal - tiny amt yolk (eutharian animals)
mesolecithal - middle amt yolk (amphibians)
macrolecithal - lots of yolk (many birds/fish)
affect of more yolk on division
more yolk slows cell division BY ………….****
development in birds
- CLEAVAGE/BLASTODISC FORMATION - cell division forming flattened disk of cells on yolk (animal pole): BLASTODISC
- GASTRULATION - EPIBLAST (outer layer) migrates inwards through the PRIMATIVE STREAK, hypoblast guiding movement of epiblast cells
*** epiblast on bottom become EPIDERMIS (endoderm?????????) - NEURULATION - neural tube formation is the same as in other vertebrates, differentiation of mesoderm IN THE TRUNK REGION SEE DIAGRAM, invagination of endoderm forms the early midgut
** DORSAL AORTAS visible on either side of the notochord
**LATERAL BODY FOLDS form on either side of the embryo (kind of above the hypomere mesoderm
***everything happens anterior to posterior, so ant could be in neurulation post could be in gastrulation
blastodisc structure
top - EPIBLAST
bottom - HYPOBLAST
hollow space between layers - BLASTOCOEL
yolk
nutritional matter, rich in lipids, proteins etc
4 extra embryonic membranes
amnion, chorion, allantois, yolk sac
where do certain membranes develop (phylogeny)
ONLY amniotes have amnion, chorion, allantois
embryonic membrane origins
AMNION and CHORION - SOMATOPLEURE = ectoderm and somatic hypomere mesoderm
ALLANTOIS and YOLK SAC - SPLANCHNOPLEURE = endoderm and splanchnic hypomere mesoderm
Allantois function/origin
from splanchnopleure
sequesters nitrogenous waste from the embryo
Yolk sac function/origin
from splanchnopleure
grows ventrally and surrounds embryo
forms VITELLINE VESSELS to supply embryo w/ nutrients from the yolk
amnion function/origin
from somatopleure
waterproof membrane, surrounds membrane and fills w/ amniotic fluid
chorion function/origin
from somatopleure
fuses w/ outer section of allantois - chorioallantoic membrane
positioning of embryonic membranes in an egg - see diagram in summary!!!!!!!!!!!!!!!!!!!!!!
chorioallantoic membrane
splanchnic hypomere mesoderm - from allantois in membrane forms allantoic vessels to exchange gases with the environment through the shell + calcium from the shell
oviparous
egg laying
anamniotes
embryos do not produce an allantois, amnion, or chorion
